Pathophysiology of hearing loss associated with Connexin 26 dysfunction

 描述(申请人提供)：听力损失是最常见的先天性感觉障碍。连接蛋白26(Cx26)的突变是导致听力损失的最常见的遗传原因。Cx26在耳蜗的支持细胞中形成缝隙连接，但与Cx26相关的听力障碍的病理生理机制尚不清楚。小鼠的研究表明，缝隙连接在耳蜗发育和成熟功能中起重要作用：1)在新生期，缝隙连接介导的细胞间钙信号(ICS)波是功能成熟所必需的，Cx26基因敲除导致主要结构异常；2)在听力成熟的动物中，缝隙连接可能参与K循环、耳蜗放大以及ICS和MAPK依赖的反应，这概括了它们的发育作用。人类Cx26功能障碍的听力损失表型具有高度的变异性和突变依赖性，这表明Cx26在发育和功能上的不同作用可能是有意义的。为了开发针对不同类型Cx26相关性听力损失的靶向治疗方法，需要对其病理生理机制有深入的了解。在这项研究中，我们解决了围绕Cx26相关性听力损失的病理生理学的文献中的一个主要局限性。绝大多数研究是在新生小鼠身上进行的，这些小鼠早期、完全地敲除了Cx26基因，并随后出现了耳蜗发育异常。我们的目标是1)评估ICS和缝隙连接在沙土鼠耳蜗离体模型中的作用；2)研究Cx26功能错乱(通过可诱导的条件敲除、基因剂量模型和特定的功能点突变)在其他正常发育的小鼠耳蜗中的后果。表型将通过评估缝隙连接功能、ICS行为和缝隙连接成分、下游MAPK效应器和突触标记的表达谱在器官水平上进行评估，并在整个动物生理水平上通过评估听觉脑干反应和噪音导致的听力损失来评估。通过确定Cx26功能障碍如何影响耳蜗和听觉功能，我们将能够为广泛的Cx26相关听力损失患者开发有针对性的治疗方法。

 DESCRIPTION (provided by applicant): Hearing loss is the most common congenital sensory impairment. Mutations in Connexin 26 (Cx26) comprise the most common genetic causes of hearing loss. Cx26 forms gap junctions in supporting cells of the cochlea, but the pathophysiology of Cx26- associated hearing impairment is unclear. Mouse studies have suggested major roles in cochlear development and mature function: 1) in the neonatal period, gap-junction- mediated intercellular Ca2+ signaling (ICS) waves are necessary for functional maturation, and Cx26 knockout results in major structural abnormalities; 2) in hearing- mature animals, gap junctions may be involved in K+ recycling, cochlear amplification, and an ICS and MAPK-dependent response to acoustic trauma that recapitulates their developmental role. The hearing-loss phenotype of Cx26 dysfunction in humans is highly variable and mutation-dependent, suggesting that differential effects on the developmental and functional roles of Cx26 may be meaningful. In order to develop targeted therapy for different kinds of Cx26-associated hearing loss, a thorough understanding of its pathophysiologic mechanisms is required. In this study, we address a major limitation in the literature surrounding the pathophysiology of Cx26-associated hearing loss. The vast majority of studies have been conducted in neonatal mice with early, complete cochlea-specific knockout of Cx26 and subsequent cochlear developmental abnormalities. We aim to 1) evaluate the role of ICS and gap junctions in an ex vivo model of the hearing gerbil cochlea; and 2) investigate the consequences of functional derangements in Cx26 (through an inducible conditional knockout, gene dosage model, and specific functional point mutations) in the otherwise normally developed mouse cochlea. Phenotype will be assessed both at the organ level, by assessing gap-junction function, ICS behavior, and expression profiles of gap-junction constituents, downstream MAPK effectors, and synaptic labeling, and at the whole-animal physiologic level, by evaluating auditory brainstem responses and noise- induced hearing loss. By determining how Cx26 dysfunction affects cochlear and auditory function, we will be able to develop targeted therapies for a wide range of individuals with Cx26-associated hearing loss.