Studying the Molecular Regulation of MGE Projection Neuron Identity by St18

内侧神经节隆起（MGE）是位于腹侧的神经前体结构域， 端脑它的皮质中间神经元的产生得到了很好的研究，这是一个广泛分布的局部前神经元群体， 刺激调节皮质节律的神经元。MGE还产生投射神经元， 前脑，排列在离散的核团中，向远端点对点地投射。中间神经元和投射神经元身份代表 两个完全不同的族群，有着不同的功能MGE如何在IN的生产和 然而，PN是不被理解的。 我们已经确定了一个转录因子，St18，似乎调节这一基本划定。我们之前 描述了一个模型系统，以研究MGE的发展，使用诱导表达的候选因素。当St18被引入时， 在这个系统中引入的细胞在很大程度上采用了投射神经元身份。此外，当这些细胞被移植到 在子宫内，它们仍然存在于腹侧前脑，并采用长距离轴突投射，使人想起苍白球部 外膜（GPe）。此外，在我们对St18条件性功能丧失突变小鼠的初步分析中，我们观察到一种特殊的 GPe神经元的cific损失，而所有其他MGE谱系似乎幸免。 目的1）确定St18诱导的表达是否足以指导MGE祖细胞 朝向投射神经元身份（技术：ESC定向分化，神经元培养，体外迁移测定， UBM移植，RNA-seq）。目的2）通过分析St18对MGE投射神经元命运的影响，测试St18是否是MGE投射神经元命运所必需的。 St18条件性功能丧失小鼠（技术：小鼠遗传学，轴突投射的病毒和染料示踪，scRNA- seq）。目的3）在MGE祖细胞分化过程中操纵St18，以探索其作用的时间窗，并测试其如何在MGE祖细胞分化过程中发挥作用。 在指导投射神经元身份中调节基因表达（技术：ESC指导分化，体外mor- phology and migration assays，ChIP-seq）。重要的是，在我们的研究过程中，我们将执行多层次的表达 和ChIP-seq分析，以揭示St18调控下的基因网络和细胞通路， 支配投射神经元身份的各个方面：神经元迁移、极性、过程形态发生。总之，我们是 独特地定位于解决MGE祖细胞如何调节MGE中投射神经元与中间神经元的身份 脉通过这些努力，我们的目标是更广泛地了解投射和中间神经元身份是如何分配的 在整个神经系统中。

PROJECT SUMMARY: The medial ganglionic eminence (MGE) is a neural progenitor domain located in the ventral telencephalon. It is well-studied for its production of cortical interneurons, a broadly distributed population of locally-pro- jecting neurons that regulate cortical rhythmicity. The MGE also produces projection neurons that remain in the ventral forebrain, arranged in discrete nuclei that project distally point-to-point. Interneuron and projection neuron identity represent two fundamentally-distinct populations, with distinct functions. How the MGE delineates between the production of IN and PN, however, is not understood. We have identified a transcription factor, St18 that appears to regulate this fundamental delineation. We previously described a model system to study MGE development using induced expression of candidate factors. When St18 was intro- duced in this system, the cells largely adopted a projection neuron identity. Further, when these cells were transplanted in utero, they remained in the ventral forebrain and adopted long-range axonal projections reminiscent of globus pallidus pars externa (GPe). Moreover, in our initial analysis of the St18 conditional loss-of-function mutant mouse, we observed a spe- cific loss of GPe neurons, while all other MGE lineages appear spared. In this proposal, we will; Aim 1) Determine whether St18 induced expression is sufficient to direct MGE progenitors towards projection neuron identity (Techniques: ESC directed differentiation, neuronal culture, in vitro migration assays, UBM transplantation, RNA-seq). Aim 2) Test whether St18 is necessary for MGE projection neuron fate by analysis of St18 conditional loss-of-function mouse (Techniques: mouse genetics, viral and dye tracing of axon projections, scRNA- seq). Aim 3) Manipulate St18 during MGE progenitor differentiation to probe the time window of its action and test how it regulates gene expression in directing projection neuron identity (Techniques: ESC directed differentiation, in vitro mor- phology and migration assays, ChIP-seq). Importantly, in the course of our study, we will perform a multi-level expression and ChIP-seq analysis to uncover the gene networks and cellular pathways under the regulation of St18 that collectively govern aspects of projection neuron identity: neuronal migration, polarity, process morphogenesis. In summary, we are uniquely positioned to address how MGE progenitors regulate projection neuron versus interneuron identity in the MGE lineage. Through these efforts, we aim to inform more broadly as to how projection and interneuron identity is assigned throughout the nervous system.