TGF-beta superfamily members do not promote smooth muscle-specific alternative splicing, a late marker of vascular smooth muscle cell differentiation.
Smooth muscle (SM) specific alternate splicing of a number of genes is a late marker of the differentiated vascular smooth muscle cell (VSMC) phenotype and is one of the first differentiation characteristics to be lost during de-differentiation and in disease. An understanding of how this aspect of VSMC phenotype is regulated may provide insights into the earliest events of the atherosclerotic process. TGF-beta1 is a potent regulator of VSMC differentiation and can induce expression of SM-specific contractile proteins in both pluripotent stem cells and de-differentiated VSMCs. The purpose of this study was to test the hypothesis that members of the TGFbeta-superfamily can also effect SM-specific alternative splicing. Firstly, we established that SM-specific splicing of alpha-tropomyosin, vinculin and SM-myosin heavy chain (MHC) increases during rat fetal/neonatal development and is decreased in VSMCs following balloon-induced carotid injury in the rat. Treatment of cultured rat VSMCs with TGFbeta-superfamily members resulted in a significant reduction in the ratio of SM to non-muscle (NM) alpha-tropomyosin, but did not effect SM-specific alternative splicing of vinculin or SM-MHC. Treatment of pluripotent C3H10T1/2 cells with TGF-beta1, which increased SM differentiation marker expression, did not increase SM-specific alpha-tropomyosin splicing. Taken together, these results demonstrate differential regulation of SM-specific alternative splicing and indicate that although TGF-beta1 promotes VSMC differentiation marker expression, TGF-beta1 cannot act as the sole trigger of VSMC differentiation.
King-Briggs
K E
KE
Department of Medicine, Cambridge University, Addenbrooke's Hospital, UK.
Shanahan
C M
CM
D017398:Alternative Splicing / Q000187:drug effects* / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn; D015415:Biomarkers; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002404:Catheterization / Q000009:adverse effects; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D002478:Cells, Cultured; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects* / Q000293:injuries / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000235:genetics; D009928:Organ Specificity; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D051381:Rats; D011921:Rats, Inbred WKY; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D014335:Tropomyosin / Q000235:genetics; D016596:Vinculin / Q000235:genetics
D015415:Biomarkers; D019485:Bone Morphogenetic Proteins; D012333:RNA, Messenger; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014335:Tropomyosin; D016596:Vinculin; D018995:Myosin Heavy Chains