| Summary: | 博士 === 國立清華大學 === 生物資訊與結構生物研究所 === 101 === Cardiac chamber formation, including cardiac looping and valve formation, is a vital process involving the action of protease during embryonic heart development. Nevertheless, the regulation of these proteases during cardiac chamber formation is poorly understood. Previously, a novel vascular protease, PRSS23, is shown to be highly expressed at the heart during murine cardiac development. However, its functional role in vivo remains unclear to date. We thus aim to characterize the functional role of PRSS23 during cardiac development in this study.
To investigate the functional role of PRSS23 in cardiogenesis, we used a transgenic zebrafish line with fluorescent labeled vasculatures as the research system. Expression of prss23 was detected in the ventricle, atrium and atrioventricular (AV) canal during zebrafish embryonic development. We found morpholino knockdown of Prss23 caused severe cardiac defects as the developing heart failed to undergo loop formation, accompanied by the malformation of the atrioventricular canal. When zPrss23 DNA with mutative catalytic triad was co-injected with morpholino, the cardiac looping phenotype was rescued, but the valve formation was not. This data implied the malformation of AV canal was not caused by cardiac looping. Then we found morpholino knockdown of Prss23 repressed the cardiomyocyte proliferation during cardiac looping and inhibited the endothelial to mesenchymal transition (EndoMT) at the AV canal during the cardiac valve formation. Moreover, in human aortic endothelial cell-based assays, PRSS23 knockdown by shRNA not only repressed the TGF-β-induced EndoMT but also reduced Snail transcription suggesting Snail signaling is downstream of PRSS23 during EndoMT. We further demonstrated that human PRSS23 and SNAIL could rescue the prss23 morpholino-induced AV canal defect in zebrafish embryos, indicating PRSS23’s function in valvulogenesis is evolutionarily conserved.
We demonstrated for the first time that the initiation of EndoMT in valvulogenesis depends on PRSS23-Snail signaling, and the functional role of PRSS23 during AV valve formation is evolutionar
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