大前庭水管综合征（EVA）是最常见的遗传性聋病之一，发病机制可能与SLC26A4突变所致的内耳离子环境紊乱有关。前期，我们在一个潜在的EVA新致病基因——催化生成HCO3-离子的碳酸酐酶II基因CA2中发现两例突变，在各自的EVA病例中分别与SLC26A4突变形成双基因杂合突变。我们的前期研究显示这两个基因在功能和转录调控上都紧密关联，CA2/SLC26A4双基因杂合突变极有可能共同引发内耳HCO3-离子平衡破坏而致聋。为验证该假说，我们将利用免疫共沉淀、免疫组化等方法研究二者蛋白的相互结合及内耳共表达情况，研究CA2突变对二者相互结合的干扰及对CA2酶催化活性的干扰；利用两个基因纯合敲除小鼠分别研究二者在内耳表达水平的内在联系；在更大样本量的EVA病例中进行CA2突变筛查，同时建立 双基因杂合敲除小鼠模型，验证其致聋模式。本项目有望为EVA的发病机制和治疗研究提供新的理论依据和突破方向。

Enlargement of the vestibular aqueduct (EVA) is one of the most common hereditary deafness, the disturbance of anion and PH in inner ear caused by mutation in anion transporter gene SLC26A4 may be responsible for the pathogenesis. In our preliminary results, two mutations in a potential EVA pathogenic gene CA2, carbonic anhydrase II gene catalyzing the formation of HCO3-, were identified in two EVA patients who also carried heterozygous SLC26A4 mutations. Our previous study also showed the function and transcriptional control of CA2 strongly correlated with SLC26A4. So, we propose the hypothesis: double-heterozygous mutation of CA2/SLC26A4 is likely to lead to the disturbance of HCO3- in inner ear and result in EVA deafness. To test this hypothesis, protein interaction and co-expression of CA2 and SLC26A4 in inner ear, interference on protein interaction of these two proteins and the catalytic activity of CA2 by CA2 mutation will be studied by co-immunoprecipitation and immunohistochemistry. Transcriptional control of CA2 and SLC26A4 in inner ear will be studied by Ca2-/- and Slc26a4-/- knockout mouse, respectively. EVA deafness caused by double-heterozygous mutation of CA2/SLC26A4 will be further verified by mutation screening of CA2 in large number of EVA patients and the analysis of clinical phenotypes in Ca2+/-;Slc264+/-double-heterozygous knockout mouse.This study is expected to provide us new theoretical basis and breakthrough for exploring the pathogenesis and treatment of EVA