Inherited hearing impairment is a remarkably heterogeneous monogenic condition, involving hundreds of genes, most of them with very small (< 1%) epidemiological contributions. The exception is GJB2, the gene encoding connexin-26 and underlying DFNB1, which is the most frequent type of autosomal recessive non-syndromic hearing impairment (ARNSHI) in most populations (up to 40% of ARNSHI cases). DFNB1 is caused by different types of pathogenic variants in GJB2, but also by large deletions that keep the gene intact but remove an upstream regulatory element that is essential for its expression. Such large deletions, found in most populations, behave as complete loss-of-function variants, usually associated with a profound hearing impairment. By using CRISPR-Cas9 genetic edition, we have generated a murine model (Dfnb1em274) that reproduces the most frequent of those deletions, del(GJB6-D13S1830). Dfnb1em274 homozygous mice are viable, bypassing the embryonic lethality of the Gjb2 knockout, and present a phenotype of profound hearing loss (> 90 dB SPL) that correlates with specific structural abnormalities in the cochlea. We show that Gjb2 expression is nearly abolished and its protein product, Cx26, is nearly absent all throughout the cochlea, unlike previous conditional knockouts in which Gjb2 ablation was not obtained in all cell types. The Dfnb1em274 model recapitulates the clinical presentation of patients harbouring the del(GJB6-D13S1830) variant and thus it is a valuable tool to study the pathological mechanisms of DFNB1 and to assay therapies for this most frequent type of human ARNSHI.

中文翻译：

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del(GJB6-D13S1830) 缺失的小鼠模型概括了人类 DFNB1 听力障碍的表型：生成以及功能和组织病理学研究

遗传性听力障碍是一种非常异质的单基因疾病，涉及数百个基因，其中大多数基因的流行病学贡献非常小（< 1%）。 GJB2 是个例外，它是编码 connexin-26 和潜在 DFNB1 的基因，它是大多数人群中最常见的常染色体隐性遗传非综合征性听力障碍 (ARNSHI) 类型（占 ARNSHI 病例的 40%）。 DFNB1 是由 GJB2 中不同类型的致病变异引起的，但也由大的缺失引起，这些缺失保持了基因完整，但删除了对其表达至关重要的上游调控元件。这种大的缺失存在于大多数人群中，表现为完全功能丧失的变异，通常与严重的听力障碍有关。通过使用 CRISPR-Cas9 基因编辑，我们生成了一个小鼠模型 (Dfnb1em274)，它可以重现最常见的缺失 del(GJB6-D13S1830)。 Dfnb1em274 纯合小鼠能够存活，绕过了 Gjb2 敲除的胚胎致死性，并呈现出与耳蜗特定结构异常相关的严重听力损失（> 90 dB SPL）表型。我们发现，Gjb2 表达几乎被消除，其蛋白质产物 Cx26 在整个耳蜗中几乎不存在，这与之前的条件敲除不同，在之前的条件敲除中，并非所有细胞类型都获得了 Gjb2 消除。 Dfnb1em274 模型概括了携带 del(GJB6-D13S1830) 变异的患者的临床表现，因此它是研究 DFNB1 病理机制和分析这种最常见的人类 ARNSHI 类型的治疗方法的宝贵工具。