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。三种不同功能的小眼在视网膜上形成一个镶嵌体。在小眼藓中，R7含有UV-Rh 3，而R8含有蓝-Rh 5。在yommatidia中，R7含有UV-Rh 4和R8 green-Rh 6。这两类以30：70的比例随机分布在视网膜中。这是由R7中表达rh 4并排除rh 3的随机决定导致的。R8中的坐标表达允许小眼的形成，其专门用于区分较短（p）或较长（y）波长的光。位于背缘区的小眼（Ommatidia）专门探测偏振光矢量。我们已经确定了许多因素，有助于选择视紫红质的各种类别的光感受器。在以下目标中，我们建议进一步研究调节无刺（ss）表达随机选择以及光感受器特定子集的空间控制的机制。1.幼虫眼睛和成年大脑中感光细胞选择的调节：幼虫眼睛包含两种类型的感光细胞：四种表达蓝色-Rh 5，而八种包含绿色-Rh 6，让人想起成年R8细胞中的Rh 5：Rh 6比例。我们将比较这两个系统中这些视紫红质的调节。在变态时，幼虫的眼睛变成了视网膜外的视网膜，其中包含四个绿色的Rh 6光感受器。我们将研究蜕皮激素信号如何导致八个绿色Rh 6光感受器的死亡和四个蓝色Rh 5光感受器到绿色Rh 6的反式决定。2.无刺的随机表达的调节：我们将继续我们的尝试，以了解如何在R7细胞的一个子集中激活ss的转录。我们将探讨含片抑制ss的可能性，并因此可能负责其随机激活。我们将剖析ss启动子，并确定控制其在视网膜中表达的因素。3.特化小眼的局部分布：我们还将分析ss效应子dve的功能，dve是一种同源框基因，似乎参与了表达ss的细胞中rh 3的抑制。我们还将研究其与Iro-C基因的关系，Iro-C基因控制小眼的两种亚型的发育（小眼和一种新的类型，在眼睛的背侧部分的yR 7中共表达Rh 3和Rh 4）。4. FRT-piggyBac筛选以鉴定调节R7亚型特化的新基因。我们利用由罗立群实验室提供的4,000个FRT-piggybac插入系设计了一个遗传筛选。我们将为每个插入产生完整的突变体眼睛，并将使用水浸荧光镜检查用视紫红质GFP报告基因目视评估亚型比率。这种无偏见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：果蝇的眼睛是一个非常强大的模型系统，可以用来理解不同种类的光感受器如何发育形成视网膜马赛克，视网膜马赛克负责眼睛的功能：运动检测，昏暗的光线或彩色视觉。我们提出继续研究让光感受器承担特定命运的事件，表达一种视紫红质色素，排除所有其他色素。这些过程的调节因子的鉴定将导致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.