TBC1D24为一新近发现的耳聋基因，其不同类型突变可导致具有多样化临床表型的遗传性耳聋，但在内耳的具体功能和突变致聋机制不明。申请者课题组在前期研究中发现该基因p.S178L杂合突变可导致显性非综合征性耳聋，听力表型显著有别于隐性突变。我们发现Tbc1d24在小鼠内耳特异性表达于螺旋神经节神经元及毛细胞静纤毛，体外研究显示p.S178L突变导致TBC1D24促细胞树突状分支能力的异常性升高，可能为功能获得性突变。本申请拟构建Tbc1d24条件性敲除小鼠，通过听觉生理、内耳病理及分子生物学等研究手段明确该基因在内耳不同表达区域的具体功能和作用通路，探索其功能缺失性突变的致聋机制；构建p.S178L突变敲入小鼠，通过和Tbc1d24敲除小鼠的比较研究验证该突变所特有的致聋机制。本研究有望以TBC1D24为切入点在分子层面上更深入的理解听觉的发生机制和发病机制，促进相关聋病的诊断、干预和预防。

TBC1D24 was recently identified as a deafness gene. Mutations in TBC1D24 may lead to genetic hearing loss with variable phenotypes. The inner ear function and the pathogenic mechanism of TBC1D24 are not clear. In previous studies, we revealed that the p.S178L mutation of TBC1D24 may lead to autosomal dominant non-syndromic deafness with significantly different phenotypes from its recessive counterpart. We showed that in the mouse inner ear, Tbc1d24 is specifically expressed in the spiral ganglion neurons and the stereocilia of the hair cells. Our in vitro study showed that the p.S178L mutation resulted in a significant increase of TBC1D24’s ability to prompt cellular elongation and arborization, suggesting that it is a gain-of-function mutation. In this study, we propose to generate a conditional knock-out mouse model for Tbc1d24. By analyses of this model in auditory physiology, inner ear pathology and molecular biology, we aim to elucidate the function and the underlying pathways of TBC1D24 in different locations of inner ear, and to explore the pathogenic mechanism associated with the loss-of-function mutations of TBC1D24. In addition, we propose to generate a knock-in mouse model for the p.S178L mutation of TBC1D24. By comparative study of the knock-in and the knock-out mouse models, we aim to understand the unique pathogenic mechanism associated with the p.S178L mutation. The proposed study of TBC1D24 may provide important insights into the mechanism of hearing and deafness and may improve the diagnosis, intervention and prevention of the associated hearing impairment.