Project description:A number of microRNAs have been shown to regulate skeletal muscle development and differentiation. MicroRNA-222 is downregulated during myogenic differentiation and its overexpression leads to alteration of muscle differentiation process and specialized structures. By using RNA induced silencing complex (RISC) pulldown followed by RNA sequencing, combined with in silico microRNA target prediction, we have identified two new targets of microRNA-222 involved in the regulation of myogenic differentiation, Ahnak and Rbm24. Specifically, the RNA binding protein Rbm24 is a major regulator of muscle specific alternative splicing and its downregulation by microRNA-222 results in defective exon inclusion impairing the production of muscle-specific isoforms of Coro6, Fxr1 and NACA transcripts. Reconstitution of normal levels of Rbm24 in cells overexpressing microRNA-222 rescues muscle-specific splicing. In conclusion, we have identified a new function of microRNA-222 leading to alteration of myogenic differentiation at the level of alternative splicing, and we provide evidence that this effect is mediated by Rbm24 protein. We built linear models using 2 different experiments and two conditions (miR222 over expression (n=1) and control siRNA(n=2)) with the linear formula (~condition + experiment).
Project description:A number of microRNAs have been shown to regulate skeletal muscle development and differentiation. MicroRNA-222 is downregulated during myogenic differentiation and its overexpression leads to alteration of muscle differentiation process and specialized structures. By using RNA induced silencing complex (RISC) pulldown followed by RNA sequencing, combined with in silico microRNA target prediction, we have identified two new targets of microRNA-222 involved in the regulation of myogenic differentiation, Ahnak and Rbm24. Specifically, the RNA binding protein Rbm24 is a major regulator of muscle specific alternative splicing and its downregulation by microRNA-222 results in defective exon inclusion impairing the production of muscle-specific isoforms of Coro6, Fxr1 and NACA transcripts. Reconstitution of normal levels of Rbm24 in cells overexpressing microRNA-222 rescues muscle-specific splicing. In conclusion, we have identified a new function of microRNA-222 leading to alteration of myogenic differentiation at the level of alternative splicing, and we provide evidence that this effect is mediated by Rbm24 protein.
Project description:Myotonic dystrophes (DM), the most common adult muscular dystrophy, are the first recognized examples of RNA-mediated diseases in which expression of mutant RNAs containing expanded CUG or CCUG repeats interfere with the splicing of other mRNAs. Using whole-genome microarrays, we found that alternative splicing of the BIN1 mRNA is altered in DM skeletal muscle tissues, resulting in the expression of an inactive form of BIN1 deprived of phosphoinositide-binding and membrane-tubulating activities. BIN1 is involved in tubular invaginations of the plasma membrane and is essential for biogenesis of the muscle T-tubules, which are specialized skeletal muscle membrane structures essential to correct excitation-contraction (E-C) coupling. Mutations in the BIN1 gene cause centronuclear myopathy (CNM) that shares some histopathological features with DM, and both diseases are characterized by muscle weakness. Consistent with a loss-of-function of BIN1, muscle T-tubules were altered in DM patients, and membrane tubulation was restored upon expression of the correct splicing form of BIN1 in DM muscle cells. By deciphering the mechanism of BIN1 splicing mis-regulation we demonstrate that the splicing regulator, MBNL1, which is sequestered by expanded CUG and CCUG in DM, binds the BIN1 pre-mRNA and regulates directly its alternative splicing. Finally, reproducing BIN1 splicing alteration in mice is sufficient to reproduce the DM features of T-tubule alterations and muscle weakness. We propose that alteration of BIN1 alternative splicing regulation leads to muscle weakness, a predominant pathological feature of DM. Exon-Array analysis of control and CDM1 muscle primary cultures 10 days of differentiation
Project description:The RNA-binding protein Rbm24 has recently been identified as a pivotal splicing factor in the developing heart. Loss of Rbm24 in mice disrupts cardiac development by governing a large number of muscle- specific splicing events. Since Rbm24 knockout mice are embryonically lethal, the role of Rbm24 in the adult heart remained unexplored. Here, we used adeno-associated viruses (AAV9) to investigate the effect of increased Rbm24 levels in adult mouse heart. Using high-resolution microarrays, we found 893 differentially expressed genes and 1102 differential splicing events in 714 genes in hearts overexpressing Rbm24. We found splicing differences in cardiac genes, such as PDZ and Lim domain 5, Phospholamban, and Titin, but did not find splicing differences in previously identified embryonic splicing targets of Rbm24, such as skNAC, αNAC, and Coro6. Gene ontology enrichment analysis demonstrated increased expression of extracellular matrix (ECM)-related and immune response genes. Moreover, we found increased expression of Tgfβ-signaling genes, suggesting enhanced Tgfβ-signaling in these hearts. Ultimately, this increased activation of cardiac fibroblasts, as evidenced by robust expression of Periostin in the heart, and extensive cardiac fibrosis. These results indicate that Rbm24 may function as a regulator of cardiac fibrosis, potentially through the regulation of TgfβR1 and TgfβR2 expression.
Project description:Aged skeletal muscle is markedly affected by fatty muscle infiltration and strategies to reduce the occurrence of adipocytes within skeletal muscle, the intramuscular adipose tissue (IMAT), are urgently needed. Fibroblast growth factor-2 (FGF-2) is a critical growth factor for muscle tissue. Here, we show that FGF-2 not only stimulates muscle growth, but also promotes intramuscular adipogenesis. Using multiple screening assays for upstream and downstream signaling of microRNA (miR)-29a we located the secreted protein and adipogenic inhibitor SPARC to an FGF-2 signaling pathway that is conserved between skeletal muscle cells from mice and humans and that is activated in skeletal muscle from aged mice. FGF-2 induces the miR-29a/SPARC axis through transcriptional activation of FRA-1 which binds and activates an evolutionary conserved AP-1 site element proximal in the miR-29a promoter. Genetic deletions in muscle cells and AAV-mediated overexpression of FGF-2 or SPARC in mouse skeletal muscle revealed that this axis regulates differentiation of fibro/adipogenic progenitors in vitro and intramuscular fat formation in vivo. Thus, our data highlight an ambivalent role of FGF-2 for adult skeletal muscle and reveal a novel pathway to combat fat accumulation in aged skeletal muscle.
Project description:Hnrnpu is the largest member of the heterogenous nuclear ribonucleoprotein family of RNA binding proteins. Hnrnpu is involved in pre-mRNA alternative splicing regulation. We used high throughput sequencing to determine how Hnrnpu regulates skeletal muscle physiology.
Project description:Myotonic dystrophes (DM), the most common adult muscular dystrophy, are the first recognized examples of RNA-mediated diseases in which expression of mutant RNAs containing expanded CUG or CCUG repeats interfere with the splicing of other mRNAs. Using whole-genome microarrays, we found that alternative splicing of the BIN1 mRNA is altered in DM skeletal muscle tissues, resulting in the expression of an inactive form of BIN1 deprived of phosphoinositide-binding and membrane-tubulating activities. BIN1 is involved in tubular invaginations of the plasma membrane and is essential for biogenesis of the muscle T-tubules, which are specialized skeletal muscle membrane structures essential to correct excitation-contraction (E-C) coupling. Mutations in the BIN1 gene cause centronuclear myopathy (CNM) that shares some histopathological features with DM, and both diseases are characterized by muscle weakness. Consistent with a loss-of-function of BIN1, muscle T-tubules were altered in DM patients, and membrane tubulation was restored upon expression of the correct splicing form of BIN1 in DM muscle cells. By deciphering the mechanism of BIN1 splicing mis-regulation we demonstrate that the splicing regulator, MBNL1, which is sequestered by expanded CUG and CCUG in DM, binds the BIN1 pre-mRNA and regulates directly its alternative splicing. Finally, reproducing BIN1 splicing alteration in mice is sufficient to reproduce the DM features of T-tubule alterations and muscle weakness. We propose that alteration of BIN1 alternative splicing regulation leads to muscle weakness, a predominant pathological feature of DM.
Project description:Circadian rhythms have been implicated in regulating skeletal muscle structure and function, but no mechanisms have connected the molecular clock to sarcomeric proteins. We identified an isoform shift in the sarcomeric ruler, titin, and showed that the skeletal muscle molecular clock regulates titin isoform and subsequently sarcomere length through RBM20, an RNA binding protein that controls titin splicing.
Project description:Cellular quiescence is coupled with cellular development, tissue homeostasis, and cancer progression. Both quiescence and cell cycle re-entry are controlled by active and precise regulation of gene expression. However, the roles of long noncoding RNAs (lncRNAs) during these processes remain to be elucidated. By performing a genome-wide transcriptome analyses, we identify thousands of differentially expressed lncRNAs, including ~30 of the less-characterized class of microRNA-host-gene lncRNAs (lnc-MIRHGs), during cellular quiescence and during serum-stimulation in human diploid cells. We observe that the mature MIR222HG display serum-stimulated induction due to enhanced pre-RNA splicing. Serum-stimulated binding of the pre-mRNA splicing factor SRSF1 to a micro-exon, which partially overlaps with the primary miR-222 precursor, facilitates enhanced MIR222HG splicing. In serum-stimulated cells, SRSF1 negatively regulates the Drosha/DGCR8-catalyzed cleavage of pri-miR-222, thereby increasing the cellular pool of the mature MIR222HG. Further, loss-of-function studies indicate that the mature MIR222HG facilitates the serum-stimulated cell cycle re-entry in a microRNA-independent manner. Mechanistically, MIR222HG, along with ILF3/2 complex, forms RNA:RNA duplex with DNM3OS lncRNA, thereby promoting DNM3OS stability. The current study identifies a mechanism in which the interplay between splicing versus microprocessor complex dictates the serum-induced expression of lnc-MIRHG MIR222HG for efficient cell cycle re-entry.