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International Journal of Molecular... Jun 2018The protein toxin cytotoxic necrotizing factor 1 (CNF1), which acts on the Rho GTPases that are key regulators of the actin cytoskeleton, is emerging as a potential...
The protein toxin cytotoxic necrotizing factor 1 (CNF1), which acts on the Rho GTPases that are key regulators of the actin cytoskeleton, is emerging as a potential therapeutic tool against certain neurological diseases characterized by cellular energy homeostasis impairment. In this brief communication, we show explorative results on the toxin’s effect on fibroblasts derived from a patient affected by myoclonic epilepsy with ragged-red fibers (MERRF) that carries a mutation in the m.8344A>G gene of mitochondrial DNA. We found that, in the patient’s cells, besides rescuing the wild-type-like mitochondrial morphology, CNF1 administration is able to trigger a significant increase in cellular content of ATP and of the mitochondrial outer membrane marker Tom20. These results were accompanied by a profound F-actin reorganization in MERRF fibroblasts, which is a typical CNF1-induced effect on cell cytoskeleton. These results point at a possible role of the actin organization in preventing or limiting the cell damage due to mitochondrial impairment and at CNF1 treatment as a possible novel strategy against mitochondrial diseases still without cure.
Topics: Adenosine Triphosphate; Bacterial Toxins; DNA, Mitochondrial; Electron Transport Complex IV; Escherichia coli; Escherichia coli Proteins; Fibroblasts; Gene Expression; Humans; MERRF Syndrome; Male; Membrane Transport Proteins; Middle Aged; Mitochondria; Mitochondrial Precursor Protein Import Complex Proteins; Mutation; Pilot Projects; Primary Cell Culture; Receptors, Cell Surface; Stress Fibers
PubMed: 29933571
DOI: 10.3390/ijms19071825 -
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 -
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 -
Journal of Neurosciences in Rural... 2018This review aims at summarising and discussing the current status concerning the clinical presentation, pathogenesis, diagnosis, and treatment of spinal cord affection... (Review)
Review
This review aims at summarising and discussing the current status concerning the clinical presentation, pathogenesis, diagnosis, and treatment of spinal cord affection in mitochondrial disorders (MIDs). A literature search using the database Pubmed was carried out by application of appropriate search terms and their combinations. Involvement of the spinal cord in MIDs is more frequent than anticipated. It occurs in specific and non-specific MIDs. Among the specific MIDs it has been most frequently described in LBSL, LS, MERRF, KSS, IOSCA, MIRAS, and PCH and only rarely in MELAS, CPEO, and LHON. Clinically, spinal cord involvement manifests as monoparesis, paraparesis, quadruparesis, sensory disturbances, hypotonia, spasticity, urinary or defecation dysfunction, spinal column deformities, or as transverse syndrome. Diagnosing spinal cord involvement in MIDs requires a thoroughly taken history, clinical exam, and imaging studies. Additionally, transcranial magnetic stimulation, somato-sensory-evoked potentials, and cerebro-spinal fluid can be supportive. Treatment is generally not at variance compared to the underlying MID but occasionally surgical stabilisation of the spinal column may be necessary. It is concluded that spinal cord involvement in MIDs is more frequent than anticipated but may be missed if cerebral manifestations prevail. Spinal cord involvement in MIDs may strongly determine the mobility of these patients.
PubMed: 29725177
DOI: 10.4103/jnrp.jnrp_446_17 -
Revista de Neurologia Apr 2018The differential diagnosis of diseases that are accompanied by adult-onset girdle weakness is broad and includes motor neurone, neuromuscular junction or muscular...
INTRODUCTION
The differential diagnosis of diseases that are accompanied by adult-onset girdle weakness is broad and includes motor neurone, neuromuscular junction or muscular diseases. The 8344A>G mutation of the MTTK gene of mitochondrial DNA usually presents with involvement of multiple organs associated (or not) with girdle weakness. To date no cases of isolated girdle weakness have been reported as the presenting symptom of this mutation.
CASE REPORT
A 57-year-old male, with a four-year history of isolated clinical signs of progressive girdle weakness. He is the brother of a 59-year-old woman with the same clinical features. Muscular biopsy played a decisive role in the diagnosis and was characteristic of mitochondrial myopathy. The genetic analysis revealed the 8344A>G mutation of the MTTK gene of mitochondrial DNA.
CONCLUSIONS
The 8344A>G mutation of mitochondrial DNA can be associated with clinical signs and symptoms of adult-onset girdle weakness, and must therefore be included as part of its differential diagnosis.
Topics: Age of Onset; DNA, Mitochondrial; Diagnosis, Differential; Genetic Association Studies; Humans; MERRF Syndrome; Magnetic Resonance Imaging; Male; Middle Aged; Muscle Weakness; Muscle, Skeletal; Mutation, Missense; Phenotype; Point Mutation; RNA, Transfer, Lys
PubMed: 29645070
DOI: No ID Found -
Journal of Pediatric Genetics Mar 2018Congenital hearing loss is one of the most common birth defects worldwide, with around 1 in 500 people experiencing some form of severe hearing loss. While over 400... (Review)
Review
Congenital hearing loss is one of the most common birth defects worldwide, with around 1 in 500 people experiencing some form of severe hearing loss. While over 400 different syndromes involving hearing loss have been described, it is important to be familiar with a wide range of syndromes involving hearing loss so an early diagnosis can be made and early intervention can be pursued to maximize functional hearing and speech-language development in the setting of verbal communication. This review aims to describe the presentation and genetics for some of the most frequently occurring syndromes involving hearing loss, including neurofibromatosis type 2, branchio-oto-renal syndrome, Treacher Collins syndrome, Stickler syndrome, Waardenburg syndrome, Pendred syndrome, Jervell and Lange-Nielsen syndrome, Usher syndromes, Refsum disease, Alport syndrome, MELAS, and MERRF.
PubMed: 29441214
DOI: 10.1055/s-0037-1617454 -
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 -
Frontiers in Neurology 2017Myoclonus epilepsy with ragged-red fibers (MERRFs), an inherited mitochondrial disorder, has characteristic morphological changes of ragged-red fibers (RRFs) in muscle...
Myoclonus epilepsy with ragged-red fibers (MERRFs), an inherited mitochondrial disorder, has characteristic morphological changes of ragged-red fibers (RRFs) in muscle biopsy, in the absence of which mitochondrial etiology is usually not considered in patients with phenotypes suggestive of MERRF. In these circumstances, MERRF can only be diagnosed using genetic analyses. The symptoms, pathological findings, and imaging results being age dependent, we can construct a protocol based on these characteristics to understand the disease's natural course and to manage patients more effectively. The absence of RRFs should not preclude a MERRF diagnosis.
PubMed: 29033892
DOI: 10.3389/fneur.2017.00520 -
Seizure Aug 2017Myoclonic epilepsy with ragged-red fibers (MERRF) syndrome is a rare syndromic mitochondrial disorder (MID) with a broad phenotypic but narrow genotypic heterogeneity.... (Review)
Review
Myoclonic epilepsy with ragged-red fibers (MERRF) syndrome is a rare syndromic mitochondrial disorder (MID) with a broad phenotypic but narrow genotypic heterogeneity. One of the predominant phenotypic features in addition to myopathy is epilepsy. The most frequent seizure type in MERRF is generalised myoclonic seizure but also focal myoclonic, focal atonic, generalised tonic-clonic, generalised atonic, generalised myoclonic-atonic, typical absences, or tonic-clonic seizures of unknown onset have been reported. There are no guidelines available for the management of epilepsy in MERRF syndrome but several expert opinions and general recommendations for the treatment of mitochondrial epilepsy have been published. According to these recommendations the antiepileptic drugs (AEDs) of choice are levetiracetam, topiramate, zonisamide, piracetam, and benzodiazepines. Perampanel has not been applied in MERRF patients but is promising in non-mitochondrial myoclonic epilepsy. Mitochondrion-toxic agents, including mitochondrion-toxic AEDs, such as valproate, carbamazepine, phenytoin, and barbiturates, should be avoided as well as AEDs potentially enhancing the frequency of myoclonus, such as phenytoin, carbamazepine, lamotrigine, vigabatrin, tiagabine, gabapentin, pregabalin, and oxcarbazepine.
Topics: Anticonvulsants; Epilepsy; Humans; MERRF Syndrome
PubMed: 28686997
DOI: 10.1016/j.seizure.2017.06.010 -
BMJ Case Reports Jun 2017Madelung's disease (benign symmetric lipomatosis) is a rare syndrome in which there are multiple lipomas around the neck, upper limbs and trunk in the context of chronic...
Madelung's disease (benign symmetric lipomatosis) is a rare syndrome in which there are multiple lipomas around the neck, upper limbs and trunk in the context of chronic alcoholism. We report on a female patient with lipomas and slightly progressive myoclonus, neuropathy, myopathy, ataxia and respiratory systemic involvement (labelled in the past as Madelung's disease). Multisystem involvement and family history of lipomas led to the development of mitochondrial genetic tests, which can assess two concurrent mitochondrial mutations: the m.8344A>G mutation in MT-TK gene, related MERRF (myoclonic epilepsy with ragged-red fibre) phenotype and m.14484T>C mutation in the MT-ND6 gene responsible for Leber hereditary optic neuropathy phenotype.
Topics: Ataxia; Female; Gait; Humans; Lipoma; Lipomatosis, Multiple Symmetrical; MERRF Syndrome; Middle Aged; Mitochondria; Mitochondrial Diseases; Movement Disorders; Mutation; Myoclonus; NADH Dehydrogenase; Neck; Outcome Assessment, Health Care; Phenotype; Rare Diseases
PubMed: 28630220
DOI: 10.1136/bcr-2016-218861