Regulation of neurogenesis in the cerebellum

描述（由申请人提供）发育神经生物学的一个基本方面，我们仍然没有完全理解的是位置信息如何与神经遗传程序的局部调节协调以在大脑中建立特定模式。在体内，这个问题在小脑中可以通过实验获得。近交系小鼠品系显示复杂但不变的小脑叶状模式，其由有限数量的限定神经元亚型组成的简单层状结构支撑，从而促进了调节神经发生的潜在机制的表征。使用突变小鼠模型检查小脑皮质图案化的缺陷已经证实小脑图案化与成神经细胞的分化程序密切相关，但调节如何发生仍不清楚。我们的初步研究结果表明，某些分子的调控膜/细胞骨架的相互作用，在轴突的指导也发挥重要作用，在调节神经源性反应的图案信息。其中之一是神经系统特异性蛋白GAP-43。我们已经知道，GAP-43是分化的神经元对引起CNS模式化的信号做出反应所必需的。例如，我们的GAP-43敲除小鼠未能在皮质或端脑连合中形成地形图，因为在这两种情况下GAP-43（-/-）神经元都不能对免疫球蛋白超家族（Ig-SF）介导的轴突生长和引导信号作出反应。然而差距-43（-/-）小鼠在小脑图案化方面也有严重缺陷，这在轴突发生之前是明显的，但在神经发生被细胞外图案化程序调节期间是明显的。该FRICA资助的目的是了解GAP-43缺失时小脑模式中断的分子机制。我们描述了3个实验：第一，确定小脑发育的最早阶段需要GAP-43功能。第二，当GAP-43缺失时，研究小脑中的两种已知神经源性调节因子（bFGF和BDNF）是否可以发挥作用-我们已经知道bFGF需要GAP-43，并且BDNF可以刺激生长轴突中的GAP-43磷酸化。最后，我们将描述GAP-43的缺失如何影响调节分化小脑神经元细胞周期的lg-SF信号转导。这项研究将主要在印度进行，作为NIH资助#RO 1 NS 33118的扩展。

DESCRIPTION (provided by applicant) A fundamental aspect of developmental neurobiology that we still do not fully understand is how positional information coordinates with local regulation of neurogenetic programs to establish specific patterns in the brain. In vivo, the issue is experimentally accessible in the cerebellum. Inbred mice strains show complex yet invariant patterns of cerebellar foliation that is underpinned by a simple laminar structure comprised of a limited number of defined neuronal subtypes, facilitating characterization of the underlying mechanisms regulating neurogenesis. Examining defects in patterning of cerebellar cortex using mutant mouse models has confirmed that cerebellar patterning is intimately tied to the differentiation program of the neuroblasts, but how regulation occurs is still unclear. Our preliminary results suggest that certain molecules crucial for regulating membrane/cytoskeletal interactions during axon guidance also play important roles in regulating the neurogenic response to patterning information. One of these is the nervous system-specific protein GAP-43. We already know that GAP-43 is required in order for differentiated neurons to respond to signals that give rise to patterning in the CNS. For example, our GAP-43 knockout mouse fails to form either topographic maps in cortex, or telencephalic commissures, because in both cases GAP-43 (-/-) neurons are unable to respond to immunoglobulin superfamily (Ig-SF) mediated axon outgrowth and guidance signals. However the GAP-43 (-/-) mouse also has severe defects in cerebellar patterning that are evident before axonogenesis but during the time that neurogenesis is being regulated by extracellular patterning programs. The objective of this FRICA grant is to understand the molecular mechanisms underlying the disruption of patterning in the cerebellum that occurs when GAP-43 is absent. We describe 3 experiments: First, to determine the earliest stage of cerebellar development that requires GAP-43 function. Second to investigate whether 2 known neurogenic regulators in the cerebellum (bFGF and BDNF) can function when GAP-43 is absent - we already know that bFGF requires GAP-43 and that BDNF can stimulate GAP-43 phosphorylation in growing axons. Finally we will characterize how absence of GAP-43 affects transduction of lg-SF signals that regulate the cell cycle in differentiating cerebellar neurons. This research will be performed primarily in India as an extension on NIH grant# RO1 NS33118.