Background:
Mutations in mitochondrial tRNA (mt-tRNA) genes have been
found to be associated with both syndromic and non-syndromic hearing impairment.
However, the pathophysiology underlying mt-tRNA mutations in clinical expression of
hearing loss remains poorly understood.
Objective:
The aim of this study was to explore the potential association between mttRNA
mutations and hearing loss.
Methods and Results:
We reported here the molecular features of a pedigree with
maternally transmitted non-syndromic hearing loss. Among 12 matrilineal relatives, five
of them suffered variable degree of hearing impairment, but none of them had any
medical history of using aminoglycosides antibiotics (AmAn). Genetic screening of the
complete mitochondrial genomes from the matrilineal relatives identified the coexistence
of mt-tRNAHis G12192A and mt-tRNAThr G15927A mutations, together with a
set of polymorphisms belonging to human mitochondrial haplogroup B5b1b.
Interestingly, the G12192A mutation occurred 2-bp from the 3’ end of the TψC loop of
mt-tRNAHis, which was evolutionarily conserved from various species. In addition, the
well-known G15927A mutation, which disrupted the highly conserved C-G base-pairing
at the anticodon stem of mt-tRNAThr, may lead to the failure in mt-tRNA metabolism.
:
Furthermore, a significant decreased in ATP production and an increased ROS
generation were observed in polymononuclear leukocytes (PMNs) which were isolated
from the deaf patients carrying these mt-tRNA mutations, suggested that the G12192A
and G15927A mutations may cause mitochondrial dysfunction that was responsible for
deafness. However, the absence of any functional mutations/variants in GJB2, GJB3,
GJB6 and TRMU genes suggested that the nuclear genes may not play important roles
in the clinical expression of non-syndromic hearing loss in this family.
Conclusion:
Our data indicated that mt-tRNAHis G12192A mutation may increase the
penetrance and expressivity of deafness-associated m-tRNAThr G15927A mutation in
this family.
The mitochondrial transfer RNAAsp A7551G mutation may contribute to the clinical expression of deafness associated with the A1555G mutation in a pedigree with hearing impairment
