Abstract 9025: Repression of Versican Expression by mir-143
Smooth muscle cells (SMCs) retain remarkable plasticity to undergo phenotypic modulation in which the expression of smooth muscle markers is markedly attenuated while conversely expression of extracellular matrix (ECM) is dramatically up-regulated. Myocardin is perhaps the most potent transcription factor for stimulating expression of smooth muscle-specific genes, little is known however, whether myocardin can orchestrate ECM expression to act in concert with smooth muscle differentiation program. In this study we demonstrated myocardin coordinates smooth muscle differentiation by inducing transcription of microRNA-143 (miR-143) which attenuates ECM versican protein expression. Previous studies have shown that versican is a chondroitin sulfate proteoglycan of the ECM that is produced by synthetic SMCs and promotes SMC migration and proliferation. Our data demonstrated that myocardin significantly represses versican expression in multiple cell lines. Furthermore, we found that this occurs through myocardin's induction of miR-143. By a modified reverse transcribed PCR we found miR-143 specifically binds to 3’ untranslated region (UTR) of versican mRNA. Reporter assays validated that miR-143 targets versican 3’UTR by binding to an evolutionarily conserved miR-143 binding site. Furthermore, over-expression of miR-143 significantly represses versican expression while conversely depletion of endogenous miR-143 results in up-regulation of versican expression. Finally, we demonstrated that myocardin represses versican through induction of miR-143. This study provides the first evidence that myocardin, in addition to activating smooth muscle-specific genes, regulates ECM expression through induction of microRNAs during smooth muscle differentiation.
- © 2010 by American Heart Association, Inc.