Leber's hereditary optic neuropathy caused by a mutation in mitochondrial tRNA^Thr in eight Chinese pedigrees.

PURPOSE:The purpose of this study was to investigate the pathophysiology underlying Leber's hereditary optic neuropathy (LHON)-associated mitochondrial tRNA mutation. METHODS:Severn hundred ninety-seven Han Chinese subjects underwent clinical and genetic evaluation and analysis of mitochondrial DNA (mtDNA). The cybrid cell lines were constructed by transferring mitochondria from lymphoblastoid cell lines derived from a Chinese family into mtDNA-less (ρ^o) cells. These cell lines were assayed by tRNA Northern blot and Western blot analyses, respiratory enzymatic activities, the rate of ATP production and the generation of reactive oxygen species. RESULTS:The tRNA^Thr 15927G>A mutation was identified in eight probands with suggestively maternal inheritance among 352 Han Chinese probands lacking these known LHON-associated mtDNA mutations. The m.15927G>A mutation affected a highly conserved guanine at position 42 at the anticodon-stem of tRNA^Thr, destabilizing the conservative base pairing (28C-42G). We therefore hypothesized that the m.15927G>A mutation, and altered the structure and function of tRNA^Thr. Northern blot analysis revealed 60% decrease in the steady-state level of tRNA^Thr in the mutant cell lines. Western blot analysis showed the variable reductions of 4 mtDNA encoding proteins, especially for marked decrease of ND1 and CYTB observed in mutant cell lines. Furthermore, we demonstrated that the m.15927G>A mutation decreased the activities of mitochondrial complexes I and III, markedly diminished mitochondrial ATP levels, and increased the production of reactive oxygen species in the mutant cells. CONCLUSIONS:Our data demonstrated the first mitochondrial tRNA mutation leading to LHON. Our findings may provide new insights into the understanding of pathophysiology of LHON. Copyright © 2017 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

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