Late photoreceptor cell differentation in D melanogaster

这一提议的长期目标是了解分子和细胞机制，这些机制允许获得终端光感受器细胞(PR)的命运。果蝇PR‘s的形成是理解细胞类型决定和分化的一个范例。在幼虫阶段，一系列精确的顺序诱导过程导致在每个小眼里招募8个PR。然而，它们的最终分化，包括横纹肌的形态发生和视蛋白的表达，只有在蛹发育的三天后才完成。人们认为，在幼虫发育过程中，PR细胞的命运是不可逆转的，当每个PR表达一组特定的转录调节因子时。PI的初步研究表明，Spalt复合体基因是建立横纹肌形态和内侧PR的视蛋白表达所需的晚期基因，但不需要它们正确地投射到视叶。这些数据表明，在不同的基因调控下，PR的分化是一个两步过程。为了进一步了解末端分化过程中涉及的机制，提出了以下具体目标：通过分析(1)单个Spalt基因(Spalt main和Spalt相关)的功能丧失表型；(2)Spalt基因错误表达导致的功能获得表型，探讨Spalt基因在末端PR分化中的作用。(3)Spalt和OTD之间的遗传互作，另一个参与PR末端分化的基因，将被讨论。(4)SPALT下游靶点的确定将通过测试我们以前发现的在内部PR中表达的基因的作用来进行。决定视网膜细胞命运和分化的总体策略在脊椎动物和果蝇视网膜中是相同的，所使用的许多因素也是相同的。了解视网膜细胞如何适应其最终的细胞形态和结构，对于发育过程和许多人类视网膜疾病具有明显的意义。

The long-term goal of this proposal is to understand the molecular and cellular mechanisms, which allow the acquisition of the terminal photoreceptor cell (PR) fate. The formation of PR's in Drosophila melanogaster serves as a paradigm to understand cell type determination and differentiation. During larval stages, an exquisitely precise series of sequential inductive processes leads to the recruitment of eight PR's in each ommatidium. However, their final differentiation, including rhabdomere morphogenesis and opsin expression is only completed three days later during pupal development. It is thought that PR cell fate is irreversibly established during larval development, when each PR expresses a particular set of transcriptional regulators. The PI's preliminary studies show that spalt complex genes are required late for the establishment of rhabdomere morphology and opsin expression in inner PR's, but not for their correct projection to the optic lobe. These data indicate that PR differentiation occurs as a two-step process under different genetic regulation. The following specific aims are proposed to further understand the mechanisms involved in the terminal differentiation processes: The role of the spalt genes in terminal PR differentiation will be addressed by analyzing (1) the loss-of-function phenotype of individual spalt genes (spalt major and spalt related); (2) the gain-of-function phenotype induced by the misexpression of the spalt genes. (3) Genetic interactions between spalt and otd, another gene involved in terminal PR differentiation, will be addressed. (4) The identification of downstream targets of spalt will be carried out by testing the role of genes that we previously identified to be expressed in inner PR's. The overall strategy of retinal cell fate determination and differentiation is the same in vertebrate and Drosophila retina, as are many of the factors employed. The understanding of how retinal cells adopt their final cell shape and structures is of obvious significance to developmental processes and to many human retinal diseases.