Hedgehog Signaling in Photoreceptor Differentiation and Maintenance

描述（由申请人提供）：Hedgehog （Hh）蛋白家族在决定神经细胞命运和维持成体神经干细胞潜能方面发挥重要作用。先前的研究和我们的初步结果表明，Sonic hedgehog基因（Shh）促进视网膜祖细胞增殖并影响早期出生的视网膜神经元的特异性。然而，Hh信号在哺乳动物感光细胞发育和存活中的确切功能尚不清楚。本研究将使用分子遗传学方法来阐明Hh信号在小鼠光感受器发育和维持过程中的作用。利用转基因小鼠系和表达Cre重组酶的逆转录病毒进行Cre/loxP重组，可以消除Hh受体的基本成分Smoothened （Smo）。破坏Hh信号对出生后祖细胞增殖和细胞命运承诺的影响，以及对光受体分化和形态发生的影响将通过分子标记和电子显微镜进行分析。Hh信号在光感受器维持和存活中的作用将通过在成熟视网膜中切除Smo基因或Shh基因，然后进行功能和形态学分析来表征。本研究结果将阐明哺乳动物光感受器分化和生存过程中一个重要信号通路的功能。此外，这些研究将为光感受器变性的机制提供新的见解，并为开发新的治疗视网膜疾病的方法提供机会。

DESCRIPTION (provided by applicant): The Hedgehog (Hh) family of proteins plays important roles in the determination of neuronal cell fates and the maintenance of adult neural stem cell potentials. Previous studies and our preliminary results indicate that Sonic hedgehog (Shh) promotes retinal progenitor cell proliferation and affects specification of early born retinal neurons. However, the precise function of Hh signaling in mammalian photoreceptor cell development and survival is not well understood. The proposed research will use molecular genetic approaches to elucidate the roles of Hh signaling during mouse photoreceptor development and maintenance. The essential Hh receptor component Smoothened (Smo) will be eliminated by Cre/loxP recombination using transgenic mouse lines and retroviruses expressing Cre recombinase. The effects of disrupting Hh signaling on postnatal progenitor proliferation and cell fate commitment, and on photoreceptor differentiation and morphogenesis will be analyzed using molecular markers and electron microscopy. The roles of Hh signaling in photoreceptor maintenance and survival will be characterized by ablating the Smo gene or the Shh gene in the mature retina followed by functional and morphological analyses. Results of the proposed research will elucidate the function of an important signaling pathway in mammalian photoreceptor differentiation and survival. Moreover, these studies will provide new insights into mechanisms of photoreceptor degeneration and opportunities to develop novel therapies for combating retinal diseases. PUBLIC HEALTH RELEVANCE: The proposed research will study the influence of an important class of proteins called "hedgehog" on the formation and survival of photoreceptor cells, which undergo degeneration in various retinal diseases. The outcomes of these studies will enhance our abilities to protect photoreceptor cells and to direct the differentiation of neural stem cells towards functional photoreceptor cells for retinal disease therapy.