Prevalence of mitochondrial gene mutations among hearing impaired patients

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. (J Med Genet 2000;37:38-40)

Extensive and rapid screening for major mitochondrial DNA point mutations in patients with hereditary hearing loss

“…29 In Japan, the mutation was detected in 3% of all patients with SNHL. 30 As patients with the m.1555A4G mutation are susceptible to aminoglycoside ototoxicity, [7][8][9] screening for this mutation is therefore beneficial for people who are going to be administered aminoglycoside. Furthermore, this mutation has also been demonstrated in patients with non-syndromic HL without defined past medication histories of aminoglycoside, and even in patients without any apparent maternal inheritance.…”

Maternally inherited hearing impairment in a family with the mitochondrial DNA A7445G mutation

“…Other surveys suggest the A1555G and A3243G mutations are the most common cause of maternally inherited NSSHI in some populations. [12][13][14] Although the A7445G mutation was not found in these surveys, nor in nine other families with possible matrilineal NSSHI we studied, our study shows the importance of screening for this mutation in cases of NSSHI and also highlights the difficulty sometimes encountered in establishing mitochondrial inheritance.…”

Multiple origins of the mtDNA 7472insC mutation associated with hearing loss and neurological dysfunction

“…Although the 7472insC mutation was not present in 117 individuals with familial hearing loss from Finland the A1555G and A3243G mutations were present in 2.5% and 4.3% of individuals respectively. 9 The A1555G mutation was present in 5.4% of Japanese individuals with hearing loss 10 and in Spain this figure was 27.7% in familial, progressive hearing loss. 11 Such differences suggest population differences do exist, although selection criteria of the individuals may also account for some of these differences.…”