A/J是典型的增龄性聋小鼠模型，新近发现其听力减退与柠檬酸合成酶(CS)基因突变有关。前期结果显示，A/J出生后第一天内耳即有高水平的Caspases表达，泛Caspases抑制剂能降低A/J的听力阈值；体外降低HEI-OC1耳蜗细胞Cs-mRNA水平能显著提高Caspase3的表达；CS是三羧酸循环的关键酶, 预测Cs基因突变导致的内质网应激、线粒体代谢障碍和最终的细胞凋亡在A/J小鼠的听力减退中起重要作用。拟在耳蜗细胞株表达Cs突变基因，观察变异蛋白（H55N)在内质网和线粒体的异常分布和引起的内质网应激；以RNAi技术建立CS低表达的耳蜗细胞模型，研究CS不足所致线粒体代谢与氧化应激标志物的变化；探讨内质网应激和线粒体损害相关凋亡途径的活化及其调控机制；在体证实关键指标并做靶向药物的干预。旨在揭示Cs突变致A/J小鼠听力减退的机制，为增龄性聋发病机制的研究提供新途径或防治提供新理论。

A/J mice are a typical mouse model of age related hearing loss（AHL）and a mutation in gene of citrate synthase (Cs) is related to the hearing loss by a recent study. Our preliminary research showed that high mRNA levels of Caspases occurred in the inner ears of A/J mice at birth day and a pan-caspase inhibitor preserved the hearing of A/J mice. Further study revealed that knockdown of Cs by RNA interference (RNAi) up-regulated caspase-3 in HEI-OC1cells. CS is a key enzyme in tricarboxylic acid cycle. We propose that mutation in Cs gene may lead to endoplasmic reticulum stress (ERS), mitochondrial metabolic disorder and, finally, cell apoptosis, which plays an important role in the hearing loss of A/J mice. Therefore, in the present study, the mutant genes will firstly be cloned and expressed in HEI-OC1 cells. The mutant proteins will be localized and ERS will be identified in the cells. Secondly, cell models with low expression of Cs gene will be developed by RNAi techniques and indicators related to energy metabolic disorders and oxidative stress in the mitochondrion will be detected. Thirdly, key molecules in the apoptotic pathways related to ERS and mitochondrion will be screened and their regulation mechanism be identified. Finally, alteration of key molecules in oxidative stress or apoptotic pathways will be proved in A/J mice and be targeted by specific drugs to improve the mouse hearing. This study aims to explore the molecular mechanism for mutation in Cs gene contributing to hearing loss in A/J mice. The project will provide new approaches to studying the development of AHL or provide new theories guiding the intervention of AHL on human.