Formation of the Enteric Nervous System

描述(申请人提供)：肠神经系统(ENS)的神经元，即肠神经元，位于胃肠道(GI)、胰腺和胆囊内。它们控制消化系统的运动、分泌和吸收。肠神经元缺陷会导致腹胀和便秘，这是患有先天性巨结肠的患者的一种情况。受体酪氨酸激酶Ret对ENS的形成至关重要，Ret的突变与先天性巨结肠症有关。最近的研究表明，生长停滞基因1(Gas1)的蛋白产物可以与Ret结合并调节Ret信号。我的实验室研究了Gas1在小鼠发育过程中的作用。这一建议是基于我们观察到的Gas1突变小鼠在肠道神经元的数量、位置和轴突投射方面存在缺陷。我们之前已经证明，Gas1促进了Sonic Hedgehog(Shh)信号的传递。Shh突变体与Gas1突变体在肠神经细胞中有类似的缺陷。我们建议检验Gas1介导Shh和Ret信号以指导肠神经元的定位和轴突投射的假设。在目标1中，我们将定义Gas1突变体中GI区的缺陷。在目标2中，我们将检查Gas1突变体ens是否改变了Shh和/或Ret信号。在目标3中，我们将使用体外外植体和肠化神经球来确定Gas1是否介导Shh和Ret信号之间的串扰。我们将测试这一假设，即Gas1介导Shh定向的抑制活性，以保持肠神经元胞体及其轴突远离表达Shh的肠上皮。我们还将测试Gas1是否对ENS中Ret的下游效应器进行负向调节。我们的目标是验证Gas1调节Shh和Ret信号以控制肠道祖细胞/神经元定位和轴突树枝形成的假设。 公共卫生相关性：我们建议研究控制肠道神经系统形成的分子机制。有两条主要的信号通路与肠神经元定位和轴突树枝形成有关，Ret和Shh信号通路。我们计划研究Gas1，一种可以与Shh和Ret结合的蛋白质，在肠神经细胞定位和轴突树枝形成中的作用。这些研究的结果将有助于我们了解肠道神经系统是如何形成的。由于Shh和Ret信号通路直接与人类疾病和癌症有关，我们的结果可能为设计治疗方法来纠正与dys调节的Shh和Ret信号通路相关的疾病提供信息。

DESCRIPTION (provided by applicant): Neurons of the enteric nervous system (ENS), i.e. the enteric neurons, are located within the gastrointestinal (GI) tract, pancreas, and gall bladder. They control the movement, secretion, and absorption of the digestive system. Deficiency of enteric neurons causes abdominal distention and constipation, a condition of patients suffering from the Hirschsprung's disease. The receptor tyrosine kinase Ret is critical for ENS formation and mutations in RET have been associated with the Hirschsprung's disease. Recent studies showed that the protein product of the Growth arrest specific gene 1 (Gas1) could bind to Ret and modulate Ret signaling. My laboratory studies the role of Gas1 during mouse development. This proposal is based on our observation that Gas1 mutant mice have defects in the number, position, and axonal projection of enteric neurons. We have previously shown that Gas1 facilitates Sonic Hedgehog (Shh) signaling. The Shh mutant has similar defects in enteric neurons as the Gas1 mutant. We propose to test the hypothesis that Gas1 mediates Shh and Ret signaling to direct the positioning and axonal projection of enteric neurons. In Aim 1, we will define the defects of the GI tract in the Gas1 mutant. In Aim 2, we will examine whether the Gas1 mutant ENS has altered Shh and/or Ret signaling. In Aim 3, we will determine whether Gas1 mediates a cross-talk between Shh and Ret signaling using in vitro explant and enteric neurospheres. We will test the hypothesis that Gas1 mediates Shh-directed inhibitory activity to keep enteric neuron cell bodies and their axons away from the gut epithelium, where Shh is expressed. We will also test whether Gas1 negatively regulates downstream effectors of Ret in the ENS. Our goal is to test the hypothesis that Gas1 modulates Shh and Ret signaling to control enteric progenitor/neuron positioning and axon arborization. PUBLIC HEALTH RELEVANCE: We propose to study the molecular mechanism controlling the formation of the enteric nervous system. Two major signaling pathways have been implicated in enteric neuron positioning and axonal arborization, Ret and Shh signaling pathways. We plan to investigate the role of Gas1, a protein that can bind to Shh and to Ret, in enteric neuron positioning and axonal arborization. Results from these studies will help us to understand how the enteric nervous system is formed. As Shh and Ret pathways have been directly implicated in human diseases and cancers, our results may provide information for designing therapeutic means to correct diseases related to dys-regulated Shh and Ret signaling pathways.