Project description:Myocardin-related transcription factors (MRTFs) play a central role in the regulation of actin expression and cytoskeletal dynamics. Stimuli that promote actin polymerization allow for shuttling of MRTFs to the nucleus where they activate serum response factor (SRF), a regulator of actin and other cytoskeletal protein genes. SRF is an essential regulator of skeletal muscle differentiation and numerous components of the muscle sarcomere, but the potential involvement of MRTFs in skeletal muscle development has not been examined. We explored the role of MRTFs in muscle development in vivo by generating mutant mice harboring a skeletal muscle-specific deletion of MRTF-B and a global deletion of MRTF-A. These double knockout (dKO) mice were able to form sarcomeres during embryogenesis. However, the sarcomeres were abnormally small and disorganized, causing skeletal muscle hypoplasia and perinatal lethality. Transcriptome analysis demonstrated dramatic dysregulation of actin genes in MRTF dKO mice, highlighting the importance of MRTFs in actin cycling and myofibrillogenesis. MRTFs were also necessary for the survival of skeletal myoblasts and for the efficient formation of intact myotubes. Our findings reveal a central role for MRTFs in sarcomere formation during skeletal muscle development and point to the potential involvement of these transcriptional coactivators in skeletal myopathies. Gene expression profile was generated comparing wild type (WT) and HSA-Cre, MRTF-A/B double knockout mice, by deep seqencing, with three biological replicates, using Illumina HiSeq 2500.
Project description:Actr5 is one of the subunits of the ATPase-dependent chromatin remodeling complex INO80. In muscle tissues such as skeletal muscle, heart, and aorta, the expression of Actr5 is much lower than that in non-muscle tissues. During skeletal and smooth muscle development, it interacts with transcription factors such as MyoD, MyoG, SRF, and myocardin to play a repressive role in muscle differentiation, but its physiological role in cardiac development is not entirely clear. To investigate the role of Actr5 in the heart, AAV6 expression vectors containing Actr5 gene were infected into mice, and total RNA were extracted from the heart, followed by DNA microarray analysis.
Project description:Myocardin-related transcription factors (MRTFs) play a central role in the regulation of actin expression and cytoskeletal dynamics. Stimuli that promote actin polymerization allow for shuttling of MRTFs to the nucleus where they activate serum response factor (SRF), a regulator of actin and other cytoskeletal protein genes. SRF is an essential regulator of skeletal muscle differentiation and numerous components of the muscle sarcomere, but the potential involvement of MRTFs in skeletal muscle development has not been examined. We explored the role of MRTFs in muscle development in vivo by generating mutant mice harboring a skeletal muscle-specific deletion of MRTF-B and a global deletion of MRTF-A. These double knockout (dKO) mice were able to form sarcomeres during embryogenesis. However, the sarcomeres were abnormally small and disorganized, causing skeletal muscle hypoplasia and perinatal lethality. Transcriptome analysis demonstrated dramatic dysregulation of actin genes in MRTF dKO mice, highlighting the importance of MRTFs in actin cycling and myofibrillogenesis. MRTFs were also necessary for the survival of skeletal myoblasts and for the efficient formation of intact myotubes. Our findings reveal a central role for MRTFs in sarcomere formation during skeletal muscle development and point to the potential involvement of these transcriptional coactivators in skeletal myopathies.
Project description:Mechanosensitive Gene Regulation by Myocardin-Related Transcription Factors is Required for Cardiomyocyte Integrity in Load-Induced Ventricular Hypertrophy
Project description:Background: Cardiac transcription factors are master regulators during heart development. Recently, some were shown to transdifferentiate noncardiac mesoderm cells and cardiac fibroblasts into cardiomyocytes. However, the individual roles of each transcription factors in activating cardiac gene program have not been elucidated. We examined cardiac-specific and genome-wide gene expression in fibroblasts induced with cardiac transcription factors Nkx2.5 (N), Tbx5 (T), Gata4 (G), Myocardin (M) alone or different combinations. Methodology/Principal Findings: We applied different combinations of human Nkx2.5 (N), Tbx5 (T), Gata4 (G) and Myocardin (M) lentiviruses into 10T1/2 fibroblasts. Immunostaining and quantitative reverse transcription polymerase chain reaction (qRT-PCR) showed that N, T, G or M alone did not induce expression of cardiac marker genes M-NM-1-myosin heavy chain (M-NM-1MHC) and cardiac troponin T (cTnT). Only T+M and T+G+M combinations induced M-NM-1MHC and cTnT expression. Microarray-based gene ontology analysis revealed that T alone inhibited most genes involved in cardiac-related processes and activated genes involved in Wnt receptor signaling pathway and in aberrant processes. M alone inhibited genes involved in Wnt receptor signaling pathway and activated genes involved in cardiac-related processes and in aberrant processes. G alone inhibited genes involved in ectoderm development. T+G+M combination was the most effective activator of genes associated with cardiac-related processes including muscle cell differentiation, sarcomere, striated muscle contraction, regulation of heart contraction, and glucose metabolism and fatty acid oxidation (two significant forms of cardiomyocyte energy metabolism). And unlike T, M, G alone or T+M, T+G+M did not activate genes associated with aberrant processes. Conclusions: Tbx5, Gata4 and Myocardin play different roles in activating cardiac gene program and in avoiding aberrant gene program activation. The combination of T+G+M activated cardiac gene program and avoided aberrant gene program activation. Two weeks after doxycline induction, total RNA was isolated from 10T1/2-tTA cells infected with different combinations of Tbx5, Gata4, and Myocardin lentiviruses. Biological triplicated.
Project description:Vestigial-like (Vgll) proteins are transcriptional co-factors that have been reported to bind Tead family transcription factors to regulate various functions ranging from wing development in the fly to muscle fibre composition and immune function in mice. Here, we characterise Vgll3 in the skeletal muscle lineage. Vgll3 is expressed at low levels in unchallenging muscle but its expression increases in mechanically stimulated and regenerating muscle. VGLL3 is also >3-fold more expressed in the muscles of Duchenne muscular dystrophy patients than in healthy controls and VGLL3 expression is highest in PAX3-FOXO1-associated alveolar rhabdomyosarcoma when compared to other rhabdomyosarcomas, related tumours and adult muscle. Immunoprecipitation of over expressed VGLL3-flag followed by proteomics reveals that VGLL3 binds Tead1,3,4 transcription factors in myoblasts and myotubes. However, unlike Yap, there is no evidence for interaction with a regulatory system such as a kinase cascade. VGLL3 overexpression affects reduces the expression of members of the Hippo negative feedback loop and affects the expression of genes with important functions in muscle or signalling such as Myf5, Pitx2/3 as well as genes that encode Wnt members and IGF-binding proteins. It mainly represses gene expression and regulates similar genes as YAP1 S127A and TAZ S89A but not in a clear agonistic or antagonistic fashion. A loss of Vgll3 almost completely blocks the proliferation of human myoblasts and VGLL3 overexpression promotes myoblasts differentiation. In vivo, the loss of Vgll3 does not prevent normal skeletal muscle development presumably due to feedback signalling and/or redundancy. Collectively, this work identifies Vgll3 as a disease-related transcriptional co-factor that competes with the Hippo effectors Yap and Taz to control myoblast proliferation and differentiation.
Project description:ABSTRACT Aims Forced differentiation of non-muscle cells into heart muscle cells using cardiac transcription factors (cTFs) may constitute a novel strategy to accomplish myocardial regeneration. Methods We investigated the potential of the cTF myocardin to induce cardiomyocyte differentiation and compared the myocardin-induced gene expression program to that of fully differentiated cardiomyocytes using oligonucleotide microarray hybridizations, quantitative RT-PCR analyses and immunofluorescence microscopy. The experiments were performed in the recently described human cardiomyocytes progenitor cells (hCMPCs), which differentiate into fully functional cardiomyocytes upon stimulation with 5-azacytidine and transforming growth factor β1. Results and Conclusions Forced myocardin expression stimulated transcription of a surprisingly large repertoire of heart muscle-specific genes in hCMPCs but did not cause their differentiation into functional cardiomyocytes. Specifically, myocardin gene transfer did not stimulate the synthesis of several sarcomeric (regulatory) proteins and ion channel constituents. The heart and smooth muscle-enriched isoforms of myocardin stimulate equally well the transcription of many of their cardiomyocyte-specific and virtually all of their smooth muscle target genes. However, the heart muscle-enriched myocardin species is a much more potent transactivator of a subset of genes encoding mainly cardiomyocyte-specific myofibrillar components. This may explain the underestimation of myocardin's cardiomyogenic potential in previous studies utilizing the smooth muscle-enriched isoform of this cTF.
Project description:Background: Cardiac transcription factors are master regulators during heart development. Recently, some were shown to transdifferentiate noncardiac mesoderm cells and cardiac fibroblasts into cardiomyocytes. However, the individual roles of each transcription factors in activating cardiac gene program have not been elucidated. We examined cardiac-specific and genome-wide gene expression in fibroblasts induced with cardiac transcription factors Nkx2.5 (N), Tbx5 (T), Gata4 (G), Myocardin (M) alone or different combinations. Methodology/Principal Findings: We applied different combinations of human Nkx2.5 (N), Tbx5 (T), Gata4 (G) and Myocardin (M) lentiviruses into 10T1/2 fibroblasts. Immunostaining and quantitative reverse transcription polymerase chain reaction (qRT-PCR) showed that N, T, G or M alone did not induce expression of cardiac marker genes α-myosin heavy chain (αMHC) and cardiac troponin T (cTnT). Only T+M and T+G+M combinations induced αMHC and cTnT expression. Microarray-based gene ontology analysis revealed that T alone inhibited most genes involved in cardiac-related processes and activated genes involved in Wnt receptor signaling pathway and in aberrant processes. M alone inhibited genes involved in Wnt receptor signaling pathway and activated genes involved in cardiac-related processes and in aberrant processes. G alone inhibited genes involved in ectoderm development. T+G+M combination was the most effective activator of genes associated with cardiac-related processes including muscle cell differentiation, sarcomere, striated muscle contraction, regulation of heart contraction, and glucose metabolism and fatty acid oxidation (two significant forms of cardiomyocyte energy metabolism). And unlike T, M, G alone or T+M, T+G+M did not activate genes associated with aberrant processes. Conclusions: Tbx5, Gata4 and Myocardin play different roles in activating cardiac gene program and in avoiding aberrant gene program activation. The combination of T+G+M activated cardiac gene program and avoided aberrant gene program activation.