Scrutinize bHLH transcription factors mediated organ of Corti cell fate determina

描述（由申请人提供）：碱性螺旋环螺旋转录因子对内耳感觉神经发育至关重要：Atoh 1调节毛细胞（HC）的分化，Neurog 1和Neurod 1分别调节神经元的特化和分化。HC中的Delta和Jagged配体和支持细胞（SC）中的Notch受体的表达指导支持细胞分化。此外，来自毛细胞和其他来源的扩散因子巩固了拓扑正确的分化。人类的听力缺陷可导致HC和SC的不可逆损失。Corti器官（OC）的重建需要两种类型的HC（内毛细胞（IHC）和外毛细胞（OHC））以及几种类型的SC的拓扑正确组织。具体的细胞类型如何在正确的位置分化尚不清楚。bHLH基因Neurod 1的缺失导致Atoh 1的过早、异常表达。Neurod 1的缺失与Atoh 1表达的改变相结合，导致一些外毛细胞（OHC）转化为内毛细胞（IHC）。在Aim 1a中，我将在Neurod 1敲除小鼠中使用Atoh 1-Cre介导的R26-YFP报告基因将Atoh 1的表达与Delta-Notch效应子（Hes 1，Hes 5，Hey 2）和扩散性分子（Fgf 8，Fgf 10，Fgf 20，BMP 4）的表达相关联。在Aim 2a中，我将分析一种新的小鼠模型，该模型错误表达Neurog 1与“自我终止”Atoh 1-Cre（Atoh 1- Cre; Atoh 1f/kiNeurog 1）。在Aim 2b中，我将研究Neurod 1的缺失与Neurog 1的错误表达（Atoh 1-Cre; Atoh 1f/kiNeurog 1; Neurod 1-/-）如何影响某些HC标志物并改变OC中的Delta-Notch模式。这些突变体将严格测试调控OC模式的分子机制的假定因果关系，包括HC和SC分化，超出不能区分拓扑结构和细胞特异性效应的相关证据。

DESCRIPTION (provided by applicant): Basic helix loop helix transcription factors are crucial for inner ear neurosensory development: Atoh1 regulates the differentiation of hair cells (HCs) and Neurog1 and Neurod1 regulate specification and differentiation of neurons, respectively. Expression of Delta and Jagged ligands in HCs and Notch receptors in supporting cells (SCs) guides supporting cell differentiation. In addition, diffusible factors from hair cells and other sources consolidate topologically correct differentiation. Hearing defects in human can result in irreversible loss of HCs and SCs. Reconstitution of organ of Corti (OC) requires topologically correct organization of the two types of HCs, inner (IHC) and outer (OHC) hair cells, as well as several types of SCs. How specific cell types differentiate in the right location is unknown. Deletion of the bHLH gene Neurod1 results in the premature, aberrant expression of Atoh1. Loss of Neurod1 in conjunction with an altered expression of Atoh1 results in the conversion of some outer hair cells (OHCs) into inner hair cells (IHCs). In Aim1a, I will correlate in the Neurod1 null mouse, the expression of Atoh1 using Atoh1-Cre mediated R26-YFP reporter with the expression of Delta-Notch effectors (Hes1, Hes5, Hey2) and diffusible molecules (Fgf8, Fgf10, Fgf20, BMP4). In Aim2a, I will analyze a novel mouse model that misexpresses Neurog1 in combination with 'self-terminating' Atoh1-Cre (Atoh1- Cre; Atoh1f/kiNeurog1). In Aim2b, I will investigate how the absence of Neurod1 in combination with the misexpression of Neurog1 (Atoh1-Cre; Atoh1f/kiNeurog1; Neurod1-/-) will affect certain HC markers and alter Delta-Notch patterning in the OC. These mutants will critically test the presumed causalities of molecular mechanism that regulate the patterning of the OC, including HCs and SCs differentiation, beyond correlative evidence that cannot distinguish between topology and cell specific effects.