The Development Of Stria Vascularis And Transcriptomic Analysis In Porcine Model Of Waardenburg Syndrome

Waardenburg syndrome 2A is a common syndromic hereditary deafness,it mainly caused by mutation of Mitf-M gene,which leads to melanocyte dysplasia and decrease on melanin synthesis,manifested with systemic hypopigmentation.For a lack of intermediate cells derived from melanocyte in the inner ear,thereby reducing the endocochlear potential,which in turn leads to extensive hair cell damage and eventually manifests as severe sensorineural deafness.The porcine model with spontaneous mutation of the Mitf-M gene has a defect in pigmentation,auditory function and morphological changes of the inner ear consistent with the human Waardenburg syndrome type 2A.It’s cochlear development and auditory formation process are closer to humans than the mouse model.This study is based on the model to analyze cochlear stria vascularis’ morphology and molecular biology,in order to provide evidence for the pathogenesis and intervention of stria vascularis’development and related diseases.The stria vascularis is a highly vascularized tissue,which composed of marginal cells,basal cells,intermediate cells and capillary network.It plays an important role in maintaining the endocochlear potential and ion transport cycle.Previous studies have mainly believed that Mitf supports the survival of intermediate cells and maintains the intact structure of the stria vascularis.However how Mitf acts as a transcription factor involved in stria vascularis function and auditory formation is still not studied.Therefore,this study used the techniques of RNA-Seq sequencing,immunofluorescence and electron microscopy to analyze the roles of Mitf gene involved in the formation of stria vascularis’biological process and pathways.The mice are widely used in hereditary deafness research,and Mitf-M knockout mice also exhibited a phenotype similar to human Waardenburg syndrome type 2A,but considering the differences between mice and human,such as evolutionary relationship,auditory development.Also the limitations to get cochlear of normal people and the patients for medical research,so it is difficult to compare the specific differences in the regulation of Mitf-M mutation of mice and human cochlear stria vascularis.However,pigs’auditory development,the morphology and structure of auditory organs are more similar to human.Therefore,we analyzed cochlear stria vascularis of the Mitf-M mutant pig(or mutant mouse)and normal control pig(or normal mouse).The transcriptomic data were compared to analyze the differences in the regulation of the Mitf-M mutation between the two species’ cochlear stria vascularis and to compare the species specificity between the two species of cochlear stria vascularis.The different genes of the Mitf M gene mutation and the normal pigs’ cochlear stria vascularis tissues are mainly concentrated in the functionai classification of melanin secretion,ion transport and PI3K-AKT signaling pathway,cell-matrix adhesion.It is suggested that Mitf is closely related to the formation of potassium secretion and the PI3K-AKT signaling pathway.In order to study the effect of Mitf gene on stria vascularis development and morphogenesis,we analyse the cochlear stria vascularis of the two groups,combined with the expression of marker genes,to investigate the Mitf gene’s effect on stria vascularis.At beginning the Mitf-M mutation doesn’t damage the stria vascular typical structures such as macrophages,tight junctions,and capillary networks.The differences in the expression of the Mitf-M mutation between the mouse and Rongchang pig cochlear stria vascularis were compared The common differential genes between the two species are mainly concentrated in biological processes such as tyrosine metabolism,melanin formation and ion transport.There were 99 and 177 genes in pigs and mice showing species-specific changes,respectively.Indicating that Mitf as a transcription factor has species specificity for target gene recognition.In addition,there is also a big specificity in the different species’ stria vascularis.It indicates that the structure of pigs and mice’s stria vascularis are similar,but different key genes are used in regulating ion function and structure development,which also suggests that there may be big different gene expression and regulation between model animals and humans.So,the pig model,closer to human evolution,may be a more appropriate model for studying stria vascularis-related diseases.