Investigating molecular mechanisms and function of tanycyte-derived neurogenesis in the postnatal hypothalamus

项目摘要 近年来，有证据表明，伸长细胞具有在神经元中产生神经元的能力。 出生后的下丘脑伸展细胞是放射状的胶质细胞，在两种细胞中都非常类似神经祖细胞。 形态学和基因表达谱。虽然饮食和激素的提示可以调节 在神经发生中，伸长细胞增殖和伸长细胞衍生的神经发生的总体水平较低， 在成年小鼠中几乎检测不到。控制神经原性能力的分子机制 伸长细胞，以及伸长细胞衍生的神经元的精确生理功能仍然不清楚。 识别刺激伸长细胞源性神经发生的分子机制，以促进 伸展细胞衍生的神经元调节体重和代谢，是一种新的潜在的治疗， 肥胖和代谢紊乱如II型糖尿病。 最近，来自Blackshaw实验室的研究已经确定了核因子一（Nfi）家族转录 转录因子Nfia/B/x在调节下丘脑神经原性能力中起着关键作用， 伸长细胞在雄性小鼠的正常饮食条件下，Nfia/B/x缺陷型伸长细胞显示出增强的 增殖和神经发生。Nfia/B/x缺陷型伸长细胞的单细胞RNA测序分析和 结果表明，所有伸长细胞衍生的神经元中有相当大一部分是GABA能的 亚型这些GABA能神经元的一个子集表达瘦素受体（Lepr）并对瘦素作出反应。 布莱克肖实验室还表明，长形细胞衍生的神经元存活下来，整合到下丘脑回路中， 和火自发动作电位。通过分析对照组和对照组之间差异表达的基因， 在Nfia/B/x缺陷的伸长细胞中，我们已经表明Shh和Wnt信号在伸长细胞中上调， Nfia/B/x损失。我们还观察到Nfia/B/x缺陷型伸长细胞中Notch途径的下调。 在发育过程中，Shh和Wnt通路促进下丘脑的神经发生。虽然Notch 信号通路促进视网膜Müller胶质细胞和皮质星形胶质细胞的静止。鉴于这些发现，我 假设伸长细胞的神经原性能力在出生后被积极抑制， 下丘脑神经发生后，并假设伸展细胞衍生的神经元调节身体 体重平衡和新陈代谢。为了解决这些假设，我提出以下两个目标： 目的1：研究外源性调节因子，积极或消极地控制tanycyte-derived 在青少年和年轻成人下丘脑的神经发生。这项工作将确定分子机制 和基因调控网络，积极或消极地调节tanycyte-derived神经发生， 出生后的下丘脑 目的2：探讨伸长细胞源性神经元在体重平衡和代谢中的作用。 这些研究将提供关键的见解，在控制中的生理功能的伸长细胞衍生的神经元 体重平衡和新陈代谢。

PROJECT SUMMARY In recent years, evidence now shows that tanycytes possess the ability to generate neurons in the postnatal hypothalamus. Tanycytes are radial glial cells that closely resemble neural progenitors in both morphology and gene expression profiles. While dietary and hormonal cues can regulate tanycyte-derived neurogenesis, the overall levels of tanycyte proliferation and tanycyte-derived neurogenesis are low and virtually undetectable in adult mice. The molecular mechanisms controlling neurogenic competence in tanycytes, and the precise physiological function of tanycyte-derived neurons remains poorly defined. Identifying molecular mechanisms that stimulate tanycyte-derived neurogenesis, to promote differentiation of tanycyte-derived neurons that modulate body weight and metabolism, is a new potential therapeutic for treating obesity and metabolic disorders such as type II diabetes. Recently, studies from the Blackshaw lab have identified the Nuclear Factor One (Nfi) family transcription factors (TFs), Nfia/b/x, as playing a critical role in regulating neurogenic competence in hypothalamic tanycytes. Under normal dietary conditions in male mice, Nfia/b/x-deficient tanycytes show enhanced proliferation and neurogenesis. Single-cell RNA-sequencing analysis of Nfia/b/x-deficient tanycytes and tanycyte-derived cells indicates that a substantial fraction of all tanycyte-derived neurons are GABAergic subtypes. A subset of these GABAergic neurons expresses the Leptin receptor (Lepr) and responds to leptin. The Blackshaw lab has also shown that tanycyte-derived neurons survive, integrate into hypothalamic circuits, and fire spontaneous action potentials. By analyzing genes differentially expressed between control and Nfia/b/x-deficient tanycytes, we have shown that Shh and Wnt signaling is upregulated in tanycytes following loss of Nfia/b/x. We also observed the downregulation of the Notch pathway in Nfia/b/x-deficient tanycytes. During development, Shh and Wnt pathways promotes neurogenesis in the hypothalamus. While Notch signaling pathway promote quiescence in retinal Müller glia and cortical astrocytes. Given these findings, I hypothesize that neurogenic competence in tanycytes is actively suppressed in the postnatal hypothalamus after neurogenesis and, hypothesize that tanycyte-derived neurons regulate body weight homeostasis and metabolism. To address these hypotheses, I propose the following two Aims: AIM 1: To investigate extrinsic regulators that positively or negatively control tanycyte-derived neurogenesis in the juvenile and young adult hypothalamus. This work will identify molecular mechanisms and gene regulatory networks that positively or negatively regulate tanycyte-derived neurogenesis in the postnatal hypothalamus. AIM 2: To determine the role of tanycyte-derived neurons on bodyweight homeostasis and metabolism. These studies will provide key insights into the physiological function of tanycyte-derived neurons in controlling body weight homeostasis and metabolism.