Whole mitochondrial genome screening in maternally inherited non-syndromic hearing impairment using a microarray resequencing mitochondrial DNA chip

Mutations in the mitochondrial tRNASer(AGY) gene are associated with deafness, retinal degeneration, myopathy and epilepsy

“…Although these pathogenic MTTS2 mutations are associated with a variety of clinical presentations including diabetes mellitus, myopathy, neurodevelopmental delay, encephalopathy and seizures, it is interesting to note that all four are also linked to deafness, [6][7][8] and, like the vast majority of deafness-associated mt-tRNA mutations, 33 both m.12264C4T and m.12261T4C were shown here to exhibit a high threshold for pathogenicity. Two additional MTTS2 sequence variants have also been linked to auditory symptoms; m.12236G4A has been associated with hearing loss 10 and m.12224C4T, associated with haplogroup D4, has been found to modulate the penetrance of hearing loss associated with the MT-RNR1 mutation, m.1555A4G. 34 Similar to MTTS1, 35 the MTTS2 gene is emerging as an important hot spot for deafness-associated mutations.…”

“…4,5 These mutations are m.12258C4A, which can lead to progressive deafness and either diabetes mellitus 6 or retinitis pigmentosa, 7 and m.12262C4A, which has been shown to cause progressive mitochondrial myopathy, deafness and sporadic seizures. 8 A further three MTTS2 mutations have been described: m.12207G4A, which is associated with a MELAS-like phenotype, 9 m.12236G4A, which is linked to non-syndromic hearing impairment, 10 and m.12246C4A, which is associated with chronic intestinal pseudo-obstruction with myopathy and ophthalmoplegia. 11 However, due to a lack of functional investigations (eg, single-fibre analysis, trans-mitochondrial cybrid studies), their pathogenicity has not yet been unequivocally proven.…”

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

“…56,57 The Mitochip uses hybridization for detecting mutations or polymorphisms, so that the probes mtDNA mutation screening for hereditary HL T Kato et al should be designed. 56 Although version 2.0 of Mitochip has been improved for detecting mutations, the present version has not been designed for analysis of Asian mtDNA, as it is based on the revised Cambridge reference sequence.…”

“…56,57 The Mitochip uses hybridization for detecting mutations or polymorphisms, so that the probes mtDNA mutation screening for hereditary HL T Kato et al should be designed. 56 Although version 2.0 of Mitochip has been improved for detecting mutations, the present version has not been designed for analysis of Asian mtDNA, as it is based on the revised Cambridge reference sequence. 25,26 As it is necessary to distinguish pathological mtDNA mutations from non-pathogenic mtSNPs, this study used 11 pairs of primers for multiple PCR amplifications and multiple sequence-specific oligonucleotide probes customized for the Japanese population, which were designed to carefully detect either mutant or wild-type mtDNA, even when mtSNPs were present in the vicinity of the mutation sites.…”

A novel method of detecting mitochondrial m.1494C>T and m.1555A>G mutations in a single PCR reaction using base-quenched probe

“…During recent years, certain techniques, including restriction fragment length polymorphism (RFLP) genotyping, direct DNA sequence, and the resequencing Mitochip array have been described and are even commercially available for detecting mtDNA mutations [3,9,17,19], however, potential risk of contamination makes it difficult to avoid using electrophoresis detection method. Although fluorescence resonance energy transfer (FRET) by using two fluorescent dyes in close proximity is one of the most powerful and promising methods for SNP genotyping [20], the expensive costs of fluorescent modification and requirement of special equipment may limit its application widely in the clinical testing.…”