Connexin Function and Mechanisms of Cx26 Deficiency Induced Hearing Loss

Cx26 缺陷引起的听力损失的连接蛋白功能和机制

• 批准号: 10278375
• 负责人: Hong-Bo Zhao
• 金额: $ 50.41万
• 依托单位: UNIVERSITY OF KENTUCKY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-19 至 2026-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10278375
• 关键词: Affect; Archives; Basilar Membrane; Birth; Caliber; Cells; Child; Childhood; Clinical; Cochlea; Connexins; Cytoskeleton; Development; Diagnosis; GJB2 gene; Gap Junctions; Gene Expression; Genes; Hair Cells; Human; Impairment; In Situ; Incidence; Induced Mutation; Knowledge; Laboratories; Lead; Life; Mechanics; Membrane; MicroRNAs; Molecular; Mus; Mutation; National Institute on Deafness and Other Communication Disorders; Nucleotides; Outer Hair Cells; Pathologic; Pathology; Patients; Permeability; Pillar Cell; Recycling; Role; Supporting Cell; Temporal bone structure; Testing; Therapeutic Intervention; Viral; congenital deafness; deafness; developmental disease; gap junction channel; gene therapy; genetic deafness; hearing impairment; hearing restoration; hereditary hearing loss; intercellular communication; mouse model; mutation screening; normal hearing; novel; organ growth; preventive intervention; promoter; public health relevance; transcription factor

Summary Mutations of gap junction gene Cx26 (GJB2) cause the most of hereditary deafness, ranging from profound congenital deafness at birth to mild late-onset hearing loss in childhood. Mouse models show that Cx26 deficiency can induce cochlear developmental disorders, hair cell degeneration, endocochlear potential (EP) reduction, and active cochlear amplification declining. We further found that the cochlear developmental disorder rather than hair cell degeneration is a primary cause for congenital deafness, whereas late-onset hearing loss is associated with reduction of outer hair cell (OHC) electromotility even hair cells have no connexin expression. We also evidenced that K+-recycling hypothesis is not the deafness mechanism of Cx26 deficiency. However, detailed mechanisms of these pathological changes induced by Cx26 deficiency remain unclear. Moreover, little is known about pathological changes in the human cochlea. Recently, gene therapy with viral-expression of Cx26 in the cochlea was failed to restore hearing. The main reason is lack of required knowledge of Cx26 function in the cochlea and deafness mechanisms by Cx26 deficiency. In this proposal, we will continually investigate Cx26 function and cellular and molecular mechanisms of Cx26 deficiency-induced congenital deafness and late-onset hearing loss. Cx26 deficiency causes the cochlear developmental disorder, indicating that gap junction (GJ) channels as an intercellular communication conduit are crucial for the cochlear development. Many factors, such as promoters, transcription factors, and miRNAs, can regulate gene expressions during development. However, none of these regulators is permeable to GJ channels except miRNAs. miRNAs can regulate gene expression broadly and have a critical role in the organ development. Deficiency of miRNAs can cause cochlear developmental disorders. In this study, we will first test whether Cx26 deficiency can disrupt miRNA expression and intercellular communication in the cochlea to affect cochlear development in the congenital deafness. Secondly, we will define how Cx26 deficiency decline OHC electromotility leading to late-onset hearing loss, which patients are good candidates for administration of preventive and therapeutic interventions due to normal hearing in their earlier life. Recently, connexin non-channel function has been emerged. Besides forming GJ channels, connexins can participate in cell cytoskeleton formation. We will test whether Cx26 deficiency can impair cytoskeleton formation in the OHC’s supporting cells, thereby changing OHC-loading (membrane tension) and declining OHC electromotility and active cochlear amplification. Finally, we will use backward-mutation screening approach to screen Cx26 mutations in the archival human temporal bones from patients with nonsyndromic hearing loss, whose pathological changes in the cochlea have been diagnosed, to identify mutation-induced pathological changes in the human cochlea. Apparently, these studies will reveal detailed deafness mechanisms by Cx26 deficiency. Such information is urgently required for developing efficient therapies.

总结 缝隙连接基因Cx26（GJB2）突变是导致遗传性耳聋的主要原因， 从出生时的先天性耳聋到儿童期的轻度迟发性听力损失。小鼠模型显示Cx26 缺乏可导致耳蜗发育障碍、毛细胞变性、耳蜗内电位（EP） 减少，主动耳蜗放大下降。我们进一步发现，耳蜗发育 先天性耳聋的主要原因不是毛细胞变性，而是迟发型 听力损失与外毛细胞（OHC）电活动性的降低有关，即使毛细胞没有 连接蛋白表达。我们还证明了K+再循环假说不是Cx26的耳聋机制 缺陷然而，Cx26缺陷引起的这些病理变化的详细机制仍然存在 不清楚此外，对人类耳蜗的病理变化知之甚少。最近，基因治疗 耳蜗中Cx26的病毒表达未能恢复听力。主要原因是缺乏必要的 了解Cx26在耳蜗中的功能以及Cx26缺陷引起的耳聋机制。 在这个计划中，我们将继续研究Cx26的功能和细胞和分子机制， Cx26缺陷导致的先天性耳聋和迟发性听力损失。Cx26缺陷导致 耳蜗发育障碍，表明间隙连接（GJ）通道作为细胞间通讯 管道对耳蜗发育至关重要。许多因子，如启动子、转录因子和转录因子， miRNAs在发育过程中可以调节基因表达。然而，这些监管机构都不是渗透性的 GJ通道，除了miRNAs。miRNAs可以广泛地调节基因表达，并在基因表达调控中发挥关键作用。 器官发育。miRNAs的缺乏可导致耳蜗发育障碍。在这项研究中，我们将 首先测试Cx26缺陷是否会破坏miRNA表达和细胞间通讯， 先天性耳聋耳蜗发育的影响。其次，我们将定义Cx26如何 OHC缺乏导致电活动下降，导致迟发性听力损失，这是患者的良好候选人 由于他们早年听力正常，因此需要进行预防和治疗干预。 近年来，连接蛋白的非通道功能被提出。除了形成GJ通道，连接蛋白还可以 参与细胞骨架的形成。我们将测试Cx26缺陷是否会损害细胞骨架 在OHC的支持细胞中形成，从而改变OHC负载（膜张力）并降低 OHC电活动和主动耳蜗放大。最后，我们将使用反向突变筛选 一种筛选非综合征患者颞骨中Cx26突变的方法 听力损失，其耳蜗的病理变化已被诊断，以确定突变引起的 人类耳蜗的病理变化。显然，这些研究将揭示详细的耳聋 Cx26缺陷的机制。这些信息对于开发有效的治疗方法是迫切需要的。