SAN DIEGO and TORONTO, Oct. 27, 2020 (GLOBE NEWSWIRE) -- Aptose Biosciences Inc. (Nasdaq: APTO; TSX: APS), a clinical-stage company developing highly differentiated therapeutics that target the underlying mechanisms of cancer, will release its financial results for the quarter ended September 30, 2020 on Tuesday, November 10, 2020, after the close of the market.

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Aptose to Release Third Quarter Ended September 30, 2020 Financial Results and Hold Conference Call on November 10, 2020

Global News Feed Comments Off on Aptose to Release Third Quarter Ended September 30, 2020 Financial Results and Hold Conference Call on November 10, 2020 | October 27th, 2020

WALTHAM, Mass., Oct. 27, 2020 (GLOBE NEWSWIRE) -- Repligen Corporation (NASDAQ:RGEN), a life sciences company focused on bioprocessing technology leadership, today announced that it has entered into a definitive agreement to acquire privately-held ARTeSYN Biosolutions (“ARTeSYN”) for approximately $200 million, comprised of approximately $130 million in cash and approximately $70 million in Repligen common stock. ARTeSYN Biosolutions is projected to generate approximately $30 million in revenue (pro forma) in 2020, led by the success of its single-use chromatography and filtration systems which are considered the gold standards in downstream bioprocessing due to their performance, automation and low hold-up volumes. The proposed acquisition of ARTeSYN, combined with the recent acquisitions of Engineered Molding Technologies (“EMT”) and Non-Metallic Solutions (“NMS”) further establishes Repligen as a premier player in single-use systems and associated integrated flow path assemblies.

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Repligen Corporation Announces Agreement to Acquire Bioprocess Systems Innovator ARTeSYN Biosolutions and Completes Acquisition of Non-Metallic...

Global News Feed Comments Off on Repligen Corporation Announces Agreement to Acquire Bioprocess Systems Innovator ARTeSYN Biosolutions and Completes Acquisition of Non-Metallic… | October 27th, 2020

Company announcement no. 42 - 20 27 October 2020

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Transactions in connection with and conclusion of share buyback program

Global News Feed Comments Off on Transactions in connection with and conclusion of share buyback program | October 27th, 2020

ROCKVILLE, Md., Oct. 27, 2020 (GLOBE NEWSWIRE) -- Supernus Pharmaceuticals, Inc. (Nasdaq: SUPN), a pharmaceutical company focused on developing and commercializing products for the treatment of central nervous system (CNS) diseases, today announced that the Company expects to report business results for the third quarter of 2020 after 5:00 p.m. ET on Tuesday, November 3, 2020.

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Supernus to Host Third Quarter 2020 Financial Results Conference Call

Global News Feed Comments Off on Supernus to Host Third Quarter 2020 Financial Results Conference Call | October 27th, 2020

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CLINUVEL to Trial Innovative Drug in Stroke

Global News Feed Comments Off on CLINUVEL to Trial Innovative Drug in Stroke | October 27th, 2020

June 27, 2020

Following promising phase 1 testing, Mayo Clinic is launching phase 2 of a randomized clinical trial of stem cell treatment for patients with severe spinal cord injury. The clinical trial, known as CELLTOP, involves intrathecal injections of autologous adipose-derived stem cells.

"The field of spinal cord injury has seen advances in recent years, but nothing in the way of a significant paradigm shift. We currently rely on supportive care. Our hope is to alter the course of care for these patients in ways that improve their lives," says Mohamad Bydon, M.D., a neurosurgeon at Mayo Clinic in Rochester, Minnesota.

The first participant in the phase 1 trial was a superresponder who, after stem cell therapy, saw significant improvements in the function of his upper and lower extremities.

"Not every patient who receives stem cell treatment is going to be a superresponder. Among the 10 participants in our phase 1 study, we had some nonresponders and moderate responders," Dr. Bydon says. "One objective in our future studies is to delineate the optimal treatment protocols and understand why patients respond differently."

In CELLTOP phase 2, 40 patients will be randomized to receive stem cell treatment or best medical management. Patients randomized to the medical management arm will eventually cross over to the stem cell arm.

Study participants must be age 18 or older and have experienced traumatic spinal cord injury within the past year. The spinal cord injuries must be American Spinal Injury Association (ASIA) grade A or B.

The initial participant in CELLTOP phase 1 sustained a C3-4 ASIA grade A spinal cord injury. As described in the February 2020 issue of Mayo Clinic Proceedings, the neurological examination at the time of the injury revealed complete loss of motor and sensory function below the level of injury.

After undergoing urgent posterior cervical decompression and fusion, as well as physical and occupational therapy, the patient demonstrated improvement in motor and sensory function. But that progress plateaued six months after the injury.

Stem cells were injected nearly a year after his injury and several months after his improvement had plateaued. Clinical signs of efficacy in both motor and sensory function were observed at three, six, 12 and 18 months following the stem cell injection.

"Our patient also reported a strong improvement with his grip and pinch strength, as well as range of motion for shoulder flexion and abduction," Dr. Bydon says.

Spinal cord injury has a complex pathophysiology. After the primary injury, microenvironmental changes inhibit axonal regeneration. Stem cells can potentially provide trophic support to the injured spinal cord microenvironment by modulating the inflammatory response, increasing vascularization and suppressing cystic change.

"In the phase 2 study, we will begin to learn the characteristics of individuals who respond to the therapy in terms of their age, severity of injury and time since injury," says Anthony J. Windebank, M.D., a neurologist at Mayo's campus in Minnesota and director of the Regenerative Neurobiology Laboratory. "We will also use biomarker studies to learn about the characteristics of responders' cells. The next phase would be studying how we can modify everyone's cells to make them more like the cells of responders."

CELLTOP illustrates Mayo Clinic's commitment to regenerative medicine therapies for neurological care. "Our findings to date will be encouraging to patients with spinal cord injuries," Dr. Bydon says. "We are hopeful about the potential of stem cell therapy to become part of treatment algorithms that improve physical function for patients with these devastating injuries."

Bydon M, et al. CELLTOP clinical trial: First report from a phase I trial of autologous adipose tissue-derived mesenchymal stem cells in the treatment of paralysis due to traumatic spinal cord injury. Mayo Clinic Proceedings. 2020;95:406.

Regenerative Neurobiology Laboratory: Anthony J. Windebank. Mayo Clinic.

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Stem cell treatment after spinal cord injury: The next ...

Spinal Cord Stem Cells Comments Off on Stem cell treatment after spinal cord injury: The next … | October 27th, 2020

At least six international studies have reported T cell reactivity against SARS-CoV-2 in 20% to 50% of people with no known exposure to the virus. Experts suggest doing three tests simultaneously: RTPCR, antibody test, and a T-cell assay, which will give a picture to policymakers if the State or the country has achieved herd immunity against SARS-CoV-2.

A type of white blood cell, T cells are part of the immune system and develop from stem cells in the bone marrow. They help protect the body from infection. Also called T lymphocyte and thymocyte.

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T-cell mediated immunity can be acquired due to previous exposure to other beta coronaviruses which cause the common cold. Knowing a threshold for herd immunity can allow the government to focus on that section of the population who do not have immunity. But they also caution that very few basic science labs in the country like NIMHANS, IISc, or the National Centre for Biological Sciences can do T cell assays in their labs as it is cumbersome and expensive.

Assessing how much of the population has IgG (non-neutralising antibodies), the current active Covid case burden, and T-cell induced protection, simultaneously will give a clear picture of the health of the population, with respect to Covid-19.

"Currently, we do not know when the pandemic will end. If we know how much of the population is immune, it is easier to decide how much of our resources should be allocated to fight Covid, the economy, etc. If done at the state or the sub-state level, we can understand which region needs more resources," said Dr Giridhar Babu, epidemiologist, and member of the State Covid-19 technical advisory committee (TAC).

In the serosurvey undertaken in Karnataka whose results are yet to be announced, with samples from all the eight zones of Bengaluru included, unlike the serosurveys of Delhi, Mumbai, Pune, and Punjab, Karnataka are supposed to have done all three: RTPCR, antibody, and antigen tests simultaneously in the statewide survey.

Coronavirus India update: State-wise total number of confirmed cases, deaths on October 23

Dr V Ravi, Senior Professor and Head, Neurovirology, NIMHANS, and member of State Covid-19 TAC, told DH, "T cell response assay is very cumbersome and complicated to do. Peripheral blood has to be drawn, lymphocytes separated, culture them, stimulate them with antigens, and then take a readout. It is expensive and resource-intensive. Basic science institutes like IISc, NCBS, National Institute of Immunology, ISER, some of them may have the capacity for doing it, but not the medical college laboratories."

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Covid-19: Has Karnataka achieved herd immunity? Simultaneous triple tests will give true picture - Deccan Herald

Bone Marrow Stem Cells Comments Off on Covid-19: Has Karnataka achieved herd immunity? Simultaneous triple tests will give true picture – Deccan Herald | October 24th, 2020

INTRODUCTION

Cleidocranial dysplasia (CCD) is a hereditary disease characterized by incomplete closure of the fontanelle, abnormal clavicle, short stature, and skeletal dysplasia. It has been reported that there are multiple Runx2 mutations in human CCD syndrome (1, 2). Mature osteoblasts defect and bone mineralization disorders were observed in Runx2-deficient mice. The Runx2-heterozygous mice show similar phenotypes to the CCD syndrome (24). RUNX2 triggers mesenchymal stem cells (MSCs) to differentiate into osteoblasts (3, 5). According to the skeletal pathology studies in humans and mice, it is important to accurately regulate Runx2 activity during bone formation and bone remodeling (6, 7). However, the molecular regulation of Runx2 activity remains to be further studied.

The evolutionarily conserved Hippo pathway is essential for tissue growth, organ size control, and cancer development (811). Numerous evidences revealed the important roles of Hippo components in regulating bone development and bone remodeling. YAP, the essential downstream effector of Hippo pathway, regulates multiple steps of chondrocyte differentiation during skeletal development and bone repair (12). YAP also promotes osteogenesis and suppresses adipogenic differentiation by regulating -catenin signaling (13). VGLL4, a member of the Vestigial-like family, acts as a transcriptional repressor of YAP-TEADs in the Hippo pathway (14). Our previous work found that VGLL4 suppressed lung cancer and gastric cancer progression by directly competing with YAP to bind TEADs through its two TDU (Tondu) domains (9, 15). We also found that VGLL4 played a critical role in heart valve development by regulating heart valve remodeling, maturation, and homeostasis (16). Moreover, our team found that VGLL4 regulated muscle regeneration in YAP-dependent manner at the proliferation stage and YAP-independent manner at the differentiation stage (17). Our previous studies suggest that VGLL4 plays an important role to regulate cell differentiation in multiple organs. However, the function of VGLL4 in skeletal formation and bone remodeling is unknown.

Here, we reveal the function of VGLL4 in osteoblast differentiation and bone development. Our in vivo data show that global knockout of Vgll4 results in a wide variety of skeletal defects similar to Runx2 heterozygote mice. Our in vitro studies reveal that VGLL4 deficiency strongly inhibits osteoblast differentiation. We further demonstrate that TEADs can bind to RUNX2, thereby inhibiting the transcriptional activity of RUNX2 independent of YAP binding. VGLL4 could relieve the inhibitory function of TEADs by breaking its interaction with RUNX2. In addition, deletion of VGLL4 in MSCs shows similar skeletal defects with the global Vgll4-deficient mice. Further studies show that knocking down TEADs or overexpressing RUNX2 in VGLL4-deficient osteoblasts reverses the inhibition of osteoblast differentiation.

To study the function of VGLL4 in bone, we first measured -galactosidase activity in Vgll4LacZ/+ mice (16). -Galactosidase activity was enriched in trabecular bones, cortical bones, cranial suture, and calvaria cultures (fig. S1, A to C). Furthermore, in bone marrow MSCs (BMSCs), Vgll4LacZ/+ mice displayed -galactosidase activity in osteoblast-like cells (fig. S1D). During osteoblast differentiation in vitro, osteoblast marker genes such as alkaline phosphatase (Alp) and Sp7 transcription factor (Osterix) were increased and peaked at day 7. Vgll4 showed similar trend in this process at both mRNA and protein levels (Fig. 1A and fig. S1, E and F). To further clarify the important role of VGLL4 in bone development, we used a Vgll4Vgll4-eGFP/+ reporter mouse line in which VGLL4enhanced green fluorescent protein (eGFP) fusion protein expression is under the control of the endogenous VGLL4 promoter, and GFP staining reflects VGLL4 expression pattern in skeletal tissues (16). GFP staining was performed at embryonic day 18.5, week 1, week 2, and week 4 stages. The results indicated that the VGLL4 expression level was increased during bone development (fig. S1G). In addition, VGLL4 was enriched in trabecular bones, cortical bones, chondrocytes, cranial suture, and calvaria (fig. S1, G and K to M). We then observed the colocalization of VGLL4-eGFP with markers of MSCs (CD105), osteoblasts [osteocalcin (OCN)], and chondrocytes [collagen 2a1 (Col2a1)] in long bone and calvaria (fig. S1, H to M). Next, we analyzed VGLL4 expression pattern during osteoblast development in vivo (fig. S1N), which was similar to Alp and Osterix expression patterns in mouse BMSCs of different ages. Together, both in vivo and in vitro data suggest that VGLL4 may play roles in osteoblast differentiation and bone development.

(A) Immunoblotting showed the expression profile of VGLL4 during osteoblast differentiation in C57BL/6J mouse BMSCs. Samples were collected at 0, 1, 4, 7, and 10 days after differentiation. (B) Skeletons of WT and Vgll4/ mice at postnatal day 1 (P1) were double-stained by Alizarin red/Alcian blue (n = 5). Scale bar, 5 mm. (C) Quantification of body length in (B). (D) Skull preparations from control and Vgll4/ mouse newborns were double-stained with Alizarin red and Alcian blue at P1. -QCT images of skulls were taken from control and Vgll4/ mice at P4. Scale bar, 5 mm. (E) Quantification of skull defect area in (D). (F) Clavicle preparations from control and Vgll4/ mouse newborns were double-stained with Alizarin red and Alcian blue at P1 and quantification of clavicle length. Scale bar, 5 mm. (G) Alp staining and Alizarin red staining of calvarial cells from WT and Vgll4/ mice after cultured in osteogenic medium. Scale bar, 3 mm. (H) Relative mRNA levels were quantified by RT-PCR. (I) Hematoxylin and eosin (H&E) staining of femur from WT and Vgll4/ mice at embryonic day 16.5. Scale bar, 125 m. (J) In situ hybridization for Col11 immunostaining. Scale bar, 125 m. In (C), (E), (F), and (H), data were presented as means SEM; *P < 0.05, **P < 0.01, and ***P < 0.001, ns, no significance; unpaired Students t test. Photo credit: Jinlong Suo, State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai.

To investigate the potential function of VGLL4 in bone, we next analyzed the phenotype of Vgll4 knockout (Vgll4/) mice (16). The newborn Vgll4 knockout mice were significantly smaller and underweight compared with their control littermates (Fig. 1, B and C, and fig. S2, A and B). In particular, the membranous ossification of the skull was impaired in Vgll4/ newborns compared with the control littermates (Fig. 1, D and E). Furthermore, Vgll4 knockout mice developed a marked dwarfism phenotype with short legs and short clavicles (Fig. 1, C and F). To assess the role of VGLL4 in osteoblast differentiation, calvarial cells from Vgll4/ mice and wild-type (WT) mice were cultured in osteogenic medium. The activity of Alp in the Vgll4 deletion group was significantly reduced at the seventh day of differentiation (Fig. 1G, top) and was markedly weakened over a 14-day culture period as revealed by Alizarin red S staining (Fig. 1G, bottom). The declined osteogenesis in Vgll4 knockout cells was confirmed by the decreased expression of a series of osteogenic marker genes (Fig. 1H), including Alp, Osterix, and collagen type1 1 (Col11). In addition, in Vgll4/ mice, bone development was severely impaired with remarkable decrease in bone length and almost a complete loss of bone ossification (Fig. 1I). Consistently, immunohistochemical analysis of bone tissue sections from embryos at embryonic day 14.5 further confirmed the defects of bone formation and impaired osteoblast differentiation in Vgll4/ mice (Fig. 1J). Together, our study suggests that VGLL4 is likely to regulate MSC fate by enhancing osteoblast differentiation.

Given that the smaller size of mice is often caused by dysplasia, we also paid attention to the development of cartilage after Vgll4 deletion. As we expected, cartilage development was delayed in Vgll4-deficient mice determined by Safranin O (SO) staining (fig. S2C). Immunohistochemical analysis of collagen X (Col X) further confirmed the delay of cartilage development in Vgll4/ mice (fig. S2D). However, additional experiments would be required to determine the regulatory mechanism behind the observed chondrodysplasia. Although dwarfism was observed and trabecular bones were significantly reduced in the adult Vgll4/ mice, no significant cartilage disorder was observed by SO staining (fig. S2E). In adults, bone is undergoing continuous bone remodeling, which involves bone formation by osteoblasts and bone resorption by osteoclasts. We speculated that Vgll4 deletion might lead to decreased osteoclast activity. To distinguish this possibility, we performed histological analysis by tartrate-resistant acid phosphatase (TRAP) staining to detect osteoclast activity. The results showed that osteoclast activity was comparable between Vgll4/ mice and their control littermates (fig. S2F). Together, our results suggest that the phenotypes observed in Vgll4/ mice are mainly due to the defect of osteoblast activity.

To further explore the role of Vgll4 in the commitment of MSCs to the fate of osteoblasts, we generated Prx1-cre; Vgll4floxp/floxp mice (hereafter Vgll4prx1 mice) (fig. S3A). Prx1-Cre activity is mainly restricted to limbs and craniofacial mesenchyme cells (18, 19). Western blot analysis confirmed that VGLL4 was knocked out in BMSCs (fig. S3B). Vgll4prx1 mice survived normally after birth and had normal fertility. However, Vgll4prx1 mice exhibited marked dwarfism that was independent of sex (Fig. 2, A and B, and fig. S3C), which was similar to the phenotype of Vgll4/ mice. In particular, the membranous ossification of the skull and clavicle was also impaired in Vgll4prx1 mouse newborns compared with control littermates (Fig. 2, C to E). To assess the role of VGLL4 in osteoblast differentiation, BMSCs from Vgll4prx1 and Vgll4fl/fl mice were cultured in osteogenic medium. Markedly decreased ALP activity and mineralization were observed in Vgll4prx1 mice (Fig. 2, F and G). The declined osteogenesis in Vgll4 knockout osteoblasts was also proved by the decreased expression of a series of osteogenic marker genes, including Alp, Osterix, and Col1a1 (Fig. 2H). Normal Runx2 expression was detected in Vgll4prx1 mice (Fig. 2H). To further verify the role of VGLL4 in osteoblast differentiation, BMSCs from Vgll4fl/fl mice were infected with GFP and Cre recombinase (Cre) lentivirus and then cultured in osteogenic medium. Vgll4fl/fl BMSCs infected with Cre lentivirus showed markedly decreased ALP activity and mineralization (fig. S4A). Reduced VGLL4 expression by Cre lentivirus was confirmed by reverse transcription polymerase chain reaction (RT-PCR) (fig. S4B). The declined osteogenesis was also proved by the decreased expression of a series of osteogenic marker genes, including Alp, Osterix, and Col1a1 (fig. S4B).

(A) Skeletons of Vgll4fl/fl and Vgll4prx1 mice at P1 were double-stained by Alizarin red and Alcian blue. Scale bar, 5 mm. (B) Quantification of body length in (A) (n = 6). (C) Skull and clavicle preparation from Vgll4fl/fl and Vgll4prx1 mouse newborns were double-stained with Alizarin red and Alcian blue at P1. Scale bars, 5 mm. (D) Quantification of the defect area of skulls in (C) (n = 6). (E) Quantification of clavicle length in (C) (n = 6). (F) Alp staining and Alizarin red staining of BMSCs from Vgll4fl/fl and Vgll4prx1 mice after cultured in osteogenic medium. Scale bars, 3 mm. (G) Alp activity was measured by phosphatase substrate assay. (H) Relative mRNA levels were quantified by RT-PCR. (I) 3D -QCT images of trabecular bone (top) and cortical bone (bottom) of distal femurs. (J to N) -QCT analysis for trabecular bone volume per tissue volume (BV/TV, Tb) (J), trabecular number (Tb.N/mm) (K), trabecular thickness (Tb.Th/mm) (L), trabecular separation (Tb.Sp/mm) (M), and cortical bone thickness (Cor.Th/mm) (N). (O) Representative images of von Kossa staining of 12-week-old Vgll4fl/fl and Vgll4prx1 mice. Scale bar, 500 m. (P) Representative images of calcein and Alizarin red S labeling of proximal tibia. Scale bar, 50 m. (Q) Quantification of MAR. (R and S) ELISA analysis of serum PINP (ng ml1) and CTX-1 (ng ml1) from 10-week-old Vgll4fl/fl and Vgll4prx1 mice (n = 5). In (B), (D), (E), (G), (H), (J) to (N), and (Q) to (S), data were presented as means SEM; *P < 0.05, **P < 0.01, and ***P < 0.001; ns, no significance; unpaired Students t test. Photo credit: Jinlong Suo, State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai.

We next performed PCNA (proliferating cell nuclear antigen) staining and MTT assay to detect whether VGLL4 influences cell proliferation during bone development. No significant differences were found after VGLL4 deletion (fig. S5, A to C). We also did not detect significant changes of proliferation-related genes and YAP downstream genes (fig. S5, D and E). We next performed TUNEL (terminal deoxynucleotidyl transferasemediated deoxyuridine triphosphate nick end labeling) staining to detect whether VGLL4 influences cell apoptosis. In addition, no significant differences were found after VGLL4 deletion (fig. S5, F and G).

To further determine the function of VGLL4 in skeletal system, we did micro-quantitative computed tomography (-QCT) analysis to compare the changes in bone-related elements in the long bones of Vgll4prx1 mice and control littermates. We found that the 3-month-old Vgll4prx1 mice showed decreased bone mass per tissue volume (BV/TV) relative to age-matched control littermates (Fig. 2, I and J). Further analysis showed a reduction in trabecular number (Tb.N) of Vgll4prx1 mice compared to control mice (Fig. 2K), which was accompanied by a decrease in trabecular thickness (Tb.Th) and an increase in trabecular separation (Tb.Sp) compared to control mice (Fig. 2, L and M). Vgll4prx1 mice also showed decreased cortical bone thickness (Cor.Th) relative to the Vgll4fl/fl mice (Fig. 2N). The von Kossa staining showed reduced bone mineral deposition in 3-month-old Vgll4prx1 mice (Fig. 2O). The mineral apposition rate (MAR) was also decreased in Vgll4prx1 mice compared with control littermates by fluorescent double labeling of the mineralizing front (Fig. 2, P and Q). Consistent with the decreased bone mass in Vgll4prx1 mice, the enzyme-linked immunosorbent assay (ELISA) assay of N-terminal propeptide of type I procollagen (PINP), a marker of bone formation, revealed a reduced bone formation rate in Vgll4prx1 mice (Fig. 2R). However, the ELISA assay of C-terminal telopeptide of collagen type 1 (CTX-1), a marker of bone resorption, showed that the bone resorption rate of Vgll4prx1 mice did not change significantly (Fig. 2S). Collectively, Vgll4 conditional knockout mice mimicked the main phenotypes of the global Vgll4 knockout mice, further indicating that VGLL4 specifically regulates bone mass by promoting osteoblast differentiation.

To further determine whether the abnormal osteogenesis in Vgll4prx1 mice was caused by a primary defect in osteoblast development, we generated an osteoblast-specific Osx-cre; Vgll4floxp/floxp mice (hereafter Vgll4Osx mice) by crossing Vgll4fl/fl mice with Osx-Cre mice, a line in which Cre expression is primarily restricted to osteoblast precursors (fig. S6A) (6, 20). Vgll4Osx mice survived normally after birth and had normal fertility, but exhibited marked dwarfism in comparison with Osx-Cre mice (fig. S6, B and C), which was similar to the phenotypes of Vgll4/ and Vgll4prx1 mice. In addition, the membranous ossification of the skull and clavicle was also impaired in Vgll4Osx mice compared with control littermates (fig. S6C). -QCT analysis further confirmed the osteogenic phenotype of Vgll4Osx mice (fig. S6, D to J). Hence, the Vgll4Osx mice summarized the defects observed in the Vgll4prx1 mice, thus supporting the conclusion that VGLL4 is necessary for the differentiation and function of committed osteoblast precursors.

We next worked to figure out the mechanism how VGLL4 controls bone mass and osteoblast differentiation. The pygmy and cranial closure disorders in Vgll4/ mice were similar to that of Runx2-heterozygous mice. We therefore examined the potential interaction between VGLL4 and RUNX2. However, coimmunoprecipitation experiments did not show the interaction between VGLL4 and RUNX2 (Fig. 3A). Previous studies showed that VGLL4 could compete with YAP for binding to TEADs (9). The TEAD family contains four highly homologous proteins (8), which is involved in the regulation of myoblast differentiation and muscle regeneration (21). We determined whether the binding of VGLL4 with RUNX2 requires TEADs. Coimmunoprecipitation experiments showed that RUNX2 and TEAD14 had almost equivalent interactions (Fig. 3B). Next, we investigated whether TEADs control the transcriptional activity of Runx2. We used the 6xOSE2-luciferase reporter system that is specifically activated by RUNX2 to verify the role of TEADs (22). We performed dual-luciferase reporter assay with 6xOSE2-luciferase and Renilla in C3H10T1/2 cells, and the results showed that TEAD14 significantly inhibited the activation of 6xOSE2-luciferase induced by RUNX2 (Fig. 3C). Consistently, knockdown of TEADs by small interfering RNAs (siRNAs) markedly enhanced both basic and RUNX2-induced 6xOSE2-luciferase activity (fig. S8A). TEAD family is highly conserved, which consists of an N-terminal TEA domain and a C-terminal YAP-binding domain (YBD) (Fig. 3D) (23). Glutathione S-transferase (GST) pull-down assay revealed the direct interaction between RUNX2 and TEAD4 (Fig. 3E). Moreover, both TEA and YBD domains of TEAD4 could bind to RUNX2 (Fig. 3, F and G).

(A) Coimmunoprecipitation experiments of RUNX2 and VGLL4 in HEK-293T cells. The arrow indicated IgG heavy chain. (B) Coimmunoprecipitation experiments of RUNX2 and TEAD14 in HEK-293T cells. The arrow indicated IgG heavy chain. (C) 6xOSE2-luciferase activity was determined in C3H10T1/2 cells cotransfected with RUNX2 and TEAD14. Data were calculated from three independent replicates. (D) Schematic illustration of the domain organization for TEAD4, TEAD4-Nt, and TEAD4-Ct. (E) GST pull-down (PD) analysis between purified GST-RUNX2 and HIS-SUMO-TEAD4 proteins. (F) GST pull-down analysis between purified GST-RUNX2 and HIS-SUMO-TEAD4-TEA proteins. (G) Lysates from HEK-293T cells with Flag and Flag-RUNX2 expressions were incubated with recombinant GST-TEAD4-YBD protein. GST pull-down assay showed the binding between RUNX2 and TEAD4-YBD. (H) Cells isolated from WT mice were infected with TEAD lentivirus. Osteoblast differentiation was evaluated by Alp staining and Alizarin red staining after culture in osteoblast differentiation medium for 7 days (top) and 14 days (bottom). Data are representative of three independent experiments. Scale bars, 3 mm. (I) Alp activity quantification was measured by phosphatase substrate assay (n = 3). (J) Relative mRNA levels of Alp, Col11, and Osterix were quantified by RT-PCR. (K) Cells isolated from WT mice were infected with TEAD shRNA lentivirus. Osteoblast differentiation was evaluated by Alp staining and Alizarin red staining after culture in osteoblast differentiation medium for 7 days (top) and 14 days (bottom). Data are representative of three independent experiments. Scale bars, 3 mm. (L) Alp activity quantification was measured by phosphatase substrate assay (n = 3). (M) Relative mRNA levels of Runx2, Alp, Col11, and Osterix were quantified by RT-PCR. (N) Relative mRNA levels of Tead1-4 were quantified by RT-PCR. In (C), (I), (J), and (L) to (N), data were presented as means SEM; *P < 0.05, **P < 0.01, and ***P < 0.001; ns, no significance; unpaired Students t test.

To determine whether overexpression of TEAD14 affects osteoblast differentiation, BMSCs from WT mice were infected with TEAD14 lentivirus and then cultured in osteogenic medium. The activities of ALP in TEAD14 overexpression groups were significantly reduced at the seventh day of differentiation [Fig. 3, H (top) and I] and were significantly weakened by Alizarin red S staining over a 14-day culture period (Fig. 3H, bottom). The declined osteogenesis in TEAD14 overexpression cells was confirmed again by the decreased expression of a series of osteogenic marker genes, including Alp, Col11, and Osterix (Fig. 3J). Next, we blocked the total activities of TEAD14 by short hairpin RNA (shRNA) lentiviral infection (Fig. 3N). The activity of Alp in TEAD14 knockdown group was significantly increased [Fig. 3, K (top) and L]. Over a 14-day culture period, osteogenic differentiation was significantly enhanced by Alizarin red S staining (Fig. 3K, bottom). The enhanced osteogenesis in TEAD14 knockdown cells was further confirmed by elevated expression of a series of osteogenic marker genes, including Alp, Col11, and Osterix (Fig. 3M). These results suggest that TEAD14 act as repressors of RUNX2 to inhibit osteoblast differentiation.

To investigate the mechanistic role of VGLL4 in inhibiting osteoblast differentiation, we then verified whether VGLL4 could affect the interaction between TEADs and RUNX2. We found that VGLL4 reduced the interaction between RUNX2 and TEADs (Fig. 4A). To further illustrate the relationship between RUNX2/TEADs/VGLL4, we checked the interaction between RUNX2 and TEADs in the BMSC of Vgll4fl/fl mice treated with GFP or Cre lentivirus. We found that the interaction between RUNX2 and TEADs was enhanced in Cre-treated cells (Fig. 4B). We noticed that there were conserved binding sites of RUNX2 (5-AACCAC-3) and TEAD (5-CATTCC-3) in the promoter regions of Alpi, Osx, and Col1a1, which are three target genes of RUNX2 (17, 24). We performed TEAD4 and RUNX2 chromatin immunoprecipitation (ChIP) assays in BMSCs. The results indicated that both TEAD4 and RUNX2 bound on Alp, Osx, and Col1a1 promoters (fig. S7, A to I). VGLL4 was a transcriptional cofactor, which could not bind DNA directly. We have demonstrated that VGLL4 promoted RUNX2 activity by competing for its binding to TEADs. Consistently, VGLL4 partially blocked TEADs-repressed transcriptional activity of RUNX2 (Fig. 4C). However, overexpression of VGLL4 in TEADs knockdown cells showed no marked change on RUNX2-induced 6xOSE2-luciferase activity compared with TEAD knockdown (fig. S8B). We then asked whether loss of VGLL4-induced disorders of osteoblast differentiation is related to TEADs. We knocked down TEADs by lentiviral infection in Vgll4-deficient BMSCs and then induced these cells for osteogenic differentiation. The differentiation disorders caused by VGLL4 deletion were restored after TEAD knockdown (Fig. 4, D to F). These data supported that VGLL4 released the inhibition of TEADs on RUNX2, thereby promoting osteoblast differentiation.

(A) Coimmunoprecipitation experiments of RUNX2, TEADs, and VGLL4 in HEK-293T cells. The arrow indicated IgG heavy chain. (B) Coimmunoprecipitation experiments of RUNX2 and TEADs in BMSCs cells of Vgll4fl/fl mice treated with GFP and Cre lentivirus. (C) 6xOSE2-luciferase activity was determined in C3H10T1/2 cells cotransfected with RUNX2, TEADs, and VGLL4. (D) Cells isolated from Vgll4fl/fl and Vgll4prx1 mice were infected with GFP and TEAD shRNA lentivirus. Osteoblast differentiation was evaluated by Alp staining and Alizarin red staining after culture in osteoblast differentiation medium for 7 days (top) and 14 days (bottom). Data are representative of three independent experiments. Scale bars, 3 mm. (E) Alp activity quantification was measured by phosphatase substrate assay (n = 3). (F) Relative mRNA levels of Vgll4, Runx2, Alp, Col11, and Osterix were quantified by RT-PCR. In (B), (D), and (E), data were presented as means SEM; *P < 0.05, **P < 0.01, and ***P < 0.001; ns, no significance; unpaired Students t test.

YAP, the key transcription cofactor in the Hippo pathway, has been widely reported in regulating bone development and bone mass (12, 13). VGLL4, a previously identified YAP antagonist, directly competes with YAP for binding to TEADs (9). Therefore, we suspected that the inhibition of RUNX2 transcriptional activity caused by VGLL4 deletion might be dependent on YAP. To this end, we validated the role of YAP by 6xOSE2-luciferase reporter system. The data showed that YAP promoted RUNX2 activity in a dose-dependent manner (Fig. 5A). Moreover, TEAD4 significantly inhibited 6xOSE2-luciferase activity induced by YAP (Fig. 5B). TEAD4Y429H, a mutation that impairs the interaction between TEAD4 and YAP/TAZ (Fig. 5C) (25), did not promote 3xSd-luciferase activity induced by YAP (Fig. 5D). We found that both TEAD and TEAD4Y429H could interact with RUNX2 (Fig. 5E), and both TEAD4 and TEAD4Y429H could inhibit the activity of RUNX2 in a dose-dependent manner (Fig. 5, F and G). Restoring the expression of both TEAD4 and TEAD4Y429H could reverse the increased osteoblast differentiation in TEAD knockdown BMSCs (Fig. 5, H and I). Furthermore, overexpression of TEAD1 could further inhibit osteogenic differentiation of BMSCs after YAP knockdown (Fig. 5J). Together, these data suggest that the inhibition of RUNX2 activity by TEADs is independent of YAP binding.

(A) Effects of YAP on Runx2-activated 6xOSE2-luciferase activity in C3H10T1/2 cells. (B) 6xOSE2-luciferase activity was determined in C3H10T1/2 cells cotransfected with RUNX2, YAP, and TEAD4. (C) Schematic illustration of TEAD4 and TEAD4Y429H mutation. (D) 3xSd-luciferase activity was determined in HEK-293T cells cotransfected with YAP, TEAD4, and TEAD4Y429H. (E) Coimmunoprecipitation experiments of RUNX2, TEAD4, and TEAD4Y429H in HEK-293T cells. The arrow indicated IgG heavy chain. (F) Effects of TEAD4 on RUNX2-activated 6xOSE2-luciferase activity in C3H10T1/2 cells. (G) Effects of TEAD4Y429H on RUNX2-activated 6xOSE2-luciferase activity in C3H10T1/2 cells. (H) Cells isolated from WT mice were infected with GFP or TEAD shRNAs, TEAD4, or TEAD4Y429H lentivirus. Osteoblast differentiation was evaluated by Alp staining and Alizarin red staining after culture in osteoblast differentiation medium for 7 days (top) and 14 days (bottom). Data are representative of three independent experiments. Scale bars, 3 mm. (I) Alp activity quantification was measured by phosphatase substrate assay (n = 3). (J) Relative mRNA levels of Runx2, Alp, Col11, Osterix, Tead1, and Yap were quantified by RT-PCR. In (A), (B), (D), (F), (G), (I), and (J), data were presented as means SEM; *P < 0.05, **P < 0.01, and ***P < 0.001; ns, no significance; unpaired Students t test.

We next examined how VGLL4 breaks the interaction between RUNX2 and TEADs. It has been reported that VGLL4 relies on its own two TDU domains to interact with TEADs (9), and VGLL4 HF4A mutation can disrupt the interaction between VGLL4 and TEADs (15). We hypothesized that VGLL4 competes with RUNX2 for TEAD1 binding depending on its TDU domain. On the basis of these previous studies, we performed coimmunoprecipitation experiments and found that VGLL4 HF4A abolished the interaction between VGLL4 and TEAD1 but did not affect the interaction between TEAD1 and RUNX2 (Fig. 6A). VGLL4 partially rescued the inhibition of RUNX2 transcriptional activity by TEAD1; however, VGLL4 HF4A lost this function (Fig. 6B). We then overexpressed TEAD1 by lentivirus infection in primary calvarial cells and found that the transcriptional level of Alp was significantly inhibited. This inhibition was released by overexpressing VGLL4 but not VGLL4 HF4A (Fig. 6C). To further verify the specific regulation of RUNX2 activity by VGLL4, we performed a coimmunoprecipitation experiment with low and high doses of VGLL4 and VGLL4 HF4A. The results showed that the TEAD1-RUNX2 interaction was gradually repressed along with an increasing dose of VGLL4 but not VGLL4 HF4A (Fig. 6D). Similarly, the inhibition of RUNX2 transcriptional activity by TEAD1 was gradually released with an increasing dose of VGLL4 but not VGLL4 HF4A (Fig. 6E). Super-TDU, a peptide mimicking VGLL4, could also reduce the interaction between purified RUNX2 and TEAD4 proteins (Fig. 6F). Thus, these findings suggest that VGLL4 TDU domain competes with RUNX2 for TEADs binding to release RUNX2 transcriptional activity.

(A) Coimmunoprecipitation experiments of RUNX2, TEAD1, VGLL4, and VGLL4 HF4A in HEK-293T cells. The arrow indicated IgG heavy chain. (B) 6xOSE2-luciferase activity was determined in C3H10T1/2 cells cotransfected with RUNX2, VGLL4, VGLL4 HF4A, and TEAD1 (n = 3). (C) RT-PCR analysis of Alp expression in calvarial cells. Cells isolated from WT mice were infected with GFP, TEAD1, VGLL4, or VGLL4 HF4A lentivirus. (D) Coimmunoprecipitation experiments of RUNX2, TEAD1, and an increasing amount of VGLL4 or VGLL4 HF4A in HEK-293T cells. The arrow indicated IgG heavy chain. (E) 6xOSE2-luciferase activity was determined in C3H10T1/2 cells cotransfected with RUNX2, TEAD1, and an increasing amount of VGLL4 or VGLL4 HF4A. (F) Competitive GST pull-down assay to detect the effect of VGLL4 Super-TDU on the interaction between RUNX2 and TEAD4. (G) Cells isolated from Vgll4fl/fl and Vgll4prx1 mice were infected with GFP and RUNX2 lentivirus. Osteoblast differentiation was evaluated by Alp staining and Alizarin red staining after culture in osteoblast differentiation medium for 7 days (top) and 14 days (bottom). Data are representative of three independent experiments. Scale bars, 3 mm. (H) Alp activity quantification was measured by phosphatase substrate assay (n = 3). (I) Relative mRNA levels of Vgll4, Runx2, Alp, Col11, and Osterix were quantified by RT-PCR. (J) Schematic model of VGLL4/TEADs/RUNX2 in regulating osteogenic differentiation. In (B), (C), (E), (H), and (I), data were presented as means SEM; *P < 0.05, **P < 0.01, and ***P < 0.001; ns, no significance; unpaired Students t test.

Furthermore, we overexpressed RUNX2 by lentivirus infection in Vgll4 knockout BMSCs during osteogenic differentiation, and we found that RUNX2 could significantly restore the osteogenic differentiation disorder caused by Vgll4 deletion (Fig. 6, G to I). Together, these data suggest a genetic interaction between VGLL4/TEADs/RUNX2 and provide evidences that RUNX2 overexpression rescues osteogenic differentiation disorders caused by VGLL4 deletion.

Collectively, our study demonstrates the important roles of VGLL4 in osteoblast differentiation, bone development, and bone homeostasis. In the early stage of osteoblast differentiation, TEADs interact with RUNX2 to inhibit its transcriptional activity in a YAP bindingindependent manner. During differentiation progress, VGLL4 expression gradually increases to dissociate the interaction between TEADs and RUNX2, thereby releasing the inhibition of RUNX2 transcriptional activity by TEADs and promoting osteoblasts differentiation (Fig. 6J).

Accumulating evidences have suggested that the Hippo pathway plays key roles in regulating organ size and tissue homeostasis (8, 10). However, the transcription factors TEADs have not been reported in skeletal development and bone-related diseases. VGLL4 functions as a new tumor suppressor gene, which has been reported to negatively regulate the YAP-TEADs transcriptional complex. Our previous studies show that VGLL4 plays important roles in many tissue homeostasis and organ development, such as heart and muscle (16, 17). In this study, we provide evidences to show that VGLL4 can break TEADs-mediated transcriptional inhibition of RUNX2 to promote osteoblast differentiation and bone development independent of YAP binding.

Overall, our studies establish the Vgll4-specific knockout mouse model in the skeletal system. We show that VGLL4 deletion in MSCs leads to abnormal osteogenic differentiation with delayed skull closure and reduced bone mass. Our data also reveal that VGLL4 deletion leads to chondrodysplasia. Recent researches identified that chondrocytes have the ability to transdifferentiate into osteoblasts (2628), suggesting the possibility that loss of VGLL4 might reduce or delay the pool of chondrocytes that differentiate into osteoblasts. We identify that VGLL4 regulates the RUNX2-TEADs transcriptional complex to control osteoblast differentiation and bone development. TEADs can bind to RUNX2 and inhibit its transcriptional activity in a YAP bindingindependent manner. Recent studies pointed out that reciprocal stabilization of ABL and TAZ regulates osteoblastogenesis through transcription factor RUNX2 (29); however, we found that TEAD4-Y429H, a mutation at the binding site of TAZ and TEAD (25, 30, 31), can still significantly inhibit the activity of RUNX2. Therefore, we consider that the way TEAD regulates RUNX2 may not depend on TAZ regulation. Further research found that VGLL4, but not VGLL4 HF4A, can alleviate the inhibition by influencing the binding between RUNX2 and TEADs. It is possible that VGLL4 might influence the structure organization of the RUNX2-TEAD complex to some extent. Structural information may be required to answer this question and may provide more insights into the mechanism of VGLL4 in osteogenic differentiation.

Previous studies showed that mutations in RUNX2 cause CCD and Runx2+/ mice show a CCD-like phenotype. However, many patients with CCD do not have RUNX2 mutations. Our study may provide clues to the pathogenesis of these patients. A significant reduction of bone mass was observed in the adult mice, suggesting that VGLL4 and TEADs might be drug targets for treatment of cranial closure disorders and osteoporosis. In addition, further investigation of the clinical correlation of VGLL4 and cleidocranial dysplasia in a larger cohort will provide more accurate information for bone research. Our work also provides clues to researchers who are studying the roles of VGLL4 in tumors or other diseases. RUNX2 is highly expressed in breast and prostate cancer cells. RUNX2 contributes to tumor growth in bone and the accompanying osteolytic diseases (32). The regulation of RUNX2 transcriptional activity by TEADs and VGLL4 is likely to play essential roles in tumor, bone metastasis, and osteolytic diseases. Our work may provide clues to researchers who are studying the role of VGLL4 in bone tumors.

We demonstrate that TEADs are involved in regulating osteoblast differentiation by overexpressing and knocking down the TEAD family in vitro. However, the exact roles of TEADs in vivo need to be further confirmed by generation of TEAD1/2/3/4 conditional knockout mice. In the follow-up work, we will continue to study the mechanism of TEADs in skeletal development and bone diseases. Overall, although there are still some shortcomings, our work has greatly contributed to understand the TEADs regulation of RUNX2 activity.

Our work defines the role of VGLL4 in regulating osteoblast differentiation and bone development, and identifies that TEADs function as repressors of RUNX2 to inhibit osteoblast differentiation. We propose a model that VGLL4 dissociates the combination between TEADs and RUNX2. It is not clear whether VGLL4 is also involved in regulating other transcription factors or signaling pathways in the process of osteoblast differentiation and bone development. If that is the case, how to achieve cooperation will be another interesting issue worthy of further study.

Vgll4Lacz/+ mice, Vgll4 knockout (Vgll4/) mice, Vgll4Vgll4-eGFP/+ mice, and Vgll4 conditional knockout (Vgll4fl/fl) mice were generated as previously described (16, 17), and Vgll4fl/fl mice were crossed with the Prx1-Cre and Osx-Cre strain to generate Vgll4prx1 and Vgll4Osx mice. All mice analyzed were maintained on the C57BL/6 background. All mice were monitored in a specific pathogenfree environment and treated in strict accordance with protocols approved by the Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.

The following antibodies were used: anti-Osterix antibody (1:1000; Santa Cruz Biotechnology, SC133871), anti-RUNX2 antibodies (1:1000; Santa Cruz Biotechnology, SC-390351 and SC-10758), anti-Flag antibody (1:5000; Sigma-Aldrich, F-3165), anti-HA (hemagglutinin) antibody (1:2000; Santa Cruz Biotechnology, SC-7392), anti-HA antibody (1:1000; Sangon Biotech, D110004), anti-MYC antibody (1:1000; ABclonal Technology, AE010), anti-PCNA antibody (1:1000; Santa Cruz Biotechnology, SC-56), rabbit immunoglobulin G (IgG) (Santa Cruz Biotechnology, SC-2027), mouse IgG (Sigma-Aldrich, I5381), anti-VGLL4 antibody (1:1000; ABclonal, A18248), anti-TEAD1 antibody (1:1000; ABclonal, A6768), anti-TEAD2 antibody (1:1000; ABclonal, A15594), anti-TEAD3 antibody (1:1000; ABclonal, A7454), anti-TEAD4 antibody (1:1000; Abcam, ab58310), and antipan-TEAD (1:1000; Cell Signaling Technology, 13295).

Cells were cultured at 37C in humidified incubators containing an atmosphere of 5% CO2. Human embryonic kidney (HEK)293T cells were maintained in Dulbeccos Modified Eagle Medium (DMEM) (Corning, Corning, NY) supplemented with 10% fetal bovine serum (FBS) and 1% penicillin/streptomycin (Gibco) solution. C3H10T1/2 cells were maintained in -minimum essential medium (-MEM) (Corning, Corning, NY) supplemented with 10% FBS and 1% penicillin/streptomycin (Gibco) solution. To induce differentiation of BMSC into osteoblasts, cells were cultured in -MEM containing 10% FBS, l-ascorbic acid (50 g/ml), and -glycerophosphate (1080 mg/ml). The osteoblast differentiation level assay was performed following a previously published method (33). To quantitate Alp activity, cells incubated with Alamar Blue to calculate cell numbers and then incubated with phosphatase substrate (Sigma-Aldrich, St. Louis, MO) dissolved in 6.5 mM Na2CO3, 18.5 mM NaHCO3, and 2 mM MgCl2 after washing by phosphate-buffered saline (PBS). Alp activity was then read with a luminometer (Envision). Bone nodule formation was stained with Alizarin red S solution (1 mg/ml; pH 5.5) after 14 days of induction.

We collected femurs and tibias from mice and flushed out the bone marrow cells with 10% FBS in PBS. All nuclear cells were seeded (2 106 cells per dish) in 100-mm culture dishes (Corning) and incubated at 37C under 5% CO2 conditions. After 48 hours, nonadherent cells were washed by PBS and adherent cells were cultured in -MEM (Corning, Corning, NY) supplemented with 10% FBS and 1% penicillin/streptomycin (Gibco) solution for an additional 5 days. Mouse BMSCs in passage one were used in this study.

Total RNA was isolated from cells with TRIzol reagent (T9424, Sigma-Aldrich), and first-strand complementary DNA (cDNA) was synthesized from 0.5 g of total RNA using the PrimeScript RT Reagent Kit (PR037A, TaKaRa). The real-time RT-PCR was performed with the Bio-Rad CFX96 System. Gene expression analysis from RT-PCR was quantified relative to Hprt.

C3H10T1/2 cells were seeded overnight at 1 105 cells per well into a 12-well plate and transfected by PEI (polyethylenimine linear) with a luciferase reporter plasmid along with various expression constructs, as indicated. All wells were supplemented with control empty expression vector plasmids to keep the total amount of DNA constant. At 36 to 48 hours after transfection, the cells were harvested and subjected to dual-luciferase reporter assays according to the manufacturers protocol (Promega).

293T cells were seeded at 1 107 cells per 10-cm dish and cultured overnight. At 36 to 48 hours after transfection with PEI, cells were harvested and washed with cold PBS following experimental treatments. Then, cells were lysed with EBC buffer [50 mM tris (pH 7.5), 120 mM NaCl, and 0.5% NP-40] containing protease inhibitor cocktail (1:100; MedChem Express, HY-K0010). After ultrasonication, lysates were subjected to immunoprecipitation with anti-Flag antibodies (M2, Sigma-Aldrich) at 4C overnight, followed by washing in lysis buffer, SDSpolyacrylamide gel electrophoresis (PAGE), and immunoblotting with the indicated antibody.

RUNX2 and TEAD4-YBD were cloned into pGEX-4T-1-GST vector and expressed in Escherichia coli BL21 (DE3) cells. TEAD4 and TEAD4-TEA were cloned into HT-pET-28a-HIS-SUMO vector and expressed in E. coli BL21 (DE3) cells. The two TDU domains of VGLL4 were cloned into HT-pET-28a-MBP vector and expressed in E. coli BL21 (DE3) cells. VGLL4 Super-TDU was designed as previously described (15). GST, HIS-SUMO, and MBP-fused proteins were purified by affinity chromatography as previously described (17). The input and output samples were loaded to SDS-PAGE and detected by Western blotting.

CalceinAlizarin red S labeling measuring bone formation rate was performed as previously described (33).

Preparation of skeletal tissue and -QCT analysis were performed as previously described (34). The mouse femurs isolated from age- and sex-matched mice were skinned and fixed in 70% ethanol. Scanning was performed with the -QCT SkyScan 1176 System (Bruker Biospin). The mouse femurs were scanned at a 9-m resolution for quantitative analysis. Three-dimensional (3D) images were reconstructed using a fixed threshold.

ChIP experiments were carried out in BMSCs according to a standard protocol. The cell lysate was sonicated for 20 min (30 s on, 30 s off), and chromatin was divided into fragments ranging mainly from 200 to 500 base pairs in length. Immunoprecipitation was then performed using antibodies against TEAD4 (Abcam, ab58310), RUNX2 (Santa Cruz Biotechnology, SC-10758), and normal IgG. The DNA immunoprecipitated by the antibodies was detected by RT-PCR. The primers used were as follows: Alp-OSE2-ChIP-qPCR-F (5-GTCTCCTGCCTGTGTTTCCACAGTG-3), Alp-OSE2-ChIP-qPCR-R (5-GAAGACGCCTGCTCTGTGGACTAGAG-3), Alp-TBS-ChIP-qPCR-F (5-CCTTGCATGTAAATGGTGGACATGG-3), Alp-TBS-ChIP-qPCR-R (5-TATCATAGTCACTGAGCACTCTCTTGCG-3), Osx-OSE2-ChIP-qPCR-F (5-TTAACTGCCAAGCCATCGCTCAAG-3), Osx-OSE2-ChIP-qPCR-R (5-CCTCTATGTGTGTATGTGTGTTTACCAAACATC-3), Osx-TBS-ChIP-qPCR-F (5-ATGCCAAGAGATCCCTCATTAGGGAC-3), Osx-TBS-ChIP-qPCR-R (5-AGCTTGGTGAGCACAGCAAAGACAC-3), Col1a1-TBS/OSE2-Chip-qPCR-F (5-CTCAGCCTCAGAGCTGTTATTTATTAGAAAGG-3), and Col1a1-TBS/OSE2-Chip-qPCR-R (5-TTAATCTGATTAGAACCTATCAGCTAAGCAGATG-3). TBS indicated TEAD binding sites.

Mouse TEAD1, TEAD2, TEAD3, and TEAD4 siRNAs and the control siRNA were synthesized from Shanghai Gene Pharma Co. Ltd., Shanghai, China. siRNA oligonucleotides were transfected in C3H10T1/2 by Lipofectamine RNAiMAX (Invitrogen) following the manufacturers instructions. Two pairs of siRNAs were used to perform experiments.

Hematoxylin and eosin stain and immunohistochemistry were performed as previously described (7). Tissue sections were used for TRAP staining according to the standard protocol. Tissues were fixed in 4% paraformaldehyde for 48 hours and incubated in 15% DEPC (diethyl pyrocarbonate)EDTA (pH 7.8) for decalcification. Then, specimens were embedded in paraffin and sectioned at 7 m. Immunofluorescence was performed as previously described (33). Sections were blocked in PBS with 10% horse serum and 0.1% Triton for 1 hour and then stained overnight with anti-PCNA antibody (SC-56). Donkey anti-rabbit Alexa Fluor 488 (1:1000; Molecular Probes, A21206) was used as secondary antibodies. DAPI (4,6-diamidino-2-phenylindole) (Sigma-Aldrich, D8417) was used for counterstaining. Slides were mounted with anti-fluorescence mounting medium (Dako, S3023), and images were acquired with a Leica SP5 and SP8 confocal microscope. For embryonic mice, 5-mm tissue sections were used for immunohistochemistry staining, DIG-labeled in situ hybridization (Roche), and immunohistochemical staining (Dako).

TUNEL staining for apoptosis testing was performed as provided by Promega (G3250).

MTT assay for cell viability was performed as provided by Thermo Fisher Scientific.

We determined serum concentrations of PINP using the Mouse PINP EIA Kit (YX-160930M) according to the instructions provided. In addition, we determined serum concentrations of CTX-1 using the Mouse CTX-1 EIA Kit (YX-032033M) according to the instructions provided.

Tissue sections were used for SO staining according to the standard protocol. After paraffin sections were dewaxed into water, they were acidified with 1% acetic acid for 10 s and then fast green for 2 min, acidified with 1% acetic acid for 10 s, stained with SO for 3 min and 95% ethanol for 5 s, and dried and sealed with neutral glue.

Statistical analysis was performed by unpaired, two-tailed Students t test for comparison between two groups using GraphPad Prism Software. A P value of less than 0.05 was considered statistically significant.

Acknowledgments: We thank A. McMahon (Harvard University, Boston, MA) for providing the Prx1-Cre mouse line. We thank the cell biology core facility and the animal core facility of Shanghai Institute of Biochemistry and Cell Biology for assistance. Funding: This work was supported by the National Natural Science Foundation of China (nos. 81725010, 31625017, 81672119, and 31530043), National Key Research and Development Program of China (2017YFA0103601 and 2019YFA0802001), Strategic Priority Research Program of Chinese Academy of Sciences (XDB19000000), Shanghai Leading Talents Program, Science and Technology Commission of Shanghai Municipality (19ZR1466300), and Youth Innovation Promotion Association CAS (2018004). Author contributions: Z.W., L.Z., and W.Z. conceived and supervised the study. J.S. conceived and designed the study, performed the experiments, analyzed the data, and wrote the manuscript. X.F. made the constructs, performed the in vitro pull-down assay and ChIP experiments, analyzed the data, and revised the manuscript. L.Z. and Z.W. provided genetic strains of mice. J.S. and Z.W. bred and analyzed Vgll4/ mice. J.L. and J.W. cultured the cells and made the constructs. W.Z., L.Z., X.F., and Z.W. edited the manuscript. Competing interests: The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.

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VGLL4 promotes osteoblast differentiation by antagonizing TEADs-inhibited Runx2 transcription - Science Advances

Bone Marrow Stem Cells Comments Off on VGLL4 promotes osteoblast differentiation by antagonizing TEADs-inhibited Runx2 transcription – Science Advances | October 24th, 2020

INTRODUCTION

Ewing sarcoma (EwS) is an aggressive, poorly differentiated, human tumor characterized by a chromosomal translocation involving a member of the FET family of genes (FUS, EWSR1 and TAF15) and a member of the ETS family of transcription factors, with the EWSR1-FLI1 gene fusion the most common one (1). EwS genomes present low mutation rates with FET-ETS rearrangements as the dominant genetic aberration in the majority of tumors (2). Notably, the cell of origin of EwS is still a controversial field, although human mesenchymal stem cells (hMSCs) and human neural crest stem cells are the most accepted (35).

The EWSR1-FLI1 fusion protein, which contains the transcriptional activation and RNA binding domains of EWSR1 and the DNA binding domain of FLI1, is the main driver of tumorigenesis (3, 6). The resulting fusion oncoprotein has the ability to act as an aberrant transcription factor, leading to gene activation and repression for a well-described set of genes (3, 7). A decade ago, EWSR1-FLI1 was found to bind preferentially to DNA sites containing GGAA microsatellite repeats (8, 9). Recent studies have reported that binding of EWSR1-FLI1 multimers to GGAA repeats acts as a pioneer factor and induces the formation of de novo active enhancers by recruiting the acetyl transferases CBP/p300, E2F3, and the BRG1/BRM-associated factor chromatin remodeling complex (1012). On the other hand, it was hypothesized that monomeric EWSR1-FLI1 inhibits transcription at enhancers by displacing endogenous ETS transcription factors from GGAA motifs (10). Therefore, the mechanisms by which EWSR1-FLI1 acts as either a gene activator or repressor depend on both DNA sequence and cofactors.

Several proteins from the Polycomb group (PcG) have previously been implicated in EwS tumorigenesis. PcG was first described in Drosophila melanogaster as a key regulator of Hox genes expression. PcG proteins not only prevent differentiation by repressing lineage-specific genes but also mark bivalent chromatin regions for subsequent activation. EZH2 (the enzymatic subunit of PRC2) methylates histone H3 at lysine 27 (H3K27me3), while RING1B (the enzymatic subunit of PRC1) ubiquitinates H2A at lysine 119 (H2Aub), both considered repressive histone marks (13).

The canonical PRC1 complex (defined by the presence of four subunits, comprising one variant each of PCGF, PHC, CBX, and RING1) has mostly been associated with maintaining gene repression. However, increasing evidence indicates that PRC1 complexes containing RING1B have the potential for transcription activation, via their catalytic-independent association with UTX, an H3K27me3 demethylase, and p300 acetyltransferase (14, 15). With respect to EwS, it was recently shown that EZH2 blocks endothelial and neuroectodermal differentiation (16), BMI1 promotes tumorigenicity (17), and RING1B represses the nuclear factor B pathway (18). The molecular mechanisms behind the contribution of PcG to EwS have not been addressed. Notably, the GGAA repeats are significantly decorated with H3K27me3 in H1 human embryonic cell lines and human umbilical vein endothelial cells (HUVECs) (19). This is in stark contrast with the lack of H3K27me3 mark at EWSR1-FLI1 binding sites in EwS cells (10, 11), thus suggesting a different role of PcG in EwS. Last, comparison between malignant and nonmalignant tissues revealed a misregulation of PcG target genes in EwS (20). Together, these findings suggest a potential role of the PcG during the early steps of EwS pathogenesis. Here, we report that RING1B and EWSR1-FLI1 interact and colocalize at the same genomic loci. Notably, we find that RING1B is present at promoters and enhancers of actively transcribed EWSR1-FLI1 target genes. Furthermore, we demonstrate that modulation of RING1B interferes with EWSR1-FLI1 recruitment and with the expression of EWSR1-FLI1 targets, thus unveiling an interdependent cooperation between both proteins.

Human pediatric MSCs (hpMSCs) have been proposed as a plausible cell of origin for EwS (21). Nevertheless primary human endothelial HUVECs share high similarity in gene expression profiles with EwS cells (22). Thus, to investigate the potential contribution of epigenetic alteration in the initiation of EwS, we analyzed the role of epigenetic marks in these models and compared to established EwS cell lines. We first analyzed the levels of H3K27me3 and H3K4me3 in the human EwS-derived cell line A673 at several bona fide direct targets of EWSR1-FLI1 (table S1) by chromatin immunoprecipitation followed by quantitative polymerase chain reaction (ChIP-qPCR). Promoter of genes that are transcriptionally activated by EWSR1-FLI1, such as FCGRT, NR0B1, CACNB2, EZH2, IGF1, NKX2-2, and HOXD11, was enriched for the H3K4me3 mark, and lacked the H3K27me3 mark, in agreement with previous data (8, 20, 23, 24) (fig. S1A). On the other hand, transcriptionally repressed genes, such as KCNA5 (25), were enriched for H3K27me3. We next compared the levels of H3K27me3 and H3K4me3 at the same loci in HUVECs and in hpMSCs. In an apparently reversed situation to the A673 EwS cell line, analysis of those promoters presented strong enrichment for H3K27me3 but not for H3K4me3 (fig. S1B). Accordingly, infection of HUVECs with the EWSR1-FLI1 oncogene (Fig. 1A) not only led to the activation of these targets (FCGRT, NR0B1, CACNB2, EZH2, IGF1, NKX2-2, and HOXD11) (Fig. 1B) but also decreased the levels of H3K27me3 (Fig. 1C). This demonstrates that, although H3K27me3 is not present at oncogene binding regions in EwS cell lines such as A673, these regions are repressed by PcG before oncogene expression.

(A) Western blot showing ectopic expression of EWSR1-FLI1 upon infection of HUVECs with an empty pLIV vector or EWSR1-FLI1pLIV. (B) RT-qPCR determination of relative mRNA expression of EWSR1-FLI1 target genes upon infection of HUVECs with an empty pLIV vector or EWSR1-FLI1pLIV. Values are normalized to TBP. (C) H3K27me3 ChIP-qPCR at EWSR1-FLI1 target gene promoters in HUVECs infected with an empty pLIV vector or EWSR1-FLI1pLIV. The values of the Y axis represent the enrichment ratio of immunoprecipitated samples relative to input with subtracted immunoglobulin G (IgG). (D) Bar plots of chromatin state relative frequencies in the whole genome [background (BG)] and in published EWSR1-FLI1 binding sites (FLI1) for three selected cell lines. Genome segmentations were extracted from the Epigenome Roadmap Consortium. (E) Heatmap with percentages of each chromatin state in the whole genome (BG) as compared to the frequency within published EWSR1-FLI1 binding regions for indicated cell lines by grouping in 8 similar chromatin states the initial classification containing 15 (quiescent segments were excluded). Bold format indicates enrichments greater than 10%. Enrichment scores were calculated as the difference between the value in EWSR1-FLI1 and the value at the whole genome, normalized by the value at the whole genome. (F) Cell proliferation expressed as cell number in 293T, A673, SK-ES1, and A4573 cells transiently transfected with small interfering RNA (siRNA) against a control (siCTRL) or two different RING1B sequences (siRING1B#1 and #2). Error bars in (B), (C), and (F) indicate SD of three biological independent experiments. Statistical significance in (D) and (F) is as follows: ***P < 0.001 and *P < 0.05.

To explore the chromatin and transcriptional states of EWSR1-FLI1 binding sites (10), we measured the frequency of each chromatin state at these regions (26) and compared to the corresponding value obtained for the whole genome in several cell lines [HUVECs, H1, and H9 human embryonic cells, H1-derived MSCs, bone marrow (BM)derived MSCs, and adipose-derived MSCs]. This analysis indicated that EWSR1-FLI1 binding sites are overrepresented in chromatin states associated with zinc finger genes and repeats (ZNF/repeats) and active promoters (Fig. 1D and table S1). In cells with MSC origin (such as H1, adipose, and BM-derived cell lines), EWSR1-FLI1 binding sites are overrepresented in PcG weak repressed state, which represents flanking regions of H3K27me3 peaks summit (Fig. 1D and fig. S1, C and D). Similar results were obtained when we grouped chromatin states of similar categories (Fig. 1E). This suggests that EWSR1-FLI1 occupies flanking regions of H3K27me3 summit peaks in hMSC, which are considered to be the potential cell of origin for EwS.

Data from our group have revealed that the PRC1 subunit RING1B, is highly overexpressed in EwS primary tumors (18). We thus assessed whether RING1B modulates the growth rate of EwS cells as has been reported for other PcG subunits, such as EZH2 and BMI1 (16, 17). RING1B depletion caused a reduction in cell viability in the A673, SK-ES1, and, with a lesser extent, in A4573 EwS cell lines but not in the control cell line 293T (Fig. 1F and fig. S1E), suggesting that RING1B represents an epigenetic vulnerability for EwS cells.

Chan et al. (27) recently proposed that RING1B might play a role in modulating enhancer activity. Together with its role in promoter regulation, EWSR1-FLI1 has been recently reported to generate de novo enhancers (10). This led us to postulate whether EWSR1-FLI1 and RING1B might cooperate during EwS tumorigenesis. We first aimed to define the genome-wide localization of RING1B and its repressive histone mark H2Aub in the A673 cell line by chromatin immunoprecipitation sequencing (ChIP-seq). In two independent experiments, we identified 2573 and 3945 peaks of RING1B, and 26424 and 10269 peaks of H2Aub. Using differential binding analysis (DiffBind), which allows for the identification of statistically common peaks (28), we found 2459 RING1B and 5392 H2Aub significant peaks between duplicates (P < 0.05, fig. S2A), corresponding to 1264 target genes and 3013 target genes, respectively (table S2). Genomic distribution of peaks showed that RING1B is more abundant in intergenic regions, whereas H2Aub is mainly located in promoters (Fig. 2A). Moreover, 38% of RING1B peaks were found at intergenic regions with respect to 21.5% of H2Aub peaks, and 29.2% of RING1B peaks were in promoters with respect to 40.5% of H2Aub peaks, further supporting the potential role of RING1B at enhancers. We then categorized peaks for RING1B, H2Aub, and EWSR1-FLI1 in active or poised enhancers, and in active or poised promoters, based on H3K27me3, H3K4me3, H3K27ac, and H3K4me1 (29). To complement the above data, we performed a ChIP-seq analysis using a different antibody directed against FLI1 (fig. S2B and table S2). We found that an important fraction of RING1B peaks (35%) and EWSR1-FLI1 (46%) are located at transcriptionally active enhancers and promoters of A673 cells (Fig. 2B, left). On the other hand, as expected, 35% of RING1B peaks and 37% of H2Aub peaks showed a preference for transcriptionally repressed regulatory regions (Fig. 2B, left). We then intersected the list of genes associated to RING1B and H2Aub peaks with published data of EWSR1-FLI1 target genes in A673 cells, producing a common set of 162 genes (fig. S2C and table S3). Comparing this set with 386 genes containing only RING1B and H2Aub or the group of 324 EWSR1-FLI1/RING1B genes without H2Aub confirmed that the presence of EWSR1-FLI1 correlated with higher level of transcription (P < 1016; fig. S2D, left). Functional analysis of the common gene set of 324 EWSR1-FLI1/RING1B genes (table S3) returned Gene Ontology (GO) categories related to chondrocyte and neuronal differentiation (fig. S2D, right). EWSR1-FLI1/RING1B/H2Aub genes were also enriched in neuronal differentiation category, while the RING1B/H2Aub genes were related to general transcription. These data suggest that RING1B is a positive regulator of a specific set of genes implicated in EwS and that this activity is independent of its canonical repressive mark.

(A) Pie chart showing genomic distribution of RING1B and H2Aub peaks relative to functional categories including promoter (2.5 kb from TSS), gene body (intragenic region not overlapping with promoter), and intergenic (rest of the genome). (B) Boxplot depicting percentage of regulatory elements (active/bivalent enhancers and promoters) in each described group. (C) Venn diagram depicting the overlap between RING1B and EWSR1-FLI1 in A673 cells at the peak level. (D) Aggregated plot showing the average ChIP-seq signal of RING1B and EWSR1-FLI1 at EWSR1-FLI1 binding sites. (E) Aggregated plots showing the average ChIP-seq signal of H3K27ac, H2Aub, and H3K27me3 in the three sets of RING1B and EWSR1-FLI1 peaks. (F) Heatmap showing RING1B, EWSR1-FLI1, H3K27ac, H2Aub, and H3K27me3 ChIP-seq signals segregating in the three sets of RING1B and EWSR1-FLI1 peaks. Top MEME motif for every group is shown. (G) University of California Santa Cruz (UCSC) genome browser ChIP-seq signal tracks for RING1B, EWSR1-FLI1, H2Aub, H3K27ac, H3K4me3, and H3K27me3 at NKX2-2, CCND1, VRK1, and CAV1 gene promoters and intergenic enhancer regions. Gray boxes represent EWSR1-FLI1 and RING1B colocalization and ES super-enhancers (SEnh; as shown at VRK1 and CAV1/2).

To fully understand the association of RING1B with transcriptional activation in EwS, we intersected EWSR1-FLI1 peaks with those of RING1B and obtained 955 common regions (Fig. 2C). Notably, intersection between H2Aub and RING1B peaks returned only 589 common peaks. Among the 955 overlapping EWSR1-FLI1/RING1B peaks, we inspected for genes containing an enhancer within 100 kb and obtained 1276 genes, of which 235 (18%) were reported to be regulated by EwS super-enhancers (table S4) (11). The common targets of RING1B and EWSR1-FLI1 sites were found within active enhancers, while the majority of RING1B peaks not overlapping with EWSR1-FLI1 were located in transcriptionally repressed regulatory elements (Fig. 2B, right). The distribution of RING1B peaks was centered on EWSR1-FLI1 binding sites (Fig. 2D), suggesting that their binding occurs at the same loci. We next assessed the distribution of H3K27ac, H2Aub, and H3K27me3 in genomic regions occupied by EWSR1-FLI1, RING1B, or shared (Fig. 2E). Common peaks were decorated with H3K27ac, lacking H2Aub (Fig. 2, E and F), and presented narrow RING1B peaks located in intergenic or intronic regions (fig. S2E, right). These data suggest that common sites likely represent enhancers. Known EWSR1-FLI1 target genes such as NKX2-2, CCND1, VRK1, or CAV1 presented an intergenic peak of RING1B, which overlaps with defined super-enhancers in the case of VRK1 and CAV1 (Fig. 2G). Intronic enhancers such as JARID2 or MYOM2 (fig. S2G) constitute the majority of the 162 common RING1B, EWSR1-FLI1, and H2Aub genes (53% of sites, fig. S2C). On the other hand, RING1B-specific peaks were associated with H3K27me3 and H2Aub (Fig. 2, E and F) and presented a broader distribution [e.g., HNF1B and TAL1 (fig. S2H)] mainly located within promoter or gene body regions (fig. S2E, left). The bivalent marks H3K4me3 and H3K27me3 decorated 63% of the 932 downstream genes associated to RING1B-specific peaks (P < 10300, table S4) (29). RING1Btranscription start sites (TSS) do not overlap with EWSR1-FLI1 and are decorated with H2K27me3 and H2Aub, while RING1B-distal sites overlap with EWSR1-FLI1 and with H3K27ac (fig. S2F).

Last, de novo motif analysis revealed that EWSR1-FLI1specific sites contained predominantly (P < 10282) one single occurrence of the canonical ETS motif GGAA (Fig. 2F). When EWSR1-FLI1 was associated with RING1B, we observed a significant enrichment for multimeric GGAA repeats (P < 101072) (10). Furthermore, RING1B-sepecific sites were enriched for CG sequence, as previously reported (P < 10176) (30). Together, we identified two major types of RING1B peaks in EwS: a prominent group with narrow peaks that colocalizes with EWSR1-FLI1 at enhancers of actively transcribed genes and a second group with broader peaks located at promoters, where RING1B is associated with H2Aub.

To further characterize RING1B binding regions (table S4), we analyzed several EWSR1-FLI1 active promoters (CAV1, FCGRT, NR0B1, CACNB2, FEZF1, and KIAA1797) and enhancers (CCND1, IGF1, CAV2, JARID2, VRK1, and NKX2-2) by ChIP-qPCR. Both groups showed enrichment for RING1B, with stronger signals at enhancers (Fig. 3A). Known repressed targets of the oncogene (e.g., IGFBP3, TGFBR2, and LOX) also showed binding of RING1B. At these repressed promoters, RING1B was accompanied by its canonical repressive mark H2Aub (fig. S3A). We also validated the occupancy of RING1B in EWSR1-FLI1activated promoters (CAV1, FCGRT, NR0B1, and FEZF1) and enhancers (CCND1, CAV2, JARID2, and VRK1) in SK-ES1 cells (fig. S3B). Similar to A673 cells, H2Aub correlated with RING1B at promoters of repressed genes (IGFBP3, TGFBR2, and LOX) (fig. S3C). Last, we observed that the PRC1 and PRC2 subunits, BMI1 and EZH2, respectively, were present at repressed promoters but not in active enhancers (fig. S3, D and E), as well as in promoters with broad peaks of RING1B concomitant with H3K27me3 and H2Aub but no EWSR1-FLI1 (e.g., TAL1, IGF1R, and HNF1B) (fig. S3F). Furthermore, genome-wide analysis demonstrated that BMI1 and CBX7 (31) subunits of the PRC1 canonical complex colocalize with RING1B only at repressed regions (TAL1) as shown in Fig. 3B, while no detectable peaks are present at active enhancers where EWSR1-FLI1 is present (VRK1). Thus, while RING1B decorates EWSR1-FLI1activated promoters and enhancers, it also maintains its canonical role at several oncogene repressed regions, as well as in a subgroup of genes with no EWSR1-FLI1.

(A) RING1B ChIP-qPCR of EWSR1-FLI1 bound active promoters, repressed promoters, and active enhancers. Control regions indicate the absence of RING1B and EWSR1-FLI1 binding at these sites. The values of the Y axis represent the enrichment ratio of immunoprecipitated samples relative to input. (B) UCSC genome browser ChIP-seq signal tracks for EWSR1-FLI1, RING1B, CBX7, BMI1, H2Aub, and H3K27me3 at TAL1 promoter and VRK1 enhancer. (C) Histogram depicting percentages of activated and repressed genes in A673 and SK-ES1 cells with stable RING1B knockdown seq#2 (shRING1B#2) versus control seq#2 (shCTRL#2), with P < 0.05 and an absolute fold change (FC) > 1.25 or 1.5. (D) Western blot showing RING1B, RING1A, H2Aub, and H3K27me3 in A673 and SK-ES1 cells with either shCTRL#2 or shRING1B#2. Lamin B and histone H4 are used as loading controls. (E) Venn diagram showing intersection between differentially activated or repressed genes for EWSR1-FLI1 and RING1B in A673 cells; P < 0.05. (F) RT-qPCR determination of mRNA expression of EWSR1-FLI1 target genes with active enhancers in shCTRL and shRING1B A673 cells (#1 and #2). Values are normalized to GAPDH. (G) Same analysis as in (F) for SK-ES1 cells. Error bars in (A), (F), and (G) indicate SD of four independent biological experiments and ***P < 0.001, **P < 0.01, and *P < 0.05.

To understand whether RING1B behaves as a canonical repressor and/or activator in EwS, we analyzed the expression changes after knocking down RING1B using two different sets of short hairpin RNA (shRNA, seq#1 and seq#2; fig. S4A). The data obtained showed that 71.94 and 63.85% of genes were down-regulated in the A673 and SK-ES1 cell lines, respectively (FC < -1.5, Fig. 3C). This confirms our finding that RING1B acts predominantly as an activator, despite its presence at several EWSR1-FLI1repressed targets. Furthermore, H2Aub levels remained unchanged after RING1B knockdown (Fig. 3D), while RING1A knockdown produces a notable decrease in H2Aub levels (fig. S4B). These data suggest that RING1B main function in EwS is uncoupled from its ubiquitin ligase activity toward H2A and that RING1A is the main histone H2A mono-ubiquitin ligase. To further elucidate to what extent RING1B cooperates with EWSR1-FLI1 in transcription regulation, we intersected differentially expressed genes in RING1B knockdown cells (absolute FC > 1.25) with those affected by EWSR1-FLI1 knockdown (absolute FC > 1.5) (10), obtaining an overlap of 1078 genes. After segregating these data into down- and up-regulated genes, we found that RING1B and EWSR1-FLI1activated 229 genes and repressed 162 genes (Fig. 3E and table S5). Among the 229 activated genes, we found several developmental genes, including SOX2, SIX3, LYAR, and KIT. GO analysis showed regulation of the potassium channel and mechanisms that control actin monomers and filaments as the main categories (fig. S4C), in agreement with previous publications (25, 32). Among the activated genes, SOX2 and KIT harbored RING1B and EWSR1-FLI1 peaks in intergenic and intronic enhancer regions, respectively (fig. S4E). TGFBR2, a gene repressed by both EWSR1-FLI1 and RING1B, also contained an intronic enhancer where both proteins colocalized. Notably, the expression of known targets of EWSR1-FLI1, such as NKX2-2 or IGF1 (fig. S4D), was just below our logFC cutoff value. Nonetheless, we confirmed by reverse transcription (RT)qPCR the changes in expression levels of selected repressed and activated genes cobound by EWSR1-FLI1 and RING1B. We noticed that RING1B knockdown causes a significant reduction in the expression levels of those genes where both EWSR1-FLI1 and RING1B were co-occupying enhancer regions (Fig. 3, F and G). The expression of CAV1, NKX2-2, SOX2, IGF1, JARID2, and VRK1 was affected in stronger manner upon EWSR1-FLI1 knockdown, indicating that some cofactors could remain when RING1B is depleted (fig. S4F). The effect of RING1B knockdown was less pronounced when both proteins were enriched at promoter regions of active genes (fig. S4, G and H, left). As expected, at those genes where EWSR1-FLI1 acts as a repressor, RING1B knockdown induces a promoter reactivation (fig. S4, G and H, right). Overall, these data indicate that RING1B and EWSR1-FLI1 cooperate in gene activation, at both the promoter and enhancer levels, while RING1B retains its canonical role at those targets repressed by the oncogene. Since a large number of EWSR1-FLI1 and RING1B cotargets were not altered by RING1B knockdown, we postulate compensatory mechanism(s) or additional cofactors involved in their regulation.

Wild-type EWSR1 interacts with RING1B in the VCaP prostate cancer cell line (33). We also confirmed this interaction in SK-ES1 cells (Fig. 4A). Since RING1B and EWSR1-FLI1 are enriched at transcriptionally active regions, we next aimed to investigate whether both proteins interact. Coimmunoprecipitation experiments in HeLa cells where EWSR1-FLI13xFlag was overexpressed (34) confirmed that indeed oncogene interacts with RING1B (Fig. 4, B and C). Analysis of published mass spectrometry data demonstrated that several SWI/SNF subunits interact with RING1B (33), further supporting an active role of RING1B in EwS gene regulation. Together, our results indicate that EWSR1-FLI1 and RING1B not only colocalize at the same genomic regions but also physically interact, mainly through the EWSR1 component of the fusion protein.

(A) Western blot showing endogenous coimmunoprecipitation of RING1B with EWSR1 in the SK-ES1 cell line. (B) Western blot showing overexpression of EWSR1-FLI1-3xFlag and RING1B levels in HeLa stably transfected cells upon induction with indicated doxycycline concentrations for 24 hours. Calnexin is used as loading control. (C) Coimmunoprecipitation of RING1B with EWSR1-FLI1-3xFlag under induction conditions (0.5 g/ml). Inputs in (A) and (C) contain 10% of immunoprecipitated material and IgG is used as control. (D) Western blot showing RING1B and EWSR1-FLI1 in cytoplasm, soluble, and bound chromatin fractions in shCTRL#1 or shRING1B#1 SK-ES1 cells. Histone H4 is used as a control of bound chromatin, and GAPDH as a control of cytoplasmic fraction. Blot quantification of the same ordered samples is depicted below. (E) ChIP-qPCR analysis of FLI1, RING1B, and H3K27ac at EWSR1-FLI1activated enhancers of NKX2-2, SOX2, or IGF1 genes in shCTRL#2 and shRING1B#2 A673 cells. ENC1 is used as negative control region. The values of the Y axis represent the enrichment ratio of immunoprecipitated samples relative to input. Error bars indicate SD of three independent biological experiments. Statistical significance is as follows ***P < 0.001, **P < 0.01, and *P < 0.05. (F) Aggregated plot and boxplot showing the average ChIP-seq signal of RING1B and FLI1 peaks at RING1B and EWSR1-FLI1 binding sites, respectively, in shCTRL#2 and shRING1B#2 A673 cells. (G) UCSC genome browser ChIP-seq signal tracks for EWSR1-FLI1 and RING1B in shCTRL#2 and shRING1B#2 A673 cells at SOX2 and VRK1 enhancer regions.

Next, we analyzed whether RING1B depletion affects the EWSR1-FLI1 recruitment to chromatin. As expected, after knockdown, we observed a notable reduction of RING1B in the chromatin bound fraction (Fig. 4D). EWSR1-FLI1 was also evicted from chromatin bound and enriched in the soluble chromatin fraction (Fig. 4D). We then monitored the occupancy of EWSR1-FLI1, RING1B, and H3K27ac at several enhancers (e.g., SOX2, NKX2-2, and IGF1). The data in Fig. 4E showed that upon RING1B knockdown, enrichments at those enhancers decreased to control values [immunoglobulin G (IgG) or ENC1 region]. To assess the decrease of EWSR1-FLI1 recruitment genome-wide, we performed ChIP-seq analysis of RING1B and FLI1 in shCTRL and shRING1B A673 cells. The analysis indicated that upon RING1B depletion, EWSR1-FLI1 binding to chromatin was reduced (Fig. 4, F and G). In sum, we conclude that in EwS, RING1B exerts its main role as activator by promoting recruitment of EWSR1-FLI1 to enhancer regions.

RING1B stimulates tumor growth and metastasis in melanoma, leukemia, and breast cancers (14, 27). We observed a reduction in colony number when RING1B is depleted in the SK-ES1 cell line (fig. S5A). To gain functional insight into the cancer pathways potentially modulated by RING1B, we performed gene set enrichment analysis (GSEA) by comparing SK-ES1 shCTRL versus shRING1B cells. The top 10 most significant pathways included interferon-, epithelial-to-mesenchymal transition, hedgehog signaling, and angiogenesis, with a 0.25 Q value cutoff (fig. S5B). In EwS, disruption of angiogenic pathways has been described (4, 22). Further inspection of angiogenic gene list revealed that key genes such as PDGFA, FGFR1, SLCO2A1, CXCL6, and S100A4 were down-regulated upon RING1B depletion (fig. S5C).

To assess the relevance of RING1B in vivo, we generated xenografts by injecting SK-ES1 shCTRL or shRING1B cells (seq#1 and seq#2) subcutaneously into athymic nude mice. Cells with reduced RING1B levels showed delayed engraftment and slower tumor growth (Fig. 5A). At 21 days after injection, tumors derived from shRING1B cells were significantly smaller than those from control cells (fig. S5D). Notably, the median survival increases from 26 days for shCTRL cells to 30 days for shRING1B seq#1 and from 20 to 27 days for shRING1B seq#2 (Fig. 5B). Immunohistochemical analyses of tumors confirmed reduced levels of RING1B, while the ES marker CD99 remained essentially unchanged (Fig. 5C and fig. S5E). Furthermore, shCTRL tumors displayed higher proliferation rates than shRING1B, as shown by Ki-67 staining (Fig. 5C).

(A) Tumor volume curve in xenografts established by subcutaneous injection of shCTRL and shRING1B#1 (n = 9 and n = 10, respectively, above) or shRING1B#2 (n = 12 both groups, below) SK-ES1 cells in athymic nude mice. (B) Kaplan-Meier xenograft survival curves in shCTRL and shRING1B SK-ES1 cells (#1 and #2). (C) Immunohistochemistry staining of EWSR1-FLI1, CD99, and RING1B on sections of tumors excised from shCTRL#1 and shRING1B#1 SK-ES1 xenografts. Proliferation was analyzed by Ki67 immunohistochemistry; hematoxylin and eosin (H&E) was used as control. (D) Heatmap depicting fold changes in gene expression in six tumors excised from shCTRL#1 and shRING1B#1 SK-ES1 groups. (E) RT-qPCR levels of mRNA expression for RING1B and EWSR1-FLI1 in shCTRL#1 and shRING1B#1 SK-ES1derived tumors; ***P < 0.001. (F) RT-qPCR levels of mRNA expression for genes regulated by EWSR1-FLI1/RING1B enhancers (left) and angiogenic genes (right) in shCTRL#1 and shRING1B#1 SK-ES1 derived tumors; *P < 0.05.

To better characterize xenograft derived tumors, we performed RNA sequencing (RNA-seq) of a cohort of tumors (six for each group, Fig. 5D). GSEA analysis confirmed the enrichment of angiogenic genes in the shCTRL tumors (fig. S5, F and G). Since RING1B retains its repressive function at several promoters, we hypothesized that the delay in survival and in tumor growth upon RING1B knockdown could be related to up-regulation of tumor suppressor genes (TSG). GSEA applied to 983 genes from TSG database (https://bioinfo.uth.edu/TSGene), indicated that this gene list was enriched in shCTRL phenotype, suggesting that tumor growth and survival differences observed were not due to RING1B repression of TSG (fig. S5H). The NKX2-2, SOX2, and IGF1 genes are necessary for EwS tumor proliferation (21, 23, 35). In agreement, confirmed RING1B and EWSR1-FLI1 expression reduction (Fig. 5E) is associated to down-regulation of these genes in xenograft tumors (Fig. 5F, left), as we previously shown in EwS cells (Fig. 3, F and G). Furthermore, after RING1B knockdown, we also validated down-regulation of S100A4, SLCO2A1, and VEGFA, which are main activators of angiogenic signaling pathways (Fig. 5F, right). All these data highlight the role of RING1B as an activator in EwS tumorigenesis.

Several kinases (including AURKB, MEK1, and CK2) have been reported to modulate the activating transcriptional function of RING1B (14, 15, 36). To investigate which pathway(s) regulates RING1B at active enhancers in EwS, we analyzed the expression levels of these three kinases in a publicly available database (4) comprising a cohort of 27 tumor samples and BM-MSCs. While MEK1 and CK2 were not expressed in primary tumors with respect to BM-MSCs (control), 11 of 27 EwS tumors (40%) showed higher levels of AURKB compared to control (fig. S6A). EWSR1-FLI1 directly regulates the expression of AURKB (37), as also demonstrated by AURKB down-regulation in EwS cell lines upon oncogene knockdown (fig. S6A).

AZD1152 is a specific AURKB inhibitor, with a median inhibitory concentration (IC50) of 19 nM in EwS cell lines (38). Accordingly, we observed IC50 values of 5 and 6 nM in SK-ES1 and A4573 cells, respectively; in contrast, the IC50 for A673 was 5 M, and AZD1152 had no effect on the control cell line 293T (fig. S6B). EwS cells that survived to the treatment showed an atypical phenotype, suggesting enhanced differentiation (fig. S6C). Furthermore, viability of EwS cell lines was not affected by the inhibition of RING1B E3 ubiquitin ligase activity with PRT4165 (fig. S6B). To further elucidate the effect of AZD1152 in EwS, cell death was analyzed by Annexin V staining. A 72-hour AZD1152 treatment of A673, SK-ES1, and A4573 cells led to an increase in the early and late apoptosis populations as compared to 293T cells (Fig. 6A). Analysis of cleaved PARP levels further demonstrated that AZD1152 stimulated apoptotic pathways in EwS cell lines, with SK-ES1 being the most sensitive (Fig. 6B). It is worth noting that the levels of EWSR1-FLI1 were decreased after AZD1152 treatment in SK-ES1 and A4573, yet RING1B levels were unaffected (Fig. 6B and fig. S6, D and E, right). To understand how AURKB modulates RING1B in EwS, we analyzed H2Aub levels after AZD1152 treatment. We observed increased levels of H2Aub repressive mark after AURKB inhibition, suggesting that this kinase indeed inhibits the ubiquitin ligase activity of RING1B in EwS (Fig. 6C). Furthermore, in SK-ES1 and A4573 cells, the increase in ubiquitin ligase activity correlated with decreased expression of EWSR1-FLI1 targets co-occupied by RING1B, with more pronounced effect on those genes where both proteins colocalize at the enhancer region (Fig. 6D and fig. S6, D and E, left). For the A673 cell line, higher doses were required to reach oncogene target deregulation, as expected. Next, we reasoned that AURKB should be present at those regions where it inhibits RING1B activity. Using ChIP-qPCR, we demonstrated that AURKB is enriched in active enhancers (CAV2, driving CAV1 expression, and SOX2; Fig. 6E) and promoters (NR0B1; fig. S6F). Furthermore, EWSR1-FLI1 down-regulation could be explained by the presence of RING1B at the EWSR1 promoter, which indirectly decreases upon AZD1152 incubation (fig. S6G). Although part of AZD1152 cytotoxicity might be related to reduction of EWSR1-FLI1 availability, the data presented suggest that RING1B regulation of oncogene targets is susceptible to AURKB inhibition. The translational value of this potential targetable vulnerability is the matter of ongoing work.

(A) Annexin V staining of SK-ES1, A673, and A4573 cells after treatment with AZD1152 (20 nM). 293T cells were used as a control cell line. (B) Western blot analysis of cleaved poly(ADP-ribose) polymerase (cPARP), EWSR1-FLI1, RING1B, and AURKB after treatment with 10 or 20 nM AZD1152, in the A673, SK-ES1, A4573, and 293T cell lines. Tubulin was used as loading control. (C) Western blot analysis of H2Aub and H3S10phospho (H3S10ph) in the A673, SK-ES1, and A4573 cell lines treated with 5 or 20 nM AZD1152. Histone H4 was used as loading control. (D) RT-qPCR determination of mRNA expression of target genes with RING1B/EWSR1-FLI bound enhancers in SK-ES1 and A4573 cells after treatment with 20 nM AZD1152. RPL27 was used for normalization. DMSO, dimethyl sulfoxide. (E) AURKB ChIP-qPCR at CAV2 and SOX2 EWSR1-FLI1/RING1B enhancers (above) and control regions (below). The values of the Y axis represent the enrichment ratio of immunoprecipitated samples relative to input. Error bars in (D) and (E) indicate SD of three independent biological experiments. (F) Schematic representation illustrating the EWSR1-FLI1 recruitment by RING1B to repressed regions containing GGAA repeats. Once EWSR1-FLI1 has been recruited, additional cooperating factors such as AURKB might inhibit RING1B ubiquitin ligase activity, which, in turn, is able to participate in transcription activation.

Here, we investigated the genome-wide occupancy of RING1B in EwS. In agreement with previous data, we identified a set of regions bound by RING1B where it exerts its canonical repressive function. We also report that RING1B co-occupy together with EWSR1-FLI1 many intergenic and intronic regions decorated with H3K27ac. A strong enrichment in GGAA repeats has been described in regulatory elements where EWSR1-FLI1 binds producing active enhancers (10). The presence of GGAA repeats, as well as the H3K27ac association, indicates that cobinding of RING1B and EWSR1-FLI1 occurs in active enhancers. BMI1 or EZH2 was not found at these enhancer regions, suggesting a Polycomb-independent function for RING1B. Enhancers are key regulatory regions implicated in cell fate determination. Here, we unveiled that an aberrant transcription factor such as EWSR1-FLI1 relies on RING1B to activate enhancers, causing an altered gene expression profile, which favor cell transformation.

In accordance with RNA-seq data from melanoma and breast cancer, where a positive association of RING1B with transcription activation has been reported (14, 27), we observed in EwS cells a higher number of genes activated than repressed by RING1B. We found NKX2-2, SOX2, and IGF1 being direct targets down-regulated both in vivo and in vitro upon RING1B knockdown. In EwS, NKX2-2 and SOX2 are key players in tumorigenesis (21, 23), suggesting that modulation of their expression in vivo upon RING1B knockdown might contribute to decreased tumor volume and better survival, supporting an oncogenic role for RING1B.

Recent studies in hpMSCs have demonstrated that, before oncogene recruitment, H3K27me3 is enriched at regions where EWSR1-FLI1 could bind (39). In agreement with these data, we further demonstrate that upon EWSR1-FLI1 expression, those same regions loose H3K27me3 marks while becoming transcribed. Moreover, we report that enrichment in Polycomb repressed chromatin states is specific for H1-, adipose- and BM-derived MSCs, reinforcing hMSC as the putative cell of origin, which has already been described by other groups (4, 21). The existence of H3K27me3 repressed regions decorated only with PRC1 complex has already been described during differentiation of neural precursor cells, where RING1B and PCGF2 are retained while the PRC2 subunit Suz12 is not (40). In melanoma, CCND2 is marked with H3K27me3 before RING1B activation by phosphorylation (14). We have observed that GGAA repeats are differentially enriched in the binding motif analysis when RING1B is associated to chromatin with EWSR1-FLI1. In this scenario, given the interaction observed for RING1B and EWSR1-FLI1, it is tempting to speculate that RING1B targets EWSR1-FLI1 to specific sites. In line with this hypothesis, the reduced recruitment of EWSR1-FLI1 to chromatin (including enhancer regions, such as NKX2-2, SOX2, and IGF1) upon RING1B knockdown underlines the importance of RING1B in the initials steps of EwS tumorigenesis. Overall, our data suggest that RING1B is required for the recruitment of EWSR1-FLI1 to multimeric GGAA repeats (Fig. 6F).

We have demonstrated that RING1B is an essential partner of EWSR1-FLI1 triggering chromatin remodeling. Recent studies demonstrated the requirement of SWI/SNF, WDR5, and p300 acetyltransferase for EWSR1-FLI1induced transcription. Similarly, in synovial sarcoma, the SS18-SSX oncogenic fusion protein and the SWI/SNF complex colocalize at KDM2B-repressed target genes together with the noncanonical PRC1.1 complex to produce transcriptional active regions (41). Along the same lines, in leukemia, noncanonical PRC1.1 also targets active genes independently of H3K27me3 (42). Further mechanistic insights are needed to elucidate the contribution of PRC1.1 repressive complex in EwS, where somatic mutations in BCOR have been reported (1). The noncanonical PRC1.1 complex contains a DNA binding ZnF-CXXC domain able to target chromatin via KDM2B (43). ZNF/repeats chromatin state was statistically enriched in five of the six EwS cell lines analyzed.

Recently, different cell models have shown that the E3 ubiquitin ligase activity of RING1B is inactivated by phosphorylation (15, 36). Our results showing the recruitment of AURKB to enhancers are compatible with a model in which RING1B is unable to repress the newly formed ES enhancers, which were previously Polycomb-repressed regions. Once the oncogene binds to chromatin, RING1B would cooperate to induce transcription activation if its ubiquitin ligase activity is inhibited by phosphorylation (either directly or indirectly) (Fig. 6F). More studies are needed to clarify how oncogenic fusion proteins act as binding scaffolds to recruit a specific set of interactors to generate previously unknown functional units (such as neo-enhancers).

Inhibition of super-enhancers activity with BET inhibitors has emerged as a successful preclinical strategy in the fight against different pediatric cancers such as EwS, neuroblastoma, and rhabdomyosarcoma (4446). Inhibition of AURKB with AZD1152 increases H2Aub and decreases expression of key oncogene targets, thus suggesting that RING1B is essential for enhancer deregulation by EWSR1-FLI1. Nevertheless, as RING1B account for catalytic and noncatalytic dependencies (14), further investigation should address its clinical therapeutic implications. In agreement with our data, combined inhibition of AURKA and AURKB, as well as synergistic activity of AURKB with focal adhesion kinase inhibitors, has been described effective in EwS preclinical studies, although AURKB efficiency as single agent has not been proved (47, 48). In EwS cells, AZD1152 could affect the levels of RING1B, and this likely reverberates on the regulation of the oncogenes promoter since RING1B occupies the EWSR1 promoter (fig. S6, E and G).

In summary, we demonstrate the oncogenic dependency to high levels of RING1B in EwS. The data support a model in which RING1B plays a pivotal role for EWSR1-FLI1 recruitment to the multimeric DNA repeats. This, in turn, allows for transcriptional activation that defines the characteristic transcriptome of EwS. Given the role of RING1B in the activation of super-enhancers, which are critical elements for cell fate determination, we propose that the EwS cell of origin is predefined by high levels of RING1B.

The Ewings sarcoma cell lines A673, SK-ES1, and A4573, which carry the EWSR1-FLI1 translocation types I, II, and III, respectively, and the HEK293 cell line from human embryonic kidney infected with AgT from SV40 (293T), were cultured in RPMI 1640 media (Gibco) and supplemented with 10% fetal bovine serum, l-glutamine, and penicillin/streptomycin. Cells were cultured at 37C with 5% CO2. The A673 and SK-ES1 cell lines harboring shCTRL and shRING1B with seq#1 and seq#2 as well as A673 cell line with doxycycline inducible knockdown of EWSR1-FLI1 were previously described (11, 18). hpMSCs were isolated following published protocols (21). Ectopic expression of EWSR1-FLI1 3xFLAG C terminus in HeLa cells was induced with doxycycline (0.5 g/ml) (34).

All experiments performed with AZD1152 were incubated 72 hours, with the exception of RNA expression assays that were incubated 24 hours. For IC50 calculations, A673, SK-ES1, A4573, and 293T cell lines were seeded at 2000 cells per well in 96-well culture plates. AZD1152 and PRT4165 (Sigma-Aldrich) was added to complete growth medium; after 72 hours, cells were subjected to the ATPlite assay (PerkinElmer), and measurements were performed using a Tecan plate reader. Inhibitory concentrations were calculated using OriginPro 9.0 software.

EWSR1-FLI1 type 2 was amplified from a pSG5 vector with primers containing Bgl II and Hind III sequences (forward, 5-ggaggaaggAGATCTAATGGCGTCCACGG-3; reverse, 5-aagAAGCTTGTAGTAGCTGCCTAA-3). The PCR product was purified using an Illustra GFX PCR DNA and Gel Band Purification kit (GE Healthcare Life Sciences). The product of the amplification was subcloned into the TOPO TA Cloning Kit for Sequencing following the manufacturers instructions. TOPO-EWSR1-FLI1 plasmid and the acceptor vector pEGFP-N1 were double digested with Bgl II and Hind III at 37C. The resulting EWSR1-FLI1 band was ligated into pEGFP-N1, and ligation product was then transformed into JM109 cells.

Target sequences for siRNA are described in table S6. Transfection of small duplexes (Sigma-Aldrich) was performed with Lipofectamine RNAiMAX and Optimem (Invitrogen), using 30 pmol when cells were 80% confluent; samples were collected after a 72-hour incubation. Transient transfections of GFP constructs or empty vector were done using FuGENE XP (Roche) with 1 to 2 g of plasmid when cells were 60% confluent; samples were collected after 48 hours. Both reagents were used according to the manufacturers recommendations.

Empty pLIV and EWSR1-FLI1pLIVexpressing lentiviruses were provided by N. Riggi (University Institute of Pathology Lausanne, Switzerland). Lentiviruses were produced in Lenti-X 293T packaging cells (Takara, Cultek) at a low passage number. For each plate, 7 g of the lentiviral plasmid, 5 g of the envelope plasmid (VSV-G), and 6 g of the packaging plasmid (PAX8) were prepared and introduced by calcium phosphate transfection, according to standard protocols. The supernatant containing lentiviruses was collected 48 hours after transfection. The HUVEC cell line was seeded at 3000 cells/cm2 and transduced with 3:1 of the lentiviral supernatant with fresh media containing Polybrene (Sigma-Aldrich) at 6 g/ml. Cells were selected with fresh growth media containing puromycin (0.3 g/ml) for 72 hours. A control dish without the transduction media was also selected with puromycin, to control for killing of nontransduced cells.

Histone extracts of cultured cells were isolated using the EpiQuick Histone Extraction kit (Epigentek) following the manufacturers instructions. Total cell extracts were prepared in IPH buffer [50 mM tris-HCl (pH 8), 150 mM NaCl, 5 mM EDTA, and 0.5% NP-40] with EDTA-free protease inhibitor cocktail (Roche). For protein, fractionation standard protocols were used. Histone or total protein extracts were quantified by Bradford assay. Immunoprecipitation was performed with total cellular extracts incubated at 4C overnight with primary antibody. After incubation of immunoprecipitated samples on protein A/G and agarose beads (Santa Cruz Biotech), 30 to 50 g of whole protein extracts or 5 g of histones was resolved by polyacrylamide gel electrophoresis. Western blotting was performed using standard protocols. Incubation with primary antibodies was done at 4C overnight and LI-COR secondary antibodies that are detectable by near-infrared fluorescence were used for detection (table S6). Blots were scanned with an Odyssey CLx Infrared Imaging System at medium intensities.

Treated cells were fixed in 70% ethanol, stained with 25 l of propidium iodide (PI) (1 mg/ml), and 25 l of ribonuclease (RNase) (10 mg/ml), and incubated 30 min at 37C. For Annexin V binding, the Alexa Fluor 488 fluorophore kit (Invitrogen) was used for apoptotic cell detection. After culture and treatment, cells were resuspended in annexin binding buffer with 5 l of Alexa Fluor 488 Annexin V and 1 l of PI working solution (100 g/ml). After 15 min, samples were run in Gallios multicolor flow cytometer (Beckman Coulter) set up with the 3-lasers, 10 colors standard configuration. Histograms and cytograms were further analyzed with FlowJo 10.2.

Total RNA was isolated and purified from collected cells using the RNeasy Mini Kit (Qiagen) according to the manufacturers protocol. After quantification using the NanoDrop software (Thermo Fisher Scientific), RT was performed. A 1-g aliquot of each RNA sample was converted to cDNA in a reaction catalyzed by a retrotranscriptase enzyme (M-MLV Reverse Transcriptase Promega). Random primers and RNase inhibitor (RNasin Plus RNase Inhibitor, Promega) were also added to the reaction. cDNA obtained was analyzed by qPCR using SYBR Green PCR Master Mix (ABI). cDNA was amplified with specific oligonucleotides (table S6). Each cDNA sample was run in triplicate, and its levels were analyzed using the 7500 Fast PCR instrument (Applied Biosystems). To compare between different conditions studied, relative quantification of each target was normalized to a housekeeping gene. Last, data were analyzed using the comparative 2-ct method.

Gene expression microarrays were performed at the Microarray Analysis Service, Hospital del Mar Medical Research Institute (IMIM, Barcelona). RNA samples were amplified, labeled according to a GeneChip WT PLUS Reagent kit, and hybridized to Human Gene 2.0 ST (Affymetrix) in a GeneChip Hybridization Oven 640. Washing and scanning were performed using the Expression Wash, Stain, and Scan Kit and the GeneChip System of Affymetrix (GeneChip Fluidics Station 450 and GeneChip Scanner 3000 7G). After quality control, raw data were background corrected, quantile-normalized, and summarized to a gene level using the robust multichip average; a total of 48,144 transcript clusters, excluding controls, were obtained, which roughly corresponds to genes and other RNAs, such as long intergenic noncoding RNAs and microRNAs. NetAffx 36 annotations, based on the human genome 19, were used to summarize data into transcript clusters and to annotate analyzed data. Linear Models for Microarray (limma), a moderated t statistics model, was used for detecting differentially expressed genes between the conditions. All data analyses were performed in R (version 3.4.3) with R/Bioconductor packages aroma.affymetrix, Biobase, affy, limma, genefilter, ggplots, and Vennerable. Genes with a P less than 0.05 were selected as significant.

Raw sequencing reads in the fastq files were mapped with STAR version 2.6.a (49). GENCODE release 29, based on the GRCh38 reference genome, and the corresponding GTF file were used. The table of counts was obtained with featureCounts function in the package subread, version 1.6.4. The differential gene expression analysis (DEG) was assessed with voom+limma in the limma package version 3.40.2 and using R version 3.6.0. Raw library size differences between samples were treated with the weighted trimmed mean method implemented in the edgeR package. Clustering method used is Ward.D2 with correlation distances and principal components analysis. For the differential expression analysis, read counts were converted to log2 counts per million, and the mean-variance relationship was modeled with precision weights using voom approach in limma package. Raw data are accessible at the NCBI Gene Expression Omnibus (GEO) accession code GSE131286.

Intersection of DEG for A673 shRING1B knockdown with those for A673 shEWSR1-FLI1 with accession number GSE61953 (10) was obtained by calculating a delta-score as described by the authors. Absolute FC > 1.25 and 1.5 for RING1B and EWSR1-FLI1 datasets were selected, respectively. Overlaps for positive and negative gene sets were obtained using Vennerable R package and BioVenn. Functional analysis of the intersection between RING1B and EWSR1-FLI1 gene lists was performed in Enrichr. Normalized enrichment scores on A673 and SK-ES1 shRING1B versus shCTRL were obtained with GSEA using the Hallmark gene set collection. GSEA was used to analyze enrichment on the list of 983 down-regulated TSG in tumor samples versus normal tissue from TSGene database (50) (https://bioinfo.uth.edu/TSGene/). Analysis of expression levels for AURKB, CSNK2A1, and MAP2K1 were performed using information from GEO2R GSE7007 for the probes 209464_at, 212075_s_at, and 202670_at, respectively.

Immunohistochemical analyses were performed following standard techniques. The antibodies used are given in table S6. Tumors were fixed in formalin and embedded in paraffin for subsequent processing. Consecutive, sections were deparaffinized, rehydrated, and heated with Epitope Retrieval Solution (pH 6.0) (Novocastra Laboratories). Reactions were developed with Novolink Polymer Detection System (Novocastra Laboratories). Immunoreactivity was visualized by diaminobenzidine, and nuclei were counterstained with hematoxylin. Tissue was then dehydrated with alcohol, permeated with xylene, and mounted with Permount organic mounting solution (Thermo Fisher Scientific). Images were evaluated by a pathologist to select regions of interest and analyzed with the Dotslide Microscope and Olympia Software (Olympus). Similar regions of every sample were selected from every section.

Cells were treated with 1% formaldehyde at room temperature for 10 min, and the cross-linking reaction was stop by adding 500 l glycine (1.25 M). Cells were resuspended in lysis buffer [0.1% SDS, 0.15 M NaCl, 1% Triton X-100, 1 mM EDTA, 20 mM tris (pH 8), and protease inhibitors (1 mg/ml)] and sonicated with Bioruptor Pico (Diagenode) for 10 cycles until chromatin was sheared to an average fragment length of 200 bp. After centrifugation, a small fraction of eluted chromatin was measured with Qubit. Starting with 30 g of sample, immunoprecipitation for each antibody was performed overnight (table S6); 50 l of Dynabeads Protein A (Invitrogen) was then added and incubated for 2 hours at 4C under rotation. Immunoprecipitates were washed once with TSE I [0.1% SDS, 1% Triton X-100, 2 mM EDTA, 20 mM tris-HCl (pH 8), and 150 mM NaCl], TSE II [0.1% SDS, 1% Triton X-100, 2 mM EDTA, 20 mM tris-HCl (pH 8), and 500 mM NaCl], and TSE III [0.25 M LiCl, 1% Nonidet P-40, 1% deoxycholate, 1 mM EDTA, and 10 mM tris-HCl (pH 8)] and then twice with tris-EDTA buffer. Washed pellets were eluted with 120 l of a solution of 1% SDS and 0.1 M NaHCO3. Eluted pellets were decross-linked for 5 hours at 65C and purified on 50 l of tris-EDTA buffer with the QIAquick PCR Purification Kit (Qiagen). Differences in the DNA content at each binding region (sequences in table S6) from every immunoprecipitation assay were determined by real-time PCR using the ABI 7700 sequence detection system and SYBR Green master mix protocol (Applied Biosystems). Each immunoprecipitation was done in triplicate, and PCR assays were performed using fixed amounts of input and immunoprecipitated DNA. For every amplicon, standard curves to calculate efficiency and melting curves to confirm single amplicons were obtained. The reported data represent real-time PCR values normalized to input DNA and are expressed as percentage (%) of bound/input signal.

Libraries were prepared using the NEBNext Ultra DNA Library Prep from Illumina according to the manufacturers protocol. Briefly, 5 ng of input and ChIP-enriched DNA were subjected to end repair and addition of A bases to 3 ends, ligation of adapters, and USER excision. All purification steps were performed using AgenCourt AMPure XP beads (Qiagen). Library amplification was performed by PCR using NEBNext Multiplex Oligos from Illumina. Final libraries were analyzed using Agilent high sensitivity chip to estimate the quantity and to check size distribution and then were quantified by qPCR using the KAPA Library Quantification Kit (KapaBiosystems) before amplification with Illuminas cBot. Libraries were loaded onto the flow cell sequencer 1 50 on Illuminas HiSeq 2500.

ChIP-seq samples were mapped against the hg19 human genome assembly using BowTie with the option m 1 to discard those reads that could not be uniquely mapped to just one region. A second replicate of RING1B and H2Aub was sequenced to evaluate the statistical significance of the results. Model-based analysis of ChIP-seq (MACS) was run individually on each replicate with the default parameters but with the shift size adjusted to 100 bp to perform the peak calling against the corresponding control sample (51). DiffBind was initially run over the peaks reported by MACS for each pair of replicates of the same experiment to generate a consensus set of peaks (28). Next, DiffBind was run again over each pair of replicates of the same experiment, samples and inputs, to find the peaks from the consensus set that were significantly enriched in both replicates in comparison to the corresponding controls (categories, DBA_CONDITION; block, DBA_REPLICATE; and method, DBA_DESEQ2_BLOCK). DiffBind RING1B peaks with P < 0.05 and H2Aub peaks with P < 0.05 and false discovery rate < 0.00001 were selected for further analysis. The genome distribution of each set of peaks was calculated by counting the number of peaks fitted on each class of region according to RefSeq annotations. Promoter is the region between 2.5 kb upstream and 2.5 kb downstream of the TSS. Genic regions correspond to the rest of the gene (the part that is not classified as promoter), and the rest of the genome is considered to be intergenic. Peaks that overlapped with more than one genomic feature were proportionally counted the same number of times. Each set of target genes was retrieved by matching the ChIP-seq peaks in the region 2.5 kb upstream of the TSS until the end of the transcripts as annotated in RefSeq. Reports of functional enrichments of GO categories were generated using the EnrichR tool. Aggregated plots showing the average distribution of ChIP-seq reads around the summit of each peak were generated by counting the number of reads for each region and then averaging the values for the total number of mapped reads of each sample and the total number of peaks in the particular gene set. To perform the comparison between two sets of peaks, a minimum overlap of one nucleotide was necessary to consider one match. The heatmap displaying the density of ChIP-seq reads 5 kb around the summit of each peak set were generated by counting the number of reads in this region for each individual peak and normalizing this value with the total number of mapped reads of the sample. Peaks on each ChIP heatmap were ranked by the logarithm of the average number of reads in the same genomic region. On the other hand, we separated the single peaks of RING1B into distal and TSS (5 kb around one RefSeq gene) to generate the heatmap of ChIP-seq signal strength of RING1B, EWSR1-FLI1, H3K27me3, H2Aub, and H3K27ac over the two classes of RING1B peaks detected above (distal and TSS). To build our collection of enhancers and promoters, we reanalyzed published ChIP-seq samples of H3K4me1, H3K27ac, H3K27me3, and H3K4me3 in A673 cells (10). H3K27ac and H3K27me3 peaks were used to discriminate between active or repressed regulatory regions. Promoters were defined as ChIP peaks of H3K27 found up to 2.5 kb from the TSS of one gene and enhancers on intergenic areas outside promoters or within gene introns. H3K4me3 was required to be present in promoters but absent in enhancers. We defined four classes of regulatory elements: active enhancers (H3K27ac), active promoters (H3K27ac + H3K4me3), poised enhancers (H3K27me3), and bivalent promoters (H3K27me3 + H3K4me3). The MEME-ChIP tool was used to perform motif-finding analysis of the sequences bound by each factor. The UCSC genome browser was used to generate the screenshots of each group of experiments along the manuscript (52). Raw data, genome-wide profiles, and peaks of each ChIP-seq experiment are accessible at the NCBI GEO accession code GSE131286.

We have determined the composition of 3945 EWSR1-FLI1 biding sites in terms of 15 chromatin states from the segmentations generated by Epigenome Roadmap Consortium (GEO code: GSE61953) for six different cell types: HUVECs (E122), H1 (E003) and H9 ES cells (E008), H1-derived mesenchymal stem cells (E006), BM-derived MSCs (E026), and adipose-derived MSC (E025) (26). The statistical significance of the relative frequency of each stage at every cell type was assessed in comparison to the same value measured along the whole genome, using the Fishers exact test. The R package GenomicRanges from Bioconductor was used for calculations of compositions. Next, to generate the final heatmap, we have grouped certain states for semantic similarity (active TSS category includes active and flanking active TSS states; transcription includes flanking, strong, and weak states; enhancers account for both genic and intergenic; bivalent TSS include also flanking bivalent promoters and PcG repressed include both repressed and weak repressed). Thus, the relative frequencies of the new eight states were recalculated, while quiescent state was discarded from the analysis. Last, the enrichment percentage at a particular stage was calculated as the difference between the relative frequency at the EWSR1-FLI1 ChIP-seq sites minus the relative frequency at the whole genome normalized by the relative frequency at the whole genome again.

In vivo studies were performed after the approval of the Institutional Animal Research Ethics Committee. Athymic nude mice (Envigo) were injected subcutaneously with 4 106 cells for shCTRL#seq1 and shRING1B#seq1 and 2 106 for seq#2. shCTRL cells were resuspended in 200 l of Matrigel (Becton Dickinson) with phosphate-buffered saline and injected into both flanks (5 mice n = 10 for seq#1 and 6 mice, n = 12 for seq#2). The same procedure was performed for the SK-ES1 shRING1B cell line. Tumor growth was monitored three times a week by measuring tumor volume with a digital caliper. Mice were euthanized when tumors reached a size of 2.5 cm in any dimension. Survival curves were calculated using the Kaplan-Meier method and were compared with a log-rank test. At the end of the experiment, tumors were excised; half of each specimen was frozen in liquid nitrogen for RNA extraction, and the other was fixed in 10% formalin for immunohistochemistry experiments.

Acknowledgments: We thank N. Riggi for reagents and technical advice and M. Martnez-Balbs for technical advice and critical reading of the manuscript. We also thank G. Pascual-Pasto, S. Mateo, and M. Suol for technical advice, S. Perez-Jaume for statistical advice, and L. Nonell from the Microarray Analysis Service, Hospital del Mar Medical Research Institute (IMIM, Barcelona) for technical advice. Last, we are grateful to the Band of Parents at Hospital Sant Joan de Du for supporting the overall research activities of the developmental tumor laboratory, PCCB. Funding: S.S.-M. and the project were supported by the Spanish Association Against Cancer (AECC) consolidated groups grant (GCB13131578) consortium. The project also had the support from the Asociacion Pablo Ugarte (APU). E.F.-B. was supported by the Spanish government grant, Instituto de Salud Carlos III (PI16/00245) to J.M. The work in the Di Croce laboratory was supported by grants from the Spanish of Economy, Industry and Competitiveness (MEIC) (BFU2016-75008-P), and Fundacion Vencer El Cancer (VEC). Author contributions: S.S.-M., L.D.C., and J.M. designed the study, conducted experiments, and wrote the manuscript. J.M. supervised all the work. S.S.-M., E.F.-B., M.S.-J., P.T., C.B., E.P., L.H.-P., and D.J.G.-D. performed the experiments. E.B. and S.G. performed all the bioinformatic analysis. I.H.-M., O.M.T., A.M.C., C.L., and E.. provided expertise and feedback. All authors reviewed the manuscript. Competing interests: The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.

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RING1B recruits EWSR1-FLI1 and cooperates in the remodeling of chromatin necessary for Ewing sarcoma tumorigenesis - Science Advances

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Global News Feed Comments Off on Director/PDMR Shareholding | October 24th, 2020

NOT FOR DISTRIBUTION TO U.S. NEWSWIRE SERVICES OR FOR RELEASE, PUBLICATION, DISTRIBUTION OR DISSEMINATION DIRECTLY, OR INDIRECTLY, IN WHOLE OR IN PART, IN OR INTO THE UNITED STATES

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ProMIS Neurosciences Announces Up to $3 Million Private Placement Offering of Special Warrants

Global News Feed Comments Off on ProMIS Neurosciences Announces Up to $3 Million Private Placement Offering of Special Warrants | October 24th, 2020

New analysis of contemporary real-world data presented at American Society of Nephrology (ASN) Kidney Week 2020 New analysis of contemporary real-world data presented at American Society of Nephrology (ASN) Kidney Week 2020

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U.S. Veterans with Decreased Renal Function Shown to Be at Higher Risk for Adverse Cardiovascular Events if They Have Moderately Elevated Triglyceride...

Global News Feed Comments Off on U.S. Veterans with Decreased Renal Function Shown to Be at Higher Risk for Adverse Cardiovascular Events if They Have Moderately Elevated Triglyceride… | October 24th, 2020

BEDMINSTER, N.J., Oct. 23, 2020 (GLOBE NEWSWIRE) -- Matinas BioPharma Holdings, Inc. (NYSE AMER: MTNB), a clinical-stage biopharmaceutical company, today announced that the Company will host a conference call and live audio webcast on Friday, November 6, 2020 at 8:30 a.m. ET to discuss operational and financial results for the third quarter ended September 30, 2020.

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Matinas BioPharma to Webcast Conference Call Discussing Third Quarter 2020 Financial and Operational Results on November 6, 2020

Global News Feed Comments Off on Matinas BioPharma to Webcast Conference Call Discussing Third Quarter 2020 Financial and Operational Results on November 6, 2020 | October 24th, 2020

RALEIGH, N.C., Oct. 23, 2020 (GLOBE NEWSWIRE) -- BioDelivery Sciences International, Inc. (NASDAQ: BDSI), a rapidly growing specialty pharmaceutical company dedicated to patients living with serious and complex chronic conditions, today announced that it will report its third quarter 2020 financial results before the open of the U.S. financial markets on Thursday, November 5, 2020. The Company will host a conference call and webcast at 8:30 AM Eastern Time to discuss the results and provide an update on business operations.

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BioDelivery Sciences to Report Third Quarter 2020 Financial Results on November 5, 2020

Global News Feed Comments Off on BioDelivery Sciences to Report Third Quarter 2020 Financial Results on November 5, 2020 | October 24th, 2020

Call scheduled for Wednesday, November 11th at 4:30 pm Eastern Time Call scheduled for Wednesday, November 11th at 4:30 pm Eastern Time

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Beyond Air® Schedules Second Fiscal Quarter 2021 Financial Results Conference Call and Webcast

Global News Feed Comments Off on Beyond Air® Schedules Second Fiscal Quarter 2021 Financial Results Conference Call and Webcast | October 24th, 2020

LAKE FOREST, Ill., Oct. 23, 2020 (GLOBE NEWSWIRE) -- Assertio Holdings, Inc. (“Assertio” or the “Company”) (Nasdaq: ASRT), a commercial-stage pharmaceutical company, today announced that its third quarter 2020 financial results will be released on Friday, November 6, 2020. Following the announcement, Assertio’s management team will host a live webcast at 8:30 a.m. Eastern Time to review the Company’s financial and operating results, and provide a general business update.

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Assertio to Release Third Quarter 2020 Financial Results and Host Webcast on November 6, 2020

Global News Feed Comments Off on Assertio to Release Third Quarter 2020 Financial Results and Host Webcast on November 6, 2020 | October 24th, 2020

SYDNEY, Australia, Oct. 23, 2020 (GLOBE NEWSWIRE) -- Immutep Limited (ASX: IMM; NASDAQ: IMMP) ("Immutep” or “the Company”), is pleased to announce it has signed a Material Transfer Agreement (“Agreement”) with the University Hospital Pilsen, Czech Republic to enable an investigator-initiated randomized Phase II clinical trial evaluating its lead product candidate eftilagimod alpha (“efti” or “IMP321”) in hospitalized patients with COVID-19. The necessary approvals from the Czech Republic’s State Institute for Drug Control (SUKL- competent authority) and ethics committee have now been obtained, enabling the recruitment of patients to commence immediately. Initial interim results are expected to be reported from early 2021.

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Immutep Announces the Start of an Investigator-Initiated Phase II Study in COVID-19 Patients

Global News Feed Comments Off on Immutep Announces the Start of an Investigator-Initiated Phase II Study in COVID-19 Patients | October 24th, 2020

COPENHAGEN, Denmark, Oct. 23, 2020 (GLOBE NEWSWIRE) -- Ascendis Pharma A/S (Nasdaq: ASND), a biopharmaceutical company that utilizes its innovative TransCon technologies to address unmet medical needs, today announced the European Commission (EC) has granted Orphan Designation to TransCon PTH for the treatment of hypoparathyroidism (HP).

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Ascendis Pharma A/S Receives Orphan Designation for TransCon™ PTH for Treatment of Hypoparathyroidism in Europe

Global News Feed Comments Off on Ascendis Pharma A/S Receives Orphan Designation for TransCon™ PTH for Treatment of Hypoparathyroidism in Europe | October 24th, 2020

Orphazyme A/SCompany announcement                                                                                       No. 67/2020                                                                                                          Company Registration No. 32266355

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Orphazyme accelerates arimoclomol pre-launch activities and updates financial outlook for 2020

Global News Feed Comments Off on Orphazyme accelerates arimoclomol pre-launch activities and updates financial outlook for 2020 | October 24th, 2020

NEW YORK, Oct. 23, 2020 (GLOBE NEWSWIRE) -- NetworkNewsAudio – 180 Life Sciences Corp., a clinical-stage biotechnology company that has entered into a definitive merger agreement with KBL Merger Corp. (NASDAQ: KBLM) (KBL Merger Corp. Rights NASDAQ: KBLMR) (KBL Merger Corp. Warrant NASDAQ: KBLMW), announces the availability of a broadcast titled “Banking on the Next Blockbuster Drug.”

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Innovative Companies with Blockbuster Potential Catch SPAC Attention

Global News Feed Comments Off on Innovative Companies with Blockbuster Potential Catch SPAC Attention | October 24th, 2020