Regulation of Neural Precursors: Role of Neuropeptides

描述（由申请人提供）：腺苷酸环化酶激活肽（PACAP）是分泌素家族中的一种神经肽，在一系列脑部疾病中具有潜在意义，包括精神发育迟滞、自闭症、神经退行性疾病、CNS损伤和脑肿瘤。由于PACAP和PACAP受体基因表达在神经发生的早期阶段广泛存在，因此已经提出了关于这种肽的特定发育作用的几种假设。例如，体外和体内研究表明，PACAP作为一种自分泌或旁分泌因子，在发育中的神经系统的几个区域中控制神经细胞增殖、存活和表型。本文提出PACAP通过激活蛋白激酶A（proteinkinase A，PKA），拮抗丝裂原/模式因子音刺猬（sonic hedgehog，Shh）的作用，控制后脑和小脑发育过程，并利用遗传模型研究PACAP在发育中的重要作用及其具体机制。这些模型包括：1）PACAP基因已被同源重组破坏的小鼠，2）由于Shh受体/肿瘤抑制基因ptc-1突变而表达过度活跃Shh信号传导系统的转基因小鼠，3）过表达PACAP的非洲爪蟾胚胎mRNA注射系统，以及4）PACAP应答性胚胎后脑和出生后小脑颗粒细胞前体培养物。在这些模型中，将使用形态学和表型标志物、基因表达以及细胞增殖和凋亡指标研究PACAP的作用。这些结果有望揭示PACAP的重要发育功能，并提供相关信号通路的信息。这项工作可能会导致诊断和治疗脑发育疾病，退行性疾病和脑肿瘤的新策略。

DESCRIPTION (provided by applicant): Pituitary adenylyl cyclase activating peptide (PACAP) is a neuropeptide in the secretin family with potential significance in a range of brain afflictions, including mental retardation, autism, neurodegenerative diseases, CNS injury, and brain tumors. Because PACAP and PACAP receptor gene expression is widespread at very early stages of neurogenesis, several hypotheses regarding specific developmental actions of this peptide have been proposed. For example, in vitro and in vivo studies indicate that PACAP acts as an autocrine or paracrine factor to control neural cell proliferation, survival and phenotype in several regions of the developing nervous system. It is propose here that PACAP acts to control processes in the developing hindbrain and cerebellum by antagonizing the action of the mitogen/patterning factor sonic hedgehog (Shh) via protein kinase A activation.In this proposal, genetic models will be used to identify and investigate the essential developmental roles of PACAP and the specific mechanisms involved. These models include 1) mice in which the PACAP gene have been disrupted by homologous recombination, 2) transgenic mice that express an overactive Shh signaling system due to a mutation in the Shh receptor/tumor suppressor gene ptc-1, 3) a Xenopus embryo mRNA injection system which overexpresses PACAP, and 4) PACAP-responsive embryonic hindbrain and postnatal cerebellar granule cell precursor cultures. The action of PACAP will be investigated in these models using morphologic and phenotypic markers, gene expression, and indicators of cell proliferation and apoptosis. The results are expected to reveal critical developmental functions of PACAP and provide information on the relevant signaling pathways. The work may lead to new strategies for the diagnosis and treatment of diseases of brain development, degenerative diseases and brain tumors.