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Oxidative Medicine and Cellular... 2017Myoclonus epilepsy associated with ragged-red fibers (MERRF) is a maternally inherited mitochondrial disease affecting neuromuscular functions. Mt.8344A>G mutation in...
Myoclonus epilepsy associated with ragged-red fibers (MERRF) is a maternally inherited mitochondrial disease affecting neuromuscular functions. Mt.8344A>G mutation in mitochondrial DNA (mtDNA) is the most common cause of MERRF syndrome and has been linked to an increase in reactive oxygen species (ROS) level and oxidative stress, as well as impaired mitochondrial bioenergetics. Here, we tested whether WJMSC has therapeutic potential for the treatment of MERRF syndrome through the transfer of mitochondria. The MERRF cybrid cells exhibited a high mt.8344A>G mutation ratio, enhanced ROS level and oxidative damage, impaired mitochondrial bioenergetics, defected mitochondria-dependent viability, exhibited an imbalance of mitochondrial dynamics, and are susceptible to apoptotic stress. Coculture experiments revealed that mitochondria were intercellularly conducted from the WJMSC to the MERRF cybrid. Furthermore, WJMSC transferred mitochondria exclusively to cells with defective mitochondria but not to cells with normal mitochondria. MERRF cybrid following WJMSC coculture (MF+WJ) demonstrated improvement of mt.8344A>G mutation ratio, ROS level, oxidative damage, mitochondrial bioenergetics, mitochondria-dependent viability, balance of mitochondrial dynamics, and resistance against apoptotic stress. WJMSC-derived mitochondrial transfer and its therapeutic effect were noted to be blocked by F-actin depolymerizing agent cytochalasin B. Collectively, the WJMSC ability to rescue cells with defective mitochondrial function through donating healthy mitochondria may lead to new insights into the development of more efficient strategies to treat diseases related to mitochondrial dysfunction.
Topics: Cells, Cultured; Energy Metabolism; Humans; MERRF Syndrome; Mesenchymal Stem Cells; Mitochondria; Wharton Jelly
PubMed: 28607632
DOI: 10.1155/2017/5691215 -
Stem Cell Research Nov 2016Human iPSC line iMERRF-C7 was generated from PBMCs of a patient with mitochondrial disorder MERRF. Using Sendai virus, the reprogramming factors Oct3/4, Sox2, Klf4, and...
Human iPSC line iMERRF-C7 was generated from PBMCs of a patient with mitochondrial disorder MERRF. Using Sendai virus, the reprogramming factors Oct3/4, Sox2, Klf4, and cMyc were delivered non-integratively. The resulting iPSCs expressed pluripotency markers, could differentiate into the three germ layers in vivo, had normal genomic structure, and retained the disease-causing m.8344 mutation with similar heteroplasmic level.
Topics: Animals; Base Sequence; Cell Line; Cellular Reprogramming; Female; Genetic Loci; Genetic Vectors; Humans; Induced Pluripotent Stem Cells; Karyotype; Kruppel-Like Factor 4; Leukocytes, Mononuclear; MERRF Syndrome; Mice; Mice, Inbred NOD; Mice, SCID; Microscopy, Fluorescence; Polymorphism, Single Nucleotide; Sendai virus; Sequence Analysis, DNA; Teratoma; Transcription Factors
PubMed: 27934592
DOI: 10.1016/j.scr.2016.11.008 -
Scientific Reports Mar 2016Myoclonus epilepsy associated with ragged-red fibers (MERRF) is a mitochondrial disorder characterized by myoclonus epilepsy, generalized seizures, ataxia and myopathy....
Myoclonus epilepsy associated with ragged-red fibers (MERRF) is a mitochondrial disorder characterized by myoclonus epilepsy, generalized seizures, ataxia and myopathy. MERRF syndrome is primarily due to an A to G mutation at mtDNA 8344 that disrupts the mitochondrial gene for tRNA(Lys). However, the detailed mechanism by which this tRNA(Lys) mutation causes mitochondrial dysfunction in cardiomyocytes or neurons remains unclear. In this study, we generated human induced pluripotent stem cells (hiPSCs) that carry the A8344G genetic mutation from patients with MERRF syndrome. Compared with mutation-free isogenic hiPSCs, MERRF-specific hiPSCs (MERRF-hiPSCs) exhibited reduced oxygen consumption, elevated reactive oxygen species (ROS) production, reduced growth, and fragmented mitochondrial morphology. We sought to investigate the induction ability and mitochondrial function of cardiomyocyte-like cells differentiated from MERRF-hiPSCs. Our data demonstrate that that cardiomyocyte-like cells (MERRF-CMs) or neural progenitor cells (MERRF-NPCs) differentiated from MERRF-iPSCs also exhibited increased ROS levels and altered antioxidant gene expression. Furthermore, MERRF-CMs or -NPCs contained fragmented mitochondria, as evidenced by MitoTracker Red staining and transmission electron microscopy. Taken together, these findings showed that MERRF-hiPSCs and MERRF-CM or -NPC harboring the A8344G genetic mutation displayed contained mitochondria with an abnormal ultrastructure, produced increased ROS levels, and expressed upregulated antioxidant genes.
Topics: Adolescent; Cell Dedifferentiation; Cell Differentiation; Cells, Cultured; DNA, Mitochondrial; Female; Humans; Induced Pluripotent Stem Cells; MERRF Syndrome; Mitochondria, Heart; Myocytes, Cardiac; Organelle Shape; Oxygen Consumption; Point Mutation; Reactive Oxygen Species
PubMed: 27025901
DOI: 10.1038/srep23661 -
Molecular Genetics and Metabolism... Mar 2016m.3291T > C mutation in the MT-TL1 gene has been infrequently encountered in association with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like...
m.3291T > C mutation in the MT-TL1 gene has been infrequently encountered in association with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), however remains poorly characterized from a clinical perspective. In the following report we describe in detail the phenotypic features, long term follow up (> 7 years) and management in a Caucasian family with MELAS due to the m.3291T > C mutation and review the literature on m.3291T > C mutation. The clinical phenotype in the proposita included overlapping features of MELAS, MERRF (Myoclonic epilepsy and ragged-red fiber syndrome), MNGIE (Mitochondrial neurogastrointestinal encephalopathy), KSS (Kearns-Sayre Syndrome) and CPEO (Chronic progressive external ophthalmoplegia).
PubMed: 27014580
DOI: 10.1016/j.ymgmr.2016.02.003 -
Human Molecular Genetics Mar 2016Mutations in mitochondrial (mt) genes coding for mt-tRNAs are responsible for a range of syndromes, for which no effective treatment is available. We recently showed...
Mutations in mitochondrial (mt) genes coding for mt-tRNAs are responsible for a range of syndromes, for which no effective treatment is available. We recently showed that the carboxy-terminal domain (Cterm) of human mt-leucyl tRNA synthetase rescues the pathologic phenotype associated either with the m.3243A>G mutation in mt-tRNA(Leu(UUR)) or with mutations in the mt-tRNA(Ile), both of which are aminoacylated by Class I mt-aminoacyl-tRNA synthetases (mt-aaRSs). Here we show, by using the human transmitochondrial cybrid model, that the Cterm is also able to improve the phenotype caused by the m.8344A>G mutation in mt-tRNA(Lys), aminoacylated by a Class II aaRS. Importantly, we demonstrate that the same rescuing ability is retained by two Cterm-derived short peptides, β30_31 and β32_33, which are effective towards both the m.8344A>G and the m.3243A>G mutations. Furthermore, we provide in vitro evidence that these peptides bind with high affinity wild-type and mutant human mt-tRNA(Leu(UUR)) and mt-tRNA(Lys), and stabilize mutant mt-tRNA(Leu(UUR)). In conclusion, we demonstrate that small Cterm-derived peptides can be effective tools to rescue cellular defects caused by mutations in a wide range of mt-tRNAs.
Topics: Amino Acid Sequence; Amino Acyl-tRNA Synthetases; Apoptosis; Cell Line, Tumor; Cell Proliferation; Gene Expression; Humans; MELAS Syndrome; MERRF Syndrome; Mitochondria; Models, Molecular; Molecular Sequence Data; Osteoblasts; Peptides; Phenotype; Point Mutation; Protein Domains; Protein Structure, Secondary; RNA, Transfer, Leu; RNA, Transfer, Lys; Sequence Alignment
PubMed: 26721932
DOI: 10.1093/hmg/ddv619 -
Beijing Da Xue Xue Bao. Yi Xue Ban =... Dec 2015To demonstrate the clinical manifestation, diagnosis and treatment of myoclonus epilepsy with ragged-red-fibers (MERRF), a case of MERRF was presented with review of the... (Review)
Review
To demonstrate the clinical manifestation, diagnosis and treatment of myoclonus epilepsy with ragged-red-fibers (MERRF), a case of MERRF was presented with review of the literature. A 4-year-7-month-old girl was diagnosed with MERRF. She had tremor, fatigue and developmental delay for more than 2 years. Laboratory tests showed that the serum and urine lactic acid and pyruvic acid increased significantly. Electroencephalogram showed diffuse and focal spike slow wave and slow wave in right central and parietal regions. Electromyogram showed neurological damage. Gene mutational analysis showed mtDNA 8344 A>G mutation. The mutational rate was 78%. Mitochondrial disease MERRF syndrome was diagnosed. Cocktails therapy with vitamins B1, B6, B12, L-carnitine, and coenzyme Q10 was administrated to the patient. MERRF is a rare disease. The diagnosis can be made by gene mutational analysis. Cocktail therapy may slow down the deterioration of the disease. Gene therapy is still experimental.
Topics: Child, Preschool; DNA, Mitochondrial; Electroencephalography; Electromyography; Female; Humans; MERRF Syndrome; Mutation
PubMed: 26679672
DOI: No ID Found -
Molecular Therapy : the Journal of the... Oct 2015We have designed mitochondrially targeted transcription activator-like effector nucleases or mitoTALENs to cleave specific sequences in the mitochondrial DNA (mtDNA)...
We have designed mitochondrially targeted transcription activator-like effector nucleases or mitoTALENs to cleave specific sequences in the mitochondrial DNA (mtDNA) with the goal of eliminating mtDNA carrying pathogenic point mutations. To test the generality of the approach, we designed mitoTALENs to target two relatively common pathogenic mtDNA point mutations associated with mitochondrial diseases: the m.8344A>G tRNA(Lys) gene mutation associated with myoclonic epilepsy with ragged red fibers (MERRF) and the m.13513G>A ND5 mutation associated with MELAS/Leigh syndrome. Transmitochondrial cybrid cells harbouring the respective heteroplasmic mtDNA mutations were transfected with the respective mitoTALEN and analyzed after different time periods. MitoTALENs efficiently reduced the levels of the targeted pathogenic mtDNAs in the respective cell lines. Functional assays showed that cells with heteroplasmic mutant mtDNA were able to recover respiratory capacity and oxidative phosphorylation enzymes activity after transfection with the mitoTALEN. To improve the design in the context of the low complexity of mtDNA, we designed shorter versions of the mitoTALEN specific for the MERRF m.8344A>G mutation. These shorter mitoTALENs also eliminated the mutant mtDNA. These reductions in size will improve our ability to package these large sequences into viral vectors, bringing the use of these genetic tools closer to clinical trials.
Topics: Animals; Cell Line; DNA, Mitochondrial; Deoxyribonucleases; Electron Transport Complex I; Gene Dosage; Gene Expression; Gene Order; Genetic Therapy; Genetic Vectors; Humans; Hydrolysis; Mitochondria; Mitochondrial Diseases; Mitochondrial Proteins; Mutation; Oxidative Phosphorylation; Point Mutation; Protein Transport; Transcription Factors
PubMed: 26159306
DOI: 10.1038/mt.2015.126 -
Journal of Postgraduate Medicine 2015Mitochondrial diseases have a special predilection to involve the brain in view of its high metabolic demand and the tendency for the formation of excitatory...
Mitochondrial diseases have a special predilection to involve the brain in view of its high metabolic demand and the tendency for the formation of excitatory neurotransmitters when there is deficiency of intracellular ATP. These diseases have a great phenotypic variation and need a high degree of suspicion. However, some specific syndromes are well defined, both genotypically and phenotypically. Some of the drugs are potentially fatal mitochondrial poisons and an insight into that may be lifesaving as well as prevent serious morbidities.We report a typical case of myoclonic epilepsy with ragged red fibers (MERRF) with classical phenotype and genotype. There was rapid multiaxial deterioration with the introduction of sodium valproate which partly reversed on introducing mitochondrial cocktail and withdrawal of the offending drug.Sodium valproate, phenobarbitone, chloramphenicol and many anti-viral agents are mitochondrial poisons that increase the morbidity and mortality in patients with mitochondrial disease. More harm to the patient can be avoided with insight into this information.
Topics: Adolescent; Drug Therapy, Combination; Epilepsies, Myoclonic; Female; Humans; MERRF Syndrome; Mitochondria; Mitochondrial Diseases
PubMed: 26119441
DOI: 10.4103/0022-3859.150905 -
Free Radical Biology & Medicine Nov 2015Mitochondria are a source of reactive oxygen species (ROS). Mitochondrial diseases are the result of inherited defects in mitochondrially expressed genes. One potential... (Review)
Review
Mitochondria are a source of reactive oxygen species (ROS). Mitochondrial diseases are the result of inherited defects in mitochondrially expressed genes. One potential pathomechanism for mitochondrial disease is oxidative stress. Oxidative stress can occur as the result of increased ROS production or decreased ROS protection. The role of oxidative stress in the five most common inherited mitochondrial diseases, Friedreich ataxia, LHON, MELAS, MERRF, and Leigh syndrome (LS), is discussed. Published reports of oxidative stress involvement in the pathomechanisms of these five mitochondrial diseases are reviewed. The strongest evidence for an oxidative stress pathomechanism among the five diseases was for Friedreich ataxia. In addition, a meta-analysis was carried out to provide an unbiased evaluation of the role of oxidative stress in the five diseases, by searching for "oxidative stress" citation count frequency for each disease. Of the five most common mitochondrial diseases, the strongest support for oxidative stress is for Friedreich ataxia (6.42%), followed by LHON (2.45%), MELAS (2.18%), MERRF (1.71%), and LS (1.03%). The increased frequency of oxidative stress citations was significant relative to the mean of the total pool of five diseases (p<0.01) and the mean of the four non-Friedreich diseases (p<0.0001). Thus there is support for oxidative stress in all five most common mitochondrial diseases, but the strongest, significant support is for Friedreich ataxia.
Topics: Humans; Mitochondrial Diseases; Oxidative Stress; Reactive Oxygen Species
PubMed: 26073122
DOI: 10.1016/j.freeradbiomed.2015.05.039 -
Journal of Cardiovascular Magnetic... May 2015Mitochondrial myopathies (MM) are a heterogeneous group of inherited conditions resulting from a primary defect in the mitochondrial respiratory chain with consecutively... (Comparative Study)
Comparative Study
Characteristic cardiac phenotypes are detected by cardiovascular magnetic resonance in patients with different clinical phenotypes and genotypes of mitochondrial myopathy.
BACKGROUND
Mitochondrial myopathies (MM) are a heterogeneous group of inherited conditions resulting from a primary defect in the mitochondrial respiratory chain with consecutively impaired cellular energy metabolism. Small sized studies using mainly electrocardiography (ECG) and echocardiography have revealed cardiac abnormalities ranging from conduction abnormalities and arrhythmias to hypertrophic or dilated cardiomyopathy in these patients. Recently, characteristic patterns of cardiac involvement were documented by cardiovascular magnetic resonance (CMR) in patients with chronic progressive external ophthalmoplegia (CPEO)/Kearns-Sayre syndrome (KSS) and with mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS). The present study aimed to characterize the prevalence and pattern of cardiac abnormalities and to test the additional diagnostic value of CMR in this patient population. The hypothesis that different neuromuscular MM syndromes present with different cardiac disease phenotypes was evaluated.
METHODS
Sixty-four MM patients (50 ± 15 years, 44% male) and 25 matched controls (52 ± 14 years, 36% male) prospectively underwent cardiac evaluations including CMR (comprising cine- and late-gadolinium-enhancement (LGE) imaging). Based on the neuromuscular phenotype and genotype, the patients were grouped: (a) CPEO/KSS (N = 33); (b) MELAS/-like (N = 11); c) myoclonic epilepsy with ragged-red fibers (MERRF) (N = 3) and d) other non-specific MM forms (N = 17).
RESULTS
Among the 64 MM patients, 34 (53%) had at least one abnormal CMR finding: 18 (28%) demonstrated an impaired left ventricular ejection-fraction (LV-EF <60%), 14 (22%) had unexplained LV hypertrophy and 21 (33%) were LGE-positive. Compared to controls, MM patients showed significantly higher maximal wall thickness (10 ± 3 vs. 8 ± 2 mm, p = 0.005) and concentricity (LV mass to end-diastolic volume: 0.84 ± 0.27 vs. 0.67 ± 0.11, p < 0.0001) with frequent presence of non-ischemic LGE (30% vs. 0%, p = 0.001). CPEO/KSS showed a predominantly intramural pattern of LGE mostly confined to the basal LV inferolateral wall (8/10; 80%) in addition to a tendency toward concentric remodelling. MELAS/-like patients showed the highest frequency of cardiac disease (in 10/11 (91%)), a mostly concentric LV hypertrophy (6/9; 67%) with or without LV systolic dysfunction and a predominantly focal, patchy LGE equally distributed among LV segments (8/11; 73%). Patients with MERRF and non-specific MM had no particular findings. Pathological CMR findings indicating cardiac involvement were detected significantly more often than pathological ECG results or elevated cardiac serum biomarkers (34 (53%) vs. 18 (28%) vs. 21 (33%); p = 0.008).
CONCLUSION
Cardiac involvement is a frequent finding in MM patients - and particularly present in KSS/CPEO as well as MELAS/-like patients. Despite a high variability in clinical presentation, CPEO/KSS patients typically show an intramural pattern of LGE in the basal inferolateral wall whereas MELAS patients are characterized by overt concentric hypertrophy and a rather unique, focally accentuated and diffusely distributed LGE.
Topics: Adult; Aged; Cardiomyopathies; Case-Control Studies; Female; Genetic Predisposition to Disease; Germany; Humans; Hypertrophy, Left Ventricular; Kearns-Sayre Syndrome; MELAS Syndrome; MERRF Syndrome; Magnetic Resonance Imaging; Male; Middle Aged; Mitochondrial Myopathies; Myocardium; Ophthalmoplegia, Chronic Progressive External; Phenotype; Predictive Value of Tests; Prevalence; Prospective Studies; Stroke Volume; Ventricular Function, Left; Ventricular Remodeling
PubMed: 26001801
DOI: 10.1186/s12968-015-0145-x