Institut Pasteur, Unité de Génétique et Physiologie de l’Audition, Paris, France.
Hum Mol Genet. 2012 Sep 1;21(17):3835-44. doi: 10.1093/hmg/dds212. Epub 2012 Jun 7.
We report a consanguineous Iranian family affected by congenital profound sensorineural deafness segregating in an autosomal recessive mode. Auditory tests implicated at least a cochlear defect in these patients. We mapped the deafness, autosomal recessive (DFNB) locus involved by linkage analysis to a 4.8 Mb region at chromosome 21q22.3-qter. Exclusion of the DFNB8/10 gene TMPRSS3, located in this chromosomal interval, led us to identify a new deafness locus, DFNB98. Whole exome sequencing allowed us to identify a homozygous frame-shifting mutation (c.1726G>T+c.1728delC) in the gene TSPEAR (thrombospondin-type laminin G domain and EAR repeats). This truncating mutation (p.V576LfsX37) impeded the secretion of the encoded protein by cells transfected with the mutated gene. Alternative splicing of TSPEAR transcripts predict two protein isoforms, 522 and 669 amino acids in length, both of which would be affected by the mutation. These isoforms are composed of a thrombospondin-type laminin G (TSP) domain followed by seven tandemly organized epilepsy-associated repeats (EARs), probably forming a β-propeller domain. Tspear is expressed in a variety of murine tissues. Only the larger Tspear transcript was found in the cochlea, and the protein was detected by immunofluorescence at the surface of the hair bundles of sensory cells. The mammalian EAR protein family includes six known members. Defects in four of them, i.e. Lgi1, Lgi2, Vlgr1 and, we show here, TSPEAR, cause disorders with auditory features: epilepsy, which can include auditory features in humans; audiogenic seizures in animals; and/or hearing impairments in humans and mice. These observations demonstrate that EAR-containing proteins are essential for the development and function of the auditory system.
我们报道了一个伊朗的近亲家族，该家族受到常染色体隐性遗传方式先天性深度感觉神经性耳聋的影响。听力测试表明这些患者至少存在耳蜗缺陷。我们通过连锁分析将耳聋，常染色体隐性（DFNB）基因座定位在 21q22.3-qter 染色体的 4.8Mb 区域。位于该染色体区间的 DFNB8/10 基因 TMPRSS3 的排除导致我们鉴定出一个新的耳聋基因座 DFNB98。全外显子组测序使我们能够鉴定出基因 TSPEAR（血栓形成酶样丝氨酸蛋白酶域和 EAR 重复）中的纯合移码突变（c.1726G>T+c.1728delC）。这种截断突变（p.V576LfsX37）阻止了转染突变基因的细胞分泌编码蛋白。TSPEAR 转录本的选择性剪接预测了两种蛋白异构体，长度分别为 522 和 669 个氨基酸，均受突变影响。这些异构体由血栓形成酶样丝氨酸蛋白酶域（TSP）组成，其后是七个串联组织的癫痫相关重复（EAR），可能形成β-三叶螺旋结构域。Tspear 在多种鼠组织中表达。仅在耳蜗中发现较大的 Tspear 转录本，并且通过免疫荧光在感觉细胞毛束的表面检测到该蛋白。哺乳动物 EAR 蛋白家族包括六个已知成员。其中四个成员的缺陷，即 Lgi1、Lgi2、Vlgr1 和我们在这里展示的 TSPEAR，导致具有听觉特征的疾病：癫痫，在人类中可能包括听觉特征；动物中的听觉性癫痫发作；和/或人类和小鼠的听力障碍。这些观察结果表明，EAR 包含的蛋白对于听觉系统的发育和功能是必需的。
