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）：为了实现真实的色觉，动物必须具有比较具有不同吸收波长的光感受器的输出的能力。果蝇的复眼由大约 800 个称为小眼的重复单元组成，每个小眼又分为 20 个特化细胞。其中八个细胞是吸收光所需的光感受器。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。这些与人类杆状细胞相似。果蝇眼睛中的两个内部光感受器（R7 和 R8）与人类视锥细胞相似，是色觉所必需的，并且位于同一光路中，其中 R7 位于近端 R8 细胞顶部的远端。它们含有不同的视紫红质感光色素，并且它们的输出在视叶的髓质部分进行比较，每个区域都投射它们的轴突。两种不同类别的小眼随机分布在整个果蝇视网膜中：在 70% 的小眼（黄色 (y) 小眼）中，R7 包含 UV-Rh4，而 R8 包含绿色-Rh6，专门用于区分较长波长的光。在剩下的 30% 苍白 (p) 小眼中，R7 含有紫外线敏感的 Rh3，而 R8 含有蓝色-Rh5，使这些小眼非常适合区分短波长的光。我们的实验室最近发现，当转录因子 Spineless 被激活时，位于远端的 R7 细胞会随机选择成为 y 或小眼。 70% 的 R7 在化蛹期间会发生这种情况，将它们指定为 yR7。剩余的 R7 默认变为 pR7，并随后指示其底层 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传导机制，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，Dpp 信号传导在 R7 中启动，通过激活素受体 Babo（在 R8 中）在非规范途径中发挥作用，从而确定 R8 的命运。然后 Babo 可能会与疣/熔化的双稳态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，这两条信号通路都没有经过充分检查，以确定在这一命运决定中是否具有额外或冗余的作用。由于亚型指定中可能涉及其他因素，我还将对 3000 多种已知和预测的膜相关分子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。这项工作将扩展我们对视网膜图案和细胞命运建立的知识，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 Activin 信号通路的了解，所有这些通路都在这里以非规范的方式使用。 ！ 公共健康相关性：果蝇小眼光感受器中特定视紫红质的独特表达对于正确辨别和处理视觉线索至关重要。内部感光细胞（R7 和 R8）分为两种亚型（苍白 (p) 和黄色 (y)），它们随机分布在复眼中，是色觉所必需的。该提案旨在表征 pR7 (Rh3) 或 yR7 (Rh4) 中起始的亚型特异性信号机制，这些机制分别需要指定 pR8 (Rh5) 或 yR8 (Rh6)。