Role of molecular recognition in retinal patterning and synaptic organization

描述（由申请人提供）：候选人和环境：彼得富尔斯特博士将在华盛顿州立大学进行本提案中包含的研究。华盛顿州立大学是一个理想的环境，在其中进行先进的生物医学研究使用小鼠模型，并在其中推进研究计划。研究建议：我们提出的研究将使用小鼠模型来确定视网膜发育的分子机制。小鼠模型均由申请人开发，包括唐氏综合征细胞粘附分子Dscam的条件等位基因，以及小鼠突变Dscam品系的等位基因系列和Dscam同源物Dscam样1（Dscaml 1）的无效等位基因。Dscam和Dscam-Like 1对于神经系统的正常发育是必需的，并且Dscam被认为有助于唐氏综合征的病理学。在视网膜中，Dscam是索马镶嵌间隔、细胞数量调节和神经突分支和分层所必需的。我们发表的关于Dscam和Dscaml 1的结果是发现消融镶嵌图案的突变的第一个证明，并且是第一个在脊椎动物中介导isoneuronal和heteroneuronal排斥的基因。具体目标：我们建议使用Dscam和Dscaml 1突变小鼠模型来发现视网膜发育的基础机制，并探讨Dscam在哺乳动物神经系统中的功能。这将通过测试本研究提案中详述的以下假设来实现。假设：1）我们将使用Dscam小鼠突变系的等位基因系列和条件等位基因来测试DSCAM介导多种不同功能的假设，以在遗传上和时间上分离Dscam依赖的发育过程。2)我们将测试的假设，DSCAM介导的细胞类型之间的粘附和细胞类型内的排斥，并在视网膜中的DSCAM活性是由亲同性的相互作用，而不是由配体-受体机制，通过使用一个条件等位基因耦合到细胞类型特异性缺失。3)我们将测试Dscam和Dscaml 1调节正常发育细胞死亡的假设。长期目标：这项研究将揭示神经组织的基本方面，并为富尔斯特博士提供必要的资金，以建立一个成功的学术生涯，专注于假设驱动的生物医学研究。 重要性：神经突树枝化、细胞数量的调节和索马镶嵌间隔是神经发育的基本方面，目前在脊椎动物的分子水平上还没有很好的理解。我们的初步研究表明，DSCAM在哺乳动物神经系统中介导这些过程中起着至关重要的作用。使用一系列小鼠突变等位基因和条件等位基因识别DSCAM功能的机制将有助于我们理解神经系统发育和与神经发育不良相关的疾病的病因，并为神经科学界提供有价值的研究模型。 公共卫生相关性：拟议工作的主要目标是了解分子识别线索如何促进神经模式。研究将集中于发现两种识别线索的机制;唐氏综合症细胞粘附分子（Dscam）及其同源物Dscam样1（Dscaml 1）介导视网膜内的电路形成。Dscam和Dscaml 1都是神经突分层、神经突分支和细胞数量调节所必需的。因此，了解这些分子发挥作用的机制将在多个方面促进对神经发育的科学理解。此外，降低Dscam剂量降低了视网膜发育细胞死亡的发生率，表明视网膜可以提供一个极好的系统，在该系统中模拟唐氏综合征患者中发生的神经元的增强的发育细胞死亡，唐氏综合征患者由于染色体21三体而过度表达Dscam。

DESCRIPTION (provided by applicant): Candidate and Environment: Dr. Peter Fuerst will conduct the research contained within this proposal at Washington State University. Washington State University is an ideal environment in which to conduct advanced biomedical research using mouse models and in which to advance a research program. Research Proposal: The research we propose will use mouse models to identify the molecular mechanisms underpinning development of the retina. The mouse models, all developed by the applicant, include a conditional allele of the Down syndrome cell adhesion molecule, Dscam, as well as an allelic series of mouse mutant Dscam strains and a null allele of the Dscam homologue Dscam-like1 (Dscaml1). Dscam and Dscam- Like1 are essential for normal development of the nervous system and Dscam is proposed to contribute to the pathology of Down syndrome. In the retina, Dscam is required for soma mosaic spacing, regulation of cell number and neurite arborization and lamination. Our published results concerning Dscam and Dscaml1 are the first demonstrations of mutations found to ablate mosaic patterning and the first genes shown to mediate isoneuronal and heteroneuronal repulsion in vertebrates. Specific Aims: We propose to use the Dscam and Dscaml1 mutant mouse models to discover mechanisms underpinning development of the retina and to probe the function of Dscam in the mammalian nervous system. This will be accomplished by testing the following hypotheses detailed in this research proposal. Hypotheses: 1) We will test the hypothesis that DSCAM mediates multiple distinct functions using an allelic series and conditional allele of Dscam mouse mutant lines to genetically and temporally isolate Dscam-dependent developmental processes. 2) We will test the hypothesis that DSCAM mediates adhesion between cell types and repulsion within cell types and that DSCAM activity in the retina is mediated by homophillic interactions and not by a ligand-receptor mechanism by using a conditional allele coupled to cell type specific deletion. 3) We will test the hypothesis that Dscam and Dscaml1 regulate normal developmental cell death. Long-term goals: This research will uncover fundamental aspects of neural organization and provide the funding necessary for Dr. Fuerst to establish a successful academic career focused on hypothesis driven biomedical research. Significance: Neurite arborization, regulation of cell number and soma mosaic spacing are fundamental aspects of neurodevelopment that are not currently well understood at the molecular level in vertebrates. Our preliminary research indicates that DSCAM plays a vital role in mediating these processes in the mammalian nervous system. Identifying mechanisms by which DSCAM functions using a series of mouse mutant alleles and a conditional allele will contribute to our understanding of nervous system development and the causation of disorders associated with neural dysgenesis and also contribute valuable research models to the neuroscience community. PUBLIC HEALTH RELEVANCE: The primary goal of the proposed work is to understand how molecular recognition cues facilitate neural patterning. Research will focus on discovering the mechanisms by which two recognition cues; the Down Syndrome Cell Adhesion Molecule (Dscam) and its homologue Dscam-like1 (Dscaml1), mediate circuit formation within the retina. Both Dscam and Dscaml1 are required for neurite lamination, neurite arborization and regulation of cell number. Therefore, understanding the mechanism by which these molecules function will advance scientific understanding of neural development on multiple fronts. Furthermore, decreasing Dscam dosage decreases the incidence of retinal developmental cell death suggesting that the retina may provide an excellent system in which to model enhanced developmental cell death of neurons that occurs in Down syndrome patients, who overexpress Dscam as a result of Chromosome 21 trisomy.