Molecular mechanisms of decreased smooth muscle differentiation marker expression after vascular injury.
While it is well established that phenotypic modulation of vascular smooth muscle cells (VSMCs) contributes to the development and progression of vascular lesions, little is known regarding the molecular mechanisms of phenotypic modulation in vivo. Here we show that vascular injury reduces transcription of VSMC differentiation marker genes, and we identify cis regulatory elements that may mediate this decrease. Using a carotid wire-injury model in mice carrying transgenes for smooth muscle alpha-actin, smooth muscle myosin heavy chain, or a SM22alpha promoter-beta-gal reporter, we collected arteries 7 and 14 days after injury and assessed changes in endogenous protein and mRNA levels and in beta-gal activity. Endogenous levels for all markers were decreased 7 days after injury and returned to nearly control levels by 14 days. beta-gal staining in all lines followed a similar pattern, suggesting that transcriptional downregulation contributed to the injury-induced decreases. To begin to dissect this response, we mutated a putative G/C-rich repressor in the SM22alpha promoter transgene and found that this mutation significantly attenuated injury-induced downregulation. Hence, transcriptional downregulation contributes to injury-induced decreases in VSMC differentiation markers, an effect that may be partially mediated through a G/C-rich repressor element.
Regan
C P
CP
Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA.
Adam
P J
PJ
Madsen
C S
CS
Owens
G K
GK
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D015415:Biomarkers; D002454:Cell Differentiation; D017931:DNA Primers / Q000235:genetics; D015870:Gene Expression; D017930:Genes, Reporter; D017403:In Situ Hybridization; D007763:Lac Operon; D051379:Mice; D008822:Mice, Transgenic; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000293:injuries* / Q000378:metabolism* / Q000473:pathology; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics
D000199:Actins; D015415:Biomarkers; D017931:DNA Primers; D008840:Microfilament Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C058992:Tagln protein, mouse; C051615:transgelin; D001616:beta-Galactosidase; D018995:Myosin Heavy Chains