Novel mutation in the mitochondrial transfer RNACys gene in a child

Mitochondrial DNA (mtDNA) disorders are an important group of genetic diseases presenting with a multifacet array of clinical manifestations. Highly energy-dependent tissues such as central nervous system and skeletal and cardiac muscles are commonly involved either as multisystem or as isolated organ disease. Characteristic symptoms include epilepsy, myopathy, deafness and ophthalmoplegia, all associated with point mutations in the mtDNA. Pathogenic mtDNA mutations can be heteroplasmic or homoplasmic. Heteroplasmic mutations are typically associated with mutations in mt-tRNA genes. Mutations in mt-tRNAs genes are responsible for the majority of the presentations of a mitochondrial disease being associated with marked clinical heterogeneity. Although tRNA-encoding genes make up only 9% of the entire mitochondrial genome, over 40% of all point mutations reported in the mtDNA are located in tRNA genes. Here, we present a child with vomiting episodes and migraine in whom we found a novel variant in the mitochondrial tRNACys gene

Cavitating leukoencephalopathy in a child carrying the mitochondrial A8344G mutation.

Mitochondrial disorders are usually characterized by the combination of deep gray and white matter involvement on brain imaging. However, a selective white matter involvement has been reported in specific mitochondrial diseases, including Leber hereditary optic neuropathy, myoneurogastrointestina

"Double trouble” or digenic disorder in Complex I deficiency

Complex I (CI) deficiency is a defect of OXPHOS caused by mutations in the mitochondrial or nuclear genomes. To date disease-causing mutations have been reported in all mitochondrial-encoded subunits and 22 nuclear genes. In about 50% of the patients no mutations are found, suggesting that undiscovered factors are an important cause of disease. In this study we report a consanguineous family from Southern Portugal with three affected children presenting with CI deficiency and 3-methylglutaconic aciduria type IV

Syndromes associated with mitochondrial DNA depletion

This is an Open Access article distributed under the terms of the Creative Commons Attribution License.Mitochondrial dysfunction accounts for a large group of inherited metabolic disorders most of which are due to a dysfunctional mitochondrial respiratory chain (MRC) and, consequently, deficient energy production. MRC function depends on the coordinated expression of both nuclear (nDNA) and mitochondrial (mtDNA) genomes. Thus, mitochondrial diseases can be caused by genetic defects in either the mitochondrial or the nuclear genome, or in the cross-talk between the two. This impaired cross-talk gives rise to so-called nuclear-mitochondrial intergenomic communication disorders, which result in loss or instability of the mitochondrial genome and, in turn, impaired maintenance of qualitative and quantitative mtDNA integrity. In children, most MRC disorders are associated with nuclear gene defects rather than alterations in the mtDNA itself.The mitochondrial DNA depletion syndromes (MDSs) are a clinically heterogeneous group of disorders with an autosomal recessive pattern of transmission that have onset in infancy or early childhood and are characterized by a reduced number of copies of mtDNA in affected tissues and organs. The MDSs can be divided into least four clinical presentations: hepatocerebral, myopathic, encephalomyopathic and neurogastrointestinal. The focus of this review is to offer an overview of these syndromes, listing the clinical phenotypes, together with their relative frequency, mutational spectrum, and possible insights for improving diagnostic strategies.CN was supported by the Portuguese Foundation for Science and Technology (SFRH/BD/45247/2008). LSA was supported by the Portuguese Foundation for Science and Technology (FCT C2008/INSA/P4)

Complex phenotype in an Italian family with a novel mutation in SPG3A.

Mutations in the SPG3A gene represent a significant cause of autosomal dominant hereditary spastic paraplegia with early onset and pure phenotype. We describe an Italian family manifesting a complex phenotype, characterized by cerebellar involvement in the proband and amyotrophic lateral sclerosis-like syndrome in her father, in association with a new mutation in SPG3A. Our findings further widen the notion of clinical heterogeneity in SPG3A mutations

Muscle MRI in <i>TRPV4-</i> related congenital distal SMA

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Identification of a new mtDNA mutation (14724G>A) associated with mitochondrial leukoencephalopathy

Biochem Biophys Res Commun. 2007 Mar 23;354(4):937-41. Epub 2007 Jan 23. Identification of a new mtDNA mutation (14724G>A) associated with mitochondrial leukoencephalopathy. Pereira C, Nogueira C, Barbot C, Tessa A, Soares C, Fattori F, Guimarães A, Santorelli FM, Vilarinho L. Instituto de Genética Médica Jacinto de Magalhães, Praça Pedro Nunes, 88, 4099-028 Porto, Portugal. Abstract We report a novel 14724G>A mutation in the mitochondrial tRNA glutamic acid gene in a 4-year-old boy with myopathy and leukoencephalopathy. A muscle biopsy showed cytochrome c oxidase-negative ragged-red fibers and biochemical analysis of the respiratory chain enzymes in muscle homogenate revealed partial complex I and complex IV deficiencies. The mutation, which affects the dihydrouridine arm at a conserved site, was nearly homoplasmic in muscle and heteroplasmic in blood DNA of the proband, but it was absent in peripheral leukocytes from the asymptomatic mother, sister, and two maternal aunts, suggesting that it arose de novo. This report proposes to look for variants in the mitochondrial genome when dealing with otherwise undetermined leukodystrophies of childhood. PMID: 17266923 [PubMed - indexed for MEDLINE

Muscle pain in mitochondrial diseases: a picture from the Italian network

Muscle pain may be part of many neuromuscular disorders including myopathies, peripheral neuropathies and lower motor neuron diseases. Although it has been reported also in mitochondrial diseases (MD), no extensive studies in this group of diseases have been performed so far. We reviewed clinical data from 1398 patients affected with mitochondrial diseases listed in the database of the "Nation-wide Italian Collaborative Network of Mitochondrial Diseases", to assess muscle pain and its features. Muscle pain was present in 164 patients (11.7%). 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. Patients mainly complain of diffuse exercise-related muscle pain, but focal/multifocal and at rest myalgia were often also reported. Muscle pain was more commonly detected in patients with mitochondrial DNA mutations (67.8%) than with nuclear DNA changes (32.2%). Only 34% of the patients showed a good response to drug therapy. Interestingly, patients with nuclear DNA mutations tend to have a better therapeutic response than patients with mtDNA mutations. Muscle pain is present in a significant number of patients with MD, being one of the most common symptoms. Although patients with a myopathic phenotype are more prone to develop muscle pain, this is also observed in patients with a multi system involvement, representing an important and disabling symptom having poor response to current therapy

Extreme phenotypic heterogeneity in non-expansion spinocerebellar ataxias

Although the best-known spinocerebellar ataxias (SCAs) are triplet repeat diseases, many SCAs are not caused by repeat expansions. The rarity of individual non-expansion SCAs, however, has made it difficult to discern genotype-phenotype correlations. We therefore screened individuals who had been found to bear variants in a non-expansion SCA-associated gene through genetic testing, and after we eliminated genetic groups that had fewer than 30 subjects, there were 756 subjects bearing single-nucleotide variants or deletions in one of seven genes: CACNA1A (239 subjects), PRKCG (175), AFG3L2 (101), ITPR1 (91), STUB1 (77), SPTBN2 (39), or KCNC3 (34). We compared age at onset, disease features, and progression by gene and variant. There were no features that reliably distinguished one of these SCAs from another, and several genes—CACNA1A, ITPR1, SPTBN2, and KCNC3—were associated with both adult-onset and infantile-onset forms of disease, which also differed in presentation. Nevertheless, progression was overall very slow, and STUB1-associated disease was the fastest. Several variants in CACNA1A showed particularly wide ranges in age at onset: one variant produced anything from infantile developmental delay to ataxia onset at 64 years of age within the same family. For CACNA1A, ITPR1, and SPTBN2, the type of variant and charge change on the protein greatly affected the phenotype, defying pathogenicity prediction algorithms. Even with next-generation sequencing, accurate diagnosis requires dialogue between the clinician and the geneticist. Neurological Motor Disorder