| Summary: | 博士 === 中山醫學大學 === 醫學研究所 === 96 === In the developed countries, the incidence of congenital hearing loss is estimated at 1 in 1000 births, of which approximately 60% cases are attributed to genetic factors. To date, 59 auditory genes have been identified, some of which are those involved in K+ recycling and maintenance. The importance of K+ recycling and maintenance is underscored by the fact that mutations in each of MYO7A or TMIE, leads to hearing loss in human. However, in Taiwan, the data of MYO7A and TMIE genes are still insufficient; therefore, further research is worthy to conduct. The overall goal of this thesis is to establish the genetic basis for the screening, diagnosis, and pathogenesis studies of MYO7A and TMIE of non-syndromic hearing loss in Taiwan. In this study, we aim to determine the variants sited of the MYO7A and TMIE gene by using comparative genetic analysis between genomic DNA from normal individuals and hearing-impaired patients; and to understand expression of Tmie in cochlea of rat. The analysis revealed 6 variants in 3 out of 4 screened exons of the MYO7A gene (exon 7, 11, and 22). Three missense variants were found only in patients with hearing loss and were heterozygous, including Arg206Cys, Arg206His and Thr381Met. A variant, c.IVS22+58G>A, was found in intron 22 of the MYO7A gene from both patients and control group. Allele frequencies of c.IVS22+58G>A was shown to be significant between the two groups using chi-square (χ2) test (p<0.05). Therefore, we suggested the variant c.IVS22+58G>A may be protective against hearing loss in the Taiwanese. In addition, the analysis revealed 7 novel variants in the TMIE gene. Of the 7 variants, 5 variants were found in both nonsyndromic hearing loss and normal hearing group. Both allelic and genotype frequencies of these sequence changes did not differ significantly between patients and controls (P>0.05). However, a missense variant (Arg86Gln) and one promoter variant (g.-219A>T) were found only in the patients with nonsyndromic hearing loss. Additionally, we located and determined the cellular expression of Tmie within the rat cochlea using a polyclonal anti-Tmie antibody in this thesis. The expression products of Tmie were detected in the spiral limbus, spiral ligament, organ of Corti, and stria vascularis by immunohistochemistry analysis and RT-PCR. In summary, our study provides information for understanding the importance of genetic factors in nonsyndromic hearing loss of Taiwanese. Knowledge of spatial distribution of Tmie will provide important insight into the mechanisms that lead to hearing loss due to mutations in the TMIE gene.
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