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BMJ Case Reports Mar 2021We present a rare case of myoclonic epilepsy with ragged red fibres with high level of heteroplasmy presenting with optic neuropathy and a rare phenotype of lipomatosis....
We present a rare case of myoclonic epilepsy with ragged red fibres with high level of heteroplasmy presenting with optic neuropathy and a rare phenotype of lipomatosis. Cutaneous lipomas are typically thought of as a benign/isolated entity and this case emphasises importance of considering mitochondrial disease in all patients with lipomatosis especially in the presence of other systemic abnormalities.
Topics: DNA, Mitochondrial; Humans; Lipomatosis; Lipomatosis, Multiple Symmetrical; MERRF Syndrome; Mutation; Optic Nerve Diseases
PubMed: 33766967
DOI: 10.1136/bcr-2020-240463 -
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 -
Nature Communications May 2018It has been generally thought that tRNA modifications are stable and static, and their frequencies are rarely regulated. N-threonylcarbamoyladenosine (tA) occurs at...
It has been generally thought that tRNA modifications are stable and static, and their frequencies are rarely regulated. N-threonylcarbamoyladenosine (tA) occurs at position 37 of five mitochondrial (mt-)tRNA species. We show that YRDC and OSGEPL1 are responsible for tA37 formation, utilizing L-threonine, ATP, and CO/bicarbonate as substrates. OSGEPL1-knockout cells exhibit respiratory defects and reduced mitochondrial translation. We find low level of tA37 in mutant mt-tRNA isolated from the MERRF-like patient's cells, indicating that lack of tA37 results in pathological consequences. Kinetic measurements of tA37 formation reveal that the Km value of CO/bicarbonate is extremely high (31 mM), suggesting that CO/bicarbonate is a rate-limiting factor for tA37 formation. Consistent with this, we observe a low frequency of tA37 in mt-tRNAs isolated from human cells cultured without bicarbonate. These findings indicate that tA37 is regulated by sensing intracellular CO/bicarbonate concentration, implying that mitochondrial translation is modulated in a codon-specific manner under physiological conditions.
Topics: Adenosine; Apoptosis Regulatory Proteins; Base Pairing; Bicarbonates; CRISPR-Cas Systems; Carbon Dioxide; Cell Line; Cell Respiration; Fibroblasts; GTP-Binding Proteins; Gene Deletion; HEK293 Cells; HT29 Cells; HeLa Cells; Humans; MERRF Syndrome; Mitochondria; Models, Biological; Myoblasts; Nucleic Acid Conformation; Proteins; RNA Processing, Post-Transcriptional; RNA, Transfer; RNA-Binding Proteins
PubMed: 29760464
DOI: 10.1038/s41467-018-04250-4 -
Frontiers in Neurology 2019Lipomas have often been associated with mtDNA mutations and were mainly observed in patients with mutation in mitochondrial tRNAlysine which is also the most frequent...
Lipomas have often been associated with mtDNA mutations and were mainly observed in patients with mutation in mitochondrial tRNAlysine which is also the most frequent mutation associated with MERRF. Up to date, no systematic studies have been developed in order to assess the incidence of lipomas in large cohorts of mitochondrial patients.The aim of this study is to analyze the incidence and characteristics of lipomas among an Italian cohort of patients with mitochondrial diseases. A retrospective, database-based study (Nation-wide Italian Collaborative Network of Mitochondrial Diseases) of patients with lipomas was performed. A total of 22 (1.7%) patients with lipomas have been identified among the 1,300 mitochondrial patients, enrolled in the Italian database. In about 18% multiple systemic lipomatosis (MSL) was the only clinical manifestation; 54% of patients showed a classical MERRF syndrome. Myopathy, alone or in association with other symptoms, was found in 27% of patients. Lactate was elevated in all the 12 patients in which was measured. Muscle biopsy was available in 18/22 patients: in all of them mitochondrial abnormalities were present. Eighty six percent had mutations in mtDNA coding for tRNA lysine. In most of patients, lipomas were localized along the cervical-cranial-thoracic region. In 68% of the patients were distributed symmetrically. Only two patients had lipomas in a single anatomical site (1 in right arm and 1 in gluteus maximum). MSL is often overlooked by clinicians in patients with mitochondrial diseases where the clinical picture could be dominated by a severe multi-systemic involvement. Our data confirmed that MSL is a rare sign of mitochondrial disease with a strong association between multiple lipomas and lysine tRNA mutations. MSL could be considered, even if rare, a red flag for mitochondrial disorders, even in patients with an apparently isolated MSL.
PubMed: 30873109
DOI: 10.3389/fneur.2019.00160 -
Cell Death & Disease Apr 2018Degeneration or loss of inner ear hair cells (HCs) is irreversible and results in sensorineural hearing loss (SHL). Human-induced pluripotent stem cells (hiPSCs) have...
ATOH1/RFX1/RFX3 transcription factors facilitate the differentiation and characterisation of inner ear hair cell-like cells from patient-specific induced pluripotent stem cells harbouring A8344G mutation of mitochondrial DNA.
Degeneration or loss of inner ear hair cells (HCs) is irreversible and results in sensorineural hearing loss (SHL). Human-induced pluripotent stem cells (hiPSCs) have been employed in disease modelling and cell therapy. Here, we propose a transcription factor (TF)-driven approach using ATOH1 and regulatory factor of x-box (RFX) genes to generate HC-like cells from hiPSCs. Our results suggest that ATOH1/RFX1/RFX3 could significantly increase the differentiation capacity of iPSCs into MYO7A-positive cells, upregulate the mRNA expression levels of HC-related genes and promote the differentiation of HCs with more mature stereociliary bundles. To model the molecular and stereociliary structural changes involved in HC dysfunction in SHL, we further used ATOH1/RFX1/RFX3 to differentiate HC-like cells from the iPSCs from patients with myoclonus epilepsy associated with ragged-red fibres (MERRF) syndrome, which is caused by A8344G mutation of mitochondrial DNA (mtDNA), and characterised by myoclonus epilepsy, ataxia and SHL. Compared with isogenic iPSCs, MERRF-iPSCs possessed ~42-44% mtDNA with A8344G mutation and exhibited significantly elevated reactive oxygen species (ROS) production and CAT gene expression. Furthermore, MERRF-iPSC-differentiated HC-like cells exhibited significantly elevated ROS levels and MnSOD and CAT gene expression. These MERRF-HCs that had more single cilia with a shorter length could be observed only by using a non-TF method, but those with fewer stereociliary bundle-like protrusions than isogenic iPSCs-differentiated-HC-like cells could be further observed using ATOH1/RFX1/RFX3 TFs. We further analysed and compared the whole transcriptome of M1-HCs and M1-HCs after treatment with ATOH1 or ATOH1/RFX1/RFX3. We revealed that the HC-related gene transcripts in M1-iPSCs had a significantly higher tendency to be activated by ATOH1/RFX1/RFX3 than M1-iPSCs. The ATOH1/RFX1/RFX3 TF-driven approach for the differentiation of HC-like cells from iPSCs is an efficient and promising strategy for the disease modelling of SHL and can be employed in future therapeutic strategies to treat SHL patients.
Topics: Adolescent; Basic Helix-Loop-Helix Transcription Factors; Catalase; Cell Differentiation; Cilia; DNA, Mitochondrial; Embryoid Bodies; Female; Hair Cells, Auditory, Inner; Humans; Induced Pluripotent Stem Cells; MERRF Syndrome; Myosin VIIa; Point Mutation; Reactive Oxygen Species; Regulatory Factor X Transcription Factors; Regulatory Factor X1; Superoxide Dismutase
PubMed: 29740017
DOI: 10.1038/s41419-018-0488-y -
Child Neurology Open 2021In the field of mitochondrial medicine, correlation of clinical phenotype with mutation heteroplasmy remains an outstanding question with few, if any, clear thresholds...
In the field of mitochondrial medicine, correlation of clinical phenotype with mutation heteroplasmy remains an outstanding question with few, if any, clear thresholds corresponding to a given phenotype. The m.8344A>G mutation is most commonly associated with myoclonus epilepsy and ragged red fiber syndrome (MERRF) at varying levels of heteroplasmy. However, a handful of cases been previously reported in which individuals homoplasmic or nearly homoplasmic for this mutation in the blood have presented with multiple bulbar palsies, respiratory failure, and progressive neurologic decline almost uniformly following a respiratory illness. MRI brain in all affected individuals revealed symmetric T2 hyperintense lesions of subcortical gray matter structures, consistent with Leigh syndrome. Here, we present 3 cases with clinical, biochemical, and neuro-imaging findings with the additional reporting of spinal lesions. This new phenotype supports a heteroplasmy-dependent phenotype model for this mutation and recognition of this can help clinicians with diagnosis and anticipatory clinical guidance.
PubMed: 33718511
DOI: 10.1177/2329048X21991382 -
Stem Cell Research Mar 2018Mitochondrial defects are associated with clinical manifestations from common diseases to rare genetic disorders. Myoclonus epilepsy associated with ragged-red fibers...
Generation of an induced pluripotent stem cell (iPSC) line from a 40-year-old patient with the A8344G mutation of mitochondrial DNA and MERRF (myoclonic epilepsy with ragged red fibers) syndrome.
Mitochondrial defects are associated with clinical manifestations from common diseases to rare genetic disorders. Myoclonus epilepsy associated with ragged-red fibers (MERRF) syndrome results from an A to G transition at nucleotide position 8344 in the tRNA gene of mitochondrial DNA (mtDNA) and is characterized by myoclonus, myopathy and severe neurological symptoms. In this study, Sendai reprogramming method was used to generate an iPS cell line carrying the A8344G mutation of mtDNA from a MERRF patient. This patient-specific iPSC line expressed pluripotent stem cell markers, possessed normal karyotype, and displayed the capability to differentiate into mature cells in three germ layers.
Topics: Adult; Cells, Cultured; DNA, Mitochondrial; Female; Flow Cytometry; Humans; Induced Pluripotent Stem Cells; Karyotyping; MERRF Syndrome; Mutation
PubMed: 29288969
DOI: 10.1016/j.scr.2017.12.013 -
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 -
Nature Communications Sep 2018Post-transcriptional RNA modifications play a critical role in the pathogenesis of human mitochondrial disorders, but the mechanisms by which specific modifications...
Post-transcriptional RNA modifications play a critical role in the pathogenesis of human mitochondrial disorders, but the mechanisms by which specific modifications affect mitochondrial protein synthesis remain poorly understood. Here we used a quantitative RNA sequencing approach to investigate, at nucleotide resolution, the stoichiometry and methyl modifications of the entire mitochondrial tRNA pool, and establish the relevance to human disease. We discovered that a N-methyladenosine (mA) modification is missing at position 58 in the mitochondrial tRNA of patients with the mitochondrial DNA mutation m.8344 A > G associated with MERRF (myoclonus epilepsy, ragged-red fibers). By restoring the modification on the mitochondrial tRNA, we demonstrated the importance of the mA58 to translation elongation and the stability of selected nascent chains. Our data indicates regulation of post-transcriptional modifications on mitochondrial tRNAs is finely tuned for the control of mitochondrial gene expression. Collectively, our findings provide novel insight into the regulation of mitochondrial tRNAs and reveal greater complexity to the molecular pathogenesis of MERRF.
Topics: Base Sequence; HEK293 Cells; Humans; MERRF Syndrome; Mitochondria; Muscle, Skeletal; Myoblasts; Nucleic Acid Conformation; Protein Biosynthesis; RNA, Transfer, Lys
PubMed: 30262910
DOI: 10.1038/s41467-018-06471-z -
Stem Cell Research Jul 2018MERRF syndrome is predominantly caused by A8344G mutation in the mitochondrial DNA (mtDNA), affecting MT-TK gene, which impairs the mitochondrial electron transport...
MERRF syndrome is predominantly caused by A8344G mutation in the mitochondrial DNA (mtDNA), affecting MT-TK gene, which impairs the mitochondrial electron transport chain function. Here, we report the generation of two isogenic induced pluripotent stem cell (iPSC) lines, TVGH-iPSC-MRF-M and TVGH-iPSC-MRF-M, from the skin fibroblasts of a female MERRF patient harboring mtDNA A8344G mutation by using retrovirus transduction system. Both cell lines share the same genetic background except containing different proportions of mtDNA with the A8344G mutation. Both cell lines exhibited the pluripotency and capacity to differentiate into three germ layers.
Topics: Adolescent; Animals; DNA, Mitochondrial; Female; Humans; Induced Pluripotent Stem Cells; MERRF Syndrome; Mice; Mutation
PubMed: 29960149
DOI: 10.1016/j.scr.2018.05.011