Regulation of Shh Signaling by Cellular Energetics

项目概要： Shh通路在发育、干细胞维持和组织稳态中起关键作用。 小脑发育过程中Shh信号失调导致髓母细胞瘤， 小儿脑肿瘤在儿童与假定的细胞起源的颗粒细胞前体（GCPs）。期间 在出生后的发育过程中，GCPs在外部颗粒层中经历快速和短暂的增殖 (EGL)在分化并向内迁移成为颗粒神经元之前响应Shh信号。 持续的Shh信号对抗这种刻板的发育模式，导致分化中断 并且GCP在外部EGL中的停留时间延长，其中小脑肿瘤被认为是开始的。因此，我们认为， 阐明调节CGP增殖和分化的机制对我们的研究具有重要意义。 对小脑肿瘤发生的理解。细胞生长和增殖失调是 需要消耗能量的合成代谢过程如蛋白质合成和脂肪生成的肿瘤。这些 合成代谢过程受到细胞能量传感器的高度调节和严格控制。关键 在能量耗尽的情况下被激活的能量传感器是AMP激活的蛋白激酶（AMPK）。 我们发现AMPK是GCPs和原发性髓母细胞瘤细胞中Shh信号的有效抑制剂。 此外，AMPK在发育中的小脑的内部EGL中被选择性激活，其中Shh信号传导是 下调，GCP开始分化。这些观察结果表明AMPK可能发挥了 在调节GCPs中Shh信号传导以用于分化、增殖和肿瘤发生中起关键作用。我们将测试 该假说的目的有三：1）阐明AMPK激活拮抗Shh的机制 2）确定AMPK在体内调节GCP增殖和分化中的作用; 3） 确定AMPK激活在体内Shh驱动的髓母细胞瘤中的作用。

Project Summary: The Shh pathway plays critical roles in development, stem cell maintenance and tissue homeostasis. Deregulated Shh signaling during cerebellar development causes medulloblastoma, the most common pediatric brain tumors in childhood with presumed cellular origin in granule cell precursors (GCPs). During postnatal development, GCPs undergo rapid and transient proliferation in the outer external granule layer (EGL) in response to Shh signaling before differentiating and migrating inward to become granule neurons. Persistent Shh signaling counters this stereotypic developmental pattern, resulting in disrupted differentiation and prolonged stay of GCPs in the outer EGL where cerebellar neoplasm is thought to initiate. Therefore, elucidating the mechanism by which CGP proliferation and differentiation are regulated is important to our understanding of cerebellar tumorigenesis. Deregulated cellular growth and proliferation are hallmarks of neoplasms that entail energy-consuming anabolic processes such as protein synthesis and lipogenesis. These anabolic processes are highly regulated and subject to stringent control by cellular energy sensors. The key energy sensor that is activated under condition of energy depletion is AMP-activated protein kinase (AMPK). We discovered that AMPK is a potent inhibitor of Shh signaling in GCPs and primary medulloblastoma cells. Moreover, AMPK is selectively activated in the inner EGL of the developing cerebellum where Shh signaling is downregulated and GCPs have begun differentiating. These observations suggest that AMPK may play a critical role in modulating Shh signaling in GCPs for differentiation, proliferation and tumorigenesis. We will test this hypothesis by three aims: 1) Elucidate the mechanism by which AMPK activation antagonizes Shh pathway activity; 2) Determine the role of AMPK in modulating GCP proliferation and differentiation in vivo; 3) Determine the effect of AMPK activation in Shh-driven medulloblastoma in vivo.