Regulation of neurogenesis in the cerebellum

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的模式。在体内，这个问题在实验上可以在小脑中找到。近交系小鼠表现出复杂而不变的小脑叶化模式，其基础是由有限数量的确定的神经元亚型组成的简单层流结构，有助于表征调节神经发生的潜在机制。使用突变小鼠模型检查小脑皮质模式缺陷，证实小脑模式与神经母细胞的分化程序密切相关，但如何发生调节仍不清楚。我们的初步结果表明，在轴突引导过程中，某些对调节膜/细胞骨架相互作用至关重要的分子也在调节对模式信息的神经源性反应中发挥重要作用。其中之一是神经系统特异性蛋白GAP-43。我们已经知道，为了使分化的神经元对中枢神经系统中产生模式的信号作出反应，GAP-43是必需的。例如，我们的GAP-43敲除小鼠无法在皮层或远端脑通信中形成地图图，因为在这两种情况下，GAP-43（-/-）神经元无法对免疫球蛋白超家族（Ig-SF）介导的轴突生长和引导信号做出反应。然而，GAP-43（-/-）小鼠也有严重的小脑模式缺陷，这种缺陷在轴突发生前就很明显，但在神经发生受细胞外模式程序调节的时候。这项资助的目的是了解当GAP-43缺失时小脑模式破坏的分子机制。我们描述了三个实验：首先，确定需要GAP-43功能的小脑发育的最早阶段。其次，研究小脑中两种已知的神经源性调节因子（bFGF和BDNF）在GAP-43缺失时是否能发挥作用——我们已经知道bFGF需要GAP-43，而BDNF可以刺激生长轴突中GAP-43的磷酸化。最后，我们将描述GAP-43缺失如何影响小脑神经元分化过程中调节细胞周期的长- sf信号的转导。这项研究将主要在印度进行，作为NIH拨款# RO1 NS33118的延伸。

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.