Genetics of the photoreceptor cell specification

描述（由申请人提供）：在突变斑马鱼的遗传筛选中分离出lot-of-杆状体（lorp25bbtl）突变体，以改变幼虫视网膜中的杆状体模式。lorp25bbtl突变体显示出杆状细胞数量的增加和紫外线锥状细胞数量的减少，可能是由于细胞命运的改变。这种表型与Nri基因敲除小鼠表现出的相反，Nri基因敲除小鼠表现出短波长敏感锥细胞（S锥细胞）数量增加和杆状细胞数量减少。突变体的初步表征表明，lorp25bbtl是转录因子tbx2b的一个次胚等位基因，并在光受体命运决定中起细胞自主作用。该应用程序提出了分子研究，以揭示tbx2b在光感受器发育中的具体功能。会议将讨论以下主题：tbx2b是光感受器基因的直接转录调节因子吗？为了回答这个问题，将在培养细胞中进行报告基因测定，以评估tbx2b与其他视网膜转录因子在各种光感受器启动子中的转录调节作用。2. 利用lorp25bbtl的uv锥缺失表型，并鉴定uv锥特异性基因，将进行一项比较lorp25bbtl和WT成人视网膜基因表达谱的微阵列实验。公共卫生相关性：遗传性疾病是发达国家致盲的主要原因之一。在美国，估计有8 000万人患有可能致盲的眼病，130万人在法律上是盲人（国家卫生统计中心，1996年）。鉴于视觉系统疾病的重要性，在斑马鱼中识别可能与人类疾病（如光感受器发育或视网膜营养不良）有关的基因的直接好处是显而易见的。先前对lorp25bbtl突变体的表征表明，其遗传途径与人类s锥增强综合征的影响直接相反。我相信，研究lorp25bbtl中受影响的基因tbx2b及其在视网膜发育中的作用，将有助于解剖这种人类综合征中受影响的发育途径，并最终增加我们对视网膜发育和生理学的理解。

DESCRIPTION (provided by applicant): The lot-of-rods (lorp25bbtl) mutant was isolated in a genetic screen of mutagenized zebrafish for changes in rod patterning in the larval retina. lorp25bbtl mutants display an increase in the number of rods and a reduction in the number of UV cones, likely due to a cell fate change. This phenotype is the opposite of that exhibited by the Nri knockout mice, which demonstrate an increase in the number of short-wavelength- sensitive cones (S cones) and a reduced number of rods. Initial characterization of the mutant shows that lorp25bbtl is a hypomorphic allele of the transcription factor tbx2b, and acts cell-autonomously in photoreceptor fate determination. This application proposes molecular studies to uncover the specific functions of tbx2b in photoreceptor development. The following topics will be addressed: 1. Is tbx2b a direct transcriptional regulator of photoreceptor genes? To answer this question a reporter gene assay in cultured cells will be performed to evaluate transcriptional modulation by tbx2b in conjunction with other retinal transcription factors in various photoreceptor promoters. 2. Taking advantage of the UV-cone depleted phenotype in lorp25bbtl and to identify UV-cone specific genes, a microarray experiment comparing the gene expression profile of lorp25bbtl and WT adult retinas will be performed. Public Health Relevance: Heritable diseases are among the leading causes of blindness in developed countries. In the United States, an estimated 80 million people suffer potentially blinding eye disease and 1.3 million people are legally blind (National Center for Health Statistics, 1996). Given the importance of visual system diseases, the direct benefits of identifying genes in zebrafish that may be involved in human disease like photoreceptor development or retinal dystrophies are obvious. Previous characterization of the lorp25bbtl mutant suggested a genetic pathway that directly contrasts that affected in the human Enhanced-S-cone Syndrome. I believe that studying tbx2b, the gene affected in lorp25bbtl, and its role in retinal development will help to dissect the developmental pathway affected in this human syndrome and ultimately will increase our understanding of retinal development and physiology.