Prevalence of mitochondrial gene mutations among hearing impaired patients

TLDR

The study used restriction fragment length polymorphism analysis to screen three mitochondrial point mutations (1555A→G, 3243A→G, 7445A→G) in 319 SNHL outpatients and 140 cochlear implantation patients in Japan, including those with aminoglycoside exposure. Approximately 3 % of SNHL outpatients and 10 % of cochlear implantation patients carried the 1555A→G mutation, with rates rising to 33 % and 59 % among those with aminoglycoside exposure, while the 3243A→G mutation was rare (0.3 %) and 7445A→G was absent; the 1555A→G mutation was thus the most prevalent mitochondrial mutation in this Japanese hearing‑impaired cohort, particularly in aminoglycoside‑induced cases.

Abstract

The frequency of three mitochondrial point mutations, 1555A→G, 3243A→G, and 7445A→G, known to be associated with hearing impairment, was examined using restriction fragment length polymorphism (RFLP) analysis in two Japanese groups: (1) 319 unrelated SNHL outpatients (including 21 with aminoglycoside antibiotic injection history), and (2) 140 cochlear implantation patients (including 22 with aminoglycoside induced hearing loss). Approximately 3% of the outpatients and 10% of the cochlear implantation patients had the 1555A→G mutation. The frequency was higher in the patients with a history of aminoglycoside injection (outpatient group 33%, cochlear implantation group 59%). One outpatient (0.314%) had the 3243A→G mutation, but no outpatients had the 7445A→G mutation and neither were found in the cochlear implantation group. The significance of the 1555A→G mutation, the most prevalent mitochondrial mutation found in this study of a hearing impaired population in Japan, among subjects with specific backgrounds, such as aminoglycoside induced hearing loss, is evident.