Investigation of Mammalian Retinal Neuron Development

描述（由申请人提供）：哺乳动物视网膜的早期发育通过分子和细胞步骤进行，其中细胞退出有丝分裂细胞周期并最终分化为七种基本类型的神经元或神经胶质之一。这一过程的异常表现在不同的疾病中，包括视神经发育不全、先天性青光眼或视锥/视杆营养不良综合征。在设计治疗或疗法来缓解或治愈这些疾病之前，必须了解视网膜发育的主要生物机制。本研究拟采用胚胎学、遗传学、神经生物学、免疫组织化学和分子生物学等方法，探讨小鼠视网膜发育过程中碱性螺旋-环-螺旋（bHLH）蛋白的调控和功能。特别是Ath 5/ATOH 7基因（小鼠中的Math 5）是视网膜神经节细胞（RGC）特化和分化所需的一种这样的分子。Math 5-/-小鼠出生后完全缺乏RGCs和视神经，并表现出锥体光感受器和无长突神经元的增加。该提案的具体目标将研究Math 5在胚胎视网膜祖细胞中的功能如何影响这些细胞的有丝分裂细胞周期状态，特别是Math 5-/-细胞中的细胞周期进程是否异常。此外，我们建议通过用另一种促进双极命运的bHLH基因Mash 1靶向替换Math 5来测试Math 5视网膜祖细胞的多能性。在这个建议中，我们提出了初步的证据，反式作用因子和顺式作用的DNA序列，控制数学5在视网膜发育过程中的表达模式。我们的目标是在拟议的实验中进一步表征这种分子遗传途径。脊椎动物Ath 5基因促进所有测试的模式生物中的RGC形成，并且它们的果蝇对应物，无调促进蝇眼中的R8光感受器形成。然而，每个基因不编排这些规范过程相同，我们将测试是否分子遗传调控的数学5是保守的或不同的果蝇无调基因。这些研究将有助于深入了解视网膜神经元形成的基本生物学机制，从而最终揭开视网膜疾病的病因。

DESCRIPTION (provided by applicant): Early development of the mammalian retina proceeds through molecular and cellular steps in which cells exit the mitotic cell cycle and terminally differentiate into one of seven basic types of neurons or glia. Abnormalities in this process are manifested in different diseases, including optic nerve aplasia, congenital glaucoma or cone/rod dystrophic syndromes. Before treatments or therapies can be designed to alleviate or cure such conditions, the primary biologic mechanisms of retinal development must be learned. This proposal uses embryological, genetic, neurobiological, immunohistochemical, and molecular methods to explore the regulation and function of mouse basic helix-loop-helix (bHLH) proteins during mouse retinal development. In particular the Ath5/ATOH7 gene (Math5 in mice) is one such molecule that is required for retinal ganglion cell (RGC) specification and differentiation. Math5-/- mice completely lack RGCs and optic nerves postnatally and exhibit increases in both cone photoreceptor and amacrine neurons. The specific aims of this proposal will investigate how Math5 function in embryonic retinal progenitors affects the mitotic cell cycle state of these cells, specifically whether cell cycle progression is aberrant in Math5-/- cells. In addition we propose to test the multipotency of Math5 retinal progenitors by targeted replacement of Math5 with another bHLH gene that promotes bipolar fates, Mash1. In this proposal we present preliminary evidence for both trans-acting factors and cis-acting DNA sequences that control the expression pattern of Math5 during retinal development. We aim to further characterize this molecular genetic pathway in proposed experiments. Vertebrate Ath5 genes promote RGC formation in all tested model organisms and their Drosophila counterpart, atonal promotes R8 photoreceptor formation in the fly eye. However, each gene does not orchestrate these specification processes identically and we will test whether molecular genetic regulation of Math5 is conserved or divergent with that of the Drosophila atonal gene. The proposed studies will yield valuable insight into the basic biologic mechanisms of retinal neuron formation so that the causes of diseases of the retina will eventually be uncovered.