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Smooth muscle phenotypic diversity is mediated through alterations in Myocardin gene splicing
Author(s) -
Ilagan Roger M.,
Genheimer Christopher W.,
Quinlan Sarah F.,
Guthrie Kelly I.,
Sangha Namrata,
Ramachandrannair Sajini,
Kelley Rusty W.,
Presnell Sharon C.,
Basu Joydeep,
Ludlow John W.
Publication year - 2011
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.22622
Subject(s) - myocardin , exon , biology , alternative splicing , rna splicing , gene , gene isoform , microbiology and biotechnology , phenotype , gene expression , genetics , serum response factor , rna
Myocardin (MYOCD) is a smooth and cardiac muscle‐specific transcriptional coactivator that is required for the proper expression of contraction‐related genes. Through its function to transactivate effector genes, MYOCD plays an essential role in mediating the switch between contractile and non‐contractile phenotypes, particularly in smooth muscle cells (SMC). There are at least two known transcript variants of MYOCD that are expressed in SMC, differing only by the presence (+) or absence (Δ) of Exon 11. To date, no functional role has been assigned to the domain encoded by Exon 11, nor have any notable differences between the ability of each isoform to activate contraction‐related genes been observed. In this study we compared sequences for Exon 11 among several mammalian species and identified a highly conserved, putative target sequence for glycogen synthase kinase 3 (GSK3) phosphorylation, suggesting a regulatory role for Exon 11 that can be modulated by alternative splicing. The function of Exon 11 was investigated by altering MYOCD splice selection in cultured porcine SMC with small interfering RNAs (siRNA) and specific chemical inhibitors, resulting in a relative increase in expression of ΔExon 11 variants in the endogenous pool of MYOCD mRNA. The relative increase in ΔExon 11 mRNAs correlated with a reduction of contractile phenotype in the porcine SMC as evidenced by morphological assessment and molecular analysis of effector genes. Together, these data suggest that MYOCD ΔExon 11 may participate in modulating SMC phenotype, potentially acting as a dominant‐negative repressor of contraction‐related genes. J. Cell. Physiol. 226: 2702–2711, 2011. © 2010 Wiley‐Liss, Inc.