Roles of Gsx factors in telencephalic neurogenesis

描述（由申请人提供）：正常的大脑功能依赖于发育过程中神经回路的正确组装。这个过程始于神经祖细胞沿着背腹轴和前后轴沿着形成图案，从而产生不同的神经元亚型。许多关键转录因子已被证明控制神经元亚型特化的过程。其中，同源异型盒基因Gsx 1和Gsx 2在小鼠端脑的侧神经节隆起（LGE）祖细胞（包括纹状体投射神经元和嗅球中间神经元）产生的神经元细胞类型的模式化和分化中发挥重要作用。不仅是神经元亚型的正确规范神经回路的形成至关重要，而且每个亚型的适当数量的生成。关于大脑发育过程中控制这种平衡的机制知之甚少。在我们之前的资助期间，我们发现，虽然Gsx 1和Gsx 2最终可以指定相同的神经元亚型，但它们对LGE祖细胞成熟的调节不同。具体而言，Gsx 2似乎将LGE祖细胞维持在未成熟（即干细胞）状态，而Gsx 1促进祖细胞成熟并从心室区（VZ）过渡到心室下区（SVZ）。因此，这些结果与这些基因的表达密切相关; Gsx 2主要限于VZ祖细胞，而Gsx 1发现富集于位于VZ/SVZ边界的祖细胞。通过这项应用，我们计划将联合收割机的坎贝尔实验室的小鼠遗传专业知识与Gebelein实验室的分子和生物化学专业知识相结合，以揭示我们的团队和其他人已经描述的Gsx小鼠突变体的遗传表型的机制。因此，本提案中概述的研究将检验Gsx 2基因表达的差异调节和独特的蛋白质修饰/相互作用是Gsx 1和Gsx 2在LGE祖细胞发育中发挥不同作用的基础这一一般假设。我们将在3个独立的具体目标中检验这一假设：1）了解控制LGE祖细胞中Gsx 2表达的顺式调节机制。2)确定Gsx 1而不是Gsx 2的选择性MAPK磷酸化是否是其在调节LGE祖细胞成熟中的独特作用的基础。3)研究Ascl 1（Mash 1）和Gsx 2之间的物理相互作用在控制LGE祖细胞成熟中的作用。我们的方法将联合收割机使用小鼠，青蛙和苍蝇的遗传学与分子和生物化学的方法来研究腹侧端脑神经元规格的转录控制。我们发育生物学部门的独特组成使我们能够采取这种广泛的方法，从而增加了我们成功的机会，更深入地了解Gsx因子如何控制端脑发育，并发现新的基因调控机制，这些机制可能是某些儿童神经系统疾病功能障碍的基础。

DESCRIPTION (provided by applicant): Normal brain function relies on the correct assembly of neural circuits during development. This process starts with the patterning of neural progenitors along the dorsal-ventral and anterior-posterior axes to give rise to distinct subtypes of neurons. A number of key transcription factors have been shown to control the process of neuronal subtype specification. Of these, the homeobox genes Gsx1 and Gsx2 play essential roles in the patterning and differentiation of neuronal cell types that arise from the lateral ganglionic eminence (LGE) progenitors of the mouse telencephalon including striatal projection neurons and olfactory bulb interneurons. Not only is the correct specification of neuronal subtypes crucial for neural circuit formation but also the generation of appropriate numbers of each subtype. Less is known about the mechanisms that control this balance during brain development. In our previous funding period for this grant, we showed that while both Gsx1 and Gsx2 can ultimately specify the same subtypes of neurons, they regulate LGE progenitor maturation differently. Specifically, Gsx2 appears to maintain LGE progenitors in an immature (i.e. stem cell) state while Gsx1 promotes progenitor maturation and transition from the ventricular zone (VZ) to the subventricular zone (SVZ). Accordingly, these results correlate well with the expression of these genes; Gsx2 is largely restricted to VZ progenitors whereas Gsx1 is found enriched in progenitors positioned at the VZ/SVZ boundary. With this application, we plan to combine the mouse genetic expertise of the Campbell lab with the molecular and biochemical expertise of the Gebelein lab to uncover the mechanisms underlying some of the genetic phenotypes our group and others have described for the Gsx mouse mutants. Thus, the studies outlined in this proposal will test the general hypothesis that differential regulation of Gsx2 gen expression and unique protein modifications/interactions underlie the distinct roles that Gsx1 and Gsx2 play in LGE progenitor development. We will test this hypothesis in 3 independent specific aims: 1) To understand the cis-regulatory mechanisms that control Gsx2 expression in LGE progenitors. 2) To determine whether selective MAPK phosphorylation of Gsx1, but not Gsx2, underlies its unique role in regulating LGE progenitor maturation. 3) To study the role of physical interactions between Ascl1 (Mash1) and Gsx2 in the control of LGE progenitor maturation. Our approach will combine the use of mouse, frog and fly genetics with molecular and biochemical approaches to study transcriptional control of neuronal specification in the ventral telencephalon. The unique makeup of our Division of Developmental Biology allows us to take this broad approach and as a result increases our chances of success to both, gain a deeper understanding of how Gsx factors control telencephalic development as well as uncover new gene regulatory mechanisms that may underlie aspects of dysfunction in certain childhood neurological disorders.