Exclusion and Coordination of Drosophila rhodopsin gene

描述（由申请人提供）：在果蝇中，色觉是由两个内部光感受器R7和R8实现的，它们表达不同的视紫红质，并比较它们在视叶髓质部分的输出。三种功能不同的小眼在视网膜上形成马赛克。在p ommatidia中，R7含有UV-Rh3，而R8含有blue-Rh5。R7中含有UV-Rh4， R8中含有green-Rh6。这两类以30:70的比例随机分布在视网膜上。这是R7随机决定表达rh4而排除rh3的结果。R8中的坐标表达允许形成专门识别较短(p)或较长(y)波长的光的小眼。位于背缘区域（DRA）的小孔体专门检测偏振光矢量。我们已经确定了许多有助于在各种类型的光感受器中选择视紫红质的因素。在接下来的目标中，我们建议进一步研究调节无脊柱（ss）表达的随机选择以及特定光感受器亚群的空间控制的机制。1. 幼虫眼和成虫眼的光感受器选择调控：幼虫眼包含两种类型的光感受器：四种表达蓝色Rh5，八种表达绿色Rh6，使人联想到成虫R8细胞中的Rh5:Rh6比例。我们将比较这两种系统对这些视紫红质的调控。在变态时，幼虫的眼睛变成含有四个绿色rh6光感受器的视网膜外小孔。我们将研究蜕皮激素信号传导如何导致8个绿色- rh6光感受器死亡，以及4个蓝色- rh5光感受器转化为绿色- rh6。2. 无棘随机表达的调控：我们将继续尝试了解R7细胞亚群中ss的转录是如何被激活的。我们将探索含片抑制ss的可能性，并可能因此负责其随机激活。我们将解剖ss启动子并确定控制其在视网膜中的表达的因素。3. 特化小眼的局部分布：我们还将分析ss的效应因子dve的功能，这是一个同源盒基因，似乎参与了表达ss的细胞中rh3的抑制。我们还将研究它与铁- c基因的关系，铁- c基因控制两种小眼亚型的发育（DRA和一种在眼背部分的yR7中共同表达rh3和Rh4的新型小眼）。4. FRT-piggyBac筛选筛选调节R7亚型规范的新基因我们利用罗立群实验室提供的4000个FRT-piggybac插入系设计了一个基因筛选。我们将为每次插入生成完整的突变眼，并使用水浸透视法使用视紫红质GFP报告器视觉评估亚型比例。这种不偏不倚的方法将使我们能够完成我们对导致视网膜马赛克形成的调控途径的理解。公共卫生相关性：果蝇的眼睛作为一个非常强大的模型系统来理解不同种类的光感受器是如何发育形成视网膜马赛克的，视网膜马赛克负责眼睛的功能：运动检测，昏暗的光或色觉。我们提出继续我们的调查事件，允许光感受器采取特定的命运，表达一种视紫红质光色素和排除所有其他。识别这些过程的调节因子将有助于更好地理解突变导致人类失明的基因。

DESCRIPTION (provided by applicant): In Drosophila, color vision is achieved by the two inner photoreceptors R7 and R8 which express different rhodopsins and compare their outputs in the medulla part of the optic lobe. Three classes of ommatidia with different functions form a mosaic in the retina. In p ommatidia, R7 contains the UV-Rh3 while R8 contains blue-Rh5. In y ommatidia, R7 contains UV-Rh4 and R8 green-Rh6. These two classes are randomly distributed in the retina with a 30:70 ratio. This results from a stochastic decision made in R7 to express rh4 and to exclude rh3. Coordinate expression in R8 allows the formation of ommatidia that specialize in the discrimination of shorter (p) or longer (y) wavelengths of light. Ommatidia located at the dorsal rim area (DRA) specialize in the detection of the vector of polarized light. We have identified many of the factors that contribute to the choice of rhodopsins in the various classes of photoreceptors. In the following aims, we propose to further investigate the mechanisms regulating the stochastic choice of spineless (ss) expression as well as the spatial control of specific subsets of photoreceptors. 1. Regulation of photoreceptor choice in the larval eye and adult brain eyelet: The larval eye contains two types of photoreceptors: four express blue-Rh5 while eight contain green-Rh6, reminiscent of the Rh5:Rh6 ratio in adult R8 cells. We will compare the regulation of these rhodopsins in these two systems. At metamorphosis, the larval eye becomes the extra-retinal eyelet that contains four green-Rh6 photoreceptors. We will investigate how Ecdysone signaling leads to the death of the eight green-Rh6 photoreceptors and to the trans-determination of the four blue-Rh5 photoreceptors into green-Rh6. 2. Regulation of the stochastic expression of spineless: We will pursue our attempts to understand how transcription of ss is activated in a subset of R7 cells. We will explore the possibility that lozenge represses ss and might thus be responsible for its stochastic activation. We will dissect the ss promoter and identify factors that control its expression in the retina. 3. Localized distribution of specialized ommatidia: We will also analyze the function of an effector of ss, dve, a homeobox gene that appears to be involved in the repression of rh3 in cells that express ss. We will also investigate its relationship to Iro-C genes that control the development of two subtypes of ommatidia (DRA and a novel type hat co-expresses Rh3 and Rh4 in yR7 in the dorsal part of the eye). 4. An FRT-piggyBac screen to identify novel genes regulating R7 subtype specification. We have devised a genetic screen using a collection of 4,000 FRT-piggybac insertion lines provided by the lab of Liqun Luo. We will generate whole mutant eyes for each insertion and will evaluate subtype ratio visually with rhodopsin GFP reporters using water immersion fluoroscopy. This unbiased approach will allow us to complete our understanding of the regulatory pathway that leads to the formation of the retinal mosaic. PUBLIC HEALTH RELEVANCE: The Drosophila eye has served as a very powerful model system to understand how different classes of photoreceptors develop to form the retinal mosaic that is responsible for the function of the eye: motion detection, dim light or color vision. We offer to pursue our investigations of the events that allow photoreceptors to take on specific fates, express one of the rhodopsin photopigments and exclude all others. The identification of regulators of these processes will lead to a better understanding of genes whose mutations cause blindness in humans.