Mutai Hideki, Kuroda Yukiko, Noji Shinobu, Ichikawa Saki, Matsuo Koichi, Tanaka Satoshi, Kataoka Naoyuki, Fujioka Masato, Matsunaga Tatsuo
Division of Hearing and Balance Research, National Institute of Sensory Organs, NHO Tokyo Medical Center, Tokyo, Japan.
Molecular Genetics, Kitasato University School of Medicine, 1-15-1, Kitazato, Minami-ku, Sagamihara, 252-0374, Kanagawa, Japan.
Sci Rep. 2025 Apr 28;15(1):14790. doi: 10.1038/s41598-025-99827-7.
Hereditary hearing loss is highly heterogeneous. SLC12A2 is linked to autosomal dominant nonsyndromic hearing loss, DFNA78, with all the pathogenic variants affecting the exon 21. The gene encodes a cotransporter NKCC1 crucial for regulating intracellular osmotic pressure and producing endolymph in the cochlea. We generated two mouse strains with heterologous Slc12a2 variants in the splice site of the exon 21 (Em1: NM_009194.3:c.2912-2 A > G and Em2: c.2912-4_2913del). Slc12a2 mice with complete skip of the exon 21 showed reduced endolymph on postnatal day 1 (P1), reduced stria vascularis (StV) and no auditory brainstem responses at 4 weeks. Reduced StV size was considered to be due to rebalance osmotic pressure, and upregulation of Cldn9 revealed by RNA-seq was considered as tissue response to repair the gaps from reduced cell sizes in the Slc12a2 cochlea. Female Slc12a2 mice also exhibited mild elevation of ABR thresholds in several sound frequencies. Slc12a2 mice showed normal hearing, presumably due to sufficient cotransporter activity from the 9 bases shorter transcript by cryptic splicing. Minigene assays indicated that a single nucleotide difference between humans and mice at the 5' end of the exon 21 affects exon 21 splicing. Slc12a2 mouse is proposed as a model for studying DFNA78 pathology.
遗传性听力损失具有高度异质性。SLC12A2与常染色体显性非综合征性听力损失DFNA78相关，所有致病变体均影响外显子21。该基因编码一种协同转运蛋白NKCC1，对调节细胞内渗透压和在耳蜗中产生内淋巴至关重要。我们构建了两种在第21外显子剪接位点带有异源Slc12a2变体的小鼠品系（Em1：NM_009194.3:c.2912-2 A > G和Em2：c.2912-4_2913del）。第21外显子完全跳跃的Slc12a2小鼠在出生后第1天（P1）内淋巴减少，血管纹（StV）减少，4周时无听觉脑干反应。StV大小减小被认为是由于渗透压重新平衡，RNA测序显示Cldn9上调被认为是组织对Slc12a2耳蜗中细胞大小减小所产生间隙的修复反应。雌性Slc12a2小鼠在几个声音频率下也表现出ABR阈值轻度升高。Slc12a2小鼠听力正常，推测是由于通过隐蔽剪接产生的9个碱基较短的转录本具有足够的协同转运蛋白活性。小基因分析表明，人类和小鼠在第21外显子5'端的单核苷酸差异影响外显子21的剪接。Slc12a2小鼠被提议作为研究DFNA78病理学的模型。
