Mitochondrial DNA Content and the MTND4 Gene Expression in Leber's Hereditary Optic Neuropathy / 대한진단검사의학회지

ABSTRACT

BACKGROUND: Leber's hereditary optic neuropathy (LHON) is characterized by acute or subacute bilateral visual loss, primarily caused by a mitochondrial DNA (mtDNA) point mutation. However the pathogenic mechanism of visual loss has not been clearly unraveled. We investigated the pathogenetic mechanism of LHON by the analysis of mtDNA content and the MTND4 expression. METHODS: mtDNA contents were absolutely quantified in 17 patients, 8 carriers and 47 normal subjects using real-time PCR. All patients and carriers had the 11778G>A mutation of mtDNA. For real-time PCR assay of mtDNA content, the reference ranges were established by age groups and the reproducibility was assessed by intra-run and inter-run assays. We also quantified the expression of two mitochondrial genes (MTND4 harboring 11778G>A and MTCYB) relative to a nuclear gene (GAPDH) in the three subject groups. RESULTS: The mean mtDNA contents in the patients, carriers and normal subjects were 894.9 (+/- 186.9), 848.5 (+/-221.7) and 1148.6 (+/-406.9) copies/cell, respectively. Patients and carriers had significantly lower mtDNA contents than normal subjects (P=0.001 and P=0.048, respectively). The RNA expression of both MTND4 and MTCYB tended to be lower in patients and carriers than in normal subjects (statistically insignificant), but MTND4/MTCYB ratios were similar among the three groups. CONCLUSIONS: mtDNA content and the MTND4 expression are decreased in LHON patients and carriers, and it may be caused by mitochondrial depletion. The mitochondrial depletion may be an additional cause of respiratory defect.