Smooth Muscle Cell Genome Browser: Enabling the Identification of Novel Serum Response Factor Target Genes

Lee

J Neurogastroenterol Motil

et al. 2015

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Background/Aims Smooth muscle cells (SMCs) characteristically express serum response factor (SRF), which regulates their development. The role of SRF in SMC plasticity in the pathophysiological conditions of gastrointestinal (GI) tract is less characterized. Methods We generated SMC-specific Srf knockout mice and characterized the prenatally lethal phenotype using ultrasound biomicroscopy and histological analysis. We used small bowel partial obstruction surgeries and primary cell culture using cell-specific enhanced green fluorescent protein (EGFP) mouse lines to study phenotypic and molecular changes of SMCs by immunofluorescence, Western blotting, and quantitative polymerase chain reaction. Finally we examined SRF change in human rectal prolapse tissue by immunofluorescence. Results Congenital SMC-specific Srf knockout mice died before birth and displayed severe GI and cardiac defects. Partial obstruction resulted in an overall increase in SRF protein expression. However, individual SMCs appeared to gradually lose SRF in the hypertrophic muscle. Cells expressing low levels of SRF also expressed low levels of platelet-derived growth factor receptor alpha (PDGFRα low ) and Ki67. SMCs grown in culture recaptured the phenotypic switch from differentiated SMCs to proliferative PDGFRα low cells. The immediate and dramatic reduction of Srf and Myh11 mRNA expression confirmed the phenotypic change. Human rectal prolapse tissue also demonstrated significant loss of SRF expression. Conclusions SRF expression in SMCs is essential for prenatal development of the GI tract and heart. Following partial obstruction, SMCs down-regulate SRF to transition into proliferative PDGFRα low cells that may represent a phenotype responsible for their plasticity. These findings demonstrate that SRF also plays a critical role in the remodeling process following GI injury.

Section: Discussionsupporting

confidence: 64%

Serum Response Factor Is Essential for Prenatal Gastrointestinal Smooth Muscle Development and Maintenance of Differentiated Phenotype

Lee

J Neurogastroenterol Motil

et al. 2015

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J Neurogastroenterol Motil

“…22,23 They express as many as 447 ion channel and transporter isoforms, indicating that SMC excitability is regulated by a complex coordinated effort of numerous ion channels and transporters. 10 Within the ion channel family, calcium channels were the most abundantly expressed in SMCs, 10 and the predominance of calcium channel expression is consistent with the current paradigm for excitation-contraction coupling, which is primarily regulated by Ca 2+ via calcium channels. 22 Many highly expressed and SMC-restricted ion channel isoforms and regulators such as Kcnmb1, Ryr3, Jph2, and Dmpk appear to be regulated by SRF.…”

Section: Smooth Muscle Cell Transcriptomesupporting

confidence: 65%

“…10 SMCs express 16 000 genes, which are transcribed into 55 000 transcriptional variants. The most highly expressed genes are related to muscular contraction.…”

Section: Smooth Muscle Cell Transcriptomementioning

confidence: 99%

“…Genome-wide SRF binding CArG boxes were mapped in mice 10 and humans. 6 A large number of CArG boxes (98 236) are conserved between the 2 species.…”

Section: Cargome and Serum Response Factor Binding Sitesmentioning

confidence: 99%

“…A smooth muscle genome and CArGome browser containing genome-wide CArG boxes alongside SMC transcriptome data has been built and available to search and identify new CArG-containing genes. 10 In addition to SRF-dependent protein-coding contractile mRNA genes, the SRF was recognized as an important regulator of many microRNA (miRNA) genes. 11 Many SRF-induced miRNA genes have been identified and they appear to be abun-dantly and predominantly expressed in SMCs.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Multi-phenotypic Role of Serum Response Factor in the Gastrointestinal System

2016

Self Cite

Serum response factor (SRF) is a master transcription factor of the actin cytoskeleton that binds to highly conserved CArG boxes located within the majority of smooth muscle cell (SMC)-restricted promoters/enhancers. Although most studies of SRF focus on skeletal muscle, cardiac muscle, and vascular SMCs, SRF research has recently expanded into the gastrointestinal (GI) system. Genome scale analyses of GI SMC transcriptome and CArG boxes (CArGome) have identified new SRF target genes. In addition to circular and longitudinal smooth muscle layers, SRF is also expressed in GI mucosa and cancers. In the GI tract, SRF is the central regulator of genes involved in apoptosis, dedifferentiation, proliferation, and migration of cells. Since SRF is the cell phenotypic modulator, it may play an essential role in the development of myopathy, hypertrophy, ulcers, gastric and colon cancers within the GI tract. Given the multifunctional role displayed by SRF in the digestive system, SRF has received more attention emerging as a potential therapeutic target. This review summarizes the findings in SRF research pertaining to the GI tract and provides valuable insight into future directions.

Actin‐related protein 5 suppresses the cooperative activation of cardiac gene transcription by myocardin and MEF2

Morita

Hayashi

2023

FEBS Open Bio

MYOCD is a transcription factor important for cardiac and smooth muscle development. We previously identified that actin‐related protein 5 (ARP5) binds to the N‐terminus of MYOCD. Here, we demonstrate that ARP5 inhibits the cooperative action of the cardiac‐specific isoform of MYOCD with MEF2. ARP5 overexpression in murine hearts induced cardiac hypertrophy and fibrosis, whereas ARP5 knockdown in P19CL6 cells significantly increased cardiac gene expression. ARP5 was found to bind to a MEF2‐binding motif of cardiac MYOCD and inhibit MEF2‐mediated transactivation by MYOCD. RNA‐seq analysis revealed 849 genes that are upregulated by MYOCD‐MEF2 and 650 genes that are repressed by ARP5. ARP5 expression increased with cardiomyopathy and was negatively correlated with the expression of Tnnt2 and Ttn, which were regulated by cardiac MYOCD‐MEF2. Overall, our data suggest that ARP5 is a potential suppressor of cardiac MYOCD during physiological and pathological processes.