Formation of the Enteric Nervous System

描述（由申请人提供）：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。它们控制着消化系统的运动、分泌和吸收。肠道神经元缺乏会导致腹胀和便秘，这是先天性巨结肠病患者的一种症状。受体酪氨酸激酶Ret对ENS的形成至关重要，Ret的突变与巨结肠病有关。最近的研究表明，生长抑制特异性基因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Gas1在小鼠发育过程中的作用。这一建议是基于我们观察到Gas1突变小鼠在肠神经元的数量、位置和轴突投射上存在缺陷。我们之前已经证明Gas1促进Sonic Hedgehog （Shh）信号传导。Shh突变体在肠神经元中具有与Gas1突变体相似的缺陷。我们提出验证Gas1介导Shh和Ret信号来指导肠神经元的定位和轴突投射的假设。在目的1中，我们将定义Gas1突变体的胃肠道缺陷。在Aim 2中，我们将研究Gas1突变体ENS是否改变了Shh和/或Ret信号。在Aim 3中，我们将利用体外外植体和肠内神经球确定Gas1是否介导Shh和Ret信号之间的串扰。我们将验证Gas1介导Shh定向抑制活性的假设，以阻止肠神经元细胞体及其轴突远离Shh表达的肠上皮。我们还将测试Gas1是否负调控ens中Ret的下游效应物。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突的假设。

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.