Myocardin regulates expression of contractile genes in smooth muscle cells and is required for closure of the ductus arteriosus in mice
Jianhe Huang, … , Jonathan A. Epstein, Michael S. Parmacek
Jianhe Huang, … , Jonathan A. Epstein, Michael S. Parmacek
Published January 10, 2008
Citation Information: J Clin Invest. 2008;118(2):515-525. https://doi.org/10.1172/JCI33304.
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Myocardin regulates expression of contractile genes in smooth muscle cells and is required for closure of the ductus arteriosus in mice

Abstract

Myocardin (Myocd) is a potent transcriptional coactivator that has been implicated in cardiovascular development and adaptation of the cardiovascular system to hemodynamic stress. To determine the function of myocardin in the developing cardiovascular system, MyocdF/F/Wnt1-Cre+ and MyocdF/F/Pax3-Cre+ mice were generated in which the myocardin gene was selectively ablated in neural crest–derived SMCs populating the cardiac outflow tract and great arteries. Both MyocdF/F/Wnt1-Cre+ and MyocdF/F/Pax3-Cre+ mutant mice survived to birth, but died prior to postnatal day 3 from patent ductus arteriosus (PDA). Neural crest–derived SMCs populating the ductus arteriosus (DA) and great arteries exhibited a cell autonomous block in expression of myocardin-regulated genes encoding SMC-restricted contractile proteins. Moreover, Myocd-deficient vascular SMCs populating the DA exhibited ultrastructural features generally associated with the SMC synthetic, rather than contractile, phenotype. Consistent with these findings, ablation of the Myocd gene in primary aortic SMCs harvested from Myocd conditional mutant mice caused a dramatic decrease in SMC contractile protein expression. Taken together, these data demonstrate that myocardin regulates expression of genes required for the contractile phenotype in neural crest–derived SMCs and provide new insights into the molecular and genetic programs that may underlie PDA.

Authors

Jianhe Huang, Lan Cheng, Jian Li, Mary Chen, Deying Zhou, Min Min Lu, Aaron Proweller, Jonathan A. Epstein, Michael S. Parmacek

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Figure 6

Ultrastructural changes in vascular SMCs populating the DA of MyocdF/F/Wnt1-Cre+ mutant mice.

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Ultrastructural changes in vascular SMCs populating the DA of MyocdF/F/W...
The DA of P2 MyocdF/F control (A, C, E, and G) and MyocdF/F/Wnt1-Cre+ mutant (B, D, F, and H) mice (n = 3 of each) were isolated, fixed, stained, and analyzed by electron microscopic analyses. (A and B) Low-power view demonstrating luminal occlusion of the DA in a control mouse (A), but widely PDA in the MyocdF/F/Wnt1-Cre+ mutant mouse (E). Original magnification, ×500. (C) The tunica media of the DA in control mice exhibits regular circumferential organization with typical spindle-like morphology of SMCs. (D) By contrast, there is a loss of SMC mass with marked variability in SMC size and morphology as well as a concomitant increase in ECM in the mutant DA. Original magnification, ×25,000. (E) SMC morphology and ultrastructure in control MyocdF/F DA demonstrating abundant myofibrils. Original magnification, ×25,000. (F) SMC morphology and ultrastructure in MyocdF/F/Wnt1-Cre+ mutant DA. There is a marked decrease in myofibrils (large arrows) and a concomitant increase in synthetic organelles including rough endoplasmic reticulum (small arrows). Original magnification, ×100,000. (G and H) Comparison of SMC morphology in control (G) and mutant (H) DA demonstrating a relative increase in organelles associated with synthetic functions, including rough endoplasmic reticulum (arrows) and vacuoles (V) in MyocdF/F/Wnt1-Cre+ mutant SMC (H) compared with the control SMC (G). m, mitochondria; n, nucleus. Original magnification, ×100,000.