Mechanisms of neural progenitor division in the developing brain

描述(申请人提供)：神经发生是神经前体细胞产生神经元的基本发育过程。在发育中的大脑皮层，放射状胶质细胞对称分裂自我更新，不对称分裂产生神经元和其他前体细胞。我们缺乏对调节放射状胶质细胞分裂的细胞生物学机制的基本了解。此外，我们对放射状胶质细胞分裂是如何在分子水平上定义的了解有限，包括转录后调控的作用。这项建议的总体目标是阐明这些基本监管水平的贡献。 在神经发生方面，通过利用一种新的小鼠神经发生突变体。这个突变体对Magoh来说是单倍体充足的，Magoh是外显子连接RNA结合复合体(EJC)的一种成分。我们之前由美国国立卫生研究院资助的研究表明，Magoh突变体表现出小头畸形，大脑比正常小30%，这主要是由于神经前体细胞减少。我们发现，Magoh对神经前体细胞的正常有丝分裂是必不可少的，并发现Magoh调节微管相关蛋白Lis1，这是神经发生所必需的。此外，我们还发现，Magoh控制着关键神经前体决定因素的表达。总而言之，我们的发现表明，Magoh是神经发生的一种新的中枢调节因子，但我们对Magoh在大脑中的功能缺乏基本的了解。我们认为，Magoh在神经前体细胞中有两个关键功能：调节适当的有丝分裂和作用于转录后调控模块，控制关键神经发生基因的表达。我们的中心假设是，Magoh通过影响有丝分裂纺锤体和mRNA代谢来调节放射状胶质细胞的不对称分裂。为了解决这一假设，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。我们将在活体脑切片中使用条件遗传分析和放射状胶质细胞分裂的实时成像。其次，我们将通过阐明Magoh对微管和Lis1的调节来定义其如何调节有丝分裂。我们将确定Magoh如何调节Lis1的水平，以及Lis1是否在Magoh的下游有丝分裂中发挥作用。第三，我们将确定Magoh在神经发生中的关键信使核糖核酸靶点，并确定EJC在其调控中的作用。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mRNAs来影响神经发生的理解。总之，我们提出的研究将拓宽我们对不对称分裂的调节和神经发育障碍的病因学的基本理解。

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.