| 1. |
- Björkman, Kristoffer, et al.
(författare)
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Broad phenotypic variability in patients with complex I deficiency due to mutations in NDUFS1 and NDUFV1.
- 2015
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Ingår i: Mitochondrion. - : Elsevier BV. - 1872-8278 .- 1567-7249. ; 21, s. 33-40
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Tidskriftsartikel (refereegranskat)abstract
- We report clinical, metabolic, genetic and neuroradiological findings in five patients from three different families with isolated complex I deficiency. Genetic analysis revealed mutations in NDUFS1 in three patients and in NDUFV1 in two patients. Four of the mutations are novel and affect amino acid residues that either are invariant among species or conserved in their properties. The presented clinical courses are characterized by leukoencephalopathy or early death and expand the already heterogeneous phenotypic spectrum. A literature review was performed, showing that patients with mutations in NDUFS1 in general have a worse prognosis than patients with mutations in NDUFV1.
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| 2. |
- Burda, P, et al.
(författare)
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Characterization and review of MTHFD1 deficiency: four new patients, cellular delineation and response to folic and folinic acid treatment.
- 2015
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Ingår i: Journal of Inherited Metabolic Disease. - : Wiley. - 0141-8955 .- 1573-2665. ; 38:5, s. 863-872
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Tidskriftsartikel (refereegranskat)abstract
- In the folate cycle MTHFD1, encoded by MTHFD1, is a trifunctional enzyme containing 5,10-methylenetetrahydrofolate dehydrogenase, 5,10-methenyltetrahydrofolate cyclohydrolase and 10-formyltetrahydrofolate synthetase activity. To date, only one patient with MTHFD1 deficiency, presenting with hyperhomocysteinemia, megaloblastic anaemia, hemolytic uremic syndrome (HUS) and severe combined immunodeficiency, has been identified (Watkins et al J Med Genet 48:590-2, 2011). We now describe four additional patients from two different families. The second patient presented with hyperhomocysteinemia, megaloblastic anaemia, HUS, microangiopathy and retinopathy; all except the retinopathy resolved after treatment with hydroxocobalamin, betaine and folinic acid. The third patient developed megaloblastic anaemia, infection, autoimmune disease and moderate liver fibrosis but not hyperhomocysteinemia, and was successfully treated with a regime that included and was eventually reduced to folic acid. The other two, elder siblings of the third patient, died at 9weeks of age with megaloblastic anaemia, infection and severe acidosis and had MTFHD1 deficiency diagnosed retrospectively. We identified a missense mutation (c.806C>T, p.Thr296Ile) and a splice site mutation (c.1674G>A) leading to exon skipping in the second patient, while the other three harboured a missense mutation (c.146C>T, p.Ser49Phe) and a premature stop mutation (c.673G>T, p.Glu225*), all of which were novel. Patient fibroblast studies revealed severely reduced methionine formation from [(14)C]-formate, which did not increase in cobalamin supplemented culture medium but was responsive to folic and folinic acid. These additional cases increase the clinical spectrum of this intriguing defect, provide in vitro evidence of disturbed methionine synthesis and substantiate the effectiveness of folic or folinic acid treatment.
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| 3. |
- Darin, Niklas, 1964, et al.
(författare)
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Benign mitochondrial myopathy with exercise intolerance in a large multigeneration family due to a homoplasmic m.3250T>C mutation in MTTL1.
- 2017
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Ingår i: European journal of neurology. - : Wiley. - 1468-1331 .- 1351-5101. ; 24:4, s. 587-593
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Tidskriftsartikel (refereegranskat)abstract
- Most mitochondrial disorders with onset in early childhood are progressive and involve multiple organs. The m.3250T>C mutation in MTTL1 has previously been described in a few individuals with a possibly riboflavin-responsive myopathy and an association with sudden infant death syndrome was suspected. We describe a large family with this mutation and evaluate the effect of riboflavin treatment.Medical data were collected with the help of a standardized data collection form. Sanger sequencing was used to screen for variants in mitochondrial DNA and the proportion of the mutation was analyzed in different tissues. Biochemical and muscle morphological investigations of muscle tissue were performed in two individuals. The effect of riboflavin treatment was evaluated in two individuals.Thirteen family members experienced exercise intolerance with fatigue and weakness. Inheritance was maternal with 100% penetrance. The course was either static or showed improvement over time. There was no evidence of other organ involvement except for a possible mild transient cardiac enlargement in one child. Muscle investigations showed isolated complex I deficiency and mitochondrial proliferation. The level of m.3250T>C was apparently 100%, i.e. homoplasmic, in all examined tissues. Riboflavin treatment showed no effect in any treated family member and there have been no cases of sudden infant death in this family.This study illustrates the importance of considering mitochondrial disorders in the work-up of individuals with exercise intolerance and provides a better understanding of the phenotype associated with the m.3250T>C mutation in MTTL1.
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| 4. |
- Grønborg, Sabine, et al.
(författare)
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Leukoencephalopathy due to Complex II Deficiency and Bi-Allelic SDHB Mutations: Further Cases and Implications for Genetic Counselling.
- 2016
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Ingår i: JIMD reports. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 2192-8304. ; 33, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- Isolated complex II deficiency is a rare cause of mitochondrial disease and bi-allelic mutations in SDHB have been identified in only a few patients with complex II deficiency and a progressive neurological phenotype with onset in infancy. On the other hand, heterozygous SDHB mutations are a well-known cause of familial paraganglioma/pheochromocytoma and renal cell cancer. Here, we describe two additional patients with respiratory chain deficiency due to bi-allelic SDHB mutations. The patients' clinical, neuroradiological, and biochemical phenotype is discussed according to current knowledge on complex II and SDHB deficiency and is well in line with previously described cases, thus confirming the specific neuroradiological presentation of complex II deficiency that recently has emerged. The patients' genotype revealed one novel SDHB mutation, and one SDHB mutation, which previously has been described in heterozygous form in patients with familial paraganglioma/pheochromocytoma and/or renal cell cancer. This is only the second example in the literature where one specific SDHx mutation is associated with both recessive mitochondrial disease in one patient and familial paraganglioma/pheochromocytoma in others. Due to uncertainties regarding penetrance of different heterozygous SDHB mutations, we argue that all heterozygous SDHB mutation carriers identified in relation to SDHB-related leukoencephalopathy should be referred to relevant surveillance programs for paraganglioma/pheochromocytoma and renal cell cancer. The diagnosis of complex II deficiency due to SDHB mutations therefore raises implications for genetic counselling that go beyond the recurrence risk in the family according to an autosomal recessive inheritance.
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| 5. |
- Jennions, Elizabeth, et al.
(författare)
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TANGO2 deficiency as a cause of neurodevelopmental delay with indirect effects on mitochondrial energy metabolism
- 2019
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Ingår i: Journal of Inherited Metabolic Disease. - : Wiley. - 0141-8955 .- 1573-2665. ; 42:5, s. 898-908
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Tidskriftsartikel (refereegranskat)abstract
- Exome sequencing has recently identified mutations in the gene TANGO2 (transport and Golgi organization 2) as a cause of developmental delay associated with recurrent crises involving rhabdomyolysis, cardiac arrhythmias, and metabolic derangements. The disease is not well understood, in part as the cellular function and subcellular localization of the TANGO2 protein remain unknown. Furthermore, the clinical syndrome with its heterogeneity of symptoms, signs, and laboratory findings is still being defined. Here, we describe 11 new cases of TANGO2-related disease, confirming and further expanding the previously described clinical phenotype. Patients were homozygous or compound heterozygous for previously described exonic deletions or new frameshift, splice site, and missense mutations. All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia. Of importance, we identify two subjects (aged 12 and 17 years) who have never experienced any overt episode of the catabolism-induced metabolic crises typical for the disease. Mitochondrial complex II activity was mildly reduced in patients investigated in association with crises but normal in other patients. In one deceased patient, post-mortem autopsy revealed heterotopic neurons in the cerebral white matter, indicating a possible role for TANGO2 in neuronal migration. Furthermore, we have addressed the subcellular localization of several alternative isoforms of TANGO2, none of which were mitochondrial but instead appeared to have a primarily cytoplasmic localization. Previously described aberrations in Golgi morphology were not observed in cultured skin fibroblasts.
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| 6. |
- Roos, Sara, 1979, et al.
(författare)
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Mitochondrial complex IV deficiency caused by a novel frameshift variant in MT-CO2 associated with myopathy and perturbed acylcarnitine profile
- 2019
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Ingår i: European Journal of Human Genetics. - : Springer Science and Business Media LLC. - 1018-4813 .- 1476-5438. ; 27:2, s. 331-335
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondrial myopathies are a heterogeneous group of disorders associated with a wide range of clinical phenotypes. We present a 16-year-old girl with a history of exercise intolerance since childhood. Acylcarnitine species suggestive of multiple acyl-CoA dehydrogenase deficiency were found in serum, however genetic analysis did not reveal variants in genes associated with this disorder. Biochemical analyses of skeletal muscle mitochondria revealed an isolated and extremely low activity of cytochrome c oxidase (COX). This finding was confirmed by enzyme histochemistry, which demonstrated an almost complete absence of fibers with normal COX activity. Whole-exome sequencing revealed a single base-pair deletion (m.8088delT) in MT-CO2, which encodes subunit 2 of COX, resulting in a premature stop codon. Restriction fragment length polymorphism-analysis confirmed mtDNA heteroplasmy with high mutant load in skeletal muscle, the only clinically affected tissue, but low levels in other investigated tissues. Single muscle fiber analysis showed segregation of the mutant genotype with respiratory chain dysfunction. Immuno-histochemical studies indicated that the truncating variant in COX2 has an inhibitory effect on the assembly of the COX holoenzyme.
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| 7. |
- Sofou, Kalliopi, et al.
(författare)
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Prenatal onset of mitochondrial disease is associated with sideroflexin 4 deficiency
- 2019
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Ingår i: Mitochondrion. - : Elsevier BV. - 1567-7249. ; 47, s. 76-81
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Tidskriftsartikel (refereegranskat)abstract
- Prenatal onset of mitochondrial disease has been described in two cases with recessive mutations in the sideroflexin 4 gene (SFXN4). We present a third case with complex I deficiency associated with novel mutations in SFXN4. Our patient presented with intrauterine growth retardation, neonatal lactic acidosis, and developed macrocytic anemia and optic nerve hypoplasia. Muscle mitochondrial investigations revealed ultrastructural abnormalities, severe deficiency of complex I enzyme activity, and loss of subunit proteins. Whole-exome sequencing revealed bi-allelic SFXN4 mutations: a 1-base deletion, c.969delG, leading to frameshift and a premature stop codon, p.(G1n323Hisfs*20), and a stop-loss mutation in the C-terminal region, c.1012 T > C; p. (*388Glnext2), resulting in elongation of the protein by two amino acids. Expression analysis of mRNA from muscle showed loss of SFXN4 transcripts.
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| 8. |
- Sofou, Kalliopi, et al.
(författare)
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Whole exome sequencing reveals mutations in NARS2 and PARS2, encoding the mitochondrial asparaginyl-tRNA synthetase and prolyl-tRNA synthetase, in patients with Alpers syndrome.
- 2015
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Ingår i: Molecular genetics & genomic medicine. - : Wiley. - 2324-9269. ; 3:1, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- Alpers syndrome is a progressive neurodegenerative disorder that presents in infancy or early childhood and is characterized by diffuse degeneration of cerebral gray matter. While mutations in POLG1, the gene encoding the gamma subunit of the mitochondrial DNA polymerase, have been associated with Alpers syndrome with liver failure (Alpers-Huttenlocher syndrome), the genetic cause of Alpers syndrome in most patients remains unidentified. With whole exome sequencing we have identified mutations in NARS2 and PARS2, the genes encoding the mitochondrial asparaginyl-and prolyl-tRNA synthetases, in two patients with Alpers syndrome. One of the patients was homozygous for a missense mutation (c.641C>T, p.P214L) in NARS2. The affected residue is predicted to be located in the stem of a loop that participates in dimer interaction. The other patient was compound heterozygous for a one base insertion (c.1130dupC, p.K378 fs*1) that creates a premature stop codon and a missense mutation (c.836C>T, p.S279L) located in a conserved motif of unknown function in PARS2. This report links for the first time mutations in these genes to human disease in general and to Alpers syndrome in particular.
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| 9. |
- Tarailo-Graovac, Maja, et al.
(författare)
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Identification of a large intronic transposal insertion in SLC17A5 causing sialic acid storage disease.
- 2017
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Ingår i: Orphanet journal of rare diseases. - : Springer Science and Business Media LLC. - 1750-1172. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Sialic acid storage diseases are neurodegenerative disorders characterized by accumulation of sialic acid in the lysosome. These disorders are caused by mutations in SLC17A5, the gene encoding sialin, a sialic acid transporter located in the lysosomal membrane. The most common form of sialic acid storage disease is the slowly progressive Salla disease, presenting with hypotonia, ataxia, epilepsy, nystagmus and findings of cerebral and cerebellar atrophy. Hypomyelination and corpus callosum hypoplasia are typical as well. We report a 16year-old boy with an atypically mild clinical phenotype of sialic acid storage disease characterized by psychomotor retardation and a mixture of spasticity and rigidity but no ataxia, and only weak features of hypomyelination and thinning of corpus callosum on MRI of the brain.The thiobarbituric acid method showed elevated levels of free sialic acid in urine and fibroblasts, indicating sialic acid storage disease. Initial Sanger sequencing of SLC17A5 coding regions did not show any pathogenic variants, although exon 9 could not be sequenced. Whole exome sequencing followed by RNA and genomic DNA analysis identified a homozygous 6040bp insertion in intron 9 of SLC17A5 corresponding to a long interspersed element-1 retrotransposon (KF425758.1). This insertion adds two splice sites, both resulting in a frameshift which in turn creates a premature stop codon 4bp into intron 9.This study describes a novel pathogenic variant in SLC17A5, namely an intronic transposal insertion, in a patient with mild biochemical and clinical phenotypes. The presence of a small fraction of normal transcript may explain the mild phenotype. This case illustrates the importance of including lysosomal sialic acid storage disease in the differential diagnosis of developmental delay with postnatal onset and hypomyelination, as well as intronic regions in the genetic investigation of inborn errors of metabolism.
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