Homoplasmy of the G7444A mtDNA and heterozygosity of the GJB2 c.35delG mutations in a family with hearing loss

ObjectiveMitochondrial mutations have been shown to be responsible for syndromic as well as non-syndromic hearing loss. The G7444A mitochondrial DNA mutation affects COI/the precursor of tRNASer(UCN), encoding the first subunit of cytochrome oxidase. Here we report on the first Greek family with the G7444A mitochondrial DNA mutation.MethodsClinical, cytogenetic, and molecular methods were employed in this study.ResultsWe describe the high variability of phenotypes among three family members harboring the G7444A mutation and also the frequent GJB2 c.35delG mutation of the nuclear genome in heterozygosity. Their phenotypes ranged from normal hearing to deafness, while the proband presented with several other symptoms.ConclusionsThe G7444A mitochondrial DNA mutation has been reported in only a few cases worldwide, alone or in cosegregation with other mitochondrial DNA mutations, but to our knowledge, never before in coexistence with the GJB2 c.35delG mutation.