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Tra2beta as a novel mediator of vascular smooth muscle diversification.

ABSTRACT: Transformer splicing regulatory proteins determine the sexually dimorphic traits of Drosophila. The role of the vertebrate homologs of Tra-2 in phenotypic specification is undefined. We are using the alternative splicing of the MYPT1 E23 exon as a model for the study of smooth muscle diversification into fast and slow contractile phenotypes. Tra2beta mRNA and protein is expressed at up to 10-fold higher levels in fast smooth muscle tissues such as the rat portal vein and small mesenteric artery, in which E23 is spliced, as compared to the slow smooth muscle tissues of the large arteries and veins, in which E23 is skipped. Tra2beta is upregulated up to 10-fold concordant with the initiation of E23 splicing as the rat portal vein and avian gizzard implement the fast program of gene expression in the perinatal period. In disease models such as portal hypertension and mesenteric artery high/low flow, the portal vein and first order mesenteric artery dynamically downregulate Tra2beta concordant with a shift to E23 skipping and the slow program of gene expression. Tra2beta binds to a highly conserved sequence within E23 and transactivates its splicing in vitro and in vivo; this is abolished with mutation or deletion of this sequence. RNA interference-mediated knockdown of Tra2beta markedly reduces E23 splicing. We propose that Tra2beta has been conserved through evolution and redeployed for the specification of the fast smooth muscle phenotype and may serve as a novel nodal point for the investigation of this process in developmental and disease models.

SUBMITTER: Shukla S

PROVIDER: S-EPMC2737447 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Tra2beta as a novel mediator of vascular smooth muscle diversification.

Shukla Supriya S Fisher Steven A SA

Circulation research 20080731 5

Transformer splicing regulatory proteins determine the sexually dimorphic traits of Drosophila. The role of the vertebrate homologs of Tra-2 in phenotypic specification is undefined. We are using the alternative splicing of the MYPT1 E23 exon as a model for the study of smooth muscle diversification into fast and slow contractile phenotypes. Tra2beta mRNA and protein is expressed at up to 10-fold higher levels in fast smooth muscle tissues such as the rat portal vein and small mesenteric artery, ...[more]

PMID: 18669920

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Project description:Mitochondria are widely described as being highly dynamic and adaptable organelles, and their movement is thought to be vital for cell function. Yet, in various native cells, including those of heart and smooth muscle, mitochondria are stationary and rigidly structured. The significance of the differences in mitochondrial behavior to the physiological function of cells is unclear and was studied in single myocytes and intact resistance-sized cerebral arteries. We hypothesized that mitochondrial dynamics is controlled by the proliferative status of the cells.High-speed fluorescence imaging of mitochondria in live vascular smooth muscle cells shows that the organelle undergoes significant reorganization as cells become proliferative. In nonproliferative cells, mitochondria are individual (? 2 ?m by 0.5 ?m), stationary, randomly dispersed, fixed structures. However, on entering the proliferative state, mitochondria take on a more diverse architecture and become small spheres, short rod-shaped structures, long filamentous entities, and networks. When cells proliferate, mitochondria also continuously move and change shape. In the intact pressurized resistance artery, mitochondria are largely immobile structures, except in a small number of cells in which motility occurred. When proliferation of smooth muscle was encouraged in the intact resistance artery, in organ culture, the majority of mitochondria became motile and the majority of smooth muscle cells contained moving mitochondria. Significantly, restriction of mitochondrial motility using the fission blocker mitochondrial division inhibitor prevented vascular smooth muscle proliferation in both single cells and the intact resistance artery.These results show that mitochondria are adaptable and exist in intact tissue as both stationary and highly dynamic entities. This mitochondrial plasticity is an essential mechanism for the development of smooth muscle proliferation and therefore presents a novel therapeutic target against vascular disease.

Dataset Information

Tra2beta as a novel mediator of vascular smooth muscle diversification.

Publications

Tra2beta as a novel mediator of vascular smooth muscle diversification.

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