MERRF/MELAS overlap syndrome in a family with A3243G mtDNA mutation

Four members of a family were found to carry the A3243G mtDNA mutation. Clinical features varied from typical MELAS to myoclonic epilepsy to simple deafness without neurological signs. Several other members of the family had symptoms consistent with a mitochondrial disease. Muscle biopsy in 3 of the 4 patients showed the most prominent mitochondrial alterations with partial deficiency of cytochrome c oxidase in the case with the mildest phenotype. Mitochondrial DNA analysis detected a variable percentage of A3243G mutation, roughly correlating with the phenotype. The interesting feature of the family lies in the great intrafamilial variability of the severity of clinical expression, encompassing MELAS and MERRF features, associated with the A3243G mtDNA mutation. A search for the most common mtDNA mutations is recommended in all patients featuring incomplete MELAS or MERRF syndromes and in all familial cases presenting minimal clinical signs.     

Novel SACS mutation in a Belgian family with sacsin-related ataxia

The authors describe the four patients in the first known Belgian family with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). A novel homozygous missense mutation, NM_014363.3: c.3491T>A in exon 9, of the SACS gene was identified in the present family, which results in an original amino acid of methionine to lysine substitution at amino acid residue 1164 (p.M1164K). Although the cardinal clinical features, i.e., spastic ataxia with peripheral neuropathy, in our patients were similar to those in Quebec patients, our patients exhibited some atypical clinical features, e.g., teenage-onset and absence of retinal hypermyelination. The present family is from Wallonia, and there could be shared ethnicity with the families of Charlevoix-Saguenay.     

Novel FHL1 mutation in a family with reducing body myopathy

Introduction: Reducing body myopathy is a rare X‐linked myopathy. It is characterized by intracytoplasmic inclusions that stain with menadione–nitroblue tetrazolium. It is caused by mutations in the FHL1 gene, which encodes the four‐and‐a‐half LIM domain 1 protein (FHL1). Methods: We performed a clinical, muscle MRI, and histopathological characterization and immunoblot and genetic analysis of the FHL1 protein in a family with 4 individuals affected by reducing body myopathy. Results: We identified a novel missense mutation in FHL1 (c.449G>C; p.C150S). The patients presented with asymmetric proximal weakness and scoliosis. Both of the boys had a more severe course with earlier onset, contractures, and death due to heart failure at 14 and 18 years of age, respectively. MRI revealed fatty infiltration of posteromedial thigh and paraspinal muscles. Histopathological findings showed FHL1‐immunoreactive inclusions. Immunoblot analysis revealed a 50% reduction of FHL1 protein. Conclusion: In this study we highlighted diagnostic clues in this myopathy and compared our data with the literature. Muscle Nerve, 2013     

A novel mutation in the GTP cyclohydrolase I gene associated with a broad range of clinical presentations in a family with autosomal dominant dopa-responsive dystonia

We examined a large family of Ashkenazi Jewish origin with autosomal dominant dopa-responsive dystonia (DRD). Mutation analysis of the GTP cyclohydrolase I gene revealed in affected members a novel point mutation (a C/A change in exon 1) resulting in a threonine-to-lysine substitution at residue 94. The mutation was characterized by variable expressivity and was associated with either a 'classical' DRD phenotype or various atypical phenotypes, such as subtle transitory equinovarus postures of the feet or isolated hand tremor. This observation demonstrates the significance of the molecular testing in establishing the clinical diagnosis of DRD. Copyright Lippincott Williams & Wilkins     

A novel heteroplasmic tRNA(Ser(UCN)) mtDNA point mutation associated with progressive external ophthalmoplegia and hearing loss

We sequenced all mitochondrial tRNA genes from a patient with sporadic external ophthalmoplegia (PEO) and 5% COX-negative fibers in muscle biopsy, who had no detectable large mtDNA deletions. Direct sequencing showed a heteroplasmic mutation at nucleotide 7506 in the dihydrouridine stem of the tRNA(Ser(UCN)) gene. RFLP analysis confirmed that 30% of muscle and 20% of urinary epithelium mtDNA harbored the mutation, which was absent in other tissues of the proband as well as in mtDNA of his mother and 100 patients with various encephalomyopathies. Several point mutations on mitochondrial tRNA genes have been reported in PEO patients without large-scale rearrangements of mtDNA but no point mutations have hitherto been found in the gene coding for tRNA(Ser(UCN)).     

The role of complex I genes in MELAS: a novel heteroplasmic mutation 3380G>A in ND1 of mtDNA

While Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) is typically associated with mutations in the mitochondrial tRNA(Leu) gene, mutations in complex I subunit genes of the mtDNA have emerged as a second significant cause. Here we report a novel mutation in the mitochondrial complex I subunit gene ND1 in a patient with late-onset MELAS. The 3380G>A mutation shows very good evidence of pathogenicity as it is heteroplasmic, undetectable in controls, alters a highly conserved amino acid, and is more abundant in ragged-red than in normal muscle fibers. These findings support the significant role of complex I mutations in MELAS.     

Novel mutation of SACS gene in a Spanish family with autosomal recessive spastic ataxia.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is an inherited neurodegenerative disorder characterized by early-onset, spastic ataxia and peripheral neuropathy. It was originally described in an inbred population of Quebec and later in some other countries. We report a new missense SACS mutation (7848C>T) in a Spanish family whose phenotype is similar to that of the previously described ARSACS patients. 7848C>T is the first SACS mutation reported in Spain confirming worldwide distribution of the disease.     

Mitochondrial myopathy associated with a novel mutation in mtDNA

A 6-year-old boy had progressive muscle weakness since age 4 and emotional problems diagnosed as Asperger syndrome. His mother and two older siblings are in good health and there is no family history of neuromuscular disorders. Muscle biopsy showed ragged-red and cytochrome coxidase (COX)-negative fibers. Respiratory chain activities were reduced for all enzymes containing mtDNA-encoded subunits, especially COX. Sequence analysis of the 22 tRNA genes revealed a novel G10406A base substitution, which was heteroplasmic in multiple tissues of the patient by RFLP analysis (muscle, 96%; urinary sediment, 94%; cheek mucosa, 36%; blood, 29%). The mutation was not detected in any accessible tissues from his mother or siblings. It appears that this mutation arose de novo in the proband, probably early in embryogenesis.     

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.     

Novel LGI1 mutation in a family with autosomal dominant partial epilepsy with auditory features

Autosomal dominant partial epilepsy with auditory features (ADPEAF) is a rare idiopathic epilepsy syndrome caused by mutations in the leucine-rich, glioma-inactivated 1 (LGI1) gene. The authors report that molecular genetic studies in seven affected family members identified a novel F318C substitution that alters a highly conserved residue in a predicted repeat domain of unknown function. This report suggests that this domain may participate in the development of the ADPEAF phenotype.     

Novel heteroplasmic mutation in the anticodon stem of mitochondrial tRNALys associated with dystonia and stroke‐like episodes

Gal A, Pentelenyi K, Remenyi V, Pal Z, Csanyi B, Tomory G, Rasko I, Molnar MJ. Novel heteroplasmic mutation in the anticodon stem of mitochondrial tRNA^Lys associated with dystonia and stroke‐like episodes.
Acta Neurol Scand: 2010: 122: 252–256.
© 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Objectives – We report a novel heteroplasmic mitochondrial tRNA^Lys mutation associated with dystonia, stroke‐like episodes, sensorineural hearing loss and epilepsy in a Hungarian family. Material and methods – A 16‐year‐old boy, his brother and mother were investigated. Thorough clinical investigation as well as electrophysiological, neuroradiological and myopathological examinations were performed. Molecular studies included the analysis of the DYT1, DDP1/TIMM8A (deafness‐dystonia peptid‐1) genes and mitochondrial DNA (mtDNA). Results –  The mtDNA analysis of the proband revealed a heteroplasmic A8332G substitution in the anticodon stem of the tRNA^Lys gene. The mutation segregated in all affected family members. Besides this mutation 16 further mtDNA polymorphisms were detected. Complex I activity of the patient’s fibroblast cultures showed decreased activity confirming mitochondrial dysfunction. Conclusion –  The novel A8332G heteroplasmic mutation is most likely a new cause of dystonia and stroke‐like episodes due to mitochondrial encephalopathy. The synergistic effect of the G8697A, A11812G and T10463C single nucleotide polymorphisms may modify the phenotype.     

Marked variation in clinical presentation and age of onset in a family with a heterozygous parkin mutation.

Parkin gene mutations have been detected in families with early-onset autosomal recessive parkinsonism. We report a novel heterozygous 40 base pair deletion in exon 3 of the parkin gene that increases the susceptibility of carriers to develop parkinsonism/dystonia and manifests remarkable variability in regard to age of onset and phenotype in a single family. After identifying the new mutation in the proband of this kindred, family members were contacted and evaluated by a movement disorders specialist using standardized protocols and prospectively set diagnostic criteria. Importantly, examining physicians and family members were blinded to the genetic testing. Five affected members in two generations carried the parkin mutation. The proband and one of his brothers had disease onset at 24 years of age while another brother had disease at age 44. One exhibited multi-focal dystonia and parkinsonism of 17 years duration, another suffered a unilateral slowly progressive parkinsonism over 13 years while the third suffered dystonia-parkinsonism of recent onset. A sibling pair in the preceding generation had mild previously undiagnosed parkinsonism. Clinicians should be aware that patients carrying a parkin gene mutation may present with dystonia-parkinsonism or very subtle parkinsonism with a markedly varied age of onset.     

Novel GCH1 mutation in a Brazilian family with dopa‐responsive dystonia

Dopa responsive Dystonia (DRD) was first described in 1971 and typically begins at childhood with gait dysfunction caused by foot dystonia progressing to affect other extremities. There is marked diurnal fluctuation and sustained improvement of symptoms with low dose levodopa therapy. Heterozygous mutation of the gene GCH1 has been shown to cause DRD. We studied GCH1 in nine patients with DRD from six families of Federal University of Minas Gerais Movement Disorders Clinic. We identified three mutations; two affected siblings carried a novel T209P mutation and two siblings from another family were compound heterozygous carriers of Met211Val and Lys224Arg mutations. To our knowledge this is the first report of GCH1 mutations underlying DRD in patients from Brazil. © 2007 Movement Disorder Society     

OXPHOS and mtDNA alterations in a family with spastic paraparesis

OBJECTIVE: To study muscle biopsies in hereditary spastic paraparesis (HSP). METHODS: We analyzed oxidative phosphorylation activities and mtDNA in 3 individuals from an HSP family. RESULTS: We found histochemical evidence for mitochondrial proliferation and cytochrome c oxidase negative fibers. Biochemically, there was an important reduction of the activities of complexes I and IV in 3 patients. In addition, multiple mtDNA deletions (ranging 4.0-7.0 kb) were found in 2 cases by PCR but not by Southern blot. CONCLUSION: We suggest the use of a muscle biopsy when examining HSP patients. HSP can represent a disorder of nuclear-mitochondrial intercommunication.     

Novel TTC19 mutation in a family with severe psychiatric manifestations and complex III deficiency

Complex III of the mitochondrial respiratory chain (CIII) catalyzes transfer of electrons from reduced coenzyme Q to cytochrome c. Low biochemical activity of CIII is not a frequent etiology in disorders of oxidative metabolism and is genetically heterogeneous. Recently, mutations in the human tetratricopeptide 19 gene (TTC19) have been involved in the etiology of CIII deficiency through impaired assembly of the holocomplex. We investigated a consanguineous Portuguese family where four siblings had reduced enzymatic activity of CIII in muscle and harbored a novel homozygous mutation in TTC19. The clinical phenotype in the four sibs was consistent with severe olivo–ponto–cerebellar atrophy, although their age at onset differed slightly. Interestingly, three patients also presented progressive psychosis. The mutation resulted in almost complete absence of TTC19 protein, defective assembly of CIII in muscle, and enhanced production of reactive oxygen species in cultured skin fibroblasts. Our findings add to the array of mutations in TTC19, corroborate the notion of genotype/phenotype variability in mitochondrial encephalomyopathies even within a single family, and indicate that psychiatric manifestations are a further presentation of low CIII.     

Novel TPM3 mutation in a family with cap myopathy and review of the literature

Cap myopathy is a rare congenital myopathy characterized by the presence of caps within muscle fibres and caused by mutations in ACTA1, TPM2 or TPM3. Thus far, only three cases with TPM3-related cap myopathy have been described. Here, we report on the first autosomal dominant family with cap myopathy in three-generations, caused by a novel heterozygous mutation in the alpha-tropomyosin-slow-encoding gene (TPM3; exon 4; c.445C>A; p.Leu149Ile). The three patients experienced first symptoms of muscle weakness in childhood and followed a slowly progressive course. They presented generalized hypotrophy and mild muscle weakness, elongated face, high arched palate, micrognathia, scoliosis and respiratory involvement. Intrafamilial variability of skeletal deformities, respiratory involvement and mild cardiac abnormalities was noted. Muscle MRI revealed a recognizable pattern of fatty muscle infiltration and masseter muscle hypertrophy. Subsarcolemmal caps were present in 6–10% of the fibres and immunoreactive with anti-tropomyosin antibodies. We conclude that the MRI-pattern of muscle involvement and the presence of masseter muscle hypertrophy in cap myopathy may guide molecular genetic diagnosis towards a mutation in TPM3. Regular respiratory examinations are important, even if patients have no anamnestic clues. We compare our findings to all cases of cap myopathy with identified mutations (n = 11), thus far reported in the literature.     

Phenotype and clinical course in a family with a new de novo Twinkle gene mutation

The Twinkle gene product is important for mtDNA replication. Only a few reports have investigated the clinically effect of mutations in this gene. We describe a new de novo mutation (1110C > A) in the PEO1 gene in a mother and her two sons. The mother had progressive ophthalmoplegia, limb weakness, sensory neuropathy, elevated resting plasma lactate, glucose intolerance and impaired VO_2max while her sons only had mild ptosis. In accordance with the clinical presentation, abnormal morphological findings in muscle and multiple deletions and depletion of mtDNA in muscle were more pronounced in the proband than in her sons.     

SPG11: a consistent clinical phenotype in a family with homozygous Spatacsin truncating mutation

Hereditary spastic paraplegias (HSP) are a heterogeneous group of neurodegenerative disorders leading to progressive spasticity of the lower limbs. Here, we describe clinical and genetic features in an Italian family affected by autosomal recessive HSP (ARHSP) with mental impairment and thin corpus callosum (TCC). In both affected subjects, genetic analysis revealed the presence of a homozygous small deletion (733_734delAT) leading to a frameshift (M245VfsX) within the coding region of SPG11 gene, encoding spatacsin. This finding is the first independent confirmation that spatacsin loss of function mutations cause ARHPS-TCC. Roberto Del Bo and Alessio Di Fonzo, These two authors equally contributed to the present work.