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Mitochondrial disorders are among the most common inborn errors of metabolism; at least 15% are caused by mitochondrial DNA(mtDNA) mutations, which occur de novo or are maternally inherited. For familial heteroplasmic mtDNA mutations, the mitochondrial bottleneck defines the mtDNA mutation load in offspring, with an often high or unpredictable recurrence risk. Oocyte donation is a safe option to prevent the transmission of mtDNA disease, but the offspring resulting from oocyte donation are genetically related only to the father. Prenatal diagnosis (PND) is technically possible but usually not applicable because of limitations in predicting the phenotype. For de novo mtDNA point mutations, recurrence risks are low and PND can be offered to provide reassurance regarding fetal health. PND is also the best option for female carriers with low-level mutations demonstrating skewing to 0% or 100%. A fairly new option for preventing the transmission of mtDNA diseases is preimplantation genetic diagnosis (PGD), in which embryos with a mutant load below a mutation-specific or general expression threshold of 18% can be transferred. PGD is currently the best reproductive option for familial heteroplasmic mtDNA point mutations. Nuclear genome transfer and genome editing techniques are currently being investigated and might offer additional reproductive options for specific mtDNA disease cases.

A multicenter comparison of mitochondrial respiratory chain and complex V enzyme activity tests was performed. The average reproducibility of the enzyme assays is 16% in human muscle samples. In a blinded diagnostic accuracy test in patient fibroblasts and SURF1 knock-out mouse muscle, each lab made the correct diagnosis except for two complex I results. We recommend that enzyme activities be evaluated based on ratios, e.g. with complex IV or citrate synthase activity. In spite of large variations in observed enzyme activities, we show that inter-laboratory comparison of patient sample test results is possible by using normalization against a control sample. (c) 2012 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

AIM To evaluate survival, clinical, and genetic characteristics of all patients with classic or type 1 lissencephaly born between 1972 and 1990 in the Netherlands, who at the time were enrolled in an observational study. METHOD We re-evaluated 24 patients (11 males, 13 females) for long-term follow-up and survival information. RESULTS Mean length of follow-up was 14 years (SD 9y 8mo). Eleven patients were alive at follow-up. All patients showed severe intellectual disability, intractable epilepsy, and complete dependency on care. Life expectancy was related to the severity of the lissencephaly on neuroimaging. Molecular analysis of the LIS1 gene was not possible at the time of the original study and was now requested by eight parents. This revealed a pathogenic nonsense mutation or deletion in seven patients. INTERPRETATION Our study provides information about the long-term course of lissencephaly and the relationship between lissencephaly severity and prognosis. It also shows that renewed attention to genetic counselling remains valued by families of patients with a severe congenital neurological disease.

Principles: MELAS, or mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes is a new distinctive clinical entity The current study was designed to assess ascending aortic elasticity in adult patients with MELAS syndrome and in gene carriers, and to compare the results with age- and gender-matched healthy controls. Methods: The study comprised eight patients with MELAS syndrome and four asymptomatic gene carriers. All subjects underwent complete 2-dimensional transthoracic echocardiography, and systolic and diastolic ascending aortic diameters (SD and DD respectively) were recorded in M-mode 3 cm above the aortic Valve from a parasternal long-axis view. Aortic elastic properties were calculated using aortic data and forearm blood pressure values. Results: SD and DD of MELAS patients and gene carriers were enlarged compared with controls. Aortic stiffness index was increased (16.4 +/- 3.7 vs 3.6 +/- 1.1, p = 0.00001), while aortic strain (0.035 +/- 0.012 % vs 0.146 +/- 0.050%, p = 0.00002) and aortic distensibility (1.03 +/- 0.30 cm(2)/dynes 10(-6) vs 4.7 0 +/- 1.69 cm(2)/dynes 10(-6), p = 0.0002) were decreased in MELAS patients compared with controls. Aortic elastic properties of gene carriers were between MELAS patients and controls. Conclusions: Increased ascending aortic stiffness and enlarged aortic dimensions Suggesting vascular remodelling were found in MELAS patients as compared with controls.

PURPOSE. Leber hereditary optic neuropathy (LHON) is recognized as the most common cause of isolated blindness in young men. The current study was designed to test whether LHON as a mitochondrial disease is associated with vascular functional alterations characterized by aortic elastic properties during echocardiography. METHODS. A total of 19 patients with typical features of LHON aged 42+/-13 years (10 males) were included. Their results were compared to 19 age- and gender-matched healthy controls. Aortic stiffness index was calculated from the echocardiographically derived aortic diameters and the clinical blood pressure data. RESULTS. In this patient population, the point mutation was present in 3460G>A position in five cases, in 11778G>A position in five cases, and in 14484T>C position in nine patients. Diastolic aortic diameter (26.0+/-2.5 mm vs 28.4+/-4.1 mm, p< 0.05) and aortic stiffness index (5.1+/-2.6 vs 12.0+/-7.9, p< 0.05) were significantly increased in LHON patients compared to controls. CONCLUSIONS. Aortic stiffness can be increased in LHON disease, but further studies are warranted to confirm these findings in a larger LHON patient population with a more reliable method focusing on the pathophysiologic background.

Benign familial infantile convulsions (BFIC) is an autosomal dominantly inherited partial epilepsy syndrome of early childhood with remission before the age of 3 years. The syndrome has been linked to loci on chromosomes 1q23, 2q24, 16p12-q12, and 19q in various families. The aim of this study was to identify the responsible locus in four unrelated Dutch families with BFIC. Two of the tested families had pure BFIC; in one family, affected individuals had BFIC followed by paroxysmal kinesigenic dyskinesias at later age, and in one family, BFIC was accompanied by later-onset focal epilepsy in older generations. Linkage analysis was performed for the known loci on chromosomes 1q23, 2q24, 16p12-q12, and 19q. The two families with pure BFIC were linked to chromosome 16p12-q12. Using recombinants from these and other published families, the chromosome 16-candidate gene region was reduced from 21.4 Mb (4.3 cM) to 2.7 Mb (0.0 cM). For the other two families, linkage to any of the known loci was unlikely. In conclusion, we confirm the linkage of pure BFIC to chromosome 16p12-q12, with further refinement of the locus. Furthermore, the lack of involvement of the known loci in two of the families indicates further genetic heterogeneity for BFIC.

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