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

项目概要 近年来，有证据表明单细胞具有在大脑中产生神经元的能力。 产后下丘脑。 Tanycytes 是放射状胶质细胞，与神经祖细胞非常相似 形态学和基因表达谱。虽然饮食和激素信号可以调节单细胞衍生的 神经发生，单胞增殖和单胞衍生的神经发生的总体水平较低并且 在成年小鼠中几乎检测不到。控制神经源性能力的分子机制 tanycyte 和 tanycyte 衍生神经元的精确生理功能仍然不清楚。 识别刺激单胞衍生神经发生的分子机制，以促进分化 调节体重和新陈代谢的单胞衍生神经元是一种新的潜在治疗方法 肥胖和代谢紊乱，如 II 型糖尿病。 最近，Blackshaw 实验室的研究发现了核因子一 (Nfi) 家族转录 因素（TF），Nfia/b/x，在调节下丘脑神经源性能力中发挥着关键作用 单细胞。在雄性小鼠的正常饮食条件下，Nfia/b/x 缺陷的 tanycytes 表现出增强 增殖和神经发生。 Nfia/b/x 缺陷型单细胞 RNA 测序分析和 长丝细胞衍生的细胞表明所有长丝细胞衍生的神经元中很大一部分是 GABA 能的 亚型。这些 GABA 能神经元的一个子集表达瘦素受体 (Lepr) 并对瘦素做出反应。 Blackshaw 实验室还表明，单胞衍生的神经元能够存活并整合到下丘脑回路中， 和火自发动作电位。通过分析对照和对照之间差异表达的基因 Nfia/b/x 缺陷的 tanycytes，我们发现 Shh 和 Wnt 信号在 tanycytes 中上调 失去 Nfia/b/x。我们还观察到 Nfia/b/x 缺陷的 tanycytes 中 Notch 通路的下调。 在发育过程中，Shh 和 Wnt 通路促进下丘脑的神经发生。而缺口 信号通路促进视网膜穆勒胶质细胞和皮质星形胶质细胞的静止。鉴于这些发现，我 假设单细胞的神经发生能力在出生后被积极抑制 神经发生后的下丘脑，假设单细胞衍生的神经元调节身体 体重稳态和新陈代谢。为了解决这些假设，我提出以下两个目标： 目标 1：研究正向或负向控制单胞衍生的外在调节因子 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 以及正向或负向调节单胞衍生神经发生的基因调控网络 产后下丘脑。 目标 2：确定单细胞衍生神经元对体重稳态和代谢的作用。 这些研究将为了解单细胞衍生神经元在控制中的生理功能提供重要见解。 体重稳态和新陈代谢。

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.