Characterizing the R8 cell subtype fate in Drosophila

果蝇 R8 细胞亚型命运的表征

• 批准号: 8398420
• 负责人: Brent S Wells
• 金额: $ 5.39万
• 依托单位: NEW YORK UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-18 至 2015-09-17
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8398420
• 关键词: Activin Receptor; Activins; Alleles; Animals; Axon; Candidate Disease Gene; Cell Communication; Cells; Color; Color Visions; Cues; Detection; Developmental Process; Discrimination; Drosophila eye; Drosophila genus; Event; Eye; Eye Development; Feedback; Gene Expression; Genes; Genetic Epistasis; Human; Insecta; Japan; Knowledge; Libraries; Ligands; Light; Maintenance; Mammals; Mediating; Membrane; Molecular; Molecular Profiling; Motion; Opsin; Optic Lobe; Optics; Output; Papio; Pathway interactions; Pattern; Phenotype; Photoreceptors; Proteins; RNA; RNA Interference; Reporter; Retina; Retinal; Retinal Cone; Rhodopsin; Role; Signal Pathway; Signal Transduction; Signaling Molecule; Specific qualifier value; Techniques; Testing; To specify; Transgenes; Tumor Suppressor Proteins; UV sensitive; Vision; Work; absorption; base; cell fate specification; cell type; compound eye; design; fly; gain of function; genetic analysis; knock-down; loss of function; melting; member; receptor; retinal rods; transcription factor; visual process; visual processing

DESCRIPTION (provided by applicant): In order to achieve true color vision, animals must have the ability to compare the outputs of photoreceptors with different wavelengths of absorption. The compound eye of Drosophila is made up of approximately 800 repeating units called ommatidia and each ommatidia is sub-divided into 20 specialized cells. Eight of these cells are photoreceptors required for absorbing light. The six outer photoreceptors (R1-R6) express the wide- spectrum rhodopsin Rh1 and are required for motion detection. These are similar to human rod cells. The two inner photoreceptors in the Drosophila eye (R7 and R8), which are similar to human cone cells, are required for color vision and lie in the same optic path where R7 sits distally on top of the proximal R8 cell. They contain distinct rhodopsin photopigments and their outputs are compared in the medulla part of the optic lobe where each projects their axons. Two distinct classes of ommatidia are stochastically distributed throughout the fly retina: In 70% of ommatidia (yellow (y) ommatidia), R7 contains UV-Rh4 while R8 contains green-Rh6, specializing them to discriminate longer wavelengths of light. In the remaining 30% pale (p) ommatidia, R7 contains UV-sensitive Rh3 while R8 contains blue-Rh5 making these ommatidia well adapted to discriminate among short wavelengths of light. Our lab has recently found that the stochastic choice to become a y or p ommatidium is made in the distally located R7 cell, when the transcription factor Spineless is activated. This occurs in 70% of R7 during pupation, specifying them as yR7. The remaining R7 become pR7 by default and subsequently instruct their underlying R8 to become pR8. Here I propose three aims designed to uncover the signaling mechanism required for R8 subtype specification, which leads to robust expression of Rh5 in pR8 and Rh6 in yR8. Recent work in our lab has suggested a role for Dpp signaling, initiated in R7, through the Activin receptor, Babo (in R8) in a non-canonical pathway to establish R8 fate. Babo may then interact with the warts/melted bi-stable loop to maintain this fate. I will examine the entire Dpp and Activin signaling pathways, neither of which have been fully examined for additional or redundant roles in this fate decision. As there are likely additional factors involved in subtype specification, I will also conduct an RNAi-based screen of over 3000 known and predicted membrane- associated and signaling molecules as well as perform subtype expression profiling of p and y R7 and R8 cells using RNAseq techniques. This work will expand our knowledge of retinal patterning and cell fate establishment, specifically following a stochastic decision. It will also add to our knowledge of the Hippo tumor suppressor pathway as well as Dpp and Activin signaling pathways, all of which are utilized in non-canonical ways here. ! PUBLIC HEALTH RELEVANCE: The exclusive expression of specific rhodopsins in the photoreceptors of the Drosophila ommatidia is crucial for correct discrimination and processing of visual cues. The inner photoreceptors (R7 and R8) are divided into two subtypes (pale (p) and yellow (y)), which are stochastically distributed across the compound eye and required for color vision. This proposal aims to characterize the subtype-specific signaling mechanisms initiating in pR7 (Rh3) or yR7 (Rh4) that are required to specify pR8 (Rh5) or yR8 (Rh6) respectively.

描述（由申请人提供）：为了实现真正的彩色视觉，动物必须具有比较不同波长吸收光感受器输出的能力。果蝇的复眼由大约800个被称为小眼的重复单位组成，每个小眼又被细分为20个专门的细胞。其中8个细胞是吸收光所需的感光细胞。六个外部光感受器（R1-R6）表达广谱视紫红质Rh1，是运动检测所必需的。这些细胞类似于人类的杆状细胞。果蝇眼睛内的两个感光细胞（R7和R8）类似于人类的视锥细胞，它们是色觉所必需的，并且位于相同的视觉路径上，R7位于近端R8细胞的上部。它们含有不同的视紫红质光色素，它们的输出在视叶的髓质部分进行比较，在那里它们各自投射轴突。两种不同的小眼细胞随机分布在整个果蝇视网膜上：在70%的小眼细胞（黄色(y)小眼细胞）中，R7含有UV-Rh4，而R8含有绿色- rh6，它们专门用于识别波长更长的光。在其余30%的淡色(p)小眼中，R7含有对紫外线敏感的Rh3，而R8含有蓝- rh5，使这些小眼能够很好地识别短波长的光。我们的实验室最近发现，当转录因子Spineless被激活时，在远端R7细胞中随机选择成为y或p小体。在化蛹期间，70%的R7发生这种情况，将它们指定为yR7。其余的R7默认变为pR7，随后指示其底层R8变为pR8。在这里，我提出了三个目标，旨在揭示R8亚型规范所需的信号机制，从而导致pR8中Rh5和yR8中Rh6的稳健表达。我们实验室最近的工作表明，在R7中启动的Dpp信号通过激活素受体Babo（在R8中）在非规范途径中起作用，以确定R8的命运。Babo可能会与疣/融化的双稳态循环相互作用，以维持这种命运。我将检查整个Dpp和激活素信号通路，它们都没有完全检查在这个命运决定中额外或多余的作用。由于可能还有其他因素参与亚型规范，我还将对超过3000种已知和预测的膜相关和信号分子进行基于rnai的筛选，并使用RNAseq技术对p和y R7和R8细胞进行亚型表达谱分析。这项工作将扩大我们对视网膜模式和细胞命运建立的认识，特别是在随机决定之后。它还将增加我们对Hippo肿瘤抑制通路以及Dpp和激活素信号通路的了解，所有这些都以非规范的方式在这里被利用。！