Sequence Analysis of Mitochondrial 12S RRNA and tRNASer（UCN） Genes in Patients with Non-syndromic Hearing Loss
|School||Nanjing Medical University|
|Course||Department of Otolaryngology,|
|Keywords||non-syndromic hearing loss mitochond rial DNA 12S rRNAgene tRNASer(UCN) gene gene mutation|
Objective: To determine the preva lence and characteristics of mitochond rialDNA (mtDNA) 12S rRNA gene and tRNASer(UCN) gene mutations in Chinese subjectswith non-syndromic hearing impairment.Methods: 135 non-syndromic hearing-impaired Chinese subjects, who werefrom 6 to 17 years old at the Nanjing City School for Deaf Children, and 126 subjectswith norma l hearing were enrolled in this study. Detailed history collection, physica lexamina tion and systematic audiologica l evaluations were conducted. The latterinclude pure-tone audiometry, acoustic immittance, auditory brainstem response(ABR) and distortion product otoacoustic emissions (DPOAE). The periphera l bloodsamples were obtained, and genomic DNA was isola ted from the periphera lleukocytes of all participants using the Puregene DNA Isola tion Kits. The subject’sDNA fragments spanning the entire mitochond rial 12S rRNA gene and tRNASer(UCN)gene were PCR amplified. Each fragment was purified and subseq uently analyzed bydirect sequencing to identify deafness-associated mutations.Results: There were totally eleven 12S rRNA sequence varia nts detected in 135hearing-impaired subjects. Of those, 4 varia nts are known deafness- associa tedmutations with variable frequencies of 4.4% in A827G, 1.5% in T961C, 0.7% inT1095C and 1.5% in A1555G. Other varia nts, such as T1005C, C1048T, T1119C,G709A, C752T and A1382C, seem to be polymorphisms rather tha n causes of disease .On the other hand, we did not find C1494T mutation in the 12S rRNA gene and anyof the known deafness-associated mutations in tRNASer(UCN) gene in all individ uals.Clinica l evaluations showed that the carriers suffered from profound sensorineuralhearing loss. We found one subject carried double mutations of A1555G and T1095C in the mtDNA 12S rRNA gene. None of the control subjects carried any known ordoubted deafness-associated mutations in 12S rRNA gene and tRNASer(UCN) gene.Conclusion: The 12S rRNA gene ma y be a hot spot for mitochond rial mutationscausing non-syndromic hearing loss in the Chinese population, with a total carrierfrequency of 7.4% for deafness-rela ted mutations. Double mutations of A1555G andT1095C in mtDNA 12S rRNA gene region ma y pla y a pivota l role in thepathogenesis of hearing loss in one patient with non-syndromic hearing impairment.