Search

Mitochondrial DNA mutations, such as A3243G, can affect changes in the structure of biomolecules, resulting in changes in the structure of Leucine transfer Ribose Nucleic Acid to form a dimer. Dimer structure modeling is needed to determine the properties of the structure. However, the lack of a structure template for the transfer of Ribose Nucleic Acid (tRNA) is challenging for the modeling of mutant structures of tRNA, especially mitochondrial tRNA that are susceptible to mutation. Therefore, this study predicted the structure of mitochondrial leucine tRNA and its stability through a knowledge-based method and molecular dynamics. Structural modeling and initial assessment were performed using RNAComposer and MolProbity, HNADOCK, and Discovery studios to form the dimer structure. Molecular dynamics simulations for stability analysis were performed using Amber and AmberTools20 software, showing that the conformational energy of the mutant leucine tRNA dimer structure was lower than the native structure. Moreover, the Root Mean Square Deviation (RMSD) of monomer native leucine tRNA was lower than the mutant, indicating that the dimer structure of mutant leucine tRNA is more stable than usual, and the normal leucine tRNA is more stable than the mutant.

Among metabolic disorders, gestational diabetes mellitus (GDM) is specified as hyperglycemia caused by glucose or carbohydrate intolerance defects. GDM is distinguished by oxidative stress, and has been connected to mitochondrial dysfunction. Previous studies have documented the relation between A12026G, A8344G and A3243G mutations in ND4, tRNALeu(UUR), and tRNALys genes in different modes of diabetes. The purpose of this study was to investigate into the relationship between GDM women and common mitochondrial mutations including A12026, A8344G, and A3243G in Saudi women. In this case-control study, we have opted 96 GDM and 102 non-GDM pregnant women and DNA was extracted using EDTA blood and based on specific primers, Polymerase Chain Reaction was followed and then Restriction Fragment Length Polymorphism (RFLP) analysis was performed. Restriction enzymes was cross-checked with Lambda DNA and 10% of the purified PCR products were performed the Sanger sequencing analysis to reconfirm the RFLP analysis of the studied results. None of the heterozygous and homozygous mutations were not observed in our study. All the subjects were turned to be homozygous normal genotypes. This study confirms that A12026, A8344G, and A3243G mutations have no role in the Saudi women with GDM. [ABSTRACT FROM AUTHOR]

The article presents a case study of a 12 years old boy who was admitted to the hospital due to nephrotic syndrome. Topics discussed include diagnosing boy for cecal volvulus, performing abdominal X-ray and gastrografin enema with magnetic resonance imaging (MRI) and death of boy due to severe cardiopulmonary dysfunction.

In this study we scrutinized the association between the A8344G/A3243G mutations and a 9-bp deletion polymorphism with gestational diabetes mellitus (GDM) in an Asian Indian population. The A3243G mutation in the mitochondrial tRNA Leu(UUR) causes mitochondrial encephalopathy myopathy, lactic acidosis, and stroke-like episodes (MELAS), while the A8344G mutation in tRNA Lys causes myoclonus epilepsy with ragged red fibers (MERRF). We screened 140 pregnant women diagnosed with GDM and 140 non-GDM participants for these mutations by PCR-RFLP analysis. Both A3243G and A8344G were associated with GDM (A3243: OR-3.667, 95% CI = 1.001–13.43, p = 0.03; A8344G: OR-11.00, 95% CI = 0.6026–200.8, p = 0.04). Mitochondrial DNA mutations contribute to the development of GDM. Our results conclude that mitochondrial mutations are associated with the GDM women in our population. Thus it is important to screen other mitochondrial mutations in the GDM women. [ABSTRACT FROM AUTHOR]

Purpose: To report a case of maternally inherited diabetes and deafness complicated by branch retinal vein occlusion and cystoid macular edema. Methods: Retrospective case report. Multimodal imaging including spectral domain optical coherence tomography, en face optical coherence tomography, and fundus autofluorescence was preformed, and the findings are presented. Findings: A 58-year-old female with a history of diabetes mellitus, hearing loss, and a previous diagnosis of age-related macular degeneration presented with decreased vision in the right eye. Clinical examination and multimodal imaging demonstrated a right inferior branch retinal vein occlusion complicated by cystoid macular edema and bilateral maculopathy suspicious for maternally inherited diabetes and deafness. Genetic testing confirmed an A3243G mitochondrial mutation. Conclusion: Multimodal retinal imaging is a key to guide diagnosis of rare genetic diseases such as maternally inherited diabetes and deafness. We report the unusual presentation of maternally inherited diabetes and deafness complicated by branch retinal vein occlusion and cystoid macular edema. [ABSTRACT FROM AUTHOR]

Background The A3243G point mutation in mitochondrial DNA (mtDNA) is associated with MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) and MIDD syndromes (maternally inherited diabetes and deafness). Both MELAS and MIDD patients can present with visual symptoms due to a retinopathy, sometimes before the genetic diagnosis is made. Case presentation Patient 1: 46 year-old woman with diabetes mellitus and hearing loss was referred for an unspecified maculopathy detected during screening evaluation for diabetic retinopathy. Visual acuity was 20/20 in both eyes. Fundus examination showed bilateral macular and peripapillary hyperpigmented/depigmented areas. Patient 2: 45 year-old woman was referred for recent vision loss in her left eye. History was remarkable for chronic fatigue, migraine and diffuse muscular pain. Visual acuity was 20/20 in her right eye and 20/30 in her left eye. Fundus exhibited several nummular perifoveal islands of retinal pigment epithelium atrophy and adjacent pale deposits in both eyes. Retinal anatomy was investigated with autofluorescence, retinal angiography and optical coherence tomography. Retinal function was assessed with automated static perimetry, fullfield and multifocal electroretinography and electro-oculography. Genetic testing of mtDNA identified a point mutation at the locus 3243. Conclusion Observation of RPE abnormalities in the context of suggestive systemic findings should prompt mtDNA testing. [ABSTRACT FROM AUTHOR]

The m.3243A>G 'MELAS' (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes) mutation is one of the most common point mutations of the mitochondrial DNA, but its phenotypic variability is incompletely understood. The aim of this study was to revise the phenotypic spectrum associated with the mitochondrial m.3243A>G mutation in 126 Italian carriers of the mutation, by a retrospective, database-based study ('Nation-wide Italian Collaborative Network of Mitochondrial Diseases'). Our results confirmed the high clinical heterogeneity of the m.3243A>G mutation. Hearing loss and diabetes were the most frequent clinical features, followed by stroke-like episodes. 'MIDD' (maternally-inherited diabetes and deafness) and 'PEO' (progressive external ophthalmoplegia) are nosographic terms without any real prognostic value, because these patients may be even more prone to the development of multisystem complications such as stroke-like episodes and heart involvement. The 'MELAS' acronym is convincing and useful to denote patients with histological, biochemical and/or molecular evidence of mitochondrial disease who experience stroke-like episodes. Of note, we observed for the first time that male gender could represent a risk factor for the development of stroke-like episodes in Italian m.3243A>G carriers. Gender effect is not a new concept in mitochondrial medicine, but it has never been observed in MELAS. A better elucidation of the complex network linking mitochondrial dysfunction, apoptosis, estrogen effects and stroke-like episodes may hold therapeutic promises. [ABSTRACT FROM AUTHOR]

A mutation in mitochondrial DNA (mtDNA) A3243G is an important cause of some serious mitochondrial diseases, and maternal inheritance of the mutation has been reported. In order to investigate the heredity of the mutation, we measured the ratio of the mutated mtDNA molecule among 32 families of identical twins. Both twins from one family showed 20.16% and 18.49% mutated molecules, and the level is significantly high in comparison with members of other families and control subjects (0.23-0.86%). Their parents, however, showed normal level of mutated molecules (0.70% and 0.66%). The high-level mutation of the twins may be due to a spontaneous event, which occurred during development of germ line of their mother, or oogenesis of their mother, or during early stage of their development. [ABSTRACT FROM AUTHOR]

Knowledge on the molecular background of mitochondrial disorders has accumulated during the past two decades, but clinical and molecular features of mitochondrial cardiomyopathies (CMPs) are only starting to be characterized. We studied the detailed cardiologic phenotype of patients with adult-onset CMPs associated with mitochondrial DNA (mtDNA) mutations and their relatives, from three families. We identified a pathogenic T3258C point mutation of mtDNA tRNALeu(UUR) in an adult patient with mitochondrial myopathy and CMP, with acute manifestation of dyspnea and elevated plasma N-terminal pro-B-type natriuretic peptide concentration. Two other families with maternally segregated CMP, fatal in three patients, had the A3243G mutation in tRNALeu(UUR) of mtDNA. Many of the mutation carriers, even if oligosymptomatic, had concentric, non-obstructive hypertrophic CMP with diastolic dysfunction or restrictive hemodynamics, or depression of systolic function especially at times when patients had lactic acidosis. Atrial fibrillation led to manifest heart failure in four patients, fatal in one. In conclusion, tRNALeu(UUR) mutations in mtDNA may underlie mitochondrial non-obstructive, sometimes fatal, hypertrophic CMPs of adult age. Such CMPs are characterized by left ventricular hypertrophy and poor tolerance of atrial arrhythmias, often leading to rapidly deteriorating systolic function and heart failure. These patients benefit of rapid intervention of tachyarrhythmias. These patients may not have neurological symptoms, and may therefore remain underdiagnosed. Our observations emphasize that patients with tRNALeu(UUR) mutations need cardiologic evaluation and follow-up. tRNALeu(UUR) mutations should be screened of patients with hypertrophic CMP and metabolic acidosis, especially if atrial arrhythmia provoked cardiac decompensation. [ABSTRACT FROM AUTHOR]

Mitochondrion harbors its own DNA, known as mtDNA, encoding certain essential components of the mitochondrial respiratory chain and protein synthesis apparatus. mtDNA mutations have an impact on cellular ATP production and many of them are undoubtedly a factor that contributes to sensorineural deafness, including both syndromic and non-syndromic forms. Hot spot regions for deafness mutations are the MTRNR1 gene, encoding the 12S rRNA, the MTTS1 gene, encoding the tRNA for Ser^{(UCN)}, and the MTTL1 gene, encoding the tRNA for Leu^{(UUR)}. We investigated the impact of mtDNA mutations in the Greek hearing impaired population, by testing a cohort of 513 patients suffering from childhood onset prelingual or postlingual, bilateral, sensorineural, syndromic or non-syndromic hearing loss of any degree for six mitochondrial variants previously associated with deafness. Screening involved the MTRNR1 961delT/insC and A1555G mutations, the MTTL1 A3243G mutation, and the MTTS1 A7445G, 7472insC and T7510C mutations. Although two patients were tested positive for the A1555G mutation, we failed to identify any subject carrying the 961delT/insC, A3243G, A7445G, 7472insC, or T7510C mutations. Our findings strongly support our previously raised conclusion that mtDNA mutations are not a major risk factor for sensorineural deafness in the Greek population. [ABSTRACT FROM AUTHOR]

Background: Hearing loss is a sensorineural disorder occuring in 1 out of 500 births. It happens due to some genetic/environmental causes or both. More than 60% of cases are noninherited and 80% non syndromic with autosomal recessive inheritance. In the present study we investigated the frequency of mtDNA A1555G, A3243 and A7445G mutations among the patients in Fars province. Materials and Methods: Seventy two non syndromic hearing loss subjects were studied. DNA was extracted using standard phenol-chloroform method. The screening of the mitochondrial gene mutations were performed using PCR-RFLP procedure. Finally, the possible mutations were confirmed by direct sequencing. Results: None of the A1555G, A3243G and A7445G mutations was detected in this study. However, destroying a MTTL1 restriction site for the investigation of A3243G mutation, revealed a G3316A with allelic variant of 1.4% in the deaf subjects. Conclusion: Our data indicated that the mitochondrial A1555G, A3243 and A7445G mutations have no role in auditory deficits in patients studied. [ABSTRACT FROM AUTHOR]

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) is a mitochondrial disorder commonly caused by the A3243G mutation. We report a patient who initially presented with visual hallucinations, headaches, and nonconvulsive status epilepticus originating in left occipital lobe who subsequently progressed to have multifocal seizures. His magnetic resonance imaging (MRI) showed subtle T2 hyperintensity at first presentation that subsequently fully resolved. He then had more typical diffusion restriction not conforming to vascular territories. Evolution of his neuroimaging and electroencephalogram (EEG) is discussed with a brief review of literature. Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes should be suspected early with occipital lobe seizures. [ABSTRACT FROM AUTHOR]

Abstract: Mutations at the DFNB1 locus which encode connexin 26 (CX26) and connexin 30 (CX30) proteins, respectively, are main cause for sporadic and familial non-syndromic hearing impairment (NSHI) in many populations. 342-kb deletion [del (GJB6-D13S1830)] of Cx30 gene is second most common connexin mutation. Specific mitochondrial DNA (mtDNA) mutations have been found to be associated with NSHI. In this study, we screened 210 NSHI patients for GJB2 mutations, ΔGJB6-D13S1830 deletion and three point mutations in mtDNA (A1555G, A3243G, A7445G) using PCR, DHPLC and sequencing in North Indian cohort. 35delG was found to be the most common mutation (10.9%), followed by W24X (3.8%) and W77X (1.9%) mutations. We did not observe GJB6-D13S1830 deletion and three mitochondrial point mutations in our cohort. Most of patients (50/58) carried monoallelic variations. Our results reveal different spectrum of GJB2 mutations specific to North Indian cohort, with 35delG being most prevalent. These results suggest that different types of GJB2 mutations affect autosomal recessive NSHI according to ethnic background. [Copyright &y& Elsevier]

Abstract: Mitochondrial encephalopathy, lactic acidosis and stroke-like episodes syndrome (MELAS) is the most frequent syndromic manifestation of A3243G mutation in mitochondrial DNA. Detection of A3243G mutation in blood is less helpful for the diagnosis of MELAS and the carriers, and the mutation ratio in blood correlates only in a limited extent with the severity of the disease. Here we compared the ratio of A3243G mutation in four easily available samples (blood, urine, hair follicle and saliva) in patients with MELAS carrying A3243G mutation as well as their maternal relatives from 32 families, to find out the samples appropriate for the detection of the patients and carriers and useful for the evaluation of clinical severity from their mutation ratio. In MELAS patients and the carriers with minor symptoms or normal phenotype, A3243G mutation ratio was significantly higher in urine than in blood. A close correlation between A3243G mutation ratio in blood and that in urine, hair follicles and saliva was found in the probands and their relatives. Clinical features closely correlated with the mutation ratio in urine. Measurement of A3243G mutation ratio in urine is a non-invasive, convenient and rapid method with its diagnostic meaning superior to blood testing. [Copyright &y& Elsevier]

Abstract: MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) is commonly associated with the A3243G mitochondrial DNA (mtDNA) mutation encoding the transfer RNA of leucine (UUR) (tRNA Leu(UUR)). The pathogenetic mechanisms of this mutation are not completely understood. Neuronal functions are particularly vulnerable to alterations in oxidative phosphorylation, which may affect the function of the neurotransmitter glutamate, leading to excitotoxicity. In order to investigate the possible effects of A3243G upon glutamate homeostasis, we assessed glutamate uptake in osteosarcoma-derived cytoplasmic hybrids (cybrids) expressing high levels of this mutation. High-affinity Na+-dependent glutamate uptake was assessed as radioactive [3H]-glutamate influx mediated by specific excitatory amino acid transporters (EAATs). The maximal rate (V max) of Na+-dependent glutamate uptake was significantly reduced in all the mutant clones. Although the defect did not relate to either the mutant load or magnitude of oxidative phosphorylation defect, we found an inverse relationship between A3243G mutation load and mitochondrial ATP synthesis, without any evidence of increased cellular or mitochondrial free radical production in these A3243G clones. These data suggest that a defect of glutamate transport in MELAS neurons may be due to decreased energy production and might be involved in mediating the pathogenic effects of the A3243G mtDNA mutation. [Copyright &y& Elsevier]

Mitochondria provide cells with most of the energy in the form of adenosine triphosphate (ATP). Mitochondria are complex organelles encoded both by nuclear and mtDNA. Only a few mitochondrial components are encoded by mtDNA, most of the mt-proteins are nuclear DNA encoded. Remarkably, the majority of the known mutations leading to a mitochondrial disease have been identified in mtDNA rather than in nuclear DNA. In general, the idea is that these pathogenic mutations in mtDNA affect energy supply leading to a disease state. Remarkably, different mtDNA mutations can associate with distinct disease states, a situation that is difficult to reconcile with the idea that a reduced ATP production is the sole pathogenic factor. This review deals with emerging insight into the mechanism by which the A3243G mutation in the mitochondrial tRNA (Leu, UUR) gene associates with diabetes as major clinical expression. A decrease in glucose-induced insulin secretion by pancreatic beta-cells and a premature aging of these cells seem to be the main process by which this mutation causes diabetes. The underlying mechanisms and variability in clinical presentation are discussed. [ABSTRACT FROM AUTHOR]

Mitochondrial cytopathy is a heterogeneous group of disorders with a wide range of clinical features. To evaluate the incidence and clinical heterogeneity of A3243G mitochondrial tRNA mutation in the Korean population, we evaluated patients who were clinically suggestive of having mitochondrial encephalomyopathy. Eighty-five patients were included in this study. All showed clinical features of mitochondrial encephalomyopathy and had three or more of the following clinical manifestations: (1) psychomotor regression, (2) hyperlacticacidemia, (3) recurrent stoke-like episodes, (4) idiopathic cardiomyopathy, (5) sensoryneural hearing loss, (6) diabetes mellitus, (7) myopathy, (8) renal disease and (9) relatives with known mitochondrial disease. The patients were clinically classified as MELAS, MERRF, Leigh syndrome, Kearns–Sayre syndrome, chronic progressive external ophthalmoplegia and uncertain. Of the 85 patients, 19 had the A3243G mutation (22.3%). Thirty-one patients showed typical clinical characteristics of MELAS. Fourteen of those 31 patients had A3243G mutation (45.1%). Four patients harboring A3243G mutations showed atypical and heterogeneous clinical features, unlike MELAS. This study revealed the frequent occurrence of A3243G mutation in Korean patients with mitochondrial disorders and their clinical features can be heterogeneous. It will be helpful to screen the presence of A3243G mutation for the genetic diagnosis of mitochondrial encephalomyopathy in Korea. [Copyright &y& Elsevier]

Las citopatías mitocondriales constituyen un variado grupo de desórdenes generados por déficits de la producción de energía en la mitocondria (1), proceso llevado a cabo a través de cinco complejos multienzimáticos ubicados en la membrana interna mitocondrial. Las subunidades que conforman estos complejos son codificadas por genoma nuclear y mitocondrial (mtDNA). Hasta el momento se ha identificado un gran cantidad de citopatías causadas por mutaciones en mtDNA; la más frecuente es MELAS (Mitochondrial Encephalomyopathy with Lactic acidosis and Stroke-like episodes) (2), de ésta, el 80% de los casos poseen la mutación A3243G en el gen del tRNALeu (3). En dicha mutación se ha encontrado hasta un 95% de heteroplasmia (4), lo cual hace que la variación en el fenotiposea muy amplia.En este trabajo se evaluó la mutación A3243G en pacientes con diagnóstico de MELAS así como a sus familiares. A Total of 4.129 children with the diagnosis of urinary tract infection (UTI) were attended at Hospital Universitario San Vicente de Paúl in Medellín, Colombia, between 1960 and 2004. Vesicoureteral reflux (VUR), the commonest anomaly associated to UTI, was found in 1.309 children (31.7%) who presented 1.914 cases of affected renal units (605 patients had bilateral reflux). This is a descriptive, retrospective work, carried out with information registered at the pediatric nephrology service by one of the authors (VPE) on children younger than 17 years, with the diagnosis of VUR. The most important registered characteristics were reviewed, and the findings were as follows: 61.1% of children were women, 29.2% had the diagnosis of VUR made during the first year of life, and 41.4% had other associated anomalies; 72.4% of children had VUR of either III or IV grades, 53.8% had unilateral reflux, 23.8% had spontaneous resolution, and 36.1% required surgical correction. In 582 (44.5% out of 1.309) of these patients, studies for renal scarring were carried out, and it was found in 371 (63.7%); 2.3% had high blood pressure, 7.4% developed chronic renal failure; 0.9% received kidney transplantation, and 2.4% died. Our findings, similar to those reported by other authors, allow us to insist on the need for adequate management of children with VUR, because of the risk of developing high blood pressure and chronic renal failure. Better diagnostic systems for VUR and renal scarring, the progress of information diffusion, and the medical interest on this subject are opportunities for making earlier diagnoses, and opportune and proper treatment of these children.

Three months previously, a 17-year-old girl had complained of right-hand side hemiparesis, and her brain magnetic resonance imaging (MRI) showed a signal change in the left temporoparietooccipital area. The 3243A>G mutation was found in mitochondrial DNA. She was diagnosed with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and was prescribed dichloroacetic acid to treat lactic acidosis. Her health improved. Two months later, she developed drowsiness and generalized weakness. A New lesion was not found on brain MRI, and electrodiagnostic findings were compatible with acute motor sensory axonal neuropathy. Her negative symptoms, such as depressed mood, loss of interest in activities, psychomotor retardation, and hypersomnia, were aggravated. She was prescribed antidepressants and psychostimulants by a psychiatrist after diagnosis of severe depression episode with catatonic features. One month later, her catatonic condition had improved with medication. Our experience shows that psychiatric diagnostic evaluation of abruptly regressed neurologic and clinical features is important, even in a patient with devastating underlying disease. [ABSTRACT FROM AUTHOR]

In stroke-like episodes (SEs) of patients with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), the detection of preclinically latent lesions is a challenge. We report regional cerebral hyperperfusion observed on arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) in the preclinical phase more than 3 months before the clinical onset of SEs in 3 MELAS patients. These hyperperfused areas were not detected by conventional MRI in the preclinical phase and developed into acute lesions at the clinical onset of SEs, suggesting that ASL imaging has the potential for predicting the emergence of SEs., (© 2013.)