scholarly journals Deep sequencing of mitochondrial DNA and characterization of a novel POLG mutation in a patient with arPEO

2020 ◽  
Vol 6 (1) ◽  
pp. e391
Author(s):  
Carola Hedberg-Oldfors ◽  
Bertil Macao ◽  
Swaraj Basu ◽  
Christopher Lindberg ◽  
Bradley Peter ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Muscle Biopsy ◽  
Deep Sequencing ◽  
Large Scale ◽  
Biochemical Characterization ◽  
Late Onset ◽  
Novel Mutation ◽  
Progressive External Ophthalmoplegia ◽  
Oxidase Deficiency

ObjectiveTo determine the pathogenicity of a novel POLG mutation in a man with late-onset autosomal recessive progressive external ophthalmoplegia using clinical, molecular, and biochemical analyses.MethodsA multipronged approach with detailed neurologic examinations, muscle biopsy analyses, molecular genetic studies, and in vitro biochemical characterization.ResultsThe patient had slowly progressive bilateral ptosis and severely reduced horizontal and vertical gaze. Muscle biopsy showed slight variability in muscle fiber size, scattered ragged red fibers, and partial cytochrome c oxidase deficiency. Biallelic mutations were identified in the POLG gene encoding the catalytic A subunit of POLγ. One allele carried a novel mutation in the exonuclease domain (c.590T>C; p.F197S), and the other had a previously characterized null mutation in the polymerase domain (c.2740A>C; p.T914P). Biochemical characterization revealed that the novel F197S mutant protein had reduced exonuclease and DNA polymerase activities and confirmed that T914P was inactive. By deep sequencing of mitochondrial DNA (mtDNA) extracted from muscle, multiple large-scale rearrangements were mapped and quantified.ConclusionsThe patient's phenotype was caused by biallelic POLG mutations, resulting in one inactive POLγA protein (T914P) and one with decreased polymerase and exonuclease activity (F197S). The reduction in polymerase activity explains the presence of multiple pathogenic large-scale deletions in the patient's mtDNA.

Multiple sclerosis and chronic progressive external ophthalmoplegia associated with a large scale mitochondrial DNA single deletion

2016 ◽  
Vol 263 (7) ◽  
pp. 1449-1451 ◽  
Author(s):  
Lorenzo Gaetani ◽  
Andrea Mignarri ◽  
Maria Di Gregorio ◽  
Paola Sarchielli ◽  
Alessandro Malandrini ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Mitochondrial Dna ◽  
Large Scale ◽  
Progressive External Ophthalmoplegia ◽  
Chronic Progressive External Ophthalmoplegia ◽  
Single Deletion

A novel mutation in the mitochondrial DNA tRNA Leu (UUR) gene associated with late-onset ocular myopathy

2007 ◽  
Vol 17 (5) ◽  
pp. 415-418 ◽  
Author(s):  
E. Maeso ◽  
A. Rueda ◽  
S. Jiménez ◽  
P. del Hoyo ◽  
R. Martín ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Late Onset ◽  
Novel Mutation

scholarly journals The Phenotypic Spectrum of 47 Czech Patients with Single, Large-Scale Mitochondrial DNA Deletions

2020 ◽  
Vol 10 (11) ◽  
pp. 766 ◽  
Author(s):  
Nicole Anteneová ◽  
Silvie Kelifová ◽  
Hana Kolářová ◽  
Alžběta Vondráčková ◽  
Iveta Tóthová ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Epithelial Cells ◽  
Large Scale ◽  
Childhood Mortality ◽  
Progressive External Ophthalmoplegia ◽  
Buccal Swab ◽  
Pcr Screening ◽  
Pearson Syndrome ◽  
Significant Difference ◽  
Dna Deletions

Background: In this retrospective study, we analysed clinical, biochemical and molecular genetic data of 47 Czech patients with Single, Large-Scale Mitochondrial DNA Deletions (SLSMD). Methods: The diagnosis was based on the long-range PCR (LX-PCR) screening of mtDNA isolated from muscle biopsy in 15 patients, and from the buccal swab, urinary epithelial cells and blood in 32 patients. Results: A total of 57% patients manifested before the age of 16. We did not find any significant difference between paediatric and adult manifestation in either the proportion of patients that would develop extraocular symptoms, or the timespan of its progression. The survival rate in patients with Pearson Syndrome reached 60%. Altogether, five patients manifested with atypical phenotype not fulfilling the latest criteria for SLSMD. No correlation was found between the disease severity and all heteroplasmy levels, lengths of the deletion and respiratory chain activities in muscle. Conclusions: Paediatric manifestation of Progressive External Ophthalmoplegia (PEO) is not associated with a higher risk of multisystemic involvement. Contrary to PEO and Kearns-Sayre Syndrome Spectrum, Pearson Syndrome still contributes to a significant childhood mortality. SLSMD should be considered even in cases with atypical presentation. To successfully identify carriers of SLSMD, a repeated combined analysis of buccal swab and urinary epithelial cells is needed.

Replication-competent human mitochondrial DNA lacking the heavy-strand promoter region

1991 ◽  
Vol 11 (3) ◽  
pp. 1631-1637
Author(s):  
C T Moraes ◽  
F Andreetta ◽  
E Bonilla ◽  
S Shanske ◽  
S DiMauro ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Promoter Region ◽  
Direct Repeat ◽  
Progressive External Ophthalmoplegia ◽  
Mitochondrial Transcription Factor ◽  
Mtdna Deletion ◽  
Heavy Strand ◽  
Light Strand

We identified two patients with progressive external ophthalmoplegia, a mitochondrial disease, who harbored a population of partially deleted mitochondrial DNA (mtDNA) with unusual properties. These molecules were deleted from mtDNA positions 548 to 4,442 and encompassed not only rRNA sequences but the heavy-strand promoter region as well. A 13-bp direct repeat was found flanking the breakpoint precisely, with the repeat at positions 535 to 547 located within the binding site for mitochondrial transcription factor 1 (mtTF1). This is the second mtDNA deletion involving a 13-bp direct repeat reported but is at least 10 times less frequent in the patient population than the former one. In situ hybridization studies showed that transcripts under the control of the light-strand promoter were abundant in muscle fibers with abnormal proliferation of mitochondria, while transcripts directed by the heavy-strand promoter, whether of genes residing inside or outside the deleted region, were not. The efficient transcription from the light-strand promoter implies that the major heavy-and light-strand promoters, although physically close, are functionally independent, confirming previous in vitro studies.

scholarly journals Suppression of Mitochondrial DNA Instability of Autosomal Dominant Forms of Progressive External Ophthalmoplegia-Associated ANT1 Mutations in Podospora anserina

Genetics ◽  
2009 ◽  
Vol 183 (3) ◽  
pp. 861-871 ◽  
Author(s):  
Riyad El-Khoury ◽  
Annie Sainsard-Chanet
Keyword(s):  
Mitochondrial Dna ◽  
Membrane Potential ◽  
Large Scale ◽  
Autosomal Dominant ◽  
Adenine Nucleotide ◽  
Podospora Anserina ◽  
Progressive External Ophthalmoplegia ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Mtdna Deletions

Maintenance and expression of mitochondrial DNA (mtDNA) are essential for the cell and the organism. In humans, several mutations in the adenine nucleotide translocase gene ANT1 are associated with multiple mtDNA deletions and autosomal dominant forms of progressive external ophthalmoplegia (adPEO). The mechanisms underlying the mtDNA instability are still obscure. A current hypothesis proposes that these pathogenic mutations primarily uncouple the mitochondrial inner membrane, which secondarily causes mtDNA instability. Here we show that the three adPEO-associated mutations equivalent to A114P, L98P, and V289M introduced into the Podospora anserina ANT1 ortholog dominantly cause severe growth defects, decreased reactive oxygen species production (ROS), decreased mitochondrial inner membrane potential (Δψ), and accumulation of large-scale mtDNA deletions leading to premature death. Interestingly, we show that, at least for the adPEO-type M106P and A121P mutant alleles, the associated mtDNA instability cannot be attributed only to a reduced membrane potential or to an increased ROS level since it can be suppressed without restoration of the Δψ or modification of the ROS production. Suppression of mtDNA instability due to the M106P and A121P mutations was obtained by an allele of the rmp1 gene involved in nucleo-mitochondrial cross- talk and also by an allele of the AS1 gene encoding a cytosolic ribosomal protein. In contrast, the mtDNA instability caused by the S296M mutation was not suppressed by these alleles.

scholarly journals Leukocyte cytokine responses in adult patients with mitochondrial DNA defects

2021 ◽  
Author(s):  
Kalpita R Karan ◽  
Caroline Trumpff ◽  
Marissa Cross ◽  
Kristin M Englestad ◽  
Anna L Marsland ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Large Scale ◽  
Cytokine Production ◽  
Ex Vivo ◽  
Mitochondrial Diseases ◽  
Preliminary Evidence ◽  
Cytokine Responses ◽  
Mtdna Deletions ◽  
Immune Challenges

Patients with oxidative phosphorylation (OxPhos) defects causing mitochondrial diseases appear particularly vulnerable to infections. Although OxPhos defects modulate cytokine production in vitro and in animal models, little is known about how circulating leukocytes of patients with inherited mitochondrial DNA (mtDNA) defects respond to acute immune challenges. In a small cohort of healthy controls (n=21) and patients (n=12) with either the m.3243A>G mutation or single, large-scale mtDNA deletions, we examined: i) cytokine responses (IL-6, TNF-α, IL-1β) in response to acute lipopolysaccharide (LPS) exposure, and ii) sensitivity to the immunosuppressive effects of glucocorticoid signaling (dexamethasone) on cytokine production. In dose-response experiments to determine the half-maximal effective LPS concentration (EC50), relative to controls, leukocytes from patients with mtDNA deletions showed 174 -179% lower responses for IL-6 and IL-1β (pIL-6=0.031, pIL-1β=0.009). Moreover, IL-6 response to LPS in presence of GC was also blunted in cells from patients with mtDNA deletions (pIL-6=0.006), but not in leukocytes from patients with the m.3243A>G mutation. Overall, these ex vivo data provide preliminary evidence that some systemic OxPhos defects may compromise immune cytokine responses and glucocorticoid sensitivity. Further work in larger cohorts is needed to define the nature of immune dysregulation in patients with mitochondrial disease, and their potential implications for disease phenotypes.

scholarly journals Phenotypic spectrum and clinical course of single large-scale mitochondrial DNA deletion disease in the paediatric population: a multicentre study

2021 ◽  
pp. jmedgenet-2021-108006
Author(s):  
Kristoffer Björkman ◽  
John Vissing ◽  
Elsebet Østergaard ◽  
Laurence A Bindoff ◽  
Irenaeus F M de Coo ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Multicentre Study ◽  
Mitochondrial Disease ◽  
Large Scale ◽  
Disease Onset ◽  
Exercise Intolerance ◽  
Progressive External Ophthalmoplegia ◽  
Muscle Involvement ◽  
Phenotypic Spectrum ◽  
Wide Range

BackgroundLarge-scale mitochondrial DNA deletions (LMD) are a common genetic cause of mitochondrial disease and give rise to a wide range of clinical features. Lack of longitudinal data means the natural history remains unclear. This study was undertaken to describe the clinical spectrum in a large cohort of patients with paediatric disease onset.MethodsA retrospective multicentre study was performed in patients with clinical onset <16 years of age, diagnosed and followed in seven European mitochondrial disease centres.ResultsA total of 80 patients were included. The average age at disease onset and at last examination was 10 and 31 years, respectively. The median time from disease onset to death was 11.5 years. Pearson syndrome was present in 21%, Kearns-Sayre syndrome spectrum disorder in 50% and progressive external ophthalmoplegia in 29% of patients. Haematological abnormalities were the hallmark of the disease in preschool children, while the most common presentations in older patients were ptosis and external ophthalmoplegia. Skeletal muscle involvement was found in 65% and exercise intolerance in 25% of the patients. Central nervous system involvement was frequent, with variable presence of ataxia (40%), cognitive involvement (36%) and stroke-like episodes (9%). Other common features were pigmentary retinopathy (46%), short stature (42%), hearing impairment (39%), cardiac disease (39%), diabetes mellitus (25%) and renal disease (19%).ConclusionOur study provides new insights into the phenotypic spectrum of childhood-onset, LMD-associated syndromes. We found a wider spectrum of more prevalent multisystem involvement compared with previous studies, most likely related to a longer time of follow-up.

scholarly journals Should we Investigate Mitochondrial Disorders in Progressive Adult-onset Undetermined Ataxias?

2020 ◽  
Author(s):  
José Luiz Pedroso ◽  
Wladimir B Rezende Pinto ◽  
Orlando G Barsottini ◽  
Acary S B Oliveira
Keyword(s):  
Mitochondrial Dna ◽  
Exome Sequencing ◽  
Whole Exome Sequencing ◽  
Muscle Biopsy ◽  
Nuclear Dna ◽  
Late Onset ◽  
Mitochondrial Disorders ◽  
Adult Onset ◽  
Whole Exome ◽  
Merrf Syndrome

Abstract Background: Despite the broad development of next-generation sequencing approaches recently, such as whole-exome sequencing, diagnostic workup of adult-onset progressive cerebellar ataxias without remarkable family history and with negative genetic panel testing for SCAs remains a complex and expensive clinical challenge. Case presentation: In this article, we report a Brazilian man with adult-onset slowly progressive pure cerebellar ataxia, which developed neuropathy and hearing loss after fifteen years of ataxia onset, in which a primary mitochondrial DNA defect (MERRF syndrome - myoclonus epilepsy with ragged-red fibers) was confirmed through muscle biopsy evaluation and whole-exome sequencing. Conclusions: Mitochondrial disorders are a clinically and genetically complex and heterogenous group of metabolic diseases, resulting from pathogenic variants in the mitochondrial DNA or nuclear DNA. In our case, a correlation with histopathological changes identified on muscle biopsy helped to clarify the definitive diagnosis. Moreover, in neurodegenerative and neurogenetic disorders, some symptoms may be evinced later during disease course. We suggest that late-onset and adult pure undetermined ataxias should be considered and investigated for mitochondrial disorders, particularly MERRF syndrome and other primary mitochondrial DNA defects, together with other more commonly known nuclear genes.

scholarly journals A novel recessive mutation affecting DNAJB6a causes myofibrillar myopathy

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Fang-Yuan Qian ◽  
Yu-Dong Guo ◽  
Juan Zu ◽  
Jin-Hua Zhang ◽  
Yi-Ming Zheng ◽  
...  
Keyword(s):  
Late Onset ◽  
Novel Mutation ◽  
Recessive Mutation ◽  
Chinese Family ◽  
The Novel ◽  
Myofibrillar Myopathy ◽  
Protein Levels ◽  
Aggregation Effect

AbstractMutations in the DNAJB6 gene have been identified as rare causes of myofibrillar myopathies. However, the underlying pathophysiologica mechanisms remain elusive. DNAJB6 has two known isoforms, including the nuclear isoform DNAJB6a and the cytoplasmic isoform DNAJB6b, which was thought to be the pathogenic isoform. Here, we report a novel recessive mutation c.695_699del (p. Val 232 Gly fs*7) in the DNAJB6 gene, associated with an apparently recessively inherited late onset distal myofibrillar myopathy in a Chinese family. Notably, the novel mutation localizes to exon 9 and uniquely encodes DNAJB6a. We further identified that this mutation decreases the mRNA and protein levels of DNAJB6a and results in an age-dependent recessive toxic effect on skeletal muscle in knock-in mice. Moreover, the mutant DNAJB6a showed a dose-dependent anti-aggregation effect on polyglutamine-containing proteins in vitro. Taking together, these findings reveal the pathogenic role of DNAJB6a insufficiency in myofibrillar myopathies and expand upon the molecular spectrum of DNAJB6 mutations.

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