Phenotypic Variants of the Deafness-Associated Mitochondrial DNA A7445G Mutation
Anita Maasz, Katalin Komlosi, Kinga Hadzsiev, Zsolt Szabo, Patrick J. Willems, Imre Gerlinger, Gyorgy Kosztolanyi, Karoly Mehes and Bela Melegh
Affiliation: Department of Medical Genetics and Child Development, University of Pecs, Postal address: H-7624, Pecs, Szigeti 12, Hungary.
A number of nuclear and mitochondrial mutations have been implicated in non-syndromic hearing loss. Among them, various mutations of mitochondrial SerUCN-tRNA and 12S rRNA genes have been found to be associated with deafness; the A7445G mitochondrial DNA (mtDNA) in this group is unique, simultaneously affecting two different mitochondrial genes, encoding the SerUCN-tRNA and the first subunit of cytochrome oxidase. Besides the hearing loss, it is mainly associated with palmoplantar keratoderma, though; different phenotypic associations have been reported. The current paper reviews the available PubMed reports on the A7445G mtDNA mutation, with special attention to the phenotypic variations. Further, a Hungarian family with the A7445G mutation is reported, in which analysis of both the affected and the non-affected members revealed the mutation in both homo- and heteroplasmic forms, independently of the hearing status of the subjects, a phenomenon previously not reported in other pedigrees. The female lineage represented a rare variant of the U4b haplogroup.
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