Abstract
BackgroundMutations in the mitochondrial DNA (mtDNA) have been associated with aminoglycoside-induced and nonsyndromic deafness in different populations. In the present study, we investigated the contribution of mutations in mitochondrial genes to the etiology of hearing loss in a Brazilian sample.MethodsUsing mass spectrometry genotyping technology, combined with direct sequencing, 50 alterations previously described in 14 mitochondrial genes were screened in 152 patients with sensorineural hearing loss and in104 normal hearing controls.ResultsFifteen known mitochondrial alterations were detected (G709A, A735G, A827G, G988A, A1555G, T4363C, T5628C, T5655C, G5821A, C7462T, G8363A, T10454C, G12236A, T1291C, G15927A). Pathogenic mutations in MT-RNR1 and MT-TK genes were detected in 3 % (5/152) of the patients with hearing loss.ConclusionsThis study contributed to show the spectrum of mitochondrial variants in Brazilian patients with hearing loss. Frequency of A1555G was relatively high (2.6 %), indicating that this mutation is an important cause of hearing loss in our population. This work reports for the first time the investigation and the detection of the tRNALys G8363A mutation in Brazilian patients with maternally inherited sensorineural hearing loss.
Highlights
Mutations in the mitochondrial DNA have been associated with aminoglycoside-induced and nonsyndromic deafness in different populations
We investigated the potential of the single nucleotide polymorphism (SNP) genotyping technology called iPLEX Gold MALDI-TOF MS, developed by Sequenom Inc. (San Diego, CA), for the simultaneous analysis of mitochondrial alterations
Samples from these individuals had been referred to the Human Molecular Genetics Laboratory of the Center for Molecular Biology and Molecular Engineering (CBMEG) at the University of Campinas (UNICAMP) by different organizations, in order to determine the etiology of Hearing loss (HL)
Summary
The iPLEXGold/MALDI-TOF MS method was used to screen 50 mtDNA mutations associated with hearing loss. A total of 256 samples obtained from 152 patients with sensorineural HL and 104 normal hearing controls were analyzed. Fifteen different mtDNA alterations were detected: G709A, A735G, A827G, A988G, A1555G, T4363C, T5628C, T5655C, G5821A, C7462T, G8363A, T10454C, G12236A, T1291C, G15927A (Table 2). Based on the MITOMAP database, status was considered ‘Confirmed’ if at least two or more independent studies have reported the pathogenicity of a specific mutation. ‘Reported’ status indicates that one or more reports have considered the mutation as possibly pathogenic (Table 2). 3 % (5/152) of the patients had ‘Confirmed’ mutations (4/A1555G and 1/G8363A). The T4363C alteration was detected in all the individuals analyzed (Table 3). All the results were confirmed by direct sequencing and showed a 100 % match for it
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