Kit^(F856S)小鼠模型耳聋病理机制初步研究

Preliminary Study on Pathological Mechanisms of Deafness Using the Kit^(F856S) Mouse Model

目的利用Kit突变耳聋小鼠模型研究探讨KIT突变导致听觉色素障碍(Auditory-pigmentary disorders,APDs)的相关致聋机制。方法建立Kit^(F856S)(Wads)小鼠模型家系,确定其表型遗传方式,并对家系中不同表型个体进行听觉电生理测试、并分别利用扫描电镜对基底膜和透射电镜对血管纹进行观察。结果该模型家系的色素分布异常伴耳聋的突变性状符合孟德尔单基因常染色体隐性遗传规律。听觉电生理测试显示该模型家系中野生型和杂合型小鼠听力与家系外野生型C57BL/6J小鼠无明显差异,纯合型表现为听力形成初期先天性中度感音神经性听力损失并进行性下降至重度,极重度。扫描电镜(SEM)显示,纯合型小鼠顶转、底转的外毛细胞有缺失。透射电镜(TEM)显示三转血管纹变薄,结构异常,中间细胞(intermediate cell,IC)及毛细血管周围驻留的巨噬样-黑素细胞(Perivascular-resident macrophage-like melanocytes,PVM)缺失。结论我们的研究表明,Kit突变可能阻断了血管纹黑素细胞的迁移和发育,导致血管纹变薄,结构异常,中间细胞及巨噬样-黑素细胞缺失以及外毛细胞的进行性变性、凋亡,最终导致听力损失。该模型是可用于KIT突变导致听觉色素障碍类疾病进一步研究的可靠模型。

Objective To investigat mechanism of deafness associated with KIT mutation and auditory-pigmentary disorders(APDs)using a Kit mutant deafness mouse model.Method A Kit^(F856S)(Wads)mouse model pedigree was established and its phenotype inheritance determined.Auditory electrophysiological tests were performed on individual animals with different phenotypes.The basilar membrane was examined by scanning electron microscopy(SEM)and the stria vascularis(SV)by transmission electron microscopy(TEM).Results The mutant characteristics of abnormal pigment distribution and deafness in this pedigree conformed to Mendelian autosomal recessive inheritance.Both wildtype and Kit^(F856Sm/+) mice showed no significant difference from C57BL/6J mice on auditory electrophysiological results.The Kit^(F856Sm/m) mice showed moderate sensorineural hearing loss at the beginning of hearing formation which progressively declined to severe to profound loss.Scanning electron microscopyshowed loss of outer hair cells in apical and basal turns in homozygous mice.Transmission electron microscopy showed atrophy of the stria vascularis in all three turns,along with abnormal structures and loss of intermediate cells(IC)and perivascular-resident macrophage-like melanocytes(PVM).Conclusion Our study showed that Kit mutation(c.2567T>C,p.^(F856S))blocks the development of melanocytes in the cochlea,resulting in SV atrophy and structural abnormalities,loss of intermediate cells and perivascular-resident macrophage-like melanocytes as well as degeneration of outer hair cells,which lead to hearing loss as a result.Therefore,this model can be reliably used in studies on KIT mutation induced auditory-pigmentary disorders.