Generation of human induced pluripotent stem cells from peripheral blood mononuclear cells of a Senior-Loken syndrome patient.

Senior-Loken syndrome (SLS) is a rare disorder primarily associated with kidney and retinal dysfunction. We generated a human induced pluripotency stem cell (hiPSC) line, designated DKHi005-A, from peripheral blood mononuclear cells of a patient with SLS using a Sendai virus reprogramming method. We confirmed that DKHi005-A cells harbor the same mutation as the patient and show a normal karyotype. DKHi005-A also has pluripotency and the capacity for differentiation into the three germ layers. This cell line is registered and available at the National Stem Cell Bank, Korea National Institute of Health.

Cybrid studies establish the causal link between the mtDNA m.3890G>A/MT-ND1 mutation and optic atrophy with bilateral brainstem lesions.

Complex I (CI) deficiency is a frequent cause of mitochondrial disorders and, in most cases, is due to mutations in CI subunit genes encoded by mitochondrial DNA (mtDNA). In this study, we establish the pathogenic role of the heteroplasmic mtDNA m.3890G>A/MT-ND1 (p.R195Q) mutation, which affects an extremely conserved amino acid position in ND1 subunit of CI. This mutation was found in a young-adult male with optic atrophy resembling Leber's hereditary optic neuropathy (LHON) and bilateral brainstem lesions. The only previously reported case with this mutation was a girl with fatal infantile Leigh syndrome with bilateral brainstem lesions. Transfer of the mutant mtDNA in the cybrid cell system resulted in a marked reduction of CI activity and CI-dependent ATP synthesis in the presence of a normally assembled enzyme. These findings establish the pathogenicity of the m.3890G>A/MT-ND1 mutation and remark the link between CI mutations affecting the mtDNA-encoded ND subunits and LHON-like optic atrophy, which may be complicated by bilateral and symmetric lesions affecting the central nervous system. Peculiar to this mutation is the distribution of the brainstem lesions, with sparing of the striatum in both patients.

The unique characteristics of Thai Leber hereditary optic neuropathy: analysis of 30 G11778A pedigrees.

Leber hereditary optic neuropathy (LHON) is characterized by acute or subacute bilateral visual loss, and affects mostly young males. The most common mitochondrial DNA mutation responsible for LHON worldwide is G11778A. Despite different genetic backgrounds, which are believed to influence the disease expression, most features of LHON are quite common in different populations. However, there seem to be a few ethnic-specific differences. Analyses of our 30 G11778A LHON pedigrees in Thailand showed some characteristics different from those of Caucasians and Japanese. In particular, our pedigrees showed a lower male to female ratio of affected persons (2.6:1) and much higher prevalence of G11778A blood heteroplasmy (37% of the pedigrees contained at least one heteroplasmic G11778A individual). Heteroplasmicity seemed to influence disease manifestation in our patients but did not appear to alter the onset of the disease. The estimated overall penetrance of our G11778A LHON population was 37% for males and 13% for females. When each of our large pedigrees were considered separately, disease penetration varied from 9 to 45% between the pedigrees, and also varied between different branches of the same large pedigree. Survival analysis showed that the secondary LHON mutations G3316A and C3497T had a synergistic deleterious effect with the G11778A mutation, accelerating the onset of the disease in our patients.

alpha-Tocopherol/lipid ratio in blood is decreased in patients with Leber's hereditary optic neuropathy and asymptomatic carriers of the 11778 mtDNA mutation.

OBJECTIVES: Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease characterised by acute or subacute bilateral visual loss in young patients. The primary aetiological event is a mutation in the mitochondrial genome (mtDNA) affecting in most cases mtDNA-encoded subunits of the respiratory chain NADH: coenzyme Q oxidoreductase (complex I). The impaired function of complex I leads to a decline in mitochondrial energy production and enhances free radical generation. METHODS: The concentrations of some non-enzymatic antioxidants (alpha-tocopherol, beta-carotene, lycopene, glutathione, free sulphydryl groups) and the lipid peroxides in the blood of patients with LHON, carriers with homoplasmic DNA mutation at 11 778, and controls were investigated using high performance liquid chromatography and spectrophotometric methods to assess the function of their antioxidant defence systems. RESULTS: The alpha-tocopherol/cholesterol+ triglyceride ratio was significantly reduced (p<0.05) both in the patients and asymptomatic carriers. The concentrations of the other antioxidants and the lipid peroxides were not different from those of control subjects. CONCLUSION: The low concentration of plasma alpha-tocopherol most probably reflects the consumption of the antioxidant by the affected tissues. Furthermore, it suggests that alpha-tocopherol may be the primary scavenger molecule against the free radicals induced by complex I deficiency.

Persistent heteroplasmy of a mutation in the human mtDNA control region: hypermutation as an apparent consequence of simple-repeat expansion/contraction.

In the genealogical and phylogenetic analyses that are reported here, we obtained evidence for an unusual pattern of mutation/reversion in the human mitochondrial genome. The cumulative results indicate that, when there is a T-->C polymorphism at nt 16189 and a C-->T substitution at nt 16192, there is an extremely high rate of reversion (hypermutation) at the latter site. The apparent reversion rate is sufficiently high that there is persistent heteroplasmy at nt 16192 in maternal lineages and at the phylogenetic level, a situation that is similar to that observed for the rapid expansion/contraction of simple repeats within the control region. This is the first specific instance in which the mutation frequency at one site in the D-loop is markedly influenced by the local sequence "context." The 16189 T-->C polymorphism lengthens a (C:G)n simple repeat, which then undergoes expansion and contraction, probably through replication slippage. This proclivity toward expansion/contraction is more pronounced when there is a C residue, rather than a T, at nt 16192. The high T-->C reversion frequency at nt 16192 apparently is the result of polymerase misincorporation or slippage during replication, the same mechanism that also causes the expansion/contraction of this simple-repeat sequence. In addition to the first analysis of this mitochondrial hypermutation process, these results also yield mechanistic insights into the expansion/contraction of simple-repeat sequences in mtDNA.

Leber's Hereditary Optic Neuropathy (LHON) with 14484/ND6 mutation in a North African patient.

We report the clinical and genetic study of a Leber's Hereditary Optic Neuropathy (LHON) patient of North African origin harboring the 14484/ND6 mutation of mtDNA. For over a year we followed the ophthalmological course of this 24-year-old male with LHON treated with idebenone and vitamin B12. Serum lactate after effort was evaluated before, during and after therapy. Muscle biopsy was obtained for morphological study. Homo/heteroplasmy of 14484/ND6 mutation was studied in different tissues. Recovery of visual acuity was documented 6 months after onset and 3 months after therapy was established. Baseline serum lactate was elevated but normalized after 3.5 months of therapy. Muscle biopsy demonstrated only a few fibers with a slightly increased subsarcolemmal SDH activity. Genetic analysis showed homoplasmic 14484/ND6 mutation in all tissues investigated. The clinical phenotype of LHON/14484 in this patient closely resembles that commonly found in European patients. Even if LHON/14484 patients are reported to have a better prognosis for visual recovery, it is possible that the evolution of visual recovery in this patient could have been influenced by therapy as suggested by changes in serum lactate levels. Bioenergetic impairment of skeletal muscle was documented by lactate levels and muscle morphology. The 14484/ND6 mutation behaves as a primary mutation regardless of mtDNA population-specific backgrounds.

Childhood Leber's hereditary optic neuropathy (ND1/3460) with visual recovery.

The authors report the clinical features and the results of genetic and biochemical studies of a child affected by ND1/3460 Leber's hereditary optic neuropathy, who demonstrates a persistent visual recovery after protracted monitoring. A 10-year-old male suffered from a severe right visual impairment that was incidentally detected. Within 2 months the left eye was also seriously involved, and visual acuity worsened to 20/300 in both eyes, associated with bilateral cecocentral scotomas and dyschromatopsia. During the following months a progressive visual improvement occurred, and 2 years later the visual acuity was 20/20 OU. After 9 years of follow-up the clinical status is unchanged. The mutation at np ND1/3460 was found to be virtually homoplasmic in the proband's mtDNA, which was extracted either from platelets or leukocytes, whereas the mother and the sister tested heteroplasmic for the same mutation. The specific activity of complex I in platelets was reduced in the proband and normal in his relatives. An abnormal resistance of NADH:ubiquinone reductase to the inhibitory effect of rotenone was found in platelet mitochondria from the proband and family members and was consistent with the degree of heteroplasmy. This pattern of biochemical abnormalities suggests a cumulative effect of the increasing percentage of mutated mtDNA on complex I function, which involves the interaction between complex I and its substrate ubiquinone in the heteroplasmic condition (asymptomatic state), and the catalytic function of complex I, as mutated mDNA turns toward the homoplasmic condition (symptomatic state).

Diagnosis of mitochondrial disease: assessment of mitochondrial DNA heteroplasmy in blood.

Mitochondrial DNA (mtDNA) mutations are an important cause of neurological disease. The identification of causative mtDNA mutations may be particularly troublesome in blood where there are often low levels of mutant mtDNA. This is evident from a recent study in which heteroplasmic mtDNA mutations in cytochrome c oxidase genes were incorrectly thought to be linked to Alzheimer's disease. We wished to explore whether analysis of blood mtDNA, prepared by a number of DNA extraction procedures, influenced the diagnosis of mtDNA disease. DNA was extracted by different procedures from 4 patients with heteroplasmic mtDNA mutations, and the level of heteroplasmy investigated by radioactive PCR-RFLP analysis. Whilst there was no consistent decrease in the level of mtDNA heteroplasmy, we observed the coamplification of a novel mtDNA pseudogene from DNA samples extracted by a simple 'boiling' procedure using primers designed to screen for the tRNALeu(UUR) A3243G mutation. This pseudogene was readily amplified from DNA extracted from rho degrees (mtDNA-less) cells, confirming its nuclear location. We believe that mtDNA pseudogenes may therefore present significant difficulties in the accurate identification of pathogenic heteroplasmic mtDNA mutations in blood.

Acquired mitochondrial impairment as a cause of optic nerve disease.

BACKGROUND: Blindness from an optic neuropathy recently occurred as an epidemic affecting 50,000 patients in Cuba (CEON) and had clinical features reminiscent of both tobacco-alcohol amblyopia (TAA) and Leber's hereditary optic neuropathy (Leber's; LHON). Selective damage to the papillomacular bundle was characteristic, and many patients also developed a peripheral neuropathy. Identified risk factors included vitamin deficiencies as well as exposure to methanol and cyanide. In all 3 syndromes, there is evidence that singular or combined insults to mitochondrial oxidative phosphorylation are associated with a clinically characteristic optic neuropathy. PURPOSE: First, to test the hypothesis that a common pathophysiologic mechanism involving impairment of mitochondria function and, consequently, axonal transport underlies both genetic optic nerve diseases such as Leber's and acquired toxic and nutritional deficiency optic neuropathies. According to this hypothesis, ATP depletion below a certain threshold leads to a blockage of orthograde axonal transport of mitochondria, which, in turn, leads to total ATP depletion and subsequent cell death. Second, to address several related questions, including (1) How does impaired energy production lead to optic neuropathy, particularly since it seems to relatively spare other metabolically active tissues, such as liver and heart? (2) Within the nervous system, why is the optic nerve, and most particularly the papillomacular bundle, so highly sensitive? Although there have been previous publications on the clinical features of the Cuban epidemic of blindness, the present hypothesis and the subsequent questions have not been previously addressed. METHODS: Patients in Cuba with epidemic optic neuropathy were personally evaluated through a comprehensive neuro-ophthalmologic examination. In addition, serum, lymphocytes for DNA analysis, cerebrospinal fluid (CSF), sural nerves, and eyes with attached optic nerves were obtained from Cuban patients, as well as from Leber's patients, for study. Finally, we developed an animal model to match the low serum folic acid and high serum formate levels found in the CEON patients, by administering to rats low doses of methanol after several months of a folic acid-deficient diet. Optic nerves and other tissues obtained from these rats were analyzed and compared with those from the Cuban patients. RESULTS: Patients from the Cuban epidemic of optic neuropathy with clinical evidence of a selective loss of the papillomacular bundle did much better once their nutritional status was corrected and exposure to toxins ceased. Patients with CEON often demonstrated low levels of folic acid and high levels of formate in their blood. Histopathologic studies demonstrated losses of the longest fibers (in the sural nerve) and those of smallest caliber (papillomacular bundle) in the optic nerve, with intra-axonal accumulations just anterior to the lamina cribrosa. Our animal model duplicated the serologic changes (low folic acid, high formate) as well as these histopathologic changes. Furthermore, ultrastructural examination of rat tissues demonstrated mitochondrial changes that further matched those seen on ultrastructural examination of tissues from patients with Leber's. CONCLUSION: Mitochondria can be impaired either genetically (as in Leber's) or through acquired insults (such as nutritional or toxic factors). Either may challenge energy production in all cells of the body. While this challenge may be met through certain compensatory mechanisms (such as in the size, shape, or number of the mitochondria), there exists in neurons a threshold which, once passed, leads to catastrophic changes. This threshold may be that point at which mitochondrial derangement leads to such ATP depletion that axonal transport is compromised, and decreased mitochondrial transport results in even further ATP depletion. Neurons are singularly dependent on the axonal transport of mitochondria. (

Platelet mitochondrial function in Leber's hereditary optic neuropathy.

We report the effect of the 11,778 and 3460 base pair mitochondrial DNA mutations, found in Leber's hereditary optic neuropathy (LHON), on platelet mitochondrial respiratory chain enzyme activity. We measured respiratory chain enzyme activities in platelets from 4 patients with the 3460 mutation, 17 patients with the 11,778 mutation and compared them with those of 41 healthy age-matched controls. We observed a 67% (P < 0.001) reduction in the mean NADH CoQ1 reductase (complex I) activity of the 3460 group compared to the control group. It has been shown previously that platelet mitochondrial biochemistry is affected by cigarette smoking. A significant reduction (25%, P < 0.03) in the mean complex I activity of the 11,778 group was only observed when the non-smokers within that group were compared to the non-smoking controls. The effect of smoking observed in this study may explain why previous workers have not observed a decrease in complex I activity associated with the 11,778 mutation. There was no significant change in the activity of complexes II/III or IV with either of these mutations. There was a significant increase (26%, P < 0.008) in citrate synthase (CS) activity with the non-smoking 11,778 group compared to the non-smoking control group, rising to 40% (P < 0.002) in those with this mutation who smoked. This reflects an increase in mitochondrial mass with the 11,778 mutation. This effect was not observed with the 3460 mutation even though the complex deficiency was much more severe.

Variable genotype of Leber's hereditary optic neuropathy patients.

Leber's hereditary optic neuropathy is caused by a single nucleotide change in the mitochondrial deoxyribonucleic acid (mtDNA). Each cell contains thousands of mitochondrial DNA molecules. We demonstrated that in certain isolated instances, the proband and close maternal lineage relatives can have mixtures of mutant and normal mitochondrial DNA molecules (heteroplasmy). The proportion of mutant mitochondrial DNA molecules was found to shift markedly across generations and within the tissues of an individual. One unaffected mother had 65% mutant mitochondrial DNA molecules whereas her affected son had essentially 100% mutant mitochondrial DNA molecules. Two affected individuals had predominantly mutant mitochondrial DNA in their blood, but significant normal mitochondrial DNA in their hair. The demonstration of heteroplasmy within maternal lineages and affected individuals means that the successful determination of the mitochondrial DNA genotype of a family or patient with Leber's hereditary optic neuropathy requires testing of more than one family member and more than one tissue from each individual.

Leber's hereditary optic atrophy: further evidence for a defect of cyanide metabolism?

We studied one patient with Leber's optic atrophy (LOA) in the acute stage and 12 at the chronic stage of the disease, and measured the activity of rhodanese in white blood cells and the level of cyanide in whole blood. In the patient with acute disease the blood cyanide level was significantly increased at first. Treatment of this patient with cyanide antagonists reduced his cyanide level, but this was not accompanied by improvement in visual function. Rhodanese activity was normal in all patients, as were the blood cyanide levels in each of the 12 patients at the chronic stage of the disease. These findings suggest a temporary disturbance of cyanide metabolism during the acute phase of the disease in this family. The abnormal metabolic mechanism was not identified.