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。这一过程始于沿背腹轴和前后轴的神经祖细胞形成模式，从而产生不同的神经元亚型。一些关键的转录因子已经被证明可以控制神经元亚型的形成过程。其中，同源盒基因Gsx1和Gsx2在小鼠端脑外侧神经节隆起（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和分化中发挥重要作用。正确的神经元亚型不仅对神经回路的形成至关重要，而且对每个亚型的产生也至关重要。对于大脑发育过程中控制这种平衡的机制，我们所知甚少。在我们之前的资助期间，我们发现虽然Gsx1和Gsx2最终都能指定相同的神经元亚型，但它们对LGE祖细胞成熟的调节方式不同。具体而言，Gsx2似乎维持LGE祖细胞处于未成熟（即干细胞）状态，而Gsx1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；Gsx2主要局限于VZ祖细胞，而Gsx1则在位于VZ/SVZ边界的祖细胞中富集。通过这个应用程序，我们计划将Campbell实验室的小鼠遗传专业知识与Gebelein实验室的分子和生化专业知识结合起来，揭示我们小组和其他人描述的Gsx小鼠突变体的一些遗传表型的潜在机制。因此，本提案中概述的研究将验证Gsx2基因表达的差异调控和独特的蛋白质修饰/相互作用是Gsx1和Gsx2在LGE祖细胞发育中发挥不同作用的一般假设。我们将在三个独立的具体目标中验证这一假设：1)了解控制LGE祖细胞中Gsx2表达的顺式调控机制。2)确定选择性MAPK磷酸化Gsx1，而不是Gsx2，是否在调节LGE祖细胞成熟中的独特作用。3)研究Ascl1 （Mash1）与Gsx2的物理相互作用在LGE祖细胞成熟调控中的作用。我们的方法将结合小鼠，青蛙和苍蝇的遗传学与分子和生化方法来研究腹端脑神经元规范的转录控制。我们发育生物学部门的独特组成使我们能够采用这种广泛的方法，从而增加了我们成功的机会，更深入地了解Gsx因子如何控制远端脑发育，以及揭示新的基因调控机制，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.