Multifunctional roles for doublecortin (DCX)in neural development

描述(申请人提供)：连接大脑是一个复杂的神经发育过程。当它出错时，人类神经疾病可能会出现，缺陷从轻微到严重不等。与这类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一个切入点。一些神经系统疾病与在多种细胞类型中普遍表达的基因有关，而另一些则与神经表达的基因有关。X-连锁基因Doublecortin(DCX)仅在神经元中表达，是I型无脑畸形的主要遗传位点，I型无脑畸形是一种导致智力低下和难治性癫痫的神经发育缺陷。因此，解开DCX的分子和细胞功能，不仅对于促进我们对DCX在发育中的功能和白脑的疾病机制的理解具有重要意义，而且更广泛地促进了我们对哪些蛋白质是构成神经元和连接大脑所必需的概念化。因此，这笔拨款的核心是了解细胞类型的特定机制，以制造功能神经元和构建功能电路。DCX在分子和细胞中的作用尚不完全清楚。很多工作都集中在DCX的微管结合能力上，与DCX突变相关的表型被认为是由于微管相关的缺陷。DCX的患者等位基因是引导我们注意DCX中对正常功能重要的残基的强大工具。令人惊讶的是，大多数DCX突变的微管缺陷尚未确定，因此是否DCX的所有细胞角色都需要微管结合是一个悬而未决的问题。事实上，许多额外的结合伙伴，如细胞黏附分子神经束素和笼状蛋白适配器，已经被确定为DCX，但这些其他相互作用伙伴的作用目前还不清楚。在初步实验中，我们已经确定了DCX的一种新功能，即内吞神经束素。令人惊讶的是，在PC12实验中，DCX介导的神经法菌素的内吞作用不需要DCX与微管结合。我们将验证DCX通过可分离的分子相互作用在包括内吞作用在内的多种细胞过程中发挥作用的假设。这项建议的目的是揭示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.