The role of microRNA in the cell fate specification of photoreceptors

 描述(由申请人提供)：产生不同的神经元亚型是形成功能神经系统的先决条件。例如，哺乳动物视网膜中视杆细胞和视锥细胞的三种亚型的产生对于接收环境光信号是必不可少的。光感受器细胞命运的异常经常与视网膜先天性和退行性疾病有关，近几十年的研究已经发现了许多光感受器细胞命运的决定基因。这些基因的突变通常与视网膜发育障碍和疾病有关。然而，这些基因如何指定不同的光感受器亚型以及它们如何被调控的分子机制仍然不完整。这项提议的重点是了解调控机制，这些机制决定了利用果蝇黑腹果蝇在两个光感受器细胞命运之间进行相互排斥的二元选择。决定哺乳动物和苍蝇之间光感受器细胞命运的调控基因的保守性是显着的。在哺乳动物中，视杆或视锥的选择是由视锥-视杆同源盒(CRX)蛋白和神经视网膜特异性亮氨酸拉链(NRL)蛋白之间的相互作用决定的。这些基因的同源基因OTD和TJ调节特定的光感受器在表达两种光色素之一--视紫红质5(Rh5)或视紫红质6(Rh6)--之间的选择。我们最近的研究表明，在果蝇的光感受器中，这些基因的功能受到河马信号通路的调节，河马信号通路也被证明在调节哺乳动物和果蝇的细胞分裂和器官生长方面高度保守。我们的初步研究强烈表明，多个microRNAs也参与了这种光感受器亚型的指定。MicroRNAs已经被证明在各种发育和疾病过程中发挥着重要的调节作用，但它们在光感受器亚型命运指定中的作用仍不清楚。在这个提案中，我们将使用遗传学和分子方法来阐明这些microRNAs如何通过调节保守的命运决定基因和光色素基因来指定光感受器亚型的命运。此外，我们还将研究新发现的Hippo信号通路如何调控这些microRNAs的生物发生。这些研究将提供神经元亚型命运指定的新的分子机制，有助于理解各种发育障碍的基础，并可能有助于设计将人类多能细胞定向分化为特定细胞类型的策略，以取代变性神经元组织中受损的细胞。

 DESCRIPTION (provided by applicant): Generation of distinct neuronal subtypes is a prerequisite for formation of a functional nervous system. For example, generation of rods and the three subtypes of cone cells in the mammalian retina are essential for receiving environmental light cues. Abnormal photoreceptor cell fate specification is frequently associated with retinal congenital and degenerative diseases and studies in the last decades have identified numerous photoreceptor cell fate determinant genes. Mutations in these genes are often linked to retinal developmental disorders and diseases. However, the molecular mechanisms underlying how these genes specify distinct photoreceptor subtypes and how they are regulated remains incomplete. This proposal is focused on understanding the regulatory mechanisms that determine a mutually exclusive binary choice between two photoreceptor cell fates using the fruit fly, Drosophila melanogaster. The conservation of the regulatory genes determining cell fate of photoreceptors between mammals and flies is remarkable. In mammals the choice between rods or cones is determined by the interplay between the cone-rod homeobox (Crx) protein and the neural retina-specific leucine zipper (NRL) protein. The Drosophila orthologues of these genes, Otd and Tj, regulate the choice of a specific photoreceptor between expressing one of two photo-pigments, rhodopsin 5 (Rh5) or rhodopsin 6 (Rh6). Our recent studies revealed that in Drosophila photoreceptors, the function of these genes is regulated by the Hippo signaling pathway, a signaling system that has also been shown to be highly conserved in regulating cell division and organ growth in both mammals and flies. Our preliminary studies have strongly suggested that multiple microRNAs are also involved in this photoreceptor subtype specification. microRNAs have been illustrated playing important regulatory roles in various developmental and disease processes, but their role in photoreceptor subtype fate specification is still unknown. In this proposal, we will use genetic and molecular approaches to elucidate how these microRNAs specify photoreceptor subtype fates by regulating conserved fate determinant genes and the photo-pigment genes. In addition, we will investigate how the biogenesis of these microRNAs is regulated by the newly identified Hippo signaling pathway. These studies will provide novel molecular mechanisms underlying neuronal subtype fate specification that will help understand the basis for a variety of developmental disorders and potentially aid in the design of strategies for directed differentiation of human pluripotent cells into specific cell types to replace the damaged cells in degenerative neuronal tissues.