Mechanisms of neural progenitor division in the developing brain

描述（由申请人提供）：神经发生是神经祖细胞产生神经元的重要发育过程。在发育中的大脑皮层中，放射状胶质细胞对称分裂以自我更新，不对称分裂以产生神经元和其他祖细胞。我们缺乏一个基本的了解调节放射状胶质细胞分裂的细胞生物学机制。此外，我们对放射状胶质细胞分裂在分子水平上的定义，包括转录后调控的作用，了解有限。本提案的总体目标是阐明这些基本监管水平的贡献 神经发生，通过开发一种新的小鼠神经发生突变体。该突变体对于Magoh来说是单倍体足够的，Magoh是外显子连接RNA结合复合物（EJC）的组分。我们之前由NIH资助的研究表明，Magoh突变体表现出小头畸形，大脑比正常人小30%，这主要是由于神经祖细胞减少。我们发现Magoh对神经祖细胞的有丝分裂至关重要，并发现Magoh调节Lis1，一种对神经发生至关重要的微管相关蛋白。此外，我们发现Magoh控制关键神经祖细胞决定因子的表达。总之，我们的发现指出Magoh是一种新的神经发生的中央调节器，但我们对Magoh在大脑中的功能缺乏基本的了解。我们提出Magoh在神经祖细胞中具有两个关键功能：调节适当的有丝分裂和在控制关键神经发生基因表达的转录后调节模块中起作用。我们的中心假设是，Magoh调节放射状胶质细胞的不对称分裂的有丝分裂纺锤体和mRNA代谢的影响。为了解决这个假设，我们将追求以下目标：首先，我们将确定Magoh调节神经元和INP产生的细胞机制。我们将使用条件遗传分析沿着放射状胶质细胞分裂的实时成像。其次，我们将通过阐明其对微管和Lis1的调节来确定Magoh如何调节有丝分裂。我们将确定Magoh如何调节Lis1水平，以及Lis1在有丝分裂中是否在Magoh下游发挥作用。第三，我们将确定Magoh在神经发生中的关键mRNA靶点，并确定EJC在其调节中的作用。在成功完成这些目标后，我们将大大提高我们对Magoh如何通过调节有丝分裂和mRNA来影响神经发生的理解。总之，我们提出的研究将扩大我们对不对称分裂调节和神经发育障碍病因学的基本理解。

DESCRIPTION (provided by applicant): Neurogenesis is an essential developmental process in which neural progenitors generate neurons. In the developing cerebral cortex, radial glia cells divide symmetrically to self-renew and asymmetrically to generate neurons and other progenitors. We lack a fundamental understanding of the cell biological mechanisms regulating radial glia divisions. In addition, we have a limited understanding of how radial glia divisions ar defined at the molecular level, including the role of post-transcriptional regulation. The overall objective of this proposal is to elucidate the contribution of these essential levels of regulation for neurogenesis, by exploiting a novel mouse neurogenesis mutant. This mutant is haploin-sufficient for Magoh, which is a component of the exon junction RNA binding complex (EJC). Our previous NIH-funded studies demonstrated that Magoh mutants exhibit microcephaly, with brains 30% smaller than normal, largely due to reduced neural progenitors. We found that Magoh is essential for proper mitosis of neural progenitors and discovered that Magoh regulates Lis1, a microtubule-associated protein essential for neurogenesis. Moreover we have found that Magoh controls expression of key neural progenitor determinants. Together, our discoveries point to Magoh as a novel central regulator of neurogenesis, yet we lack a fundamental understanding of how Magoh functions in the brain. We propose Magoh has two critical functions in neural progenitors: to regulate proper mitosis and to act in a post-transcriptional regulatory module controlling expression of key neurogenesis genes. Our central hypothesis is that Magoh regulates asymmetric division of radial glia by influencing the mitotic spindle and mRNA metabolism. To address this hypothesis we will pursue the following aims: First we will determine the cellular mechanism by which Magoh regulates neuron and INP production. We will use conditional genetic analysis along with live imaging of radial glia divisions in live brai slices. Second we will define how Magoh regulates mitosis by elucidating its regulation of microtubules and Lis1. We will determine how Magoh regulates Lis1 levels and if Lis1 functions downstream of Magoh in mitosis. Third, we will define the key mRNA targets of Magoh in neurogenesis and determine the role of the EJC in their regulation. Upon successful completion of these aims, we will have significantly advanced our understanding of how Magoh influences neurogenesis, by regulating both mitosis and mRNAs. Together, our proposed studies will broaden our fundamental understanding of the regulation of asymmetric division and the etiology of neurodevelopmental disorders.