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As the most common cause of speech disorders, the etiological study of deafness is important for the diagnosis and treatment of deafness. The mitochondrial genome has gradually become a hotspot for deafness genetic research. Mitochondria are the core organelles of energy and material metabolism in eukaryotic cells. Human mitochondria contain 20 amino acids, except for tRNALeu and tRNASer, which have 2 iso-receptors, the other 18 amino acids correspond to unique tRNAs one by one, so mutations in any one tRNA may lead to protein translation defects in mitochondria and thus affect their oxidative phosphorylation process resulting in the corresponding disease phenotype. Mitochondrial tRNAs are extensively modified with base modifications that contribute to the correct folding of tRNAs and maintain their stability. Defective mitochondrial tRNA modifications are closely associated with the development of mitochondrial diseases. The in-depth study found that modification defects of mammalian mitochondrial tRNAs are associated with deafness, especially the nucleotide modification defect of mt-tRNA-37. This article reviews the research on mitochondrial tRNAs, nucleotide modification structure of mitochondrial tRNA-37, and nuclear genes related to modification defects to provide new ideas for the etiological study of deafness.

Background : The GJB2 gene is the most common deafness gene, and epidemic characteristics have obvious racial specificity. Our study aimed to investigate the prevalence and ethnic specificity of the GJB2 gene in deafness in major ethnic groups in Northwest China, evaluate the value of molecular screening for deafness in minority populations, and explore the strategies and methods for genetic diagnosis. Methods : Ethics approval was obtained to collect 1330 cases of moderate to very severe nonsyndromic sensorineural deafness in northwestern China. The mutation characteristics of ethnic minorities were analyzed and compared with those of 464 patients with nonsyndromic sensorineural deafness among ethnic Han in the northwestern from research group by Sequence Scanner V25.0. Then, we analyzed the ethnic specificity of the mutations. Results : A total of 15 GJB2 sequence changes were detected in 1330 minority patients. The study showed that the allele frequency in Tibetan patients was significantly lower than that in Hui and Dongxiang patients, that in Uygur patients was significantly lower than that in Han and Hui patients, and that in Kazak and Tibetan patients was significantly lower than that in Han patients, and the differences between other ethnic groups were not statistically significant. Each ethnic group has a unique GJB2 gene mutation spectrum, and its hotspot mutation distribution has its own characteristics, with c.235delC, c.109 G > A, c.299-300delAT, and c.35delG being common. Conclusions : It has been confirmed that GJB2 gene mutation has a high prevalence in patients with nonsyndromic sensorineural hearing loss in Northwest China. Each ethnic group has a unique mutation spectrum for the GJB2 gene, which is related to its genetic background. It is necessary to develop a corresponding gene diagnosis strategy according to the hotspot mutations and mutation spectrum of each ethnic group.

Objective: To investigate the distribution of common inner ear and internal auditory canal malformations in children with single-sided deafness（SSD） ,and to explore the imaging etiology of SSD by comparing the quantitative parameters of key bone structures between deaf and normal ears in children with congenital SSD. Method: Forty children with SSD diagnosed in the Second Hospital of Lanzhou University from September 2016 to March 2019 were collected. All of them underwent HRCT examinations of temporal bone . The area of bone island, the width of vestibular, the width of internal auditory canal, the height of cochlear and the width of cochlear basal axis were measured. Paired t test was used to compare the difference between the hearing abnormality and normal hearing in children with SSD. Result: The rate of inner ear deformity was 62.5% in SSD group,the most common deformity was cochlear nerve canal deformity, 20 cases （50.0%） of cochlear canal stenosis and 3 cases （7.5%） of cochlear canal atresia.The second most common deformity was internal auditory canal deformity, including 5 cases （12.5%） of internal auditory canal stenosis and 1 case （2.5%） of internal auditory canal atresia. Other malformations included 1 case（2.5%） of RO, 2 cases （5.0%） of incomplete partition （IP） type II and 1 case （2.5%） of enlargement of vestibular aqueduct （EVA）. There are no significant difference in the measured results of the key structures of the inner ear between two groups except the width of cochlear nerve canal, internal auditory canal and the area of bone island. Conclusion: The main inner ear deformities in children with SSD are cochlear nerve canal stenosis and inner auditory canal stenosis. HRCT of temporal bone has high diagnostic value for inner ear deformities in children with SSD., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© by the Editorial Department of Journal of Clinical Otorhinolaryngology Head and Neck Surgery.)