Exclusion and Coordination of Drosophila rhodopsin gene

描述(申请人提供)：在果蝇中，颜色视觉是由两个内部光感受器R7和R8实现的，这两个感光器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马赛克。在小眼中，R7含有UV-Rh3，而R8含有蓝色Rh5。在y ommatdia中，R7含有UV-Rh4，R8含有绿色-Rh6。这两个类以30：70的比例随机分布在视网膜中。这是在R7中做出的表达RH4和排除Rh3的随机决定的结果。在R8中的坐标表达允许形成专门区分较短(P)或较长(Y)波长的小眼。小眼位于背侧缘区(DRA)，专门探测偏振光的矢量。我们已经确定了在不同类别的光感受器中选择视紫红质的许多因素。在以下目标中，我们建议进一步研究调控无刺(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.幼虫眼和成虫脑小孔感光器选择的调节：幼虫眼含有两种类型的光感受器：4种表达蓝色-Rh5，8种表达绿色-Rh6，这与成年R8细胞的Rh5/Rh6比例相似。我们将对这两个系统中这些视紫红质的调节进行比较。在变态过程中，幼虫的眼睛变成视网膜外的小孔，其中包含四个绿色的Rh6光感受器。我们将研究蜕皮激素信号如何导致8个绿色-Rh6光感受器死亡，以及4个蓝色-Rh5光感受器反式决定绿色-Rh6。2.无刺基因随机表达的调控：我们将继续尝试了解ss转录是如何在R7细胞的一个子集中被激活的。我们将探索糖块抑制ss的可能性，从而可能是其随机激活的原因。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.特殊小眼的局部分布：我们还将分析ss的效应器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Rh3的抑制。我们还将研究它与控制两种小眼发育的iro-C基因的关系(DRA和一种新类型的HAT在眼睛背部的yr7中共同表达Rh3和Rh4)。4.筛选调控R7亚型的新基因。我们利用罗立群实验室提供的4000个FRT-PiggyBac插入系设计了一个遗传筛查。我们将为每个插入生成完整的突变眼，并将使用水浸荧光透视仪使用视紫红质绿色荧光蛋白报告程序直观地评估亚型比。这种不偏不倚的方法将使我们能够完成对导致视网膜马赛克形成的调控途径的理解。与公共健康相关：果蝇的眼睛已经成为一个非常强大的模型系统，可以了解不同类别的光感受器是如何发展形成视网膜马赛克的，而视网膜马赛克负责眼睛的功能：运动检测、暗光或色觉。我们提出继续我们的研究，让光感受器承担特定的命运，表达一种视紫红质光色素，并排除所有其他的。识别这些过程的调节因子将有助于更好地理解其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.