Intracellular signaling by DSCAM during retinal development

描述(由申请人提供)： 为了神经系统的正常发育和功能，必须经历许多过程。神经元必须有适当的间隔，它们必须发出轴突和树突，这些轴突和树突在组织中延伸，以形成树枝并找到目标，它们必须形成突触与伙伴交流。这些缺陷中的任何一个都可能导致功能障碍和神经发育障碍。唐氏综合征细胞黏附分子(DSCAM)基因位于21号染色体上，与唐氏综合征的三体相关。在小鼠视网膜中，Dscam和非常类似的Dscam(DscamL1)参与了黏附掩蔽，这是一种对自我避免很重要的细胞过程，允许细胞间距和树突树枝。Dscam还参与了突触发育的某些方面。已知的与DSCAMS相互作用的蛋白质有：PAK1(p21激活的激酶)可以被DSCAM激活，MAGI(膜相关的反转结构域的鸟苷酸激酶)家族的支架分子与DSCAMS的c-末端相互作用。这项实验的目的是阐明DSCAM下游黏附掩蔽和突触发育过程中的信号机制。总体假设是，Dscam通过激活pak1来调节发育早期的黏附掩蔽，并通过与MAGI蛋白的相互作用对发育后期的突触成熟起重要作用。为了验证这一假设，视网膜神经节细胞将在一个系统中培养，该系统允许评估粘附性掩蔽和操纵基因表达。实验还将在小鼠身上进行，方法是制造新的小鼠品系，在这些品系中，Dscam和DscamL1具有靶向突变，这些突变不允许蛋白质与MAGI相互作用。预计结果将显示DSCAM通过不同的信号机制执行其不同的功能。这些发现将对DSCAM在唐氏综合征和包括先天性视网膜病变在内的其他神经发育障碍的病理机制中的可能作用产生影响。 公共卫生相关性： 这项建议的目的是研究唐氏综合症细胞黏附分子(Dscam)的小鼠同源基因(Dscam)及其类似的Dscam样蛋白(DscamL1)在引导视网膜发育的细胞识别事件中发挥作用的分子机制。在人类中，Dscam位于与唐氏综合症三体相关的21号染色体区域，了解Dscam功能的基本分子机制将有助于确定其在唐氏综合症和其他神经发育障碍相关表型中的可能作用。研究视网膜中的这些机制也可能为人类先天性视网膜病变提供洞察力。

DESCRIPTION (provided by applicant): In order for the nervous system to develop and function normally, many processes must occur. Neurons must be spaced appropriately, they must send out axons and dendrites that extend through the tissue to develop arbors and find targets, and they must form synapses to communicate with partners. Defects at any of these points can lead to dysfunction and neurodevelopmental disorders. The Down syndrome cell adhesion molecule (Dscam) gene is on the region of chromosome 21 that is associated with trisomies in Down syndrome. In the mouse retina, Dscam and the very similar Dscam Like (DscamL1) are involved in adhesive masking, a cellular process important for self-avoidance, allowing cell spacing and dendrite arborization. The Dscams are also involved in some aspects of synapse development. There are a few proteins known to interact with the Dscams: Pak1 (p21-activated kinase) can be activated by Dscam, and the MAGI (membrane- associated guanylate kinase with inverted domain structure) family of scaffolding molecules interacts with the c-terminus of the Dscams. The aim of the experiments described in this proposal is to elucidate the signaling mechanisms downstream of the Dscams during adhesive masking and synapse development. The overall hypothesis is that Dscams regulate adhesive masking early in development through activation of Pak1, and are important for synapse maturation later in development through interactions with the MAGI proteins. To test this hypothesis, retina ganglion cells will be cultured in a system that allows the assessment of adhesive masking and the manipulation of gene expression. Experiments will also be performed in the mouse by making new mouse lines in which Dscam and DscamL1 have targeted mutations that do not allow the proteins to interact with the MAGIs. It is expected that the results will show that the Dscams carry out their different functions through distinct signaling mechanisms. These findings will have implications for the mechanisms of the Dscams' possible role in the pathology of Down syndrome and other neurodevelopmental disorders including congenital retinopathies. PUBLIC HEALTH RELEVANCE: The aim of this proposal is to study the molecular mechanisms by which the mouse ortholog of Down syndrome cell adhesion molecule (Dscam) and the similar Dscam Like (DscamL1) function in the cellular recognition events that direct retinal development. In humans, Dscam is in region of Chromosome 21 associated with Down syndrome trisomies, and understanding the basic molecular mechanisms of the Dscams' function will help to define its possible role in the phenotypes associated with Down syndrome and other neurodevelopmental disorders. Studying these mechanisms in the retina may provide insight into human congenital retinopathies as well.