Role of molecular recognition in retinal patterning and synaptic organization

描述(由申请人提供)：候选人和环境：Peter Fuerst博士将在华盛顿州立大学进行这项提案中包含的研究。华盛顿州立大学是使用老鼠模型进行高级生物医学研究和推进研究计划的理想环境。研究建议：我们提出的研究将使用小鼠模型来确定支持视网膜发育的分子机制。所有的小鼠模型都由申请人开发，包括唐氏综合症细胞黏附分子的条件等位基因Dscam，以及一系列突变的小鼠Dscam品系和Dscam同源基因Dscam-like 1(Dscaml1)的零等位基因。Dscam和Dscam-like 1对于神经系统的正常发育是必不可少的，Dscam被认为与唐氏综合征的病理有关。在视网膜中，DSCAM对胞体镶嵌间距、细胞数量的调节以及轴突的树枝和层叠都是必需的。我们发表的关于Dscam和Dscaml1的结果首次证明了突变可以破坏马赛克图案，并首次发现了介导脊椎动物等神经和异神经排斥的基因。具体目的：我们建议使用Dscam和Dscaml1突变小鼠模型来发现支持视网膜发育的机制，并探索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细说明的以下假设来实现。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验证DSCAM介导多种不同功能的假设，以从遗传和时间上分离Dscam依赖的发育过程。2)我们将验证这样一种假设，即DSCAM介导细胞类型之间的黏附和细胞类型内的排斥，并且DSCAM在视网膜中的活性是通过同型相互作用而不是通过使用与细胞类型特异性缺失耦合的条件等位基因而不是配体-受体机制来调节的。3)我们将检验Dscam和Dscaml1调控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，并为福斯特博士建立专注于假说驱动的生物医学研究的成功学术生涯提供必要的资金。意义：神经突起分枝、调节细胞数量和胞体镶嵌间距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被很好地理解。我们的初步研究表明，DSCAM在哺乳动物神经系统的这些过程中起着至关重要的作用。利用一系列小鼠突变等位基因和条件等位基因识别DSCAM的功能机制将有助于我们理解神经系统发育和神经发育不全相关疾病的原因，并为神经科学界提供有价值的研究模型。 公共卫生相关性：这项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形成。研究将集中在发现两种识别信号-唐氏综合症细胞黏附分子(Dscam)及其同源物Dscam-like 1(Dscaml1)-介导视网膜内电路形成的机制。Dscam和Dscaml1都是轴突分层、轴突分枝和调节细胞数量所必需的。因此，了解这些分子的作用机制将促进对神经发育的多个方面的科学理解。此外，减少Dscam的剂量可以降低视网膜发育细胞死亡的发生率，这表明视网膜可能提供了一个很好的系统来模拟唐氏综合征患者神经元的增强性发育细胞死亡，唐氏综合症患者由于21号染色体三体而过度表达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.