Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder leading to rapid, painless, bilateral and usually permanent central vision loss in young adults, males are preferentially affected. The maternal transmission of this visual dysfunction in LHON families suggested that mutations in the mitochondrial DNA (mtDNA) are the molecular bases of the disorder. The ND1 G3460A, ND4 G11778A and ND6 T14484C mutations in the genes encoding the subunits of respiratory chain complex I, account for more than 50% of LHON families worldwide. These three mutations are designated to be primary mutations because they impart a high risk for LHON expression. However, matrilineal relatives within and among families, despite carrying the same LHON-associated mtDNA mutation(s), exhibit a wide range of onset, severity, and the progression of visual impairment. These findings strongly indicated that the LHON-associated primary mutation(s) are the primary factors underlying the development of vision loss, but they themselves are insufficient to produce a clinic phenotype. The prone to male, incomplete penetrance, and phenotypic variability of vision loss suggest that other modifier factors including personal factors, environmental factors, nuclear modifier genes and mitochondrial haplotypes contribute to the phenotypic expression of these mtDNA mutations. In particular, the mitochondrial haplotypes may play a synergic role in the development of vision loss in the families carrying the LHON-associated primary mtDNA mutation(s).
DNA, Mitochondrial ; genetics ; Genome, Human ; genetics ; Genomics ; Haplotypes ; Humans ; Mitochondria ; genetics ; Optic Atrophy, Hereditary, Leber ; genetics ; pathology

Leber's hereditary optic neuropathy (LHON) is a maternally transmitted disease causing acute or subacute, bilateral optic atrophy mainly in young men. It is found to be a mitochondrial disorder with the primary mitochondrial DNA (mtDNA) mutations at 11778, 3460, and 14484. The incidence of each mutation is reported to be race-dependent. Point mutations at mtDNA nucleotide position 11778 and 14484 have been reported in Korean patients with LHON, however there has been no report of mtDNA mutation at nucleotide position 3460. Molecular genetic analyses at four primary sites (11778, 14484, 15257, and 3460) of mitochondrial DNA using the polymerase chain reaction, restriction enzyme digestion, and direct sequencing were performed in a 35-yr-old man with severe visual loss. A point mutation in the mtDNA at nucleotide position 3460 was identified and a conversion of a single alanine to a threonine was confirmed. To our knowledge, this is the first report confirming mtDNA mutation at nucleotide position 3460 in Korean patients with LHON. Detailed molecular analyses would be very helpful for the correct diagnosis of optic neuropathy of unknown etiology and for genetic counseling.
Adult ; *DNA, Mitochondrial ; Humans ; Male ; Optic Atrophy, Hereditary, Leber/*genetics ; *Point Mutation

OBJECTIVETo analyze the penetrance of Leber hereditary optic neuropathy (LHON) individuals with mitochondrial DNA 11778 mutation in Shanxi.

METHODSAllele-specific PCR was used to detect mtDNA 11778 mutation in LHON patients and their families.

RESULTSIn 17 families of the 30 families that harbored mtDNA 11778 mutation, only the probands were LHON patients. In the other 13 families, besides the probands, 72 maternal relatives carried mtDNA 11778 mutation.

CONCLUSIONThe penetrance of LHON individuals with mtDNA 11778 mutation in the Shanxi area is 55.6%.

Adolescent ; Adult ; Child ; DNA, Mitochondrial ; genetics ; Female ; Humans ; Male ; Middle Aged ; Mutation ; Optic Atrophy, Hereditary, Leber ; genetics ; Penetrance

OBJECTIVETo screen for genetic mutations in 35 patients with Leber's hereditary optic neuropathy (LHON).

METHODSPolymerase chain reaction and DNA sequencing were used to screen for the presence of mitochondrial DNA mutations.

RESULTSThe total detection rate of top 3 common LHON mutations were 20.0%, which included 6 cases of ND4 11778 G to A, 1 case of ND1 3460 G to A. No ND6 14484 T to C mutation was detected. A ND4 G11719A synonymous mutation was found in all patients. In addition, 21 other mutations were discovered among 23 patients, among which 13 had a single mutation, 8 had a second mutations, and 2 had a third mutation. Among the 21 mutations, ND4 11778 G to A had a frequency of 28.6%(6/21). ND1 3552 T to A, ND6 14470 T to C, ND4 11794 T to C, ND1 3497 C to T and 3644 T to C respectively had a frequency of 19.0% (4/21), 19.0%(4/21), 14.3%(3/21), 9.5%(2/21) and 9.5%(2/21). Among the 3 patients who harbored a ND4 11794 T to C mutation, 2 were heteroplasmic and one was homoplasmic in nature.

CONCLUSIONThe ND4 11778 G to A mutation is common in the Top "3" primary mutations of patients with LHON. Candidate LHON mutation ND1 3552 T to A or ND1 3644 T to C resulted in LHON pathogenesis as single or synergistic effect. The visual impairment at onset of the disease with candidate mutation were better than the eyes with the ND4 11778 G to A mutation.

Adolescent ; Adult ; Child ; Child, Preschool ; DNA, Mitochondrial ; genetics ; Female ; Humans ; Male ; Middle Aged ; Mutation ; Optic Atrophy, Hereditary, Leber ; genetics

OBJECTIVETo find a simple, fast, accurate, and quantitative PCR-based method for mutation detection, so as to identify mitochondrial DNA 11778 G-->A point mutation in patients with Leber's hereditary optic neuropathy (LHON).

METHODOn the basis of sequencing of mtDNA from LHON proband, M primer for mutation and N primer for normal were designed to be coupled with reverse primer respectively. Specific PCRs were done on an amplifying condition with high stringency such as a well controlled annealing temperature, low Mg2+ concentration and less thermal cycles. The objective pedigree includes 10 individuals, were against 40 normal control persons.

RESULTSDifferent ratios of indicative mtDNA 11778A-->G mutation were checked out from the proband, affected maternal members and a 10 year-old boy (up to now no appearance yet), whereas not appeared on normal spouses, paternal offsprings in the family, neither did on 40 controls.

CONCLUSIONThis site-specific PCR method is a kind of general mutation analysis way, without the restriction of existence of endonuclease site. It can be applied for the gene diagnosis of known-mutation hereditary diseases such as LHON.

Adult ; DNA, Mitochondrial ; genetics ; Female ; Humans ; Male ; Optic Atrophy, Hereditary, Leber ; genetics ; Pedigree ; Point Mutation ; Polymerase Chain Reaction ; methods

OBJECTIVE: To explore the genetic basis for a child with optic atrophy and global developmental delay. METHODS: A child who had presented at the Guangzhou Women and Children's Medical Center in January 2022 was selected as the study subject. Clinical data were collected. Whole exome sequencing (WES) was carried out for the child. Candidate variant was validated by Sanger sequencing and bioinformatic analysis. RESULTS: The child, a nine-month-old female, had manifested dysopia and global developmental delay. Genetic testing revealed that she has harbored a de novo c.425G>C (p.Arg142Pro) variant of the NR2F1 gene, which has been associated with Bosch-Boonstra-Schaaf syndrome. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as pathogenic (PS2+PM1+PM2_Supporting+PM5+PP3+PP4). CONCLUSION The c.425G>C (p.Arg142Pro) variant of the NR2F1 gene probably underlay the pathogenesis in this child. Above finding has enriched the genotypic and phenotypic spectrum of the NR2F1 gene.
Female ; Humans ; Infant ; Computational Biology ; COUP Transcription Factor I/genetics* ; Genetic Testing ; Genomics ; Genotype ; Optic Atrophy/genetics*

OBJECTIVETo investigate the role of MT-ND1 m.3635G>A mutation in the pathogenesis of Leber's hereditary optic neuropathy (LHON).

METHODSBiochemical characteristics including the activity of complex Ⅰ, ATP production and oxygen consumption rate among lymphoblastoid cell lines derived from 3 carriers, 3 affected matrilineal relatives of the families and 3 controls were compared.

RESULTSComparison of mitochondrial functions in lymphoblastoid cell lines of the carriers, patients and controls showed a 51.0% decrease in the activity of complex Ⅰ in patients compared with controls (P<0.05). The m.3635G>A mutation has resulted in decreased efficiency of ATP synthesis (P<0.05). Comparison of oxygen consumption rate showed that the basal OCR (P<0.05), ATP-linked OCR (P<0.05) and the maximum OCR (P<0.05) have all reduced to some extent compared with the controls.

CONCLUSIONThese results showed that m.3635G>A, as a LHON-associated mutation, can lead to mitochondrial dysfunction.

Adenosine Triphosphate ; genetics ; Asian Continental Ancestry Group ; genetics ; Female ; Humans ; Male ; Mitochondria ; genetics ; Mutation ; genetics ; NADH Dehydrogenase ; genetics ; Optic Atrophy, Hereditary, Leber ; genetics ; Pedigree

Child ; Female ; Hereditary Sensory and Motor Neuropathy ; genetics ; Heterozygote ; Humans ; Mitochondrial Proteins ; genetics ; Mutation ; genetics ; Optic Atrophy ; genetics ; Peptide Termination Factors ; genetics

OBJECTIVELeber's hereditary optic neuropathy (LHON) is a maternally inherited degeneration of the optic nerve caused by point mutations of mitochondrial DNA (mtDNA). Many unsolved questions regarding the penetrance and pathophysiological mechanism of LHON demand efficient and reliable mutation testing. This study aims to develop a minor groove binder (MGB) probe assay for rapid detection of mtDNA11778 mutation and heteroplasmy in Chinese LHON patients by real-time polymerase chain reaction (PCR).

METHODSForty-eight patients suspected of having LHON and their maternal relatives underwent a molecular genetic evaluation, with 20 normal individuals as a control group at the same time. A real-time PCR involving two MGB probes was used to detect the mtDNA11778 mutation and heteroplasmy. A linear standard curve was obtained by pUCmLHONG and pUCmLHONA clones.

RESULTSAll 48 LHON patients and their maternal relatives were positive for mtDNA11778 mutation in our assay, 27 heteroplasmic and 21 homoplasmic. Eighteen cases did not show an occurrence of the disease, while 9 developed the disease among the 27 heteroplasmic mutation cases. Eleven did not show an occurrence of the disease, while 10 cases developed the disease among 21 homoplasmic mutation cases. There was a significant difference in the incidence between the heteroplasmic and the homoplasmic mutation types. The time needed for running a real-time PCR assay was only 80 min.

CONCLUSIONThis real-time PCR assay is a rapid, reliable method for mtDNA mutation detection as well as heteroplasmy quantification. Detecting this ratio is very important for predicting phenotypic expression of unaffected carriers.

China ; DNA Probes ; analysis ; genetics ; DNA, Mitochondrial ; analysis ; genetics ; Humans ; Mutation ; genetics ; Optic Atrophy, Hereditary, Leber ; blood ; genetics ; Polymerase Chain Reaction ; methods ; Time Factors

OBJECTIVETo report the clinical, genetic, and molecular characterization of two Chinese families with Leber's hereditary optic neuropathy (LHON).

METHODSOphthalmological examinations showed that only probands in two families exhibited visual loss at the age of 10 and 17 years respectively. The entire mitochondrial genome of two probands was PCR amplified in 24 overlapping fragments using sets of oligonucleotide primers.

RESULTSMutational analysis of mitochondrial DNA (mtDNA) in these pedigrees revealed the absence of three common LHON associated G11778A, G3460A and T144484 mutations but the presence of homoplastic LHON associated ND4 G11696A mutation, which was present in one out of 167 Chinese healthy controls.

CONCLUSIONSequence analysis of the complete mitochondrial genomes in two pedigrees showed the distinct sets of mtDNA polymorphisms, belonging to Eastern Asian haplogroup D4. The incomplete penetrance of visual loss and the presence of one in 167 controls suggested that this mutation itself is insufficient to produce a clinical phenotype and other modifier factors play a role in the phenotypic manifestation. The lack of functional mtDNA variants in these pedigrees ruled out the role of mitochondrial background in the phenotypic expression of visual loss. Therefore, nuclear modifier gene(s) or environmental factor(s) may play a role in the phenotypic expression of the LHON-associated G11696A mutation in two Chinese pedigrees.

Adolescent ; Adult ; Asian Continental Ancestry Group ; genetics ; Base Sequence ; Child ; DNA, Mitochondrial ; genetics ; Family ; Female ; Humans ; Male ; Mutation ; Optic Atrophy, Hereditary, Leber ; genetics ; Pedigree ; Phenotype