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Objective: The aim of this work was to determine the prevalence and progression of epilepsy in adult patients with mitochondrial disease.Methods: We prospectively recruited a cohort of 182 consecutive adult patients attending a specialized mitochondrial disease clinic in Newcastle upon Tyne between January 1, 2005 and January 1, 2008. We then followed this cohort over a 7-year period, recording primary outcome measures of occurrence of first seizure, status epilepticus, stroke-like episode, and death.Results: Overall prevalence of epilepsy in the cohort was 23.1%. Mean age of epilepsy onset was 29.4 years. Prevalence varied widely between genotypes, with several genotypes having no cases of epilepsy, a prevalence of 34.9% in the most common genotype (m.3243A>G mutation), and 92.3% in the m.8344A>G mutation. Among the cohort as a whole, focal seizures, with or without progression to bilateral convulsive seizures, was the most common seizure type. Conversely, all of the patients with the m.8344A>G mutation and epilepsy experienced myoclonic seizures. Patients with the m.3243A>G mutation remain at high risk of developing stroke-like episodes (1.16% per year). However, although the standardized mortality ratio for the entire cohort was high (2.86), this ratio did not differ significantly between patients with epilepsy (2.96) and those without (2.83).Interpretation: Epilepsy is a common manifestation of mitochondrial disease. It develops early in the disease and, in the case of the m.3243A>G mutation, often presents in the context of a stroke-like episode or status epilepticus. However, epilepsy does not itself appear to contribute to the increased mortality in mitochondrial disease. [ABSTRACT FROM AUTHOR]

Age-related decline in the integrity of mitochondria is an important contributor to the human ageing process. In a number of ageing stem cell populations, this decline in mitochondrial function is due to clonal expansion of individual mitochondrial DNA (mtDNA) point mutations within single cells. However the dynamics of this process and when these mtDNA mutations occur initially are poorly understood. Using human colorectal epithelium as an exemplar tissue with a well-defined stem cell population, we analysed samples from 207 healthy participants aged 17–78 years using a combination of techniques (Random Mutation Capture, Next Generation Sequencing and mitochondrial enzyme histochemistry), and show that: 1) non-pathogenic mtDNA mutations are present from early embryogenesis or may be transmitted through the germline, whereas pathogenic mtDNA mutations are detected in the somatic cells, providing evidence for purifying selection in humans, 2) pathogenic mtDNA mutations are present from early adulthood (<20 years of age), at both low levels and as clonal expansions, 3) low level mtDNA mutation frequency does not change significantly with age, suggesting that mtDNA mutation rate does not increase significantly with age, and 4) clonally expanded mtDNA mutations increase dramatically with age. These data confirm that clonal expansion of mtDNA mutations, some of which are generated very early in life, is the major driving force behind the mitochondrial dysfunction associated with ageing of the human colorectal epithelium. [ABSTRACT FROM AUTHOR]

Aims Hypertrophic remodelling and systolic dysfunction are common in patients with mitochondrial disease and independent predictors of morbidity and early mortality. Screening strategies for cardiac disease are unclear. We investigated whether myocardial abnormalities could be identified in mitochondrial DNA mutation carriers without clinical cardiac involvement. Methods and results Cardiac magnetic resonance imaging was performed in 22 adult patients with mitochondrial disease due to the m.3243A>G mutation, but no known cardiac involvement, and 22 age- and gender-matched control subjects: (i) Phosphorus-31- magnetic resonance spectroscopy, (ii) cine imaging (iii), cardiac tagging and (iv) late gadolinium enhancement (LGE) imaging. Disease burden was determined using the Newcastle Mitochondrial Disease Adult Scale (NMDAS) and urinary mutation load. Compared with control subjects, patients had an increased left ventricular mass index (LVMI), LV mass to end-diastolic volume (M/V) ratio, wall thicknesses (all P < 0.01), torsion and torsion to endocardial strain ratio (both P < 0.05). Longitudinal shortening was decreased in patients (P < 0.0001) and correlated with an increased LVMI (r = −0.52, P < 0.03), but there were no differences in the diastolic function. Among patients there was no correlation of LVMI or the M/V ratio with diabetic or hypertensive status, but the mutation load and NMDAS correlated with the LVMI (r = 0.71 and r = 0.79, respectively, both P < 0.001). The phosphocreatine/adenosine triphosphate ratio was decreased in patients (P < 0.001) but did not correlate with other parameters. No patients displayed focal LGE. Conclusion Concentric remodelling and subendocardial dysfunction occur in patients carrying m.3243A>G mutation without clinical cardiac disease. Patients with higher mutation loads and disease burden may be at increased risk of cardiac involvement. [ABSTRACT FROM PUBLISHER]

Defects of the mitochondrial respiratory chain are associated with a diverse spectrum of clinical phenotypes, and may be caused by mutations in either the nuclear or the mitochondrial genome (mitochondrial DNA (mtDNA)). Isolated complex I deficiency is the most common enzyme defect in mitochondrial disorders, particularly in children in whom family history is often consistent with sporadic or autosomal recessive inheritance, implicating a nuclear genetic cause. In contrast, although a number of recurrent, pathogenic mtDNA mutations have been described, historically, these have been perceived as rare causes of paediatric complex I deficiency. We reviewed the clinical and genetic findings in a large cohort of 109 paediatric patients with isolated complex I deficiency from 101 families. Pathogenic mtDNA mutations were found in 29 of 101 probands (29%), 21 in MTND subunit genes and 8 in mtDNA tRNA genes. Nuclear gene defects were inferred in 38 of 101 (38%) probands based on cell hybrid studies, mtDNA sequencing or mutation analysis (nuclear gene mutations were identified in 22 probands). Leigh or Leigh-like disease was the most common clinical presentation in both mtDNA and nuclear genetic defects. The median age at onset was higher in mtDNA patients (12 months) than in patients with a nuclear gene defect (3 months). However, considerable overlap existed, with onset varying from 0 to >60 months in both groups. Our findings confirm that pathogenic mtDNA mutations are a significant cause of complex I deficiency in children. In the absence of parental consanguinity, we recommend whole mitochondrial genome sequencing as a key approach to elucidate the underlying molecular genetic abnormality. [ABSTRACT FROM AUTHOR]

Mitochondria have been hypothesized to play a role in both aging and neurodegenerative diseases, such as Parkinson's disease (PD) and Alzheimer's disease. Many studies have shown the accumulation of mitochondrial DNA (mtDNA) mutations in post-mitotic tissues and more recent data have shown this also to be a feature of aging mitotic tissues. Much of this data has been correlative, until recently with the development of polymerase gamma deficient mice which accumulate high levels of mtDNA mutations and show a premature aging phenotype, that a more causative role has been proposed. This article focuses on recent developments in aging research into the role that mtDNA mutations play in the aging process. [ABSTRACT FROM AUTHOR]

The 3243A>G mutation is one of the most frequently observed mutations of mitochondrial DNA (mtDNA), and is associated with numerous clinical presentations including mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), progressive external ophthalmoplegia (PEO) and diabetes and deafness. The routine diagnosis of the 3243A>G mutation in blood is difficult as mutation levels are known to decrease in this tissue over time, while in some patients it may be absent. We have directly compared the levels of the 3243A>G mutation in skeletal muscle, blood and urinary epithelial cells in 18 patients and observed a striking correlation between the mutation load in postmitotic muscle and urinary epithelium, a mitotic tissue. These data strongly support the use of urinary epithelial cells as the tissue of choice in the noninvasive diagnosis of the 3243A>G mutation.European Journal of Human Genetics (2004) 12, 778-781. doi:10.1038/sj.ejhg.5201216 Published online 16 June 2004 [ABSTRACT FROM AUTHOR]

Discusses the reanalysis and revision of the Cambridge reference sequence (CRS) for human mitochondrial DNA. Determination of the complete mitochondrial DNA sequence using a series of 28 overlapping polymerase chain reaction-amplified fragments spanning the entire length of the mitochondrial genome; Resequencing information revealing errors and rare polymorphisms in the CRS.

Summary Background Human genome evolution has been shaped by infectious disease. Although most genetic studies have focused on the immune system, recovery after sepsis is directly related to physiological reserve that is critically dependent on mitochondrial function. We investigated whether haplogroup H, the most common type of mitochondrial DNA (mtDNA) in Europe, contributes to the subtle genetic variation in survival after sepsis. Methods In a prospective study, we included 150 individuals who were sequentially admitted to the intensive care unit in a hospital in Newcastle upon Tyne, UK. After clinical data were obtained, patients underwent mtDNA haplotyping by analysis with PCR and restriction fragment length polymorphism. As endpoints, we used death during the 6-month period or survival at 6 months. Findings Follow-up was complete for all study participants, although the haplotype of two patients could not be reliably determined. On admission to the intensive care unit, the frequency of mtDNA haplogroup H in study patients did not differ between study patients admitted with severe sepsis and 542 age-matched controls from the northeast of England. MtDNA haplogroup H was a strong independent predictor of outcome during severe sepsis, conferring a 2·12-fold (95% CI 1·02-4·43) increased chance of survival at 180 days compared with individuals without the haplogroup H. Interpretation Although haplogroup H is the most recent addition to the group of European mtDNA, paradoxically it is also the most common. Increased survival after sepsis provides one explanation for this observation. MtDNA haplotyping offers a new means of risk stratification of patients with severe infections, which suggests new avenues for therapeutic intervention. [ABSTRACT FROM AUTHOR]

The incidence and prevalence of Alzheimer''s disease (AD) and Parkinson''s disease (PD) are increasing as the population ages. Both disorders have been associated with oxidative stress and mitochondrial dysfunction, and it has been proposed that mutations in the mitochondrial genome have a key role in neurodegeneration in AD and PD patients. Two recent publications propose that heteroplasmic mtDNA mutations are involved in AD and PD. However, when these new studies are considered in relation to the sum of previous evidence, the role of mtDNA mutations in the development of either AD or PD still remains to be established. [Copyright &y& Elsevier]

The mitochondrial genome encodes 13 essential subunits of the respiratory chain and has remarkable genetics based on uniparental inheritance. Within human populations, the mitochondrial genome has a high rate of sequence divergence with multiple polymorphic variants and thus has played a major role in examining the evolutionary history of our species. In recent years it has also become apparent that parhogenic mitochondrial DNA (mtDNA) mutations play an important role in neurological and other diseases. Patients harbor many different mtDNA mutations, some of which are mtDNA mutations, some of which are inherited, but others that seem to be sporadic. It has also been suggested that mtDNA mutations play a role in aging and cancer, but the evidence for a causative role in these conditions is less clear. The accumulated data would suggest, however, that mtDNA mutations occur on a frequent basis. In this article we describe a new phenomenon: the accumulation of mtDNA mutations in human colonic crypt stem cells that result in a significant biochemical defect in their progeny. These studies have important consequences not only for understanding of the finding of mtDNA mutations in aging tissues and tumors, but also for determining the frequency of mtDNA mutations within a cell. [ABSTRACT FROM AUTHOR]