| 1. |
- Kariminejad, Ariana, et al.
(author)
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Homozygous Null TBX4 Mutations Lead to Posterior Amelia with Pelvic and Pulmonary Hypoplasia
- 2019
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In: American Journal of Human Genetics. - : Elsevier. - 0002-9297 .- 1537-6605. ; 105:6, s. 1294-1301
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Journal article (peer-reviewed)abstract
- The development of hindlimbs in tetrapod species relies specifically on the transcription factor TBX4. In humans, heterozygous loss-of-function TBX4 mutations cause dominant small patella syndrome (SPS) due to haploinsufficiency. Here, we characterize a striking clinical entity in four fetuses with complete posterior amelia with pelvis and pulmonary hypoplasia (PAPPA). Through exome sequencing, we find that PAPPA syndrome is caused by homozygous TBX4 inactivating mutations during embryogenesis in humans. In two consanguineous couples, we uncover distinct germline TBX4 coding mutations, p.Tyr113∗ and p.Tyr127Asn, that segregated with SPS in heterozygous parents and with posterior amelia with pelvis and pulmonary hypoplasia syndrome (PAPPAS) in one available homozygous fetus. A complete absence of TBX4 transcripts in this proband with biallelic p.Tyr113∗ stop-gain mutations revealed nonsense-mediated decay of the endogenous mRNA. CRISPR/Cas9-mediated TBX4 deletion in Xenopus embryos confirmed its restricted role during leg development. We conclude that SPS and PAPPAS are allelic diseases of TBX4 deficiency and that TBX4 is an essential transcription factor for organogenesis of the lungs, pelvis, and hindlimbs in humans.
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| 2. |
- Sedghi, Maryam, et al.
(author)
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Motor neuron diseases caused by a novel VRK1 variant - A genotype/phenotype study
- 2019
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In: Annals of Clinical and Translational Neurology. - : John Wiley & Sons. - 2328-9503. ; 6:11, s. 2197-2204
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Journal article (peer-reviewed)abstract
- Background Motor neuron disorders involving upper and lower neurons are a genetically and clinically heterogenous group of rare neuromuscular disorders with overlap among spinal muscular atrophies (SMAs) and amyotrophic lateral sclerosis (ALS). Classical SMA caused by recessive mutations in SMN1 is one of the most common genetic causes of mortality in infants. It is characterized by degeneration of anterior horn cells in the spinal cord, leading to progressive muscle weakness and atrophy. Non-SMN1-related spinal muscular atrophies are caused by variants in a number of genes, including VRK1, encoding the vaccinia-related kinase 1 (VRK1). VRK1 variants have been segregated with motor neuron diseases including SMA phenotypes or hereditary complex motor and sensory axonal neuropathy (HMSN), with or without pontocerebellar hypoplasia or microcephaly. Results Here, we report an association of a novel homozygous splice variant in VRK1 (c.1159 + 1G>A) with childhood-onset SMA or juvenile lower motor disease with brisk tendon reflexes without pontocerebellar hypoplasia and normal intellectual ability in a family with five affected individuals. We show that the VRK1 splice variant in patients causes decreased splicing efficiency and a mRNA frameshift that escapes the nonsense-mediated decay machinery and results in a premature termination codon. Conclusions Our findings unveil the impact of the variant on the VRK1 transcript and further support the implication of VRK1 in the pathogenesis of lower motor neuron diseases.
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| 3. |
- Abdul-Hussein, Saba, et al.
(author)
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Phenotypes of Myopathy-Related Beta-Tropomyosin Mutants in Human and Mouse Tissue Cultures
- 2013
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In: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 8:9
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Journal article (peer-reviewed)abstract
- Mutations in TPM2 result in a variety of myopathies characterised by variable clinical and morphological features. We used human and mouse cultured cells to study the effects of beta-TM mutants. The mutants induced a range of phenotypes in human myoblasts, which generally changed upon differentiation to myotubes. Human myotubes transfected with the E41K-beta-TMEGFP mutant showed perinuclear aggregates. The G53ins-beta-TMEGFP mutant tended to accumulate in myoblasts but was incorporated into filamentous structures of myotubes. The K49del-beta-TMEGFP and E122K-beta-TMEGFP mutants induced the formation of rod-like structures in human cells. The N202K-beta-TMEGFP mutant failed to integrate into thin filaments and formed accumulations in myotubes. The accumulation of mutant beta-TMEGFP in the perinuclear and peripheral areas of the cells was the striking feature in C2C12. We demonstrated that human tissue culture is a suitable system for studying the early stages of altered myofibrilogenesis and morphological changes linked to myopathy-related beta-TM mutants. In addition, the histopathological phenotype associated with expression of the various mutant proteins depends on the cell type and varies with the maturation of the muscle cell. Further, the phenotype is a combinatorial effect of the specific amino acid change and the temporal expression of the mutant protein.
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| 4. |
- Abusibaa, W. A., et al.
(author)
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Expression of the GBGT1 Gene and the Forssman Antigen in Red Blood Cells in a Palestinian Population
- 2019
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In: Transfusion Medicine and Hemotherapy. - : S. Karger AG. - 1660-3796 .- 1660-3818. ; 46:6, s. 450-454
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Journal article (peer-reviewed)abstract
- Background: The Forssman antigen (FORS1 Ag) is expressed on human red blood cells (RBCs). We investigated its presence on RBCs from Palestinian subjects and Swedish subjects by serological testing and by sequencing part of exon 7 of the GBGT1 gene, which encodes Forssman synthase. -Materials and Methods: Blood samples from Palestinian subjects (n = 211 adults and n = 73 newborns) and from Swedish subjects (n = 47 adults) were analyzed in the study. RBCs from the Palestinian samples were typed for the FORS1 Ag using a monoclonal anti-Forssman antibody. The GBGT1 gene was genotyped by DNA sequencing (all adult samples) or by using amplification refractory mutation system PCR (newborn samples). Results: All of the studied samples were negative for the FORS1 Ag by serologic typing. DNA sequencing of the 3′ end of exon 7 of the GBGT1 gene, which includes Arg296, showed that all samples had the wild-type Arg296 sequence, which is associated with an inactive form of Forssman synthase. We detected four single nucleotide polymorphisms in the adult samples; two were silent (p.Tyr232=, p.Gly290=), and two were missense (p.Arg243Cys, p.Arg243His). The allele frequencies ranged from 0.2 to 3.6%. The p.Arg243Cys SNP was a novel SNP that was detected in one Palestinian sample. Conclusion: Our results confirmed the allelic diversity of GBGT1 and identified a novel nucleotide polymorphism in this gene, p.Arg243Cys. Our results also confirmed that the FORS blood group system is a low-frequency system. © 2019 S. Karger AG, Basel. Copyright: All rights reserved.
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| 5. |
- Andersson Grönlund, Marita, 1959-, et al.
(author)
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Ophthalmological findings in children and young adults with genetically verified mitochondrial disease
- 2010
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In: British Journal of Ophthalmology. - : BMJ Publishing Group Ltd. - 0007-1161 .- 1468-2079. ; 94:1, s. 121-127
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Journal article (peer-reviewed)abstract
- AIM: To describe ophthalmological phenotypes in patients with mitochondrial disease and known genotypes.METHODS: A retrospective study was performed on 59 patients (29 male, 30 female) with a mean age of 11.8 years who had mitochondrial disease with known DNA mutations. Fifty-seven of the 59 subjects underwent a detailed ophthalmological examination including visual acuity (VA), eye motility, refraction, slit-lamp examination, ophthalmoscopy and, in almost one-half of the cases, a full-field electroretinogram (ERG).RESULTS: Forty-six (81%) of the patients had one or more ophthalmological findings such as ptosis (n = 16), reduced eye motility (n = 22) including severe external ophthalmoplegia (n = 9), strabismus (n = 4), nystagmus (n = 9), low VA (n = 21), refractive errors (n = 26), photophobia (n = 4), and partial or total optic atrophy (n = 25). Pigmentation in the macula and/or periphery was noted in 16 patients. In 10/27 investigated individuals with full field ERG, retinal dystrophy was recorded in six different genotypes representing Kearns-Sayre syndrome (n = 5), Leigh syndrome (n = 1), Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) (n = 1), Myoclonus epilepsy with red ragged fibres (MERRF) (n = 1), Leber hereditary optic neuropathy (n = 1) and mitochondrial myopathy (n = 1).CONCLUSION: The results show that a majority of patients with mitochondrial disorders have ophthalmological abnormalities. We recommend that an ophthalmological examination, including ERG, be performed on all children and adolescents who are suspected of having a mitochondrial disease.
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| 6. |
- Björkman, Kristoffer, et al.
(author)
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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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In: Mitochondrion. - : Elsevier BV. - 1872-8278 .- 1567-7249. ; 21, s. 33-40
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Journal article (peer-reviewed)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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| 7. |
- Björkman, Kristoffer, et al.
(author)
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Genotype-phenotype correlations in patients with complex I deficiency due to mutations in NDUFS1 and NDUFV1
- 2014
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In: Euromit 2014, 15-19 juni, Tampere, Finland.
-
Conference paper (other academic/artistic)abstract
- Objectives: To study genotype-phenotype correlations in genes encoding complex I electron input module subunits. Materials and methods: We studied five patients with isolated complex I deficiency, three with NDUFS1 mutations and two with NDUFV1 mutations. A literature review of all reported cases of mutations in the affected genes was performed. Results: The literature review revealed pathological mutations in NDUFS1 for 18 patients in 17 families and correspondingly in NDUFV1 for 26 patients in 19 families. Unpublished clinical data for our five patients were added. Our study showed quite variable clinical courses; death before two years of age was seen in 41% of patients while 18% were alive at seven years. There was a significant difference between the NDUFS1 and NDUFV1 groups for clinical onset and life-span. Mutations in NDUFS1 were linked to a worse clinical course with earlier onset and earlier death. Conclusions: Genotype-phenotype correlations in patients with mutations affecting the genes that encode the electron input module of complex I vary, but patients with NDUFS1 mutation tend to have a worse clinical course than patients with NDUFV1 mutation. Identifying the mutations is of importance for accurate prognostic information and genetic counseling.
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| 8. |
- Chatron, N., et al.
(author)
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Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy
- 2020
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In: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 143:5, s. 1447-1461
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Journal article (peer-reviewed)abstract
- Developmental and epileptic encephalopathies are a heterogeneous group of early-onset epilepsy syndromes dramatically impairing neurodevelopment. Modern genomic technologies have revealed a number of monogenic origins and opened the door to therapeutic hopes. Here we describe a new syndromic developmental and epileptic encephalopathy caused by bi-allelic loss-of-function variants in GAD1, as presented by 11 patients from six independent consanguineous families. Seizure onset occurred in the first 2 months of life in all patients. All 10 patients, from whom early disease history was available, presented with seizure onset in the first month of life, mainly consisting of epileptic spasms or myoclonic seizures. Early EEG showed suppression-burst or pattern of burst attenuation or hypsarrhythmia if only recorded in the post-neonatal period. Eight patients had joint contractures and/or pes equinovarus. Seven patients presented a cleft palate and two also had an omphalocele, reproducing the phenotype of the knockout Gad1(-/-) mouse model. Four patients died before 4 years of age. GAD1 encodes the glutamate decarboxylase enzyme GAD67, a critical actor of the c-aminobutyric acid (GABA) metabolism as it catalyses the decarboxylation of glutamic acid to form GABA. Our findings evoke a novel syndrome related to GAD67 deficiency, characterized by the unique association of developmental and epileptic encephalopathies, cleft palate, joint contractures and/or omphalocele.
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| 9. |
- Darin, Niklas, 1964, et al.
(author)
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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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In: European journal of neurology. - : Wiley. - 1468-1331 .- 1351-5101. ; 24:4, s. 587-593
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Journal article (peer-reviewed)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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| 10. |
- Darin, Niklas, 1964, et al.
(author)
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Functional analysis of a novel POL gamma A mutation associated with a severe perinatal mitochondrial encephalomyopathy
- 2021
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In: Neuromuscular Disorders. - : Elsevier BV. - 0960-8966. ; 31:4, s. 348-358
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Journal article (peer-reviewed)abstract
- Mutations in the mitochondrial DNA polymerase gamma catalytic subunit (POL. A) compromise the stability of mitochondrial DNA (mtDNA) by leading to mutations, deletions and depletions in mtDNA. Patients with mutations in POL gamma A often differ remarkably in disease severity and age of onset. In this work we have studied the functional consequence of POL gamma A mutations in a patient with an uncommon and a very severe disease phenotype characterized by prenatal onset with intrauterine growth restriction, lactic acidosis from birth, encephalopathy, hepatopathy, myopathy, and early death. Muscle biopsy identified scattered COX-deficient muscle fibers, respiratory chain dysfunction and mtDNA depletion. We identified a novel POL.A mutation (p.His1134Tyr) in trans with the previously identified p.Thr251Ile/Pro587Leu double mutant. Biochemical characterization of the purified recombinant POL gamma A variants showed that the p.His1134Tyr mutation caused severe polymerase dysfunction. The p.Thr251Ile/Pro587Leu mutation caused reduced polymerase function in conditions of low dNTP concentration that mimic postmitotic tissues. Critically, when p.His1134Tyr and p.Thr251Ile/Pro587Leu were combined under these conditions, mtDNA replication was severely diminished and featured prominent stalling. Our data provide a molecular explanation for the patients mtDNA depletion and clinical features, particularly in tissues such as brain and muscle that have low dNTP concentration. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
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| 11. |
- Darin, Niklas, 1964, et al.
(author)
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Inflammation and response to steroid treatment in limb-girdle muscular dystrophy 2I
- 2007
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In: Eur J Paediatr Neurol. - : Elsevier BV. ; 11:6, s. 353-7
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Journal article (peer-reviewed)abstract
- Limb-girdle muscular dystrophy (LGMD) type 2I, caused by mutations in the fukutin-related protein gene (FKRP), is one of the most common forms of LGMD in childhood. We describe two patients with LGMD2I and a Duchenne-like phenotype. In addition to the common L276I mutation, both patients had a new mutation in FKRP, L169P and P89L, respectively. Clinical onset was triggered by viral upper respiratory tract infections. In addition to the common dystrophic pattern with a weak immune histochemical staining for alpha-dystroglycan, muscle biopsy showed inflammatory changes. This was especially striking in one of the patients with up-regulation of MHC class 1 antigen, suggestive of myositis. Both patients showed a good clinical response to treatment with prednisolone, which was initiated at daily dosage of 0.35mg/kg/day. Our results provide evidence for an inflammatory involvement in the pathological expression of LGMD2I and open up the possibility that this disorder could be treatable with corticosteroids.
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| 12. |
- Darin, Niklas, 1964, et al.
(author)
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Mitochondrial myopathy with exercise intolerance and retinal dystrophy in a sporadic patient with a G583A mutation in the mt tRNA(phe) gene
- 2006
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In: Neuromuscular disorders : NMD. - : Elsevier BV. - 0960-8966 .- 1873-2364. ; 16:8, s. 504-6
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Journal article (peer-reviewed)abstract
- We describe a second patient with the 583G>A mutation in the tRNA(phe) gene of mitochondrial DNA (mtDNA). This 17-year-old girl had a mitochondrial myopathy with exercise intolerance and an asymptomatic retinopathy. Muscle investigations showed occasional ragged red fibers, 30% cytochrome c oxidase (COX)-negative fibers, and reduced activities of complex I+IV in the respiratory chain. The mutation was heteroplasmic (79%) in muscle but undetectable in other tissues. Analysis of single muscle fibers revealed a significantly higher level of mutated mtDNA in COX-negative fibers. Our study indicates that the 583G>A mutation is pathogenic and expands the clinical spectrum of this mutation.
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| 13. |
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| 14. |
- Hedberg, Carola, 1969, et al.
(author)
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Myopathy in a woman and her daughter associated with a novel splice site MTM1 mutation.
- 2012
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In: Neuromuscular disorders : NMD. - : Elsevier BV. - 1873-2364 .- 0960-8966. ; 22:3, s. 244-51
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Journal article (peer-reviewed)abstract
- We have investigated a woman and her daughter with an early onset, slowly progressive myopathy. Muscle biopsy showed in both cases severe atrophy with marked fatty replacement. Frequent fibers with internalized nuclei were present but no typical features of centronuclear myopathy. There were also many fibers with deep invaginations of the plasma membrane. The presence of necklace fibers provided clue to correct genetic diagnosis. Both patients had a novel heterozygous splice site mutation in the myotubularin gene, MTM1 (c.867+1G>T). Analysis of MTM1 cDNA revealed that the mutation resulted in aberrant splicing with variable exon skipping. The expression of normal transcripts was markedly reduced and there was reduced expression of myotubularin protein. Although the expression of the allele without the mutation was reduced we did not obtain evidence of skewed X-chromosome inactivation. Other factors than skewed X-inactivation may cause allele inactivation and manifestation of severe myopathy in heterozygous carriers of pathogenic MTM1 mutations.
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| 15. |
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| 16. |
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| 17. |
- Horvath, Rita, et al.
(author)
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Molecular basis of infantile reversible cytochrome c oxidase deficiency myopathy.
- 2009
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In: Brain : a journal of neurology. - : Oxford University Press (OUP). - 1460-2156. ; 132:Pt 11, s. 3165-74
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Journal article (peer-reviewed)abstract
- Childhood-onset mitochondrial encephalomyopathies are usually severe, relentlessly progressive conditions that have a fatal outcome. However, a puzzling infantile disorder, long known as 'benign cytochrome c oxidase deficiency myopathy' is an exception because it shows spontaneous recovery if infants survive the first months of life. Current investigations cannot distinguish those with a good prognosis from those with terminal disease, making it very difficult to decide when to continue intensive supportive care. Here we define the principal molecular basis of the disorder by identifying a maternally inherited, homoplasmic m.14674T>C mt-tRNA(Glu) mutation in 17 patients from 12 families. Our results provide functional evidence for the pathogenicity of the mutation and show that tissue-specific mechanisms downstream of tRNA(Glu) may explain the spontaneous recovery. This study provides the rationale for a simple genetic test to identify infants with mitochondrial myopathy and good prognosis.
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| 18. |
- Jesus, C., et al.
(author)
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Prevalence of antibodies to a new histo-blood system: the FORS system
- 2018
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In: Blood Transfusion. - 1723-2007. ; 16:2, s. 178-183
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Journal article (peer-reviewed)abstract
- Background. In 1987, three unrelated English families were reported with a putative blood subgroup called A pae. Swedish researchers later found evidence leading to abolishment of the A pae subgroup and establishment instead of the FORS blood group system (System 31 -ISBT, 2012). It is important to know the prevalence of antibodies in order to make the best decisions in transfusion medicine. Cells expressing the Forssman saccharide, such as sheep erythrocytes, are needed to detect the anti-Forssman antibody. The aim of this study was to define the prevalence of human anti-Forssman antibody. Materials and methods. Plasma samples from 800 individuals were studied. Sheep erythrocytes or Forssman "kodecytes" were mixed with the plasma samples using the tube technique. Plasma from an A pae individual was used as a negative control and monoclonal anti-Forssman antibody (M1/22.25.8HL cell line supernatant) was used as the positive control. Results. Of the 800 individuals tested, one was negative for the presence of anti-Forssman antibody. We compared the anti-Forssman antibody reaction pattern between genders and found that males have weaker reactions than females, both at room temperature (p= 0.026) and at 37 degrees C (p= 0.043). We also investigated the reaction pattern of anti-Forssman antibody in relation to ABO and Rh blood group types without finding any significant differences. Discussion. Sheep erythrocytes are suitable for searching for human anti-Forssman antibody. The quantity of anti-Forssman antibodies in plasma is higher in females than in males. In the population (n= 800) studied here, we found one individual lacking the anti-Forssman antibody. These results contribute to the data already published, confirming that FORS is a rare blood group.
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| 19. |
- Kariminejad, A., et al.
(author)
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Lethal multiple pterygium syndrome, the extreme end of the RYR1 spectrum
- 2016
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In: Bmc Musculoskeletal Disorders. - : Springer Science and Business Media LLC. - 1471-2474. ; 17
-
Journal article (peer-reviewed)abstract
- Background: Lethal multiple pterygium syndrome (LMPS, OMIM 253290), is a fatal disorder associated with anomalies of the skin, muscles and skeleton. It is characterised by prenatal growth failure with pterygium present in multiple areas and akinesia, leading to muscle weakness and severe arthrogryposis. Foetal hydrops with cystic hygroma develops in affected foetuses with LMPS. This study aimed to uncover the aetiology of LMPS in a family with two affected foetuses. Methods and results: Whole exome sequencing studies have identified novel compound heterozygous mutations in RYR1 in two affected foetuses with pterygium, severe arthrogryposis and foetal hydrops with cystic hygroma, characteristic features compatible with LMPS. The result was confirmed by Sanger sequencing and restriction fragment length polymorphism analysis. Conclusions: RYR1 encodes the skeletal muscle isoform ryanodine receptor 1, an intracellular calcium channel with a central role in muscle contraction. Mutations in RYR1 have been associated with congenital myopathies, which form a continuous spectrum of pathological features including a severe variant with onset in utero with fetal akinesia and arthrogryposis. Here, the results indicate that LMPS can be considered as the extreme end of the RYR1-related neonatal myopathy spectrum. This further supports the concept that LMPS is a severe disorder associated with defects in the process known as excitation-contraction coupling.
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| 20. |
- Kariminejad, A., et al.
(author)
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Truncating CHRNG mutations associated with interfamilial variability of the severity of the Escobar variant of multiple pterygium syndrome
- 2016
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In: Bmc Genetics. - : Springer Science and Business Media LLC. - 1471-2156. ; 17
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Journal article (peer-reviewed)abstract
- Background: In humans, muscle-specific nicotinergic acetylcholine receptor (AChR) is a transmembrane protein with five different subunits, coded by CHRNA1, CHRNB, CHRND and CHRNG/CHRNE. The gamma subunit of AChR encoded by CHRNG is expressed during early foetal development, whereas in the adult, the. subunit is replaced by a epsilon subunit. Mutations in the CHRNG encoding the embryonal acetylcholine receptor may cause the non-lethal Escobar variant (EVMPS) and lethal form (LMPS) of multiple pterygium syndrome. The MPS is a condition characterised by prenatal growth failure with pterygium and akinesia leading to muscle weakness and severe congenital contractures, as well as scoliosis. Results: Our whole exome sequencing studies have identified one novel and two previously reported homozygous mutations in CHRNG in three families affected by non-lethal EVMPS. The mutations consist of deletion of two nucleotides, cause a frameshift predicted to result in premature termination of the foetally expressed gamma subunit of the AChR. Conclusions: Our data suggest that severity of the phenotype varies significantly both within and between families with MPS and that there is no apparent correlation between mutation position and clinical phenotype. Although individuals with CHRNG mutations can survive, there is an increased frequency of abortions and stillbirth in their families. Furthermore, genetic background and environmental modifiers might be of significance for decisiveness of the lethal spectrum, rather than the state of the mutation per se. Detailed clinical examination of our patients further indicates the changing phenotype from infancy to childhood.
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| 21. |
- Kollberg, Gittan, 1963, et al.
(author)
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A novel homozygous RRM2B missense mutation in association with severe mtDNA depletion.
- 2009
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In: Neuromuscular disorders : NMD. - : Elsevier BV. - 0960-8966. ; 19:2, s. 147-50
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Journal article (peer-reviewed)abstract
- This report describes two brothers, both deceased in infancy, with severe depletion of mitochondrial DNA (mtDNA) in muscle tissue. Both had feeding difficulties, failure to thrive, severe muscular hypotonia and lactic acidosis. One of the boys developed a renal proximal tubulopathy. A novel homozygous c.686 G-->T missense mutation in the RRM2B gene, encoding the p53-inducible ribonucleotide reductase subunit (p53R2), was identified. This is the third report on mutations in RRM2B associated with severe mtDNA depletion, which further highlights the importance of de novo synthesis of deoxyribonucleotides (dNTPs) for mtDNA maintenance.
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| 22. |
- Kollberg, Gittan, 1963, et al.
(author)
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Low frequency of mtDNA point mutations in patients with PEO associated with POLG1 mutations.
- 2005
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In: European journal of human genetics : EJHG. - : Springer Science and Business Media LLC. - 1018-4813 .- 1476-5438. ; 13:4, s. 463-9
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Journal article (peer-reviewed)abstract
- Mitochondrial myopathy in progressive external ophthalmoplegia (PEO) has been associated with POLG1 mutations. POLG1 encodes the catalytic alpha subunit of polymerase gamma and is the only polymerase known to be involved in mtDNA replication. It has two functionally different domains, one polymerase domain and one exonuclease domain with proofreading activity. In this study we have investigated whether mtDNA point mutations are involved, directly or indirectly, in the pathogenesis of PEO. Muscle biopsy specimens from patients with POLG1 mutations, affecting either the exonuclease or the polymerase domain, were investigated. Single cytochrome c oxidase (COX)-deficient muscle fibers were dissected and screened for clonally expanded mtDNA point mutations using a sensitive denaturing gradient gel electrophoresis analysis, in which three different regions of mtDNA, including five different tRNA genes, were investigated. To screen for randomly distributed mtDNA point mutations in muscle, two regions of mtDNA including deletion breakpoints were investigated by high-fidelity PCR, followed by cloning and sequencing. Long-range PCR revealed multiple mtDNA deletions in all the patients but not the controls. No point mutations were identified in single COX-deficient muscle fibers. Cloning and sequencing of muscle homogenate identified randomly distributed point mutations at very low frequency in patients and controls (<1:50 000). We conclude that mtDNA point mutations do not appear to be directly or indirectly involved in the pathogenesis of mitochondrial disease in patients with different POLG1 mutations.
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| 23. |
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| 24. |
- Kollberg, Gittan, 1963, et al.
(author)
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Mitochondrial myopathy and rhabdomyolysis associated with a novel nonsense mutation in the gene encoding cytochrome c oxidase subunit I.
- 2005
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In: Journal of neuropathology and experimental neurology. - 0022-3069. ; 64:2, s. 123-8
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Journal article (peer-reviewed)abstract
- Mitochondrial DNA (mtDNA) mutations associated with rhabdomyolysis are rare but have been described in sporadic cases with mutations in the cytochrome b and cytochrome c oxidase (COX) genes and in 3 cases with tRNALeu mutation. We report a novel heteroplasmic G6708A nonsense mutation in the mtDNA COI gene encoding COX subunit I in a 30-year-old woman with muscle weakness, pain, fatigue, and one episode of rhabdomyolysis. Histochemical examination of muscle biopsy specimens revealed reduced COX activity in the majority of the muscle fibers (approximately 90%) and frequent ragged red fibers. Biochemical analysis showed a marked and isolated COX deficiency. Analysis of DNA extracted from single fibers revealed higher levels of the mutation in COX-deficient fibers (> 95%) compared with COX-positive fibers (1%-80%). The mutation was not detected in a skin biopsy, cultured myoblasts, or blood leukocytes. Nor was it identified in blood leukocytes from the asymptomatic mother, indicating a de novo mutation that arose after germ layer differentiation. Western blot analysis and immunohistochemical staining revealed that reduced levels of COX subunit I were accompanied by reduced levels of other mtDNA encoded subunits, as well as nuclear DNA encoded subunit IV, supporting the concept that COX subunit I is essential for the assembly of complex IV in the respiratory chain.
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| 25. |
- Kollberg, Gittan, 1963, et al.
(author)
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POLG1 mutations associated with progressive encephalopathy in childhood.
- 2006
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In: Journal of neuropathology and experimental neurology. - : Oxford University Press (OUP). - 0022-3069 .- 1554-6578. ; 65:8, s. 758-68
-
Journal article (peer-reviewed)abstract
- We have identified compound heterozygous missense mutations in POLG1, encoding the mitochondrial DNA polymerase gamma (Pol gamma), in 7 children with progressive encephalopathy from 5 unrelated families. The clinical features in 6 of the children included psychomotor regression, refractory seizures, stroke-like episodes, hepatopathy, and ataxia compatible with Alpers-Huttenlocher syndrome. Three families harbored a previously reported A467T substitution, which was found in compound with the earlier described G848S or the W748S substitution or a novel R574W substitution. Two families harbored the W748S change in compound with either of 2 novel mutations predicted to give an R232H or M1163R substitution. Muscle morphology showed mitochondrial myopathy with cytochrome c oxidase (COX)-deficient fibers in 4 patients. mtDNA analyses in muscle tissue revealed mtDNA depletion in 3 of the children and mtDNA deletions in the 2 sibling pairs. Neuropathologic investigation in 3 children revealed widespread cortical degeneration with gliosis and subcortical neuronal loss, especially in the thalamus, whereas there were only subcortical neurodegenerative findings in another child. The results support the concept that deletions as well as depletion of mtDNA are involved in the pathogenesis of Alpers-Huttenlocher syndrome and add 3 new POLG1 mutations associated with an early-onset neurodegenerative disease.
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| 26. |
- Kärppä, Mikko, et al.
(author)
-
Spectrum of myopathic findings in 50 patients with the 3243A>G mutation in mitochondrial DNA
- 2005
-
In: Brain. - : Oxford University Press (OUP). - 1460-2156 .- 0006-8950. ; 128:Pt 8, s. 1861-9
-
Journal article (peer-reviewed)abstract
- Myopathy is a typical clinical finding among patients with the 3243A>G mutation in mitochondrial DNA (mtDNA), but the variability in such findings has not been properly established. We have previously determined the prevalence of patients with 3243A>G in a defined population in northern Finland and characterized a group of patients who represent a good approximation to a population-based cohort. We report here on examinations performed on patients belonging to this cohort in order to determine the frequency of myopathy and to evaluate the clinical, histological, ultrastructural and single fibre mtDNA variability in muscle involvement. Fifty patients with 3243A>G underwent a thorough structured interview and clinical examination. Muscle histology, ultrastructure and single fibre analysis were examined in a subset of patients. A clinical diagnosis of myopathy was made in 50% of cases [95% confidence interval (CI), 36-64] and abnormalities in muscle histology were found in 72% (95% CI, 55-86). Moderate limb weakness leading to functional impairment was the most common myopathic sign, but mild weakness, ptosis and external ophthalmoplegia could also be found. The presence of intramitochondrial crystals and cytochrome c oxidase (COX)-negative fibres and variation in mitochondrial size and shape were more common in the muscles of the myopathic patients. Longitudinal variations in mutation heteroplasmy were examined in single muscle fibres from two severely affected patients. Although the total variation in mutation heteroplasmy along four ragged red fibres (RRFs) was small, the mutation heteroplasmy in five 10 microm segments was clearly lower (median 68%, range 64-74%) than that in the neighbouring segments. There were also segments with deviant mutation load in histologically normal fibres in one patient. The highest incidence of myopathy was in the fifth decade of life, but, apart from age, no other clinical variables such as gender, muscle heteroplasmy, physical inactivity or diabetes were associated with an increased risk of myopathy. The clinical presentation of myopathy is highly variable in patients with 3243A>G.
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| 27. |
- Larsson, K, et al.
(author)
-
A Western blot and molecular genetic investigation of the estrogen receptor beta in giant cell arteritis.
- 2006
-
In: Clinical and experimental rheumatology. - 0392-856X. ; 24:2 Suppl 41
-
Journal article (peer-reviewed)abstract
- OBJECTIVE: The epidemiology of giant cell arteritis (GCA) may indicate a pathogenetic relationship between GCA and female sex hormone metabolism; GCA is two to four times more common in women compared with men. Our previous analyses gave no support for the hypothesis that the pathogenesis of GCA should be related to somatic mutations in the estrogen receptor alpha (ERalpha) gene. The object of the present study was to investigate the size of the estrogen receptor beta (ERBeta), and the size and nucleotide sequence of the ERBeta gene in temporal arteries in GCA. METHODS: The ERBeta protein was analyzed by Western blot technique and the ERBeta gene by RT-PCR and direct sequencing of the PCR product. RESULTS: Western blot analysis revealed an ERBeta of normal size. There were no aberrations in size or nucleotide sequence in the ERBeta gene in the GCA patients. CONCLUSION: The present observations gave no support for the hypothesis that somatic mutations in the ERBeta gene should be involved in the pathogenesis of GCA.
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| 28. |
- Lindberg, Christopher, et al.
(author)
-
MELAS syndrome in a patient with a point mutation in MTTS1.
- 2008
-
In: Acta neurologica Scandinavica. - : Hindawi Limited. - 1600-0404 .- 0001-6314. ; 117:2, s. 128-32
-
Journal article (peer-reviewed)abstract
- BACKGROUND, OBJECTIVE AND METHODS: We describe a female patient with a mitochondrial encephalopathy, lactic acidosis and stroke-like episodes syndrome. As a child, she developed epilepsy and stroke-like episodes giving cognitive impairment and ataxia but no hearing impairment. At the age of 44 years, she suffered a cerebral sinus thrombosis which was warfarin treated. One month later, she developed an episode of severe acidosis associated with encephalopathy and myelopathy. RESULTS: She was found to harbour a 7512T>C mutation in the mitochondrial encoded tRNA(Ser(UCN)) gene (MTTS1). The mutation load was 91% in muscle and 24% in blood. Enzyme histochemical analysis of the muscle tissue showed numerous cytochrome c oxidase (COX)-negative fibres. Restriction fragment length polymorphism (RFLP) analysis of single muscle fibres showed significantly higher level (median 97%, range: 94-99%) of the mutation in the COX-negative fibres compared with COX-positive fibres (median 36%, range: 12-91%), demonstrating the pathogenic effect of the mutation. Different levels of heteroplasmy (range 34-61%) were detected in hair shafts analysed by RFLP. CONCLUSION: This case adds to the spectrum of clinical presentations, i.e. sinus thrombosis, in patients having MTTS1 mutations.
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| 29. |
- Lindgren, Ulrika, et al.
(author)
-
Mitochondrial pathology in inclusion body myositis
- 2015
-
In: Neuromuscular Disorders. - : Elsevier BV. - 0960-8966. ; 25:4, s. 281-288
-
Journal article (peer-reviewed)abstract
- Inclusion body myositis (IBM) is usually associated with a large number of cytochrome c oxidase (COX)-deficient muscle fibers and acquired mitochondrial DNA (mtDNA) deletions. We studied the number of COX-deficient fibers and the amount of mtDNA deletions, and if variants in nuclear genes involved in mtDNA maintenance may contribute to the occurrence of mtDNA deletions in IBM muscle. Twenty-six IBM patients were included. COX-deficient fibers were assayed by morphometry and mtDNA deletions by qPCR. POLG was analyzed in all patients by Sanger sequencing and C10orf2 (Twinkle), DNA2, MGME1, OPA1, POLG2, RRM2B, SLC25A4 and TYMP in six patients by next generation sequencing. Patients with many COX-deficient muscle fibers had a significantly higher proportion of mtDNA deletions than patients with few COX-deficient fibers. We found previously unreported variants in POLG and C10orf2 and IBM patients had a significantly higher frequency of an RRM2B variant than controls. POLG variants appeared more common in IBM patients with many COX-deficient fibers, but the difference was not statistically significant. We conclude that COX-deficient fibers in inclusion body myositis are associated with multiple mtDNA deletions. In IBM patients we found novel and also previously reported variants in genes of importance for mtDNA maintenance that warrants further studies. (C) 2014 Elsevier B.V. All rights reserved.
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| 30. |
- Mayr, J A, et al.
(author)
-
A novel sporadic mutation G14739A of the mitochondrial tRNA(Glu) in a girl with exercise intolerance
- 2006
-
In: Neuromuscul Disord. - : Elsevier BV. ; 16:12, s. 874-7
-
Journal article (peer-reviewed)abstract
- We describe a 7-year-old girl who presented with loss of appetite, weakness and excercise intolerance. Enzyme investigation of the respiratory chain in muscle tissue revealed a combined complex I, III and IV deficiency. A novel heteroplasmic G-->A exchange at nucleotide position 14739 was found in the MTTE gene of the tRNA glutamic acid. The mutation load in muscle was 72%, urine sediment 38%, blood 31% and fibroblasts 29% and it correlated with COX-negative fibres. Our patient presented with a predominantly myopathic phenotype. The G14739A mutation is the third reported in the mitochondrial tRNA glutamic acid gene, and it occurred in a sporadic case.
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| 31. |
- Melberg, Atle, et al.
(author)
-
A patient with two mitochondrial DNA mutations causing PEO and LHON.
- 2009
-
In: European journal of medical genetics. - : Elsevier BV. - 1878-0849 .- 1769-7212. ; 52:1, s. 47-8
-
Journal article (peer-reviewed)abstract
- We report a 22-year-old man with PEO and optic atrophy. PEO developed before the onset of optic atrophy. The patient showed mitochondrial myopathy with cytochrome c oxidase deficient fibers. In skeletal muscle the patient was homoplasmic for the mtDNA G11778A Leber hereditary optic neuropathy (LHON) mutation and heteroplasmic for the mtDNA 5 kb "common" deletion mutation. In blood only the homoplasmic LHON mutation was identified. The occurrence of two pathogenic mtDNA mutations is exceedingly rare. The clinical findings in this patient indicate that the combination of the two mtDNA mutations resulted in the expected combined phenotype since the mtDNA deletion mutation accounted for the PEO and the mtDNA G11778A point mutation for the optic atrophy.
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| 32. |
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| 33. |
- Moslemi, Ali-Reza, et al.
(author)
-
A novel mutation in the mitochondrial tRNA(Phe) gene associated with mitochondrial myopathy
- 2004
-
In: Neuromuscul Disord. ; 14:1, s. 46-50
-
Journal article (peer-reviewed)abstract
- We report a novel heteroplasmic T-->C mutation at nt position 582 within the mitochondrial tRNA(Phe) gene of a 70-year-old woman with mitochondrial myopathy. No other family members were affected, suggesting that our patient was a sporadic case. The muscle showed frequent ragged red fibers and 43% cytochrome c oxidase deficient fibers. The mutation alters a conserved base pairing in the aminoacyl acceptor stem. The mutation load was 70% in muscle homogenate and varied from 0 to 95% in individual muscle fiber segments. Cytochrome c oxidase-negative fibers showed significantly higher levels of mutated mtDNA (>75%) than Cytochrome c oxidase-positive fibers (<55%). This mutation adds to the previously described four pathogenic mutations in the tRNA(Phe) gene.
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| 34. |
- Moslemi, Ali-Reza, et al.
(author)
-
Glycogenin-1 deficiency and inactivated priming of glycogen synthesis.
- 2010
-
In: The New England journal of medicine. - : Massachusetts Medical Society. - 1533-4406 .- 0028-4793. ; 362:13, s. 1203-10
-
Journal article (peer-reviewed)abstract
- Glycogen, which serves as a major energy reserve in cells, is a large, branched polymer of glucose molecules. We describe a patient who had muscle weakness, associated with the depletion of glycogen in skeletal muscle, and cardiac arrhythmia, associated with the accumulation of abnormal storage material in the heart. The skeletal muscle showed a marked predominance of slow-twitch, oxidative muscle fibers and mitochondrial proliferation. Western blotting showed the presence of unglucosylated glycogenin-1 in the muscle and heart. Sequencing of the glycogenin-1 gene, GYG1, revealed a nonsense mutation in one allele and a missense mutation, Thr83Met, in the other. The missense mutation resulted in inactivation of the autoglucosylation of glycogenin-1 that is necessary for the priming of glycogen synthesis in muscle.
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| 35. |
- Moslemi, Ali-Reza
(author)
-
MELAS syndrome in a patient with a point mutation in MTTS1.
- 2007
-
In: Acta Neurol Scand.
-
Journal article (peer-reviewed)abstract
- Background, Objective and Methods - We describe a female patient with a mitochondrial encephalopathy, lactic acidosis and stroke-like episodes syndrome. As a child, she developed epilepsy and stroke-like episodes giving cognitive impairment and ataxia but no hearing impairment. At the age of 44 years, she suffered a cerebral sinus thrombosis which was warfarin treated. One month later, she developed an episode of severe acidosis associated with encephalopathy and myelopathy. Results - She was found to harbour a 7512T>C mutation in the mitochondrial encoded tRNA(Ser(UCN)) gene (MTTS1). The mutation load was 91% in muscle and 24% in blood. Enzyme histochemical analysis of the muscle tissue showed numerous cytochrome c oxidase (COX)-negative fibres. Restriction fragment length polymorphism (RFLP) analysis of single muscle fibres showed significantly higher level (median 97%, range: 94-99%) of the mutation in the COX-negative fibres compared with COX-positive fibres (median 36%, range: 12-91%), demonstrating the pathogenic effect of the mutation. Different levels of heteroplasmy (range 34-61%) were detected in hair shafts analysed by RFLP. Conclusion - This case adds to the spectrum of clinical presentations, i.e. sinus thrombosis, in patients having MTTS1 mutations.
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| 36. |
|
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| 37. |
- Moslemi, Ali-Reza, et al.
(author)
-
Progressive encephalopathy and complex I deficiency associated with mutations in MTND1.
- 2008
-
In: Neuropediatrics. - : Georg Thieme Verlag KG. - 0174-304X .- 1439-1899. ; 39:1, s. 24-8
-
Journal article (peer-reviewed)abstract
- Complex I of the oxidative phosphorylation system is composed of at least 45 subunits, seven of which are encoded by mitochondrial DNA (mtDNA). In this study we have investigated two children with complex I deficiency in muscle mitochondria. Patient 1 had cerebellar ataxia from early infancy and an abnormal MRI of the brain compatible with Leigh syndrome (LS). The course was rapidly progressive with frequent exacerbations and death at 2 years and 10 months of age. Patient 2 had a lactic acidosis in the newborn period and had a severe psychomotor developmental retardation. In her teens she developed hypertrophic cardiomyopathy and died at 26 years of age because of cardiac insufficiency. Sequencing analysis of mitochondrial encoded ND genes (MTND) showed two DE NOVO mutations in MTND1 in both patients. Patient 1 had a novel heteroplasmic G3890A mutation, R195Q. Patient 2 had a heteroplasmic G3481A mutation, E59K. The G3890A mutation in patient 1 is the first identified mutation in MTND1 in association with LS and complex I deficiency. The findings in this patient as well as in patient 2 demonstrate new clinical expressions of mutations in MTND1. The findings in patient 2 also illustrates that MTND mutations may be pathogenic even at a low percentage.
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| 38. |
- Moslemi, Ali-Reza, et al.
(author)
-
Two new mutations in the MTATP6 gene associated with Leigh syndrome.
- 2005
-
In: Neuropediatrics. - : Georg Thieme Verlag KG. - 0174-304X .- 1439-1899. ; 36:5, s. 314-8
-
Journal article (peer-reviewed)abstract
- In this study we have analyzed the mtDNA encoded ATPase 6 and 8 genes ( MTATP6 and MTATP8) in two children with Leigh syndrome (LS) and reduced Mg (2+) ATPase activity in muscle mitochondria. In patient 1, with a mild and reversible phenotype, mutational analysis revealed a heteroplasmic T --> C mutation at nt position 9185 (T9185C) in the MTATP6. The mutation resulted in substitution of a highly conserved leucine to proline at codon 220. The proportion of the mutation was > 97 % in the patient's blood and muscle and 85 % in blood of his asymptomatic mother. Patient 2, with severe clinical phenotype and death at 2 years of age, exhibited a novel heteroplasmic T9191C missense mutation in the MTATP6, which converted a highly conserved leucine to a proline at position 222 of the polypeptide. The proportion of the mutation was 90 % in fibroblasts and 94 % muscle tissue. This mutation was absent in the patient's parents and sister suggesting that the mutation was de novo. Our findings expand the spectrum of mutations causing LS and emphasize the role of MTATP6 gene mutations in pathogenesis of LS.
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| 39. |
- Nilsson, Johanna, et al.
(author)
-
LC-MS/MS characterization of combined glycogenin-1 and glycogenin-2 enzymatic activities reveals their self-glucosylation preferences.
- 2014
-
In: Biochimica et biophysica acta. - : Elsevier BV. - 0006-3002. ; 1844:2, s. 398-405
-
Journal article (peer-reviewed)abstract
- Glycogen synthesis is initiated by self-glucosylation of the glycosyltransferases glycogenin-1 and -2 that, in the presence of UDP-glucose, form both the first glucose-O-tyrosine linkage, and then stepwise add a series of α1,4-linked glucoses to a growing chain of variable length. Glycogen-1 and -2 coexist in liver glycogen preparations where the proteins are known to form homodimers, and they also have been shown to interact with each other. In order to study how glycogenin-1 and -2 interactions may influence each other's glucosylations we setup a cell-free expression system for in vitro production and glucosylation of glycogenin-1 and -2 in various combinations, and used a mass spectrometry based workflow for the characterization and quantitation of tryptic glycopeptides originating from glycogenin-1 and -2. The analysis revealed that the self-glucosylation endpoint was the incorporation of 4-8 glucose units on Tyr 195 of glycogenin-1, but only 0-4 glucose units on Tyr-228 of glycogenin-2. The glucosylation of glycogenin-2 was enhanced to 2-4 glucose units by the co-presence of enzymatically active glycogenin-1. Glycogenin-2 was, however, unable to glucosylate inactive glycogenin-1, at least not an enzymatically inactivated Thr83Met glycogenin-1 mutant, recently identified in a patient with severe glycogen depletion.
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| 40. |
- Nilsson, Johanna, et al.
(author)
-
Molecular pathogenesis of a new glycogenosis caused by a glycogenin-1 mutation.
- 2012
-
In: Biochimica et biophysica acta. - : Elsevier BV. - 0006-3002. ; 1822:4, s. 493-9
-
Journal article (peer-reviewed)abstract
- Glycogenin-1 initiates the glycogen synthesis in skeletal muscle by the autocatalytic formation of a short oligosaccharide at tyrosine 195. Glycogenin-1 catalyzes both the glucose-O-tyrosine linkage and the α1,4 glucosidic bonds linking the glucose molecules in the oligosaccharide. We recently described a patient with glycogen depletion in skeletal muscle as a result of a non-functional glycogenin-1. The patient carried a Thr83Met substitution in glycogenin-1. In this study we have investigated the importance of threonine 83 for the catalytic activity of glycogenin-1. Non-glucosylated glycogenin-1 constructs, with various amino acid substitutions in position 83 and 195, were expressed in a cell-free expression system and autoglucosylated in vitro. The autoglucosylation was analyzed by gel-shift on western blot, incorporation of radiolabeled UDP-(14)C-glucose and nano-liquid chromatography with tandem mass spectrometry (LC/MS/MS). We demonstrate that glycogenin-1 with the Thr83Met substitution is unable to form the glucose-O-tyrosine linkage at tyrosine 195 unless co-expressed with the catalytically active Tyr195Phe glycogenin-1. Our results explain the glycogen depletion in the patient expressing only Thr83Met glycogenin-1 and why heterozygous carriers without clinical symptoms show a small proportion of unglucosylated glycogenin-1.
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| 41. |
- Oldfors, Anders, 1951, et al.
(author)
-
Mitochondrial abnormalities in inclusion-body myositis
- 2006
-
In: Neurology. - : Ovid Technologies (Wolters Kluwer Health). - 0028-3878 .- 1526-632X. ; 66:2 Suppl 1
-
Journal article (peer-reviewed)abstract
- Mitochondrial changes are frequently encountered in sporadic inclusion-body myositis (s-IBM). Cytochrome c oxidase (COX)-deficient muscle fibers and large-scale mitochondrial DNA (mtDNA) deletions are more frequent in s-IBM than in age-matched controls. COX deficient muscle fibers are due to clonal expansion of mtDNA deletions and point mutations in segments of muscle fibers. Such segments range from 75 microm to more than 1,000 microm in length. Clonal expansion of the 4977 bp "common deletion" is a frequent cause of COX deficient muscle fiber segments, but many other deletions also occur. The deletion breakpoints cluster in a few regions that are similar to what is found in human mtDNA deletions in general. Analysis in s-IBM patients of three nuclear genes associated with multiple mtDNA deletions, POLG1, ANT1 and C10orf2, failed to demonstrate any mutations. In s-IBM patients with high number of COX-deficient fibers, the impaired mitochondrial function probably contribute to muscle weakness and wasting. Treatment that has positive effects in mitochondrial myopathies may be tried also in s-IBM.
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| 42. |
- Pagnamenta, A. T., et al.
(author)
-
An ancestral 10-bp repeat expansion in VWA1 causes recessive hereditary motor neuropathy
- 2021
-
In: Brain : a journal of neurology. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 144, s. 584-600
-
Journal article (peer-reviewed)abstract
- The extracellular matrix comprises a network of macromolecules such as collagens, proteoglycans and glycoproteins. VWA1 (von Willebrand factor A domain containing 1) encodes a component of the extracellular matrix that interacts with perlecan/collagen VI, appears to be involved in stabilizing extracellular matrix structures, and demonstrates high expression levels in tibial nerve. Vwa1-deficient mice manifest with abnormal peripheral nerve structure/function; however, VWA1 variants have not previously been associated with human disease. By interrogating the genome sequences of 74 180 individuals from the 100K Genomes Project in combination with international gene-matching efforts and targeted sequencing, we identified 17 individuals from 15 families with an autosomal-recessive, non-length dependent, hereditary motor neuropathy and rare biallelic variants in VWA1. A single disease-associated allele p.(G25Rfs*74), a 10-bp repeat expansion, was observed in 14/15 families and was homozygous in 10/15. Given an allele frequency in European populations approaching 1/1000, the seven unrelated homozygote individuals ascertained from the 100K Genomes Project represents a substantial enrichment above expected. Haplotype analysis identified a shared 220 kb region suggesting that this founder mutation arose 47000 years ago. A wide age-range of patients (6-83 years) helped delineate the clinical phenotype over time. The commonest disease presentation in the cohort was an early-onset (mean 2.0 +/- 1.4 years) non-length-dependent axonal hereditary motor neuropathy, confirmed on electrophysiology, which will have to be differentiated from other predominantly or pure motor neuropathies and neuronopathies. Because of slow disease progression, ambulation was largely preserved. Neurophysiology, muscle histopathology, and muscle MRI findings typically revealed clear neurogenic changes with single isolated cases displaying additional myopathic process. We speculate that a few findings of myopathic changes might be secondary to chronic denervation rather than indicating an additional myopathic disease process. Duplex reverse transcription polymerase chain reaction and immunoblotting using patient fibroblasts revealed that the founder allele results in partial nonsense mediated decay and an absence of detectable protein. CRISPR and morpholino vwa1 modelling in zebrafish demonstrated reductions in motor neuron axonal growth, synaptic formation in the skeletal muscles and locomotive behaviour. In summary, we estimate that biallelic variants in VWA1 may be responsible for up to 1% of unexplained hereditary motor neuropathy cases in Europeans. The detailed clinical characterization provided here will facilitate targeted testing on suitable patient cohorts. This novel disease gene may have previously evaded detection because of high GC content, consequential low coverage and computational difficulties associated with robustly detecting repeat-expansions. Reviewing previously unsolved exomes using lower QC filters may generate further diagnoses.
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| 43. |
- Pokrzywa, Malgorzata, 1977, et al.
(author)
-
Developmental MYH3 Myopathy Associated with Expression of Mutant Protein and Reduced Expression Levels of Embryonic MyHC
- 2015
-
In: PLoS One. - : Public Library of Science (PLoS). - 1932-6203. ; 10:11
-
Journal article (peer-reviewed)abstract
- Objective An essential role for embryonic MyHC in foetal development has been found from its association with distal arthrogryposis syndromes, a heterogeneous group of disorders characterised by congenital contractions. The latter probably result from severe myopathy during foetal development. Lack of embryonic muscle biopsy material and suitable animal models has hindered study of the pathomechanisms linking mutations in MYH3 to prenatal myopathy. We determined the pathomechanisms of developmental myopathy caused by recurrent p. Thr178Ile MYH3 heterozygosity, using patient-derived skeletal muscle cells in culture as an experimental disease model to emulate early embryonic development. These cultured cells were processed for discrimination and quantitative analysis of mutant and wild-type MYH3 alleles and MyHC transcripts, real-time RT-qPCR, sequence analysis, immunofluorescence microscopy, immunoblot, and proteomic assessments. Involvement of the ubiquitin proteasome system was investigated in patients with p. Thr178Ile mutations in MYH3 and MYH2. We found equal overall expression of mutant and wild-type MyHC mRNAs and proteins. Compared to the controls, however, expression of embryonic MyHC transcripts and proteins was reduced whereas expression of myosin-specific E3 ubiquitin ligase (MuRF1) was increased. We also found delayed myofibrillogenesis and atrophic myotubes but structured sarcomeres. In conclusion, this study suggests that developmental p.Thr178Ile MYH3 myopathy is associated with a combined pathomechanism of insufficient dosage of functional embryonic MyHC and production of mutant protein.
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| 44. |
- Roos, Sara, 1979, et al.
(author)
-
A novel mitochondrial tRNA Arg mutation resulting in an anticodon swap in a patient with mitochondrial encephalomyopathy.
- 2013
-
In: European journal of human genetics : EJHG. - : Springer Science and Business Media LLC. - 1476-5438 .- 1018-4813. ; 21:5, s. 571-3
-
Journal article (other academic/artistic)abstract
- We report a mutation in the anticodon of the tRNA(Arg) gene (m.10437G>A), resulting in an anticodon swap from GCU to ACU, which is the anticodon of tRNA(Trp), in a boy with mitochondrial encephalomyopathy. Enzyme histochemical analysis of muscle tissue and biochemical analysis of isolated muscle mitochondria demonstrated cytochrome c oxidase (COX) deficiency. Restriction fragment length polymorphism analysis showed that 90% of muscle and 82% of urinary epithelium mtDNA harbored the mutation. The mutation was not identified in blood, fibroblasts, hair roots, or buccal epithelial cells and it was absent in the asymptomatic mother, suggesting that it was a de novo mutation. Single-fiber PCR analysis showed that the proportion of mutated mtDNA correlated with enzyme histochemical COX deficiency. This mutation adds to the three previously described disease-causing mutations in tRNA(Arg), but it is the first mutation occurring in the anticodon of tRNA(Arg).European Journal of Human Genetics advance online publication, 11 July 2012; doi:10.1038/ejhg.2012.153.
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| 45. |
- Roos, Sara, 1979, et al.
(author)
-
Histopathological changes in skeletal muscle associated with chronic ischaemia.
- 2016
-
In: APMIS : acta pathologica, microbiologica, et immunologica Scandinavica. - : Wiley. - 1600-0463. ; 124:11, s. 935-941
-
Journal article (peer-reviewed)abstract
- Muscle biopsy is an essential part in the diagnostic workup in patients with suspected neuromuscular disorders. It is therefore important to be aware of morphological alterations that can be caused by systemic factors or natural ageing. Chronic limb ischaemia is frequent in elderly individuals. This study was performed to examine histopathological and mitochondrial changes in muscle in patients with chronic critical limb ischaemia. Muscle biopsy of skeletal muscle of the lower limb of patients with chronic ischaemia leading to amputation was performed and compared with muscle biopsies of healthy, age-matched controls. The histopathological abnormalities included fibrosis, necrosis, atrophy, glycogen depletion, internal nuclei, rimmed vacuoles, fibre type grouping, cytochrome c oxidase deficient fibres, MHC-I upregulation, and signs of microangiopathy. The only alteration found in age-matched controls was a few cytochrome c oxidase deficient fibres. There were also increased levels of multiple mitochondrial DNA deletions in ischaemic muscles compared with controls. Critical limb ischaemia is associated with significant histopathological changes in muscle tissue and also increased levels of mitochondrial DNA deletions. Since the alterations mimic different primary myopathic changes, chronic ischaemia is important to consider as a differential diagnosis in elderly individuals, investigated with muscle biopsy for muscle disease.
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| 46. |
- Roos, Sara, 1979, et al.
(author)
-
Mitochondrial DNA depletion in single fibers in a patient with novel TK2 mutations
- 2014
-
In: Neuromuscular Disorders. - : Elsevier BV. - 0960-8966 .- 1873-2364. ; 24:8, s. 713-720
-
Journal article (peer-reviewed)abstract
- The mitochondrial DNA (mtDNA) depletion syndrome is a genetically heterogeneous group of diseases caused by nuclear gene mutations and secondary reduction in mtDNA copy number. We describe a patient with progressive muscle weakness and increased creatine kinase and lactate levels. Muscle weakness was first noted at age 1.5 years and he died of respiratory failure and bronchopneumonia at age 3.5 years. The muscle biopsy showed dystrophic features with ragged red fibers and numerous cytochrome c oxidase (COX)-negative fibers. qPCR analysis demonstrated depletion of mtDNA and sequence analysis of the mitochondrial thymidine kinase 2 (TK2) gene revealed two novel heterozygous variants, c.332C > T, p.(T111I) and c.156 + 5G > C. Quantitative analysis of mtDNA in single muscle fibers demonstrated that COX-deficient fibers showed more pronounced depletion of mtDNA when compared with fibers with residual COX activity (P < 0.01, n = 25). There was no evidence of manifestations from other organs than skeletal muscle although there was an apparent reduction of mtDNA copy number also in liver. The patient showed a pronounced, albeit transient, improvement in muscle strength after onset of treatment with coenzyme Q10, asparaginase, and increased energy intake, suggesting that nutritional modulation may be a therapeutic option in myopathic mtDNA depletion syndrome. (C) 2014 Elsevier B.V. All rights reserved.
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| 47. |
- Roos, Sara, 1979, et al.
(author)
-
Subnormal levels of POLgA cause inefficient initiation of light-strand DNA synthesis and lead to mitochondrial DNA deletions and progressive external ophthalmoplegia
- 2013
-
In: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 22:12, s. 2411-2422
-
Journal article (peer-reviewed)abstract
- The POLG1 gene encodes the catalytic subunit of mitochondrial DNA (mtDNA) polymerase γ (POLγ). We here describe a sibling pair with adult-onset progressive external ophthalmoplegia, cognitive impairment and mitochondrial myopathy characterized by DNA depletion and multiple mtDNA deletions. The phenotype is due to compound heterozygous POLG1 mutations, T914P and the intron mutation c.3104 + 3A > T. The mutant genes produce POLγ isoforms with heterozygous phenotypes that fail to synthesize longer DNA products in vitro. However, exon skipping in the c.3104 + 3A > T mutant is not complete, and the presence of low levels of wild-type POLγ explains patient survival. To better understand the underlying pathogenic mechanisms, we characterized the effects of POLγ depletion in vitro and found that leading-strand DNA synthesis is relatively undisturbed. In contrast, initiation of lagging-strand DNA synthesis is ineffective at lower POLγ concentrations that uncouples leading strand from lagging-strand DNA synthesis. In vivo, this effect leads to prolonged exposure of the heavy strand in its single-stranded conformation that in turn can cause the mtDNA deletions observed in our patients. Our findings, thus, suggest a molecular mechanism explaining how POLγ mutations can cause mtDNA deletions in vivo.
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| 48. |
- Sedghi, Maryam, et al.
(author)
-
Ataxia-telangiectasia-like disorder in a family deficient for MRE11A, caused by a MRE11 variant
- 2018
-
In: Neurology: Genetics. - : Lippincott Williams & Wilkins. - 2376-7839. ; 4:6
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Journal article (peer-reviewed)abstract
- Objective We report 3 siblings with the characteristic features of ataxia-telangiectasia-like disorder associated with a homozygous MRE11 synonymous variant causing nonsense-mediated mRNA decay (NMD) and MRE11A deficiency. Methods Clinical assessments, next-generation sequencing, transcript and immunohistochemistry analyses were performed. Results The patients presented with poor balance, developmental delay during the first year of age, and suffered from intellectual disability from early childhood. They showed oculomotor apraxia, slurred and explosive speech, limb and gait ataxia, exaggerated deep tendon reflex, dystonic posture, and mirror movement in their hands. They developed mild cognitive abilities. Brain MRI in the index case revealed cerebellar atrophy. Next-generation sequencing revealed a homozygous synonymous variant in MRE11 (c.657C>T, p.Asn219=) that we show affects splicing. A complete absence of MRE11 transcripts in the index case suggested NMD and immunohistochemistry confirmed the absence of a stable protein. Conclusions Despite the critical role of MRE11A in double-strand break repair and its contribution to the Mre11/Rad50/Nbs1 complex, the absence of MRE11A is compatible with life.
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- Sedghi, M., et al.
(author)
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Ataxia-telangiectasia-like disorder in a family deficient for MRE11A, caused by a MRE11 variant
- 2018
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In: Neurology-Genetics. - : Ovid Technologies (Wolters Kluwer Health). - 2376-7839. ; 4:6
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Journal article (peer-reviewed)abstract
- Objective We report 3 siblings with the characteristic features of ataxia-telangiectasia-like disorder associated with a homozygous MREll synonymous variant causing nonsense-mediated mRNA decay (NMD) and MRE11A deficiency. Clinical assessments, next-generation sequencing, transcript and immunohistochemistry analyses were performed. The patients presented with poor balance, developmental delay during the first year of age, and suffered from intellectual disability from early childhood. They showed oculomotor apraxia, slurred and explosive speech, limb and gait ataxia, exaggerated deep tendon reflex, dystonic posture, and mirror movement in their hands. They developed mild cognitive abilities. Brain MRI in the index case revealed cerebellar atrophy. Next-generation sequencing revealed a homozygous synonymous variant in MRE11 (c.657C>T, p.Asn219=) that we show affects splicing. A complete absence of MREll transcripts in the index case suggested NMD and immunohistochemistry confirmed the absence of a stable protein. Despite the critical role of MRE11A in double-strand break repair and its contribution to the Mre11/Rad50/Nbs1 complex, the absence of MRE11A is compatible with life.
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| 50. |
- Sedghi, M., et al.
(author)
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Recessive Charcot-Marie-Tooth and multiple sclerosis associated with a variant in MCM3AP
- 2019
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In: Brain Communications. - : Oxford University Press (OUP). - 2632-1297. ; 1:1
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Journal article (peer-reviewed)abstract
- Variants in MCM3AP, encoding the germinal-centre associated nuclear protein, have been associated with progressive polyneuropathy with or without intellectual disability and ptosis in some cases, and with a complex phenotype with immunodeficiency, skin changes and myelodysplasia. MCM3AP encoded protein functions as an acetyltransferase that acetylates the replication protein, MCM3, and plays a key role in the regulation of DNA replication. In this study, we report a novel variant in MCM3AP (p.Ile954Thr), in a family including three affected individuals with characteristic features of Charcot-Marie-Tooth neuropathy and multiple sclerosis, an inflammatory condition of the central nervous system without known genetic cause. The affected individuals were homozygous for a missense MCM3AP variant, located at the Sac3 domain, which was predicted to affect conserved amino acid likely important for the function of the germinal-centre associated nuclear protein. Our data support further expansion of the clinical spectrum linked to MCM3AP variant and highlight that MCM3AP should be considered in patients with accompaniment of recessive motor axonal Charcot-Marie-Tooth neuropathy and multiple sclerosis.
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