Association of the LHON 13,708 and 15,257 mitochondrial DNA mutations with neurodegenerative diseases distinct from LHON

300 patients suffering from neurodegenerative diseases distinct from Leber hereditary optic neuropathy (LHON) were screened for the presence of mitochondrial DNA mutations. We report on nine patients, eight female and one male, who all harboured mutations at positions 13,708 and 15,257 of the mitochondrial DNA. Both mutations have previously been claimed to be associated with LHON. Based on our results, these mutations occur in a number of different neurodegenerative diseases and therefore cannot be regarded as "LHON" mutations.     

On the many faces of Leber hereditary optic neuropathy

Leber hereditary optic neuropathy (LHON) is a maternally inherited disorder, associated with mutations in the mitochondrial DNA, which is notorious for its aspecific presentations. Two pedigrees are described with cases that are atypical for LHON with respect to sex, age of onset, interval between the eyes becoming affected, course of the disease, concomitant disorders, additional test results, final visual acuity, and/or results of mtDNA analysis. Moreover, the pedigrees themselves did not suggest maternal inheritance. We analysed the diagnostic and clinical genetic difficulties related to the atypical aspects of these pedigrees. We conclude that mtDNA analysis is justified in every case of optic nerve atrophy with no clear cause. Identification of one of the three LHON specifically associated mtDNA mutations is essential to confirm the diagnosis.     

Leber hereditary optic neuropathy. Electron microscopy and molecular genetic analysis of a case

BACKGROUND: Leber hereditary optic neuropathy (LHON) is a mitochondrial genetic disorder characterized by bilateral central visual loss typically in early adulthood. Few histopathologic studies, including ultrastructural and molecular genetic analysis, have been reported. METHODS: Ocular tissue was obtained postmortem from an 81-year-old woman with LHON from the Queensland 1 pedigree characterized by mutations at nucleotide positions 4160 and 14484. Routine histopathologic studies, electron microscopy, electron-probe analysis, and molecular genetic analysis were performed. RESULTS: Marked atrophy of the nerve fiber and retinal ganglion cell layers and optic nerves was present. Results of electron microscopic examination demonstrated 1.2 microns electron-dense, double-membrane-bound inclusions, consisting of calcium by electron-probe analysis, in retinal ganglion cells. The optic nerve was homoplasmic for mutations 4160 and 14484. CONCLUSION: Optic nerve and inner retinal atrophy in LHON may be a result of metabolic mitochondrial dysfunction leading to intramitochondrial calcification. Homoplasmy for mitochondrial mutations 4160 and 14484 in the leukocyte/platelet fraction of whole blood may correlate with homoplasmy in the optic nerve.     

Ulnocarpal abutment. Treatment options

Rapid progress has been made in the identification of mitochondrial DNA mutations which are typically associated with diseases of the nervous system and muscle. The well established mitochondrial disorders are maternally inherited and males and females are equally affected. An exception is Leber's hereditary optic atrophy (LHON) which is observed much more frequently in males than in females. There are three common point mutations in LHON which can be homoplasmic or heteroplasmic. In mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) most mutations are single base changes and lie within the tRNA-Leu gene. Point mutations in myoclonic epilepsy with ragged red fibres (MERRF) usually occur within the tRNA-Lys gene but mutations of the tRNA-Leu gene are also observed. MELAS and MERRF mutations are heteroplasmic and there is considerable clinical overlap between these diseases. Point mutations within the ATPase6 gene result in either neuropathy, ataxia and retinitis pigmentosa (NARP) or in Leigh's syndrome. The latter occurs if the mutation is present in the majority of mitochondria (extreme heteroplasmy). Finally, mitochondrial DNA deletions are the cause underlying Kearns-Sayre syndrome (KSS). Apart from the well-established mitochondrial diseases, there is increasing evidence that mitochondrial mutations may also play a role in the neurodegenerative disorders Parkinson, Alzheimer and Huntington disease. The complex I defect found in Parkinson disease is especially interesting in this respect. However, no causative mitochondrial mutation has as yet been established in any of these three common disorders.     

Radiation kills human peripheral T cells by a Fas-independent mechanism

PURPOSE: To investigate the incidence and clinical significance of primary or proposed secondary mitochondrial DNA (mtDNA) mutations in Japanese patients with Leber's hereditary optic neuropathy (LHON). METHODS: Blood samples from the 80 unrelated Japanese patients with bilateral optic atrophy were screened for primary LHON mutations. Patients found to have a primary LHON mutation were then tested for 9 proposed secondary LHON mutations. We investigated the association between these mutations and clinical characteristics. RESULTS: Primary mtDNA mutations were identified in 68 patients: at np 3460 in 3 (4%) of 68 patients, at np 11,778 in 59 patients (87%), and at np 14,484 in 6 patients (9%). We identified 5 secondary mtDNA mutations (at np 3394, 4216, 7444, 9438 or 13,708) in 10 (15%) of 68 LHON patients and 3 mutations (at np 3394, 4216 or 3708) in 6 (7%) of 90 healthy Japanese individuals. No patient was positive for more than one secondary mutation. The frequency of secondary mutations was similar in the 68 LHON patients and 90 controls. The clinical features of the Japanese patients with any of the 3 primary LHON mutations were similar to those of Caucasian patients, despite different mtDNA backgrounds in these populations. The percentage of patients with familial LHON harboring the 3460 or 14,484 mutations was lower in the Japanese population. CONCLUSIONS: Japanese patients with LHON exhibited a very high incidence (87%) of the 11,778 primary mutation. Most of the proposed secondary LHON mutations were rare in the Japanese population and they, except the 7444 mutation, may not influence the clinical features of LHON.     

Osseointegrated endosseous implants, University of Liège concepts. Various clinical applications

The occurrence of optic neuropathy in patients with MS-like disorders who carry one of the pathogenetically significant LHON mutations as well as the higher incidence of maternal transmission in familial cases of MS support the hypothesis that mitochondrial genes may be implicated in susceptibility to MS. We sequenced the entire mtDNA of six children with MS who developed optic neuritis as early and prominent visual involvement. The analysis revealed a high degree of nucleotide variations relative to the standard mtDNA sequence. After excluding various synonymous nucleotide changes and common neutral polymorphisms, eight discrete novel missense mutations within the protein coding, tRNA or rRNA genes were detected. None of the eight polymorphic sites were found in common between the patients with MS. Of particular interest was the observation that five of six children carried a total of nine secondary LHON mutations at nucleotide positions 4216, 4917 or 13708. We conclude that variation in mtDNA is unlikely to contribute to genetic predisposition for MS. However, secondary LHON mutations may be regarded as additional risk factor for developing prominent optic nerve involvement. The association of individual sets of mtDNA variations with phenotypic presentation in certain subgroups of MS patients remains to be clarified.     

Leber's hereditary optic neuropathy: biochemical effect of 11778/ND4 and 3460/ND1 mutations and correlation with the mitochondrial genotype

To clarify the bioenergetic relevance of mtDNA mutations in Leber's hereditary optic neuropathy (LHON), we investigated affected individuals and healthy carriers from six Italian LHON families harboring the 11778/ND4 and the 3460/ND1 mtDNA mutations. The enzymatic activities of mitochondrial complex I and its sensitivity to the potent inhibitors rotenone and rolliniastatin-2 were studied in mitochondrial particles from platelets, in correlation with mtDNA analysis of platelets and leukocytes. In platelets homoplasmic for mutant mtDNA, both 11778/ND4 and 3460/ND1 mutations induced resistance to rotenone and the 3460/ND1 mutation also provoked a marked decrease in the specific activity of complex I. Individuals heteroplasmic in platelets for either mutation showed normal biochemical features, indicating functional complementation of wild-type mtDNA. There was no correlation between the clinical status and mtDNA homo/heteroplasmy in platelets, but the biochemical features correlated with the mitochondrial genotype of platelets. In some cases, the degree of mtDNA heteroplasmy differed in platelets and leukocytes from the same individual with a prevalence of wild-type mtDNA in the platelets. These results imply that biochemical studies on mitochondrial diseases should always be integrated with mtDNA analysis of the same tissue investigated and also suggest that the mtDNA analysis on the leukocyte fraction, as usually performed in LHON, does not necessarily reflect the mutant genotype level of other tissues. The differential tissue heteroplasmy may be more relevant than previously thought in determining disease penetrance.     

Clustering of Caucasian Leber hereditary optic neuropathy patients containing the 11778 or 14484 mutations on an mtDNA lineage

Leber hereditary optic neuropathy (LHON) is a type of blindness caused by mtDNA mutations. Three LHON mtDNA mutations at nucleotide positions 3460, 11778, and 14484 are specific for LHON and account for 90% of worldwide cases and are thus designated as "primary" LHON mutations. Fifteen other "secondary" LHON mtDNA mutations have been identified, but their pathogenicity is unclear. mtDNA haplotype and phylogenetic analysis of the primary LHON mutations in North American Caucasian patients and controls has shown that, unlike the 3460 and 11778 mutations, which are distributed throughout the European-derived (Caucasian) mtDNA phylogeny, patients containing the 14484 mutation tended to be associated with European mtDNA haplotype J. To investigate this apparent clustering, we performed chi2-based statistical analyses to compare the distribution of LHON patients on the Caucasian phylogenetic tree. Our results indicate that, unlike the 3460 and 11778 mutations, the 14484 mutation was not distributed on the phylogeny in proportion to the frequencies of the major Caucasian mtDNA haplogroups found in North America. The 14484 mutation was next shown to occur on the haplogroup J background more frequently that expected, consistent with the observation that approximately 75% of worldwide 14484-positive LHON patients occur in association with haplogroup J. The 11778 mutation also exhibited a moderate clustering on haplogroup J. These observations were supported by statistical analysis using all available mutation frequencies reported in the literature. This paper thus illustrates the potential importance of genetic background in certain mtDNA-based diseases, speculates on a pathogenic role for a subset of LHON secondary mutations and their interaction with primary mutations, and provides support for a polygenic model for LHON expression in some cases.     

The differential involvement of adrenoceptors in challenges of different intensities

We investigated a family with optic atrophy which occurred in childhood or early adulthood plus late-onset cerebellar ataxia. The magnetic resonance imaging in the proband revealed cerebellar atrophy. The proband and her brother were homoplasmic for the most common mitochondrial DNA (mtDNA) 11778 mutation associated with Leber's hereditary optic neuropathy (LHON). This study showed further evidence that central nervous system lesions can occur in cases of LHON mtDNA mutation.     

Leber's hereditary optic neuropathy masquerading as tobacco-alcohol amblyopia

OBJECTIVE: To determine the frequency of known primary mitochondrial DNA (mtDNA) mutations for Leber's hereditary optic neuropathy (LHON) in patients previously diagnosed as having tobacco-alcohol amblyopia. DESIGN: A case series of 12 patients with tobacco-alcohol amblyopia. Follow-up ranged from 2 months to 15 years. SETTING: Tertiary care. PATIENTS: Twelve patients diagnosed as having tobacco-alcohol amblyopia, based on the classic clinical presentation, were tested for all the known primary mtDNA mutations associated with LHON. All patients had a history of heavy alcohol or tobacco use or both. Twelve other patients who fit inclusion criteria were unable to be contacted or refused to participate in the study. MAIN OUTCOME MEASURES: Presence of a known primary mutation for LHON at nucleotide positions 11778, 3460, 15257, or 14484 of mtDNA. RESULTS: Two (17%) of 12 patients previously diagnosed as having tobacco-alcohol amblyopia tested positive for known LHON genetic mutations, one for the 11778 mutation and one for the 3460 mutation. CONCLUSIONS: The diagnosis of LHON should be considered in all patients diagnosed as having tobacco-alcohol amblyopia, particularly those with visual acuities of 20/200 or less. The availability of molecular genetic testing for LHON now allows confirmation of the diagnosis of LHON in patients who otherwise may be misdiagnosed.     

High frequency of mutations at position 11778 in mitochondrial ND4 gene in Japanese families with Leber''s hereditary optic neuropathy

We have investigated the presence of a point mutation at position 11778 in the ND4 gene of mitochondrial DNA in 17 Japanese families with Leber's hereditary optic neuropathy (LHON), and have identified the mutation in 14 (82.4%) of the 17 families. The prevalence of this mutation appears to be much higher in Japanese patients with LHON than in patients of other ethnic origins, such as Finnish, Dutch, German, and English families.     

Analysis of the pathogenic human mitochondrial mutation ND1/3460, and mutations of strictly conserved residues in its vicinity, using the bacterium Paracoccus denitrificans

The human mitochondrial ND1/3460 mutation changes Ala52 to Thr in the ND1 subunit of Complex I, and causes Leber's hereditary optic neuropathy (LHON) [Huoponen et al. (1991) Am. J. Hum. Genet. 48, 1147]. We have used a bacterial counterpart of Complex I, NDH-1 from Paracoccus denitrificans, for studying the effect of mutations in the ND1 subunit on the enzymatic activity. The LHON mutation as well as several other mutations in strictly conserved amino acids in its vicinity were introduced into the NQO8 subunit of NDH-1, a bacterial homologue of ND1. The enzymatic activity of the mutants in the presence of hexammineruthenium (rotenone-insensitive) and ubiquinone-1 (rotenone-sensitive) were assayed. In addition, the kinetics of the interaction of selected mutant enzymes with ubiquinone-1, ubiquinone-2, and decylubiquinone was studied. The results suggest that the mutated residues play an important role in ubiquinone reduction by Complex I.     

mtDNA haplotype analysis in Finnish families with leber hereditary optic neuroretinopathy

The mitochondrial DNA (mtDNA) sequence variation of 24 Finnish Leber hereditary optic neuroretinopathy (LHON) probands was characterized by sequencing and restriction endonuclease analyses. All LHON-associated substitutions and Caucasoid haplogroup-specific mutations were screened in the families. Analysis of the mtDNAs revealed that the Finnish LHON families have two unique features: an absence of the ND6/14484 mutation and a high number of families (10/24) without the primary mutations ND1/3460 and ND4/11778. Furthermore, the LHON families showed considerable mtDNA heterogeneity: among 24 families 22 haplotypes were detected. Overall, the haplogrouping of LHON families was similar to other European populations. However, the frequency of ND4/11778-positive families in haplogroup J was high, which may indicate that background mutations in this haplogroup together with the ND4/11778 primary mutation promote the penetrance of LHON.     

The blood-brain barrier disruption controversy: does it hold water?

OBJECTIVES: A defect in mitochondrial energy conservation is strongly suggested to be involved in the pathogenesis of Leber's hereditary optic neuropathy (LHON). The authors therefore compared the energy charge in lymphocytes among patients with LHON, their asymptomatic maternal lineages, and normal control subjects. MATERIALS AND METHODS: Blood samples were obtained from 7 patients, 10 asymptomatic maternal relatives, and 16 normal subjects. Molecular analysis confirmed that all had the homoplasmic 11,778 point mutation in the mtDNA of their blood cells. The concentrations of adenosine triphosphate (ATP), diphosphate (ADP), and monophosphate (AMP) were determined by high-performance liquid chromatography. The energy charge was calculated as (ATP + 1/2 ADP)/(ATP + ADP + AMP). RESULTS: The mean energy charges of lymphocytes were 0.871 +/- 0.049 in patients with LHON, 0.884 +/- 0.061 in their asymptomatic maternal relatives, and 0.885 +/- 0.061 in normal controls, respectively. No statistically significant difference was found among the three groups. CONCLUSIONS: Although the study did not find the anticipated change in energy charge in peripheral blood cells, this neither confirms nor rejects the notion that a defect in the mitochondrial oxidative phosphorylation system is involved in the pathogenesis of LHON.     

Evolutionary genetics of the Drosophila alcohol dehydrogenase gene-enzyme system

The mitochondrion is the only extranuclear organelle containing DNA (mtDNA). As such, genetically determined mitochondrial diseases may result from a molecular defect involving the mitochondrial or the nuclear genome. The first is characterized by maternal inheritance and the second by Mendelian inheritance. Ragged-red fibers (RRF) are commonly seen with primary lesions of mtDNA, but this association is not invariant. Conversely, RRF are seldom associated with primary lesions of nuclear DNA. Large-scale rearrangements (deletions and insertions) and point mutations of mtDNA are commonly associated with RRF and lactic acidosis, e.g. Kearns-Sayre syndrome (KSS) (major large-scale rearrangements), Pearson syndrome (large-scale rearrangements), myoclonus epilepsy with RRF (MERRF) (point mutation affecting tRNA(lys) gene), mitochondrial myopathy, lactic acidosis, and stroke-like episodes (MELAS) (two point mutations affecting tRNA(leu)(UUR) gene) and a maternally-inherited myopathy with cardiac involvement (MIMyCa) (point mutation affecting tRNA(leu)(UUR) gene). However, RRF and lactic acidosis are absent in Leber hereditary optic neuropathy (LHON) (one point mutation affecting ND4 gene, two point mutations affecting ND1 gene, and one point mutation affecting the apocytochrome b subunit of complex III), and the condition associated with maternally inherited sensory neuropathy (N), ataxia (A), retinitis pigmentosa (RP), developmental delay, dementia, seizures, and limb weakness (NARP) (point mutation affecting ATPase subunit 6 gene). The point mutations in MELAS, MIMyCa, and MERRF, and the large-scale mtDNA rearrangements in KSS and Pearson syndrome have a broader biochemical impact since these molecular defects involve the translational sequence of mitochondrial protein synthesis. The nuclear defects involving mitochondrial function generally are not associated with RRF. The biochemical classification of mitochondrial diseases principally catalogues these nuclear defects. This classification divides mitochondrial diseases into five categories. Primary and secondary deficiencies of carnitine are examples of a substrate transport defect. A lipid storage myopathy is often present. Disturbances of pyruvate or fatty acid metabolism are examples of substrate utilization defects. Only four defects of the Krebs cycle are known: fumarase deficiency, dihydrolipoyl dehydrogenase deficiency, alpha-ketoglutarate dehydrogenase deficiency, and combined defects of muscle succinate dehydrogenase and aconitase. Luft disease is the singular example of a defect in oxidation-phosphorylation coupling. Defects of respiratory chain function are manifold. Two clinical syndromes predominate, one involving limb weakness, and the other primarily affecting brain function. Leigh syndrome may result from different enzyme defects, most notably pyruvate dehydrogenase complex deficiency, cytochrome c oxidase deficiency, complex I deficiency, and complex V deficiency associated with the recently described NARP point mutation. A new group of mitochondrial diseases has emerged.(ABSTRACT TRUNCATED AT 400 WORDS)     

Treatment of sarcoidosis

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.     

Rorschach cognitive developmental indices of mentally retarded persons: a comparison with scores on Wechsler Intelligence Scale for children-revised

The complete mechanism by which pathogenic mtDNA mutations cause cellular pathophysiology and in some cases cell death is unclear. Oxidant stress is especially toxic to excitable nerve and muscle cells, cells that are often affected in mitochondrial disease. The sensitivity of cells bearing the LHON, MELAS, and MERRF mutations to oxidant stress was determined. All were significantly more sensitive to H2O2 exposure than their nonmutant cybrid controls, the order of sensitivity was MELAS > LHON > MERRF > controls. Depletion of Ca2+ from the medium protected all cell lines from oxidant stress, consistent with the hypothesis that death induced by oxidant stress is Ca(2+)-dependent. A potential downstream target of Ca2+ is the mitochondrial permeability transition, MPT, which is inhibited by cyclosporin A. Treatment of MELAS, LHON, and MERRF cells with cyclosporin A caused significant rescue from oxidant exposure, and in each case significantly greater rescue of mutant than control cells. The pronounced oxidant-sensitivity of mutant cells, and their protection by Ca2+ depletion and CsA, has potential implications for both the pathophysiological mechanism and therapy of these mitochondrial genetic diseases.     

Sexually transmitted diseases in Ulaanbaatar, Mongolia

INTRODUCTION: Anterior ischemic optic neuropathy (AION) describes a defect of the optic nerve leading to irreversible loss of vision in most cases. Pathophysiology of this disease is manifold and has been discussed as a posthemorrhagic complication as well as a neurological complication after operations with cardiopulmonary bypass. METHODS: On the basis of two cases, the clinical picture is described in relation to the available literature. Preoperative risk factors, operative data, cardiopulmonary-bypass, postoperative complications and clinical symptoms are discussed together with ophthalmologic findings in order to elucidate the pathophysiology of this process. RESULTS: There is no reliable and effective treatment of anterior ischemic optic neuropathy. Neither corticosteroids, osmotic diuretics, hemodilution nor surgical decompression of the optic nerve have proved successful. Hence, measures to avoid ischemic optic neuropathy have priority. The following risk factors were determined: History of glaucoma or other ophthalmological problems, prolonged cardiopulmonary bypass-time and myocardial ischemia, general oedema during cardiopulmonary bypass, excessive hemodilution with low hemoglobin and hematocrit, hypo- or hypertension, systemic hypothermia, need for vasoactive medication. CONCLUSIONS: Influenced by a variety of factors, pathophysiological microvascular changes provoke anterior ischemic neuropathy with sudden painless loss of vision, irreversible in most cases. Since therapeutic trials have failed, prevention of possible causes is the only way to avoid this rare but severe complication of cardiac surgery.     

Late onset dysthyroid optic neuropathy

We report three rare occurrences of late onset dysthyroid optic neuropathy. We reviewed each case in detail and found that these middle-aged patients developed onset of optic neuropathy 7 to 12 years following stabilization of clinically significant, stable ophthalmopathy. There was no corresponding reactivation of orbital inflammatory symptoms or signs. Characteristic of a Graves' ophthalmopathy, the vision was responsive to either corticosteroid or surgical decompression, or to a combination thereof. None of the patients had diabetes, hypertensive, or cardiovascular disease. We hypothesize that in these unique cases possible mechanical vascular factors may have induced decompensation of optic nerve function in otherwise stable disease.     

A three-step method of self-reflection using reflective journal writing

We report the development of a method for the simultaneous genotyping of several distinct nucleotide positions by means of fluorescence-coupled competitive primer extension. We demonstrate the application of this method for the simultaneous detection of three point mutations in the human mitochondrial genome, at nucleotide positions 3460, 11778 and 14484, which account for about 90% of cases with Leber's hereditary optic neuropathy. mtDNA fragments encompassing these nucleotide positions are initially amplified in a multiplex PCR assay. Genotyping is then carried out by a simultaneous primer extension assay using wild-type-specific (FAM-labeled) and mutant-specific (JOE-labeled) oligonucleotides. Primer extension products are separated on a 6% polyacrylamide/8 M urea gel on a fluorescence DNA sequencer. Patients' genotypes can be derived from the peak color of the different-sized extension products. As little as 10% mutant DNA can be detected in heteroplasmic mixtures of wild-type and mutant mtDNA, a degree that is sufficient for routine clinical practice.