We report here the clinical, genetic and molecular characterization of three Han Chinese pedigrees with maternally transmitted aminoglycoside-induced and nonsyndromic bilateral hearing loss. Clinical evaluation revealed the wide range of severity, age-at-onset and audiometric configuration of hearing impairment in matrilineal relatives in these families. The penetrances of hearing loss in these pedigrees were 28%, 20%, and 15%, with an average of 21%, when aminoglycoside-induced deafness was included. When the effect of aminoglycosides was excluded, the penetrances of hearing loss in these seven pedigrees were 21%, 13% and 8%, with an average of 14%. Sequence analysis of the complete mitochondrial genomes in these pedigrees showed the presence of the deafnessassociated 12S rRNA C1494T mutation, in addition to distinct sets of mtDNA polymorphism
Genetic polymorphisms in grainyhead‑like 2 (GRHL2) variants were examined for their suspected association with sudden sensorineural hearing loss (SSHL). Between January 2009 and April 2014, 190 patients with SSHL, who were diagnosed at the Departments of Otorhinolaryngology Head and Neck Surgery at Kaihua People's Hospital and Hangzhou First People's Hospital, were selected for the present study and defined as the SSHL group. A group of 210 healthy individuals were defined as the control group. Polymerase chain reaction (PCR)‑restriction fragment length polymorphism was used to detect GRHL2 genotypes, using genomic DNA isolated from peripheral blood as PCR templates. GRHL2 rs611419 genetic polymorphisms conferred a protective effect against SSHL (AT+TT vs. AA: OR=0.63, 95% CI=0.41‑0.98, P=0.038). In addition, rs10955255 polymorphisms were associated with a reduced risk of SSHL (AA vs. GG: OR=0.54, 95% CI=0.31‑0.95, P=0.032; GA+AA vs. GG: OR=0.58, 95% CI=0.38‑0.89, P=0.012). Combined genotypes of rs611419, rs10955255 and rs6989650 in the GRHL2 gene are also associated with a reduced risk of SSHL (P=0.035). In subjects who consumed alcohol, co‑occurrence of 3‑8 variant alleles conferred increased resistance to SSHL, compared with the occurrence of 0‑2 variant alleles (OR=0.40, 95% CI=0.21‑0.76, P=0.004). GRHL2 genetic polymorphisms, rs611419 and rs10955255, have a protective role against SSHL and reduce the risk of SSHL. However, rs6989650 is not associated with SSHL.
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