Investigation of the Association between Normal-tension Glaucoma and Single Nucleotide Polymorphisms in Natriuretic Peptide Gene

PURPOSE: The expression of natriuretic peptides in the neural bundles of the anterior portion of the optic nerves and their functions in regulating vessel tone and blood flow may suggest a possible role in the pathogenesis of glaucoma. The purpose of this study was to investigate the association between normal-tension glaucoma and the genetic variations of atrial natriuretic peptide (Nppa) and natriuretic peptide receptor A (Npr1) gene. METHODS: Sixty-seven Korean normal-tension glaucoma (NTG) patients and 100 healthy subjects (as normal controls) were enrolled. DNA from peripheral blood leukocytes was extracted, and the genotypes of five polymorphisms (c.94G>A, c.454T>C, IVS1+16C>T, IVS2+701G>A, and c.-764C>G) in the Nppa gene and one polymorphism (c.1023G>C) in the Npr1 gene were determined using the restriction fragment length polymorphism and the SNaPshot methods. The genotype and allele frequencies of these polymorphisms in patients with NTG and normal controls were compared using the Fisher's exact test and the chi-square test. RESULTS: In both groups, the genotype distributions were in accordance with the Hardy-Weinberg equilibrium. There was no significant difference in the frequency of the Nppa and Npr1 alleles or genotypes in the normal-tension glaucoma group as compared to the control group. CONCLUSIONS: Nppa and Npr1 gene polymorphisms are not associated with normal-tension glaucoma, suggesting that this gene does not have an important role in the pathogenesis of optic neuropathy in this disease.

Molecular Diagnosis for Mitochondrial DNA Aberrations in Chronic Progressive External Ophthalmoplegia

PURPOSE: To evaluate the spectrum of mitochondrial DNA (mtDNA) aberrations in patients with suspected chronic progressive external ophthalmoplegia (CPEO) and to establish the molecular diagnostic method for CPEO in Koreans. METHODS: We performed mtDNA analyses for single deletions with long-range PCR and direct sequencing, and for the nine important point mutations including 3243A>G and 8344A>G with PCR/RFLP in muscles, bloods and paraffin-embedded muscle sections of 16 Korean patients with suspected CPEO. RESULTS: Three novel single mtDNA deletions were identified in three patients' muscles: 3159bp deletion from np 6657 to np 9815, 7591bp from np 8429 to np 16019, and 6191bp from np 7799 to np 13989. In addition, multiple mtDNA deletions were found in one patient. None of the blood specimen had mtDNA deletions even in the patients with mtDNA deletion in muscle. All single deletion junctions were flanked by direct repeats of 6-8 bp. None of the nine mtDNA point mutations were found in muscles, bloods or paraffin-embedded muscle sections. CONCLUSIONS: We identified three novel single deletions by mtDNA analyses in the muscles of 3 patients with CPEO. However, point mutations were not found. Furthermore, we established a molecular diagnostic method for CPEO in Korea. Long-range PCR and direct sequencing of the muscles were appropriate as a molecular diagnostic method for CPEO in Koreans.

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

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.

Molecular Genetic Study on Primary and Secondary Mitochondrial DNA Mutations of Leber's Hereditary Optic Neuropathy in Koreans

PURPOSE: In order to evaluate the spectrum of mitochondrial DNA (mtDNA) mutations in the patients with suspected Leber's hereditary optic neuropathy (LHON). METHODS: We investigated 14 primary mtDNA mutations at nucleotide positions (nps 3460A, 4160C, 5244A, 9101C, 9804A, 10663C, 11778A, 13730A, 14459A, 14482G, 14484C, 14495G, 14498T, and 14568T) and one common secondary mutation (np15257A) in 82 Korean patients with suspected LHON. RESULTS: Among them, only three kinds of LHON mutations were identified in 60 (73%) of 82 probands, which were comprised of 46 (56%) cases with the 11778A, 13 (16%) with the 14484C, and 1 (1%) with the 3460A. None of the other mtDNA mutations was detected. Of the 60 probands with LHON positive mutations, 19 (32%) had relevant family histories. Heteroplasmy was determined in 2 (4%) of the 46 probands with the 11778A and 1 (8%) of 13 probands with the 14484C. CONCLUSIONS: In conclusion, the 11778A was the most common cause (56%), and higher prevalence of the 14484C and the lower prevalence of the 3460A were characteristic in Korean patients with LHON. Especially, the 3460A had a remarkable racial difference compared with Caucasians. Except 3460A, 11778A, and 14484C, the other mutations screened may not be involved in pathogenesis and not have a synergistic effect on the clinical expression of LHON in Koreans.