Mitochondrial
12S rRNA and
tRNASer(UCN) genes are the hot spots for mutations associated with
hearing loss. We reported here the clinical, genetic and molecular analysis of a Chinese pedigree with maternally inherited
sensorineural hearing loss. Molecular analysis showed that the pedigree carried both
mitochondrial DNA (
mtDNA) A1555G and G7444A mutations. The penetrance of
hearing loss in this pedigree was 58% when
aminoglycoside-induced
hearing loss was included. When the effect of
aminoglycosides was excluded, the penetrance of
hearing loss in this pedigree was 25%. The penetrance of
hearing loss was significantly higher than other families carrying only A1555G mutation. Sequence analysis of the complete mitochondrial genome in the proband showed that there were 28
mtDNA polymorphisms belonging to East-Asian haplogroup B4c1. In addition to the
deafness-associated A1555G and G7444A mutations, there were no other functionally significant variants found in this family. This indicated that
mtDNA G7444A mutation may aggravate
mitochondrial dysfunction associated with the A1555G mutation. Therefore, the coexistence of both
mtDNA mutations may contribute to high penetrance of
hearing loss.