Cell Recognition in the developing Drosophila Brain

果蝇大脑发育中的细胞识别

• 批准号: 7742980
• 负责人: S. Lawrence Zipursky
• 金额: $ 30.54万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-12-08 至 2013-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7742980
• 关键词: Address; Alleles; Alternative Splicing; Amacrine Cells; Amino Acid Sequence; Animals; Axon; Behavior; Binding; Biochemical; Biological Assay; Brain; Cells; Complementary DNA; Data; Development; Down Syndrome; Drosophila genus; Etiology; Exhibits; Exons; Extracellular Domain; Family; Genes; Genetic; Genomics; Goals; Homozygote; Human; Immunoglobulins; Knock-in Mouse; Link; Location; Mammals; Mediating; Membrane; Mental Retardation; Mus; Neurites; Neurons; Pattern; Play; Population; Process; Property; Protein Isoforms; Proteins; RNA; Reporter; Role; Structure; Syndrome; Technology; Testing; base; cell type; dosage; fly; genetic analysis; homologous recombination; in vivo; insight; mRNA Precursor; mutant; neural circuit; public health relevance; receptive field; segregation

DESCRIPTION (provided by applicant): The Drosophila Dscam gene encodes a vast family of immunoglobulin (Ig) superfamily proteins and plays a crucial role in regulating the formation of precisely organized neural circuits during development. Alternative splicing generates more than 38,016 different isoforms, including 19,008 ectodomains tethered to the membrane by one of two alternative transmembrane segments. These ectodomains share the same domain structure, but differ in amino acid sequence within three variable domains, Ig2, Ig3 and Ig7. Isoforms sharing the same combination of variable domains (i.e. they match at each variable domain) bind to each other, but they do not bind to other isoforms. Genetic analysis has revealed that Dscam plays a crucial role in a phenomenon called self-avoidance. Each neuron expresses a unique combination of isoforms and this allows its neurites to distinguish between self and non-self. Self-recognition, namely isoform-specific homophilic binding between neurites of the same cell, promotes repulsion between these processes. Self-avoidance plays an important role in the segregation of axon branches and the elaboration of dendritic fields and, thereby, contributes to the assembly of neural circuits. In this proposal, we will address three questions: 1. Is homophilic recognition crucial for all of Dscam's functions? To address this question we will generate knock-in mutants of Dscam which have lost the ability to engage in homophilic binding; 2. Are specific isoforms of Dscam expressed in distinct populations of neurons? While Dscam clearly plays a role in self-avoidance, it remains possible that different populations of neurons may use specific isoforms of Dscam to recognize other neurons. This aim is directed towards identifying such cells; and 3. Are their requirements in specific neurons for different alternative Ig domains? To address this question we will generate separate lines of flies with a single Ig2 domain, a single Ig3 domain or a single Ig7 domain. While Dscam diversity is not observed in mammals, Dscam is expressed in a cell-type specific fashion and appears to play an analogous function in self-avoidance in mouse amacrine cells. As the dosage of human Dscam has been implicated in Down Syndrome the studies described here may provide insight into the etiology of mental retardation associated with this syndrome. PUBLIC HEALTH RELEVANCE Neural circuits comprise large ensembles of cells connected to each other or "wired up" in a precise fashion. These patterns of connections play a crucial role in determining behavior from simply worms to humans. The goal of this proposal is to understand how one fruit fly gene, closely related to a human gene, facilitates the formation of precise patterns of connections during development.

描述（由申请人提供）：果蝇 Dscam 基因编码免疫球蛋白 (Ig) 超家族蛋白的一个大家族，并在发育过程中调节精确组织的神经回路的形成中发挥着至关重要的作用。选择性剪接产生超过 38,016 种不同的异构体，包括 19,008 个通过两个选择性跨膜片段之一束缚在膜上的胞外域。这些胞外域具有相同的结构域，但三个可变域（Ig2、Ig3 和 Ig7）内的氨基酸序列不同。共享相同可变结构域组合（即它们在每个可变结构域匹配）的异构体彼此结合，但它们不与其他异构体结合。遗传分析表明，Dscam 在一种称为自我回避的现象中发挥着至关重要的作用。每个神经元都表达一种独特的亚型组合，这使得它的神经突能够区分自我和非自我。自我识别，即同一细胞的神经突之间的异构体特异性同亲结合，促进了这些过程之间的排斥。自我回避在轴突分支的分离和树突域的形成中起着重要作用，从而有助于神经回路的组装。在这个提案中，我们将解决三个问题： 1. 同质识别对于 Dscam 的所有功能都至关重要吗？为了解决这个问题，我们将生成 Dscam 的敲入突变体，该突变体失去了参与同源结合的能力； 2. Dscam 的特定亚型是否在不同的神经元群体中表达？虽然 Dscam 显然在自我回避中发挥着作用，但不同的神经元群体仍然有可能使用 Dscam 的特定亚型来识别其他神经元。这一目标旨在识别此类细胞； 3. 它们对不同替代 Ig 结构域的特定神经元有何要求？为了解决这个问题，我们将生成具有单个 Ig2 结构域、单个 Ig3 结构域或单个 Ig7 结构域的单独果蝇品系。虽然在哺乳动物中没有观察到 Dscam 多样性，但 Dscam 以细胞类型特异性方式表达，并且似乎在小鼠无长突细胞的自我回避中发挥类似的功能。由于人类 Dscam 的剂量与唐氏综合症有关，此处描述的研究可能有助于深入了解与该综合症相关的智力低下的病因。公共卫生相关性神经回路由大量细胞组成，这些细胞以精确的方式相互连接或“连接”。这些连接模式在决定从简单的蠕虫到人类的行为方面发挥着至关重要的作用。该提案的目的是了解与人类基因密切相关的果蝇基因如何促进发育过程中精确连接模式的形成。