Scrutinize bHLH transcription factors mediated organ of Corti cell fate determina

描述(申请人提供)：基本螺旋环螺旋转录因子对内耳神经感觉发育至关重要：Atoh1调节毛细胞(HC)的分化，Neurog1和Neurod1分别调节神经元的规格和分化。巨噬细胞中Delta和锯齿状配体的表达以及支持细胞(SCs)中Notch受体的表达引导细胞分化。此外，来自毛细胞和其他来源的扩散因子巩固了拓扑上正确的分化。人类的听力障碍会导致HCs和SCs不可逆转的丧失。Corti器官(OC)的重建需要两种类型的毛细胞，即内(IHC)和外(OHC)毛细胞以及几种类型的SC在拓扑上正确的组织。具体的细胞类型如何在正确的位置分化尚不清楚。BHLH基因Neurod1的缺失会导致Atoh1的过早、异常表达。伴随着Atoh1基因表达的改变，Neurod1的缺失会导致一些外毛细胞转化为内毛细胞。在Aim1a中，我将在Neurod1基因缺失的小鼠中，使用Atoh1-Cre介导的R26-YFP报告基因Atoh1的表达与Delta-Notch效应分子(Hes1，Hes5，Hey2)和可扩散分子(Fgf8，Fgf10，FGF20，BMP4)的表达相关。在Aim2a中，我将分析一种新的小鼠模型，该模型错误表达Neurog1并结合“自我终止”的Atoh1-Cre(Atoh1-Cre；Atoh1f/kiNeurog1)。在Aim2b中，我将研究Neurod1的缺失与Neurog1(Atoh1-Cre；Atoh1f/kiNeurog1；Neurod1-/-)的错误表达如何影响某些HC标记并改变OC中的Delta-Notch模式。这些突变体将对调控OC模式的分子机制的假定因果关系进行批判性测试，包括HCS和SCs分化，而不是无法区分拓扑和细胞特异性影响的相关证据。

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.