FCER1G基因调控GJB2基因p.V37I突变所致听力表型差异的分子机制研究

P.V37I variant of GJB2 gene is one of the most important genetic susceptibility mutation responsible for hearing loss in Chinese Hans. Clinically, phenotype of hearing loss of p.V37I exclusive mutation cases presented great difference. However, the pathogenic mechanism remains unknown, and it is probably associated with immunological factors. We established previously Gjb2-V37I/V37I mice model and certified its specific overexpression of Fcer1g gene, which mediates immunologic reation in cochlear. Based on previous study, FCER1G gene influences intra-or extra-cellular Ca2+ ions equilibrium by immune response. Thus, we hypothesized that FCER1G is key molecular resulting in difference phenotype of p.V37I mutation of GJB2 gene by immunological signaling pathways related to disequilibrium of Ca2+ in the cochlear and ionic permeability of p.V37I mutant protein . This study will further explore regulation effect of FCER1G gene on p.V37I variant of GJB2 and its mechanism by levels of molecule, cell, tissue, animal models and clinical cases, and interve by antagonist of immunological pathways as well, in order to provide new thinking for prevention and therapy on hearing loss.

GJB2基因p.V37I突变是导致我国汉族人群听力障碍的重要遗传易感性突变，该突变所致听力表型差异极大，其致病机制尚不明确，推测免疫应答极有可能是致病的关键因素。我们前期构建了Gjb2基因p.V37I突变敲入小鼠并发现介导免疫反应的Fcer1g基因在其耳蜗内存在特异性高表达。基于已有研究：FCER1G基因可通过免疫级联反应影响细胞内外Ca2+平衡，我们提出科学假设：FCER1G基因通过改变内耳微环境中Ca2+平衡从而进一步破坏p.V37I突变蛋白的离子通透性，是调控GJB2基因p.V37I突变听力表型的关键分子。本研究拟从分子、细胞、组织、模式动物和临床病例等多层次阐明FCER1G基因调控GJB2基因p.V37I突变听力表型的分子机制，并利用阻断免疫相关信号通路的拮抗剂进行干预。本项目将从免疫应答这个新角度探讨GJB2基因p.V37I突变的致病机制，为耳聋的防治提供新思路。

GJB2基因c.109G>A突变在人群中极为常见，预计亚洲人群中超过1000万人具有c.109G>A双等位突变。多数GJB2基因突变会导致重度-极重度的先天性耳聋，但c.109G>A突变所致听力下降常表现为轻-重不等的多种听力表型，其原因尚不明确。本项目通过在全生命周期普遍人群中开展听力-基因联合筛查，我们发现中国汉族人群中GJB2基因c.109G>A双等位突变的携带率为0.528%；在新生儿中，仅14.6% p.V37I双等位突变者表现为先天性聋；非新生儿，不同年龄段的c.109G>A双等位突变者中，听力下降的外显率从9.52%-100%不等。此外，预计该突变可导致每年0.4dB的渐进听力下降。..为进一步探究导致GJB2基因c.109G>A突变所致听力表型差异的因素，前期项目组建立了Gjb2-c.109G>A突变KI小鼠模型，并发现该动物模型存在FCER1G特异性高表达，其表达量是WT小鼠的160倍。Fcer1g基因编码IgE-Fc受体的γ亚基，表达于免疫活性细胞，是参与免疫反应的重要介质。据此进一步构建了Fcer1g基因敲除小鼠模型，以及Fcer1g-KO /Gjb2-c.109G>A-KI双基因小鼠模型。在Fcer1g-KO单基因纯合小鼠中，随着年龄增加，部分小鼠听功能出现改变，但内耳毛细胞形态与结构的明显改变。在Fcer1g-KO/Gjb2-c.109G>A-KI双基因小鼠模型中，3月龄小鼠听力功能下降，其听功能进展与相关机制需进一步验证。