A Dual Role of Activin-like kinase 5 (ALK5)-mediated TGF Beta Signaling in Adult Neurogenesis

项目摘要 成年哺乳动物的大脑中增加了新的神经元，这一过程被称为成年神经发生和成年 神经发生在学习和记忆的功能结果中起着关键作用。已知的两个壁龛之一 成年神经发生是海马齿状回的颗粒下带(SGZ)。这是众所周知的 转化生长因子-β信号对发育过程中的神经发生至关重要，而其在成人神经发生中的作用仍然存在。 不清楚。由于全球转化生长因子-β基因敲除小鼠在早期新生小鼠中的致死性表型，确切的作用是 转化生长因子-β信号在成体神经发生中的作用一直是研究的难点。转化生长因子-β体内慢性给药的抑制作用 然而，通过敲除I型受体(ALK5)抑制转化生长因子-β信号在成熟和 未成熟的神经元也会导致成年神经发生受损。此外，药理调节作用 先前研究中的转化生长因子-β信号影响多种细胞类型，包括已知的神经元和小胶质细胞 在调节成人神经发生方面起间接作用。因此，要准确地理解自治 转化生长因子-β信号在成体神经发生过程中的作用 分化、成熟和迁移，成人神经干细胞特异性和诱导性基因调控模型 都是需要的。为了在该领域避开这些挑战，我们产生了神经干细胞特异性的转化生长因子-β受体类型 I(ALK5)或II型(TβRII)诱导的可诱导基因敲除(IKO)小鼠，使我们能够更具体地研究 信号通路影响成体神经干细胞及其下游子代。我们实验室的初步数据显示，在体外 SB-431542抑制转化生长因子-β信号通路促进成体神经干细胞增殖 转化生长因子-β可抑制神经干细胞的增殖。这意味着转化生长因子-β信号在发挥一个 对成年神经干细胞增殖的抑制作用。此外，来自Nestincreer-Alk5的初步体内数据 IKO小鼠提示转化生长因子-β信号对神经干细胞在星形胶质细胞体内的成熟和迁移具有重要作用。我们, 因此，假设转化生长因子-β信号在抑制细胞增殖的神经源性级联反应中具有双重作用。 同时支持未成熟神经元和成熟神经元的成熟和迁移。目标是 本研究的目的是确定转化生长因子-β信号转导通路在血管紧张素转换酶调控中的确切功能和机制。 成人神经发生的不同阶段，并在每个过程中识别不同的靶基因。虽然之前 研究提供了转化生长因子-β信号影响成人神经发生的证据，但结果相互矛盾 在整个领域中，众所周知，转化生长因子-β信号以高度依赖于上下文的方式发挥作用。具有特效性 在我们的活体小鼠模型中，这一提议将为细胞和机制过程提供新的见解 与成人神经发生有关。

Project Summary New neurons are added in the adult mammalian brain by a process known as adult neurogenesis and adult neurogenesis is a key player in functional outcomes for learning and memory. One of the two known niches of adult neurogenesis is the subgranular zone (SGZ) of the dentate gyrus (DG) in the hippocampus. It is known that TGF-β signaling is crucial for neurogenesis during development while its role in adult neurogenesis remains unclear. Due to the lethal phenotype in early neonatal mice of the global TGF-β knockout mice, the precise role of TGF-β signaling in adult neurogenesis has been challenging to study. Chronic delivery of TGF-β in vivo inhibits neurogenesis; however, inhibition of TGF-β signaling via knockout of the type I receptor (Alk5) in mature and immature neurons also leads to compromised adult neurogenesis. Additionally, pharmacological modulation of TGF-β signaling in previous studies affect multiple cells types including neurons and microglia which are known to have an indirect role in regulating adult neurogenesis. Therefore, to understand the precise autonomous requirement of TGF-β signaling in the process of adult neurogenesis during different stages such as proliferation, differentiation, maturation, and migration, adult neural stem cell specific and inducible gene modulation models are needed. To circumvent these challenges in the field, we have generated NSC- specific TGF-β receptor type I (Alk5) or type II (TβRII) inducible knockout (iKO) mice which allows us to more specifically investigate how this signaling pathway affects adult NSCs and downstream progeny. Preliminary data from our lab shows in vitro pharmacological inhibition of TGF-β signaling with SB-431542 increases the proliferation of adult neural stem cell (NSCs) while treatment with TGF-β inhibits the proliferation. This implicates TGF-β signaling in playing an inhibitory role in the proliferation of adult NSCs. Additionally, our preliminary in vivo data from NestincreER-Alk5 iKO mice suggests TGF-β signaling is important for the maturation and migration of NSCs in the SGZ. We, therefore, hypothesize a dual role of TGF-β signaling in the neurogenic cascade which inhibits the proliferation of NSCs while simultaneously supporting maturation and migration in immature and mature neurons. The goal of this current study is to determine the precise functions and mechanisms of TGF-β signaling in regulation of adult neurogenesis through different stages and identify distinct target genes in each process. Although previous studies provide evidence of TGF-β signaling influencing adult neurogenesis, there are conflicting results throughout the field as TGF-β signaling is known to act in a highly context-dependent manner. With the specificity of our in vivo mouse models, this proposal will provide novel insight on the cellular and mechanistic processes involved with adult neurogenesis.