Our observations suggest that AFG3L2 mutations are another important cause, albeit rare, of a late-onset ataxic PEO phenotype due to a disturbance of mtDNA maintenance.
C1QBP deficiency represents an important mitochondrial disorder associated with a clinical spectrum ranging from infantile lactic acidosis to childhood (cardio)myopathy and late-onset progressive external ophthalmoplegia.
At least three nuclear genes are responsible for these disorders: ANT1 and C10orf2 cause autosomal dominant PEO, while mutations of DNA polymerase gammaA (POLG1 or POLG) gene on chromosome 15q25 causes both autosomal dominant and recessive forms of PEO.
Missense mutations in the human C10orf2 gene, encoding the mitochondrial DNA (mtDNA) helicase, co-segregate with mitochondrial diseases such as adult-onset progressive external ophthalmoplegia, hepatocerebral syndrome with mtDNA depletion syndrome, and infantile-onset spinocerebellar ataxia.
The authors describe siblings with progressive external ophthalmoplegia (PEO) due to a novel heterozygous A to G transition at nucleotide 955 of C10Orf2 (Twinkle).
Therefore, we suggest that C10orf2 gene should be screened in CPEO individuals with multiple mtDNA deletions, which might help in prognosis of this disease and appropriate genetic counseling.
We report a previously undescribed 7676 base pair mitochondrial (mt)DNA deletion involving genes of complex I, complex IV subunits 2 and 3 (cytochrome oxidase [Cox] II, III), adenosine triphosphatase 8 and 6, cytochrome b and 8 transfer (t)RNA genes producing myopathy and progressive external ophthalmoplegia (PEO) in a 44-year-old right-handed Caucasian man with features of multiple sclerosis (MS).
We report a previously undescribed 7676 base pair mitochondrial (mt)DNA deletion involving genes of complex I, complex IV subunits 2 and 3 (cytochrome oxidase [Cox] II, III), adenosine triphosphatase 8 and 6, cytochrome b and 8 transfer (t)RNA genes producing myopathy and progressive external ophthalmoplegia (PEO) in a 44-year-old right-handed Caucasian man with features of multiple sclerosis (MS).
Other diseases in this group include mtDNA depletion syndromes caused by mutations on the nuclear genes encoding the mitochondrial thymidine kinase and deoxyguanosine kinase; autosomal dominant progressive external ophthalmoplegia with multiple deletions of mtDNA due to mutations in the genes encoding the muscle-isoform of mitochondrial ADP/ATP translocator; and mitochondrial DNA depletion due to toxicities of nucleoside analogues.
Results Serum FGF21 levels were significantly elevated in patients with progressive external ophthalmoplegia and DM1 compared with patients with facioscapulohumeral dystrophy, other types of mitochondrial diseases, and controls.
Overall, distinct phenotypes for expression of each of the mip1-PEO mutations were observed, including respiration-defective cells with decreased viability, dominant-negative mutant polymerases, elevated levels of mitochondrial and nuclear DNA damage and chromosomal mutations.
We report a previously undescribed 7676 base pair mitochondrial (mt)DNA deletion involving genes of complex I, complex IV subunits 2 and 3 (cytochrome oxidase [Cox] II, III), adenosine triphosphatase 8 and 6, cytochrome b and 8 transfer (t)RNA genes producing myopathy and progressive external ophthalmoplegia (PEO) in a 44-year-old right-handed Caucasian man with features of multiple sclerosis (MS).
It was commonly observed in subjects with chronic progressive external ophthalmoplegia (cPEO) and with primary myopathy without cPEO, but also-although less frequently-in multisystem phenotypes such as MELAS, MERFF, Kearns Sayre syndrome, NARP, MNGIE and Leigh syndrome.