Novel Factors that Regulate GnRH Neuronal Development

描述(申请人提供)：促性腺激素释放激素(GnRH)神经元表现出一种独特的发育程序性神经元迁移和基因表达模式。控制它们从嗅觉平台迁移到前脑的精确时间模式的机制尚不清楚；然而，导致神经元迁移失败的障碍最终导致性成熟失败。随着GnRH产生细胞系的发展，体内GnRH神经元数量少、分布不均的固有困难也随之增加：GT1-7来源于前脑中大量产生GnRH的迁移性GnRH神经元，Gn10/NLT细胞来源于嗅区中少量产生GnRH的迁移性GnRH神经元。根据两个GnRH产生细胞的不同表型，我们使用差异显示聚合酶链式反应(DdPCR)来鉴定差异表达的基因产物。其中一个克隆的cDNA是黏附相关激酶(Ark)，它是一个新的受体酪氨酸激酶家族(Ark/Ax1、Tyro3和Mer)的成员，其胞外结构域具有细胞黏附分子的特征。在移行的Gn10/NLT细胞中有Ark基因的表达，而在迁移后的GT1-7细胞中不表达。研究证实，Ark及其配体Gas6可能在GnRH神经元迁移、保护细胞程序性死亡和抑制GnRH合成中发挥作用。这一建议将进一步剖析Gas6/Ark及其家族成员Tyro3在GnRH神经元迁移中的作用以及Ark信号抑制GnRH转录的机制。GnRH神经细胞系统将为随后在活体头片模型中证实以及使用Ark和Tyro3的单转基因和双转基因敲除模型进行研究提供基础。总之，这项研究将促进我们对GnRH神经元迁移和基因表达在发育过程中的基础机制的理解。他们还将提供可能导致人类促性腺激素释放激素缺乏综合征的新候选基因，并确定支持或抗生育药物的新靶点。研究将深入了解神经元迁移的一般机制，这些机制可能会影响神经退行性疾病的治疗。

DESCRIPTION (provided by applicant): Gonadotropin releasing hormone (GnRH) neurons display a unique pattern of a developmentally programmed neuronal migration and gene expression. The mechanisms that control their precisely timed pattern of migration from the olfactory placode to the forebrain are unknown; however, disorders that cause a failure of neuronal migration ultimately result in a failure of sexual maturation. The difficulties inherent in the study of GnRH neurons due to their small number and heterogenous, dispersed population in vivo was advanced with the development of GnRH producing cell lines: GT1-7 derived from postmigratory GnRH neurons in the forebrain that make abundant GnRH, and Gn10/NLT cells derived from migratory GnRH neurons in the olfactory area that make little GnRH. Based on the divergent phenotype of the two GnRH producing cells, we used differential display polymerase chain reaction (DDPCR) to identify divergently expressed gene products. One of the cDNAs cloned was Adhesion related kinase, (Ark), a member of a novel family of receptor tyrosine kinases (Ark/Axl, Tyro3 and Mer), whose extracellular domain has features of a cell adhesion molecule. The Ark cDNA was expressed in the migratory Gn10/NLT cells and not in the postmigratory GT1-7 cells. Studies have confirmed the hypothesis that Ark and its ligand, growth arrest specific gene 6 (Gas6), may play a role in GnRH neuronal migration, protection from programmed cell death and repression of GnRH synthesis. This proposal will dissect further the role of Gas6/Ark and its family member, Tyro3, in GnRH neuronal migration and the mechanism by which Ark signaling inhibits GnRH transcription. GnRH neuronal cell systems will provide the foundation to then confirm in an in vivo head slice model and studies using single and double transgenic knockout models of Ark and Tyro3. Together this investigation will advance our understanding of the mechanisms that underly GnRH neuronal migration and gene expression across development. They will also provide new candidate genes that may underly human GnRH deficiency syndromes and identify novel targets for pro or antifertility agents. Studies will give insight into general mechanisms of neuronal migration that could impact on the treatment of neurodegenerative diseases.