Multifunctional roles for doublecortin (DCX)in neural development

描述（由申请人提供）：大脑布线是一个复杂的神经发育过程。当它出错时，人类神经系统疾病可能会出现从轻微到严重的缺陷。与这些疾病相关的基因是研究的重要途径，因为它们为理解神经发育过程和疾病的分子机制提供了切入点。一些神经系统疾病与在许多细胞类型中普遍表达的基因遗传相关，而另一些则与神经表达的基因相关。X连锁基因doublecortin（DCX）仅在神经元中表达，并且是I型无脑回畸形的主要遗传位点，I型无脑回畸形是一种神经发育缺陷，导致智力迟钝和难以控制的癫痫。因此，解开DCX的分子和细胞功能，不仅对促进我们对DCX在发育中的功能和无脑畸形的疾病机制的理解具有重要意义，而且更普遍地促进了我们对哪些蛋白质特别是制造神经元和连接大脑所需的蛋白质的概念。因此，这项资助将深入了解细胞类型特异性机制，以制造功能性神经元和构建功能性电路。DCX的分子和细胞作用仍不完全清楚。许多工作都集中在DCX的微管结合能力，与DCX突变相关的表型被假定是由于微管相关的缺陷。DCX的患者等位基因是将我们的注意力引导到DCX中对正常功能重要的残基的有力工具。令人惊讶的是，大多数DCX突变的微管缺陷尚未建立，因此DCX的所有细胞作用是否都需要微管结合是一个悬而未决的问题。许多其他的结合伙伴，如细胞粘附分子神经成束蛋白和网格蛋白衔接子，事实上已经确定了DCX，但这些其他相互作用的伙伴的作用目前还不清楚。在初步的实验中，我们已经确定了一个新的功能DCX，即神经成束蛋白的内吞作用。令人惊讶的是，在PC12测定中，DCX介导的神经成束蛋白的内吞作用不需要通过DCX结合微管。我们将测试的假设，DCX在多个细胞过程中发挥作用，包括内吞作用，通过可分离的分子相互作用。本研究的目的是揭示DCX介导的内吞作用在神经发育中的作用，包括迁移、轴突生长和引导以及树突生长。

DESCRIPTION (provided by applicant): Wiring the brain is a complex neurodevelopmental process. When it goes wrong, human neurological disorders can arise with deficiencies ranging from mild to severe. Genes associated with such disorders are important avenues for research because they provide an entry point into understanding the molecular mechanisms of both neurodevelopmental processes and diseases. Some neurological disorders are linked genetically to genes ubiquitously expressed in many cell types whereas others are linked to neurally expressed genes. The X-linked gene doublecortin (DCX) is only expressed in neurons and is a major genetic locus for type I lissencephaly, a neurodevelopmental defect causing mental retardation and untractable epilepsy. Unraveling the molecular and cellular functions of DCX, therefore, not only has significance for advancing our understanding of DCX function in development and the disease mechanisms of Lissencephaly, but more generally advances our conceptualization of which proteins in particular are required to make a neuron and wire the brain. This grant thus goes to the heart of understanding cell-type specific mechanisms for making functional neurons and building functional circuits. The molecular and cellular roles of DCX are still incompletely understood. Much work has focused on the microtubule-binding ability of DCX, and the phenotypes associated with DCX mutations are postulated to be due to microtubule-related defects. Patient alleles of DCX are powerful tools to direct our attention to residues in DCX that are important for normal function. Surprisingly, microtubule defects have not been established for most DCX mutations, and it is thus an open question whether all cellular roles of DCX require microtubule binding. Many additional binding partners, such as the cell adhesion molecule neurofascin and clathrin adaptors, have in fact been identified for DCX, but the roles of these other interacting partners are currently not understood. In preliminary experiments, we have identified a novel function of DCX, namely endocytosis of neurofascin. Surprisingly, DCX-mediated endocytosis of neurofascin does not require microtubule binding by DCX in a PC12 assay. We will test the hypothesis that DCX plays roles in multiple cellular processes, including endocytosis, via separable molecular interactions. The objective of this proposal is to uncover the contributions of DCX-mediated endocytosis in neurodevelopment, including migration, axon growth and guidance and dendrite growth.