Identification and characterization of SM-20, a novel growth factor-responsive gene in vascular smooth muscle.
Item
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Title
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Identification and characterization of SM-20, a novel growth factor-responsive gene in vascular smooth muscle.
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Identifier
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AAI9510732
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identifier
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9510732
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Creator
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Wax, Stephen Daniel.
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Contributor
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Adviser: Mark B. Taubman
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Date
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1994
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Molecular
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Abstract
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Vascular smooth muscle cell (VSMC) growth contributes to the pathogenesis of atherosclerosis, hypertension, restenosis following balloon angioplasty, and the neovascularization of solid tumors. To identify genes whose expression levels are regulated during VSMC growth, we utilized differential screening of a rat VSMC cDNA library. A novel gene, SM-20, was identified whose corresponding mRNA is approximately 3 kb. SM-20 mRNA was expressed in quiescent VSMC (baseline), and was rapidly increased 3-4 fold after one hour of treatment with the proliferative agonists serum and platelet-derived growth factor (PDGF), the hypertrophic agent angiotensin 11, and the vasodilatory agents forskolin and isoproterenol. mRNA levels rapidly returned to baseline by 3 hours. The induction of SM-20 by serum was not dependent on new protein synthesis, indicating that SM-20 is part of the immediate-early response to growth factor stimulation. Unlike other immediate-early genes studied in VSMC, SM-20 mRNA was not detected in fibroblast culture. Examination of SM-20 mRNA levels in adult rat tissues demonstrated high levels of expression in cardiac, skeletal, and smooth muscle-containing tissues, as well as the brain. Antibodies were raised against a 230 amino acid portion of the putative SM-20 peptide sequence expressed in E. coli. Western blot analysis of VSMC lysates revealed one major protein species that migrated with an apparent molecular weight that is consistent with the predicted value of 39.7 kD. Immunohistochemistry of the adult rat aorta revealed that SM-20 protein is present in medial smooth muscle cells, and was markedly elevated in the smooth muscle cells comprising the neointimal plaque formed after balloon injury. SM-20 protein was not detected in the adventitial fibroblasts or in the endothelium. Immunostaining of human atherosclerotic coronary arteries demonstrated a similar pattern of SM-20 expression as seen in the rat model. Immunostaining of C2C12 myoblast cultures revealed that SM-20 is markedly induced following myogenic differentiation. SM-20 is a novel tissue-specific gene that may play a critical role in VSMC growth as well as myogenic differentiation.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
