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L A Bindoff

Publications and source records attributed to L A Bindoff.

At least 19 recordsLinked to original sources
PubMed2001

Mitochondrial enteropathy: the primary pathology may not be within the gastrointestinal tract.

BACKGROUND: Mitochondrial DNA (mtDNA) defects are an important cause of disease. Although gastrointestinal symptoms are common in these patients, their pathogenesis remains uncertain. AIM: To investigate the role of the mtDNA defect in the production of gastrointestinal dysfunction. PATIENT: A 20 year old woman who presented at 15 years of age with recurrent vomiting and pseudo-obstruction, who did not respond to conservative management and ultimately had subtotal gastrectomy and Roux-en-y reconstruction. She subsequently presented with status epilepticus and was found to have a mitochondrial respiratory chain disorder due to a pathogenic mtDNA point mutation (A3243G). METHODS: Resected bowel was studied using light and electron microscopy and mtDNA analysed from both mucosal and muscular layers using polymerase chain reaction generated RFLP analysis. RESULTS: Histological and electron microscopic studies revealed no morphological abnormalities in the resected stomach, and molecular genetic analysis failed to identify the genetic defect in either the mucosal or muscle layers. CONCLUSION: This study suggests that in some individuals with gastrointestinal symptoms associated with established mitochondrial DNA disease, the primary pathology of the mitochondrial enteropathy lies outside the gastrointestinal tract.

Adolescent↗
PubMed2000

Longitudinal analysis of the segregation of mtDNA mutations in heteroplasmic individuals.

The mutation load of the pathogenic LHON (Leber hereditary optic neuropathy) mtDNA mutation at nucleotide 3460 has been followed over time in the WBC/platelet fraction from members of a matrilineal pedigree. Longitudinal analysis over a sampling period of five to six years indicates that, in all five heteroplasmic family members, the mutation load decreases at a mean overall rate of approximately 1% per year. There was no change in mutation load in homoplasmic wildtype or in homoplasmic mutant individuals. For the purposes of comparison, a longitudinal analysis of a silent mtDNA polymorphism at nucleotide 14560 was also carried out for members of a second matrilineal pedigree. In contrast to the results for the pathogenic mtDNA mutation, there was no change in the proportion of the silent polymorphism in the WBC/platelet fraction of four family members over a period of seven years. These results indicate that the pathogenic 3460 LHON mutation segregates under negative selection in these cell populations. One possible mechanism through which selection may operate is that, in heteroplasmic individuals, the hematopoietic stem cells are generally homoplasmic, either for the wildtype or for the mutant allele. The homoplasmic mutant stem cells, because of their mitochondrial respiratory chain defect, produce fewer mature WBCs and platelets over time than do the wildtype stem cells. Alternatively, the stem cells may be heteroplasmic and selection may act to favor proliferation of mitochondria with lower levels of the pathogenic mutation in the WBC/platelet cell populations.

DNA Mutational Analysis↗
PubMed2000

The epidemiology of pathogenic mitochondrial DNA mutations.

During the past decade, there have been many descriptions of patients with neurological disorders due to mitochondrial DNA (mtDNA) mutations, but the extent and spectrum of mtDNA disease in the general population have not yet been defined. Adults with suspected mtDNA disease in the North East of England were referred to a single neurology center for investigation over the 10-year period from 1990 to 1999 inclusive. We defined the genetic defect in these individuals. For the midyear period of 1997, we calculated the minimum point prevalence of mtDNA disease in the adults of working age (> 16-<60 years old for female subjects and <65 years old for male subjects) and the minimum prevalence of adults and children (<60 years for female subjects, <65 years for male subjects) at risk of developing mtDNA disease. mtDNA defects caused disease in 6.57 per 100,000 individuals in the adult population of working age, and 7.59 per 100,000 unaffected adults and children were at risk of developing mtDNA disease. Overall, 12.48 per 100,000 individuals in the adult and child population either had mtDNA disease or were at risk of developing mtDNA disease. These results reflect the minimum prevalence of mtDNA disease and pathogenic mtDNA mutations and demonstrate that pathogenic mtDNA mutations are a common cause of chronic morbidity. These findings have resource implications, particularly for supportive care and genetic counseling.

Adolescent↗
PubMed1999

Conversion of a reporter gene for mitochondrial gene expression using iterative mega-prime PCR.

Mammalian mitochondria possess their own multicopy genome, mtDNA. Although much is known about mtDNA replication and transcription, our knowledge of the mechanisms governing mt-RNA processing, stability and translation remains rudimentary. We have taken a step towards addressing these issues by altering the luciferase reporter gene to accommodate the variation in mitochondrial codon recognition. 19 essential substitutions have been generated by an iterative mega-primer PCR technique. To mimic mt-mRNA species and to optimise intramitochondrial translation, further engineering has produced a template which, when transcribed in vitro, generates an RNA species with only two nucleotides upstream from the initiation codon, an absence of a 3' untranslated region and a polyadenylated tail of 40 residues. It is intended that mt-luciferase (mt-luc) RNA will be an excellent reporter for revealing cis-acting elements essential for in organello RNA processing, maturation and expression. Additionally, the mt-luc gene can be readily incorporated into any novel mitochondrial transducing vectors to assess intra-organellar transcription and translation.

DNA Primers↗
PubMed1997

Maternally inherited diabetes and deafness: prevalence in a hospital diabetic population.

Maternally inherited diabetes and deafness (MIDD) is a new sub-type of diabetes and results from an A to G substitution at position 3243 of the mitochondrial tRNA(leu(UUR)) gene. This mutation is also associated with a neurological syndrome (MELAS). Recent studies have screened carefully selected diabetic populations and have reported MIDD prevalence rates ranging from undetectable to 60%. The aim of this work was to determine the importance of this sub-type in clinical practice by screening a routine hospital diabetic population. A total of 1440 patients (IDDM and NIDDM) of North European extraction attending two hospital diabetes services were initially screened by questionnaire. This identified 445 patients with one or more features of MIDD and/or MELAS and these subjects were then genotyped. Two patients were identified with the mutation giving a prevalence rate of 0.13% for the whole study population, and 0.45% for the sample with phenotypic features of MIDD. In conclusion, therefore, the 3243 mutation is associated with the phenotypically distinct MIDD sub-type, but this is rare in the routine hospital diabetic population.

Adult↗
PubMed1997

Spontaneous intracranial hypotension: clinical and magnetic resonance imaging characteristics.

The syndrome of spontaneous intracranial hypotension (SIH) is an uncommon cause of postural headache. We describe three patients with classical low pressure headache associated with low CSF pressure, one of whom presented with sudden deafness and another with a unilateral VIth nerve palsy. Initial magnetic resonance imaging (MRI) scans revealed bilateral diffuse subdural fluid collections in all three cases. Follow up MRI scans performed on two patients at 6 months demonstrated partial resolution of the subdural collections but persistent striking meningeal enhancement despite clinical recovery. These findings differ from previous reported cases wherein clinical resolution of postural symptoms was preceded or closely followed by resolution of the MRI changes.

Adult↗
PubMed1997

Intracellular mitochondrial triplasmy in a patient with two heteroplasmic base changes.

We report the clinical, biochemical, and genetic investigation of a patient with a severe mitochondrial encephalomyopathy. Genetic studies identified a novel, heteroplasmic tRNA mutation at nt 10010. This T-->C transition is located in the DHU loop of mitochondrial tRNA(Gly). In skeletal muscle, it was present at lower levels in cytochrome c oxidase (COX)-normal (87.2% +/- 11%) compared with COX-deficient fibers (97.3% +/- 2.6%); it was found in skin fibroblasts and blood cells, but at lower levels of heteroplasmy (15% +/- 6% and 17% +/- 10%, respectively). A second, heteroplasmic transition (A-->G), at nt 5656, showed a different distribution than the tRNA(Gly) mutation, with very low levels in skeletal muscle (< 3%) but higher levels in blood (22.7% +/- 3%) and skin fibroblasts (21% +/- 2%). These transitions were followed both in vivo, by repeat biopsy and blood sampling, and in vitro, by establishing primary cultures of myoblasts and skin fibroblasts. Repeat muscle biopsy showed a dramatic increase in COX-deficient fibers, but not of the tRNAGly mutation. Indeed, no significant change in heteroplasmy was measured for either substitution in muscle or blood. In vitro analysis gave very different results. The T10010C was not found in cultured myoblasts, even at early passage. In uncloned fibroblasts, the T10010C was stable (approximately 10%) for several passages but then gradually was lost. In contrast, the A5656G rose progressively from 27% to 91%. In cloned fibroblasts, different combinations of both base-pair changes and wild type could be identified, confirming the presence of clonal, intracellular triplasmy.

Adult↗
PubMed1997

A new mtDNA mutation showing accumulation with time and restriction to skeletal muscle.

We have identified a new mutation in mtDNA, involving tRNALeu(CUN) in a patient manifesting an isolated skeletal myopathy. This heteroplasmic A-->G transition at position 12320 affects the T psi C loop at a conserved site and was not found in 120 controls. Analysis of cultured fibroblasts, white blood cells/platelets, and skeletal muscle showed that only skeletal muscle contained the mutation and that only this tissue demonstrated a biochemical defect of respiratory-chain activity. In a series of four muscle-biopsy specimens taken over a 12-year period, there was a gradual increase, from 70% to 90%, in the overall level of mutation, as well as a marked clinical deterioration. Single-fiber PCR confirmed that the proportion of mutant mtDNA was highest in cytochrome c oxidase-negative fibers. This study, which reports a mutation involving tRNALeu(CUN), demonstrates clearly that mtDNA point mutations can accumulate over time and may be restricted in their tissue distribution. Furthermore, clinical deterioration seemed to follow the increase in the level of mutation, although, interestingly, the appearance of fibers deficient in respiratory-chain activity showed a lag period.

Base Sequence↗
PubMed1996

Deficiency of complex II of the mitochondrial respiratory chain in late-onset optic atrophy and ataxia.

Defects of the mitochondrial respiratory chain are increasingly being recognized as an important cause of neurological disease in humans. In many of these patients, the biochemical defect results from an abnormality of the mitochondrial genome. Respiratory chain defects involving complex II, which is entirely encoded by the nuclear genome, are comparatively rare. We report the clinical and biochemical findings in 2 elderly sisters who presented with late-onset neurodegenerative disease. In both patients, a partial deficiency of complex II (approximately 50% of control values) was shown to be present in mitochondria from muscle and platelets. The enzyme defect was not expressed in cultured skin fibroblasts or immortalized lymphocytes. There was an overexpression of the 70-kd flavoprotein subunit in muscle mitochondria from both patients, although we showed that this subunit is present in normal amounts in mitochondrial membranes. Our studies highlight the diversity of the clinical presentation of respiratory chain disease and that complex II deficiency should enter the differential diagnosis of certain patients with late-onset neurodegenerative disease.

Ataxia↗
PubMed1996

Deficiency of respiratory chain complex I is a common cause of Leigh disease.

We reviewed the clinical features and etiologies of Leigh disease in 66 patients from 60 pedigrees. Biochemical or molecular defects were identified in 50% of all pedigrees, and in 74% of the 19 pedigrees with pathologically proved Leigh disease. Isolated deficiency of respiratory chain complex I was found in 7 patients, though the complex was only assayed in 25 patients, making this the second most common biochemical abnormality after complex IV deficiency. Mutations at residue 8993 of mitochondrial DNA were found in only 2 patients. No correlation was found between the clinical features and etiologies. No defects were identified in the 8 patients with normal lactate concentrations in the cerebrospinal fluid.

Blotting, Southern↗
PubMed1996

MELAS associated with a mutation in the valine transfer RNA gene of mitochondrial DNA.

We describe a patient with the mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS) phenotype in whom initial investigations in skeletal muscle failed to show any histochemical or biochemical defect. Subsequent analysis of the mitochondrial genome identified a new heteroplasmic mutation in the valine transfer RNA gene, the first described in this region.

Adolescent↗
PubMed1995

Neonatal Fanconi syndrome due to deficiency of complex III of the respiratory chain.

Fanconi syndrome is an important presentation of respiratory chain disease. We report three patients who presented in the neonatal period with Fanconi syndrome, lactic acidosis and intrauterine growth retardation. In all three patients the major biochemical defect was in complex III of the mitochondrial respiratory chain, a relatively uncommon defect. The diagnosis could only be made by muscle biopsy as the defect was not expressed in cultured skin fibroblasts. Treatment with vitamins C and K3 and ubiquinone did not alter the course of the disease and all patients died before the age of 4 months.

Acidosis, Lactic↗
PubMed1995

Presentation and clinical investigation of mitochondrial respiratory chain disease. A study of 51 patients.

Defects of the mitochondrial respiratory chain are associated with a great variety of clinical disorders. Whilst recognition of these conditions is increasing, the need for sophisticated biochemical and molecular studies has tended to limit both their investigation and diagnosis to a few specialist centres. Using a group of 51 patients with histochemically, biochemically and/or genetically defined respiratory chain defects, we have examined both the clinical heterogeneity of these disorders and how they may be investigated most effectively in non-specialist centres. We evaluated the use of the following routinely available clinical investigations--fasting intermediary metabolites (lactate, pyruvate, ketone bodies, etc.) in blood and cerebrospinal fluid, serum creatine kinase estimation, EMG, EEG, CT, MRI and histological/histochemical muscle biopsy analysis. Our studies show that, in addition to well-recognized syndromes (e.g. chronic progressive external ophthalmoplegia, mitochondrial encephalopathy lactic acidosis and stroke like episodes, and myoclonus epilepsy with ragged red-fibres, a significant number of patients present with non-specific encephalopathic disorders. Furthermore, even within those categories of respiratory chain disease which have been genetically defined, a wide variation of presenting symptoms and signs were found. Where there was initial doubt concerning the diagnosis, the following clinical features were helpful in suggesting respiratory chain disease: ophthalmoplegia; a maternal pattern of inheritance; the presence of myopathy or deafness in association with encephalopathy. Of the clinical investigations we assessed, elevated lactate in blood or cerebrospinal fluid and low density lesions in the basal ganglia were helpful in identifying patients with respiratory chain dysfunction. Histochemical analysis of muscle was, however, the single most useful investigation being diagnostic in patients with chronic progressive external ophthalmoplegia, Kearns-Sayre syndrome and myopathy, and of significant importance in patients presenting primarily with central nervous system disease. The results of our study are used to discuss the most appropriate approach to diagnosis of this group of disorders.

Adolescent↗
PubMed1994

Molecular cloning and expression of a cDNA encoding human electron transfer flavoprotein-ubiquinone oxidoreductase.

Electron-transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) in the inner mitochondrial membrane accepts electrons from electron-transfer flavoprotein which is located in the mitochondrial matrix and reduces ubiquinone in the mitochondrial membrane. The two redox centers in the protein, FAD and a [4Fe4S]+2,+1 cluster, are present in a 64-kDa monomer. We cloned several cDNA sequences encoding the majority of porcine ETF-QO and used these as probes to clone a full-length human ETF-QO cDNA. The deduced human ETF-QO sequence predicts a protein containing 617 amino acids (67 kDa), two domains associated with the binding of the AMP moiety of the FAD prosthetic group, two membrane helices and a motif containing four cysteine residues that is frequently associated with the liganding of ferredoxin-like iron-sulfur clusters. A cleavable 33-amino-acid sequence is also predicted at the amino terminus of the 67-kDa protein which targets the protein to mitochondria. In vitro transcription and translation yielded a 67-kDa immunoprecipitable product as predicted from the open reading frame of the cDNA. The human cDNA was expressed in Saccharomyces cerevisiae, which does not normally synthesize the protein. The ETF-QO is synthesized as a 67-kDa precursor which is targeted to mitochondria and processed in a single step to a 64-kDa mature form located in the mitochondrial membrane. The detergent-solubilized protein transfers electrons from ETF to the ubiquinone homolog, Q1, indicating that both the FAD and iron-sulfur cluster are properly inserted into the heterologously expressed protein.

Amino Acid Sequence↗