A3243G Mutation Research Articles

Diligent family history to detect a mitochondrial disorder in disguise: Lessons from a case of myoclonic epilepsy

Abstract Mitochondrial disorders often present with ataxia, myoclonus, and epilepsy. Valproic acid may be selected for treating myoclonus if it is the presenting feature. While it is efficacious in suppressing cortical myoclonus, valproic acid is a known mitochondrial toxin and, therefore, not recommended. We report a family carrying the mitochondrial A8344G mutation. The proband, after being treated with valproic acid for myoclonic epilepsy, presented with gradually progressive cerebellar ataxia. He had a re-emergence of myoclonus upon withdrawal of valproic acid about 15 years later. The mitochondrial A8344G mutation, given its diverse clinical manifestations and intrafamilial phenotypic heterogeneity, evaded early recognition. Individuals carrying this mutation need life-long anti-epileptic therapy for myoclonus. Thus, it is important to recognize the mitochondrial disorder and select appropriate drugs.

Long Term Follow Up of a Family with A3243G Mitochondrial Syndrome.

To describe the clinical and multimodal imaging (MMI) features of a family (proband, sister and mother) with A3243G mitochondrial retinopathy and long-term follow up. Medical and imaging records were retrospectively evaluated. Multimodal imaging included ultra-widefield color fundus photography, fundus autofluorescence, and spectral-domain optical coherence tomography. Long-term MMI follow up ranged from 6 to 15 years and was available for each member. The proband (Case 1) exhibited rapidly progressive bilateral macular atrophy, corneal endothelial polymegathism, and an A3243G mutation in the mitochondrial DNA. The proband also endorsed a history of early-onset myocardial infarction (MI) ten years prior at the age of 42. The proband's sister (Case 2) only exhibited unilateral focal macular atrophy but admitted to a history of severe multiorgan systemic disease, including multiple sclerosis and major depression disorder. The proband's mother (Case 3), the only one with diabetes mellitus and hearing loss, originally presented with branch retinal vein occlusion in the right eye and pattern dystrophy in the left eye which evolved to geographic atrophy, OD > OS, 15 years later. A3243G mitochondrial syndrome can exhibit heterogenous ocular and systemic features, even within members of the same family. The development of the characteristic maculopathy with early-onset MI warrants genetic testing. Early cardiac and systemic screening may be recommended in individuals with characteristic retinal findings and genetic confirmation.

Lack of Association of Mitochondrial tRNA(Leu) A3243G Mutation with Allergic Chronic Rhinosinusitis Pathogenesis in South Indian Population

Lack of Association of Mitochondrial tRNA(Leu) A3243G Mutation with Allergic Chronic Rhinosinusitis Pathogenesis in South Indian Population

Generation of an induced pluripotent stem cell line (KEIUi008-A) from a hearing loss patient with an A1555G mutation in mitochondrial DNA

We report the establishment of a human induced pluripotent stem cell (iPSC) line from a 54-year-old male patient with an A1555G mutation in the mitochondrial 12S ribosomal RNA gene (MTRNR1), associated with sensorineural hearing loss. The established iPSC line expressed stemness markers or undifferentiated state markers. We also demonstrated the capacity of the cells to differentiate into the three germ layers, suggesting its pluripotency and utility in the pathological study of sensorineural hearing loss and drug screening for ear disorders.

Impaired mitochondrial morphological plasticity and failure of mitophagy associated with the G11778A mutation of LHON

Mitochondrial dynamics were examined in human dermal fibroblasts biopsied from a confirmed Leber's Hereditary Optic Neuropathy (LHON) patient with a homoplasmic G11778A mutation of the mitochondrial genome. Expression of the G11778A mutation did not impart any discernible difference in mitochondrial network morphology using widefield fluorescence microscopy. However, at the ultrastructural level, cells expressing this mutation exhibited an impairment of mitochondrial morphological plasticity when forced to utilize oxidative phosphorylation (OXPHOS) by transition to glucose-free, galactose-containing media. LHON fibroblasts also displayed a transient increase in mitophagy upon transition to galactose media. These results provide new insights into the consequences of the G11778A mutation of LHON and the pathological mechanisms underlying this disease.

Galactose-replacement unmasks the biochemical consequences of the G11778A mitochondrial DNA mutation of LHON in patient-derived fibroblasts

Leber's hereditary optic neuropathy (LHON) is a visual impairment associated with mutations of mitochondrial genes encoding elements of the electron transport chain. While much is known about the genetics of LHON, the cellular pathophysiology leading to retinal ganglion cell degeneration and subsequent vision loss is poorly understood. The impacts of the G11778A mutation of LHON on bioenergetics, redox balance and cell proliferation were examined in patient-derived fibroblasts. Replacement of glucose with galactose in the culture media reveals a deficit in the proliferation of G11778A fibroblasts, imparts a reduction in ATP biosynthesis, and a reduction in capacity to accommodate exogenous oxidative stress. While steady-state ROS levels were unaffected by the LHON mutation, cell survival was diminished in response to exogenous H2O2.

Exome Sequencing Reveals a Rare Autosomal Dominant Variant in MSTO1 Gene as a Novel Leber’s Hereditary Optic Neuropathy (LHON) Modifier in a Thai Family with High Penetrance of G11778A Mutation

Exome Sequencing Reveals a Rare Autosomal Dominant Variant in MSTO1 Gene as a Novel Leber’s Hereditary Optic Neuropathy (LHON) Modifier in a Thai Family with High Penetrance of G11778A Mutation

Collision-Induced Unfolding Reveals Disease-Associated Stability Shifts in Mitochondrial Transfer Ribonucleic Acids.

Ribonucleic acids (RNAs) remain challenging targets for structural biology, creating barriers to understanding their vast functions in cellular biology and fully realizing their applications in biotechnology. The inherent dynamism of RNAs creates numerous obstacles in capturing their biologically relevant higher-order structures (HOSs), and as a result, many RNA functions remain unknown. In this study, we describe the development of native ion mobility-mass spectrometry and collision-induced unfolding (CIU) for the structural characterization of a variety of RNAs. We evaluate the ability of these techniques to preserve native structural features in the gas phase across a wide range of functional RNAs. Finally, we apply these tools to study the elusive mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes-associated A3243G mutation. Our data demonstrate that our experimentally determined conditions preserve some solution-state memory of RNAs via the correlated complexity of CIU fingerprints and RNA HOS, the observation of predicted stability shifts in the control RNA samples, and the retention of predicted magnesium binding events in gas-phase RNA ions. Significant differences in collision cross section and stability are observed as a function of the A3243G mutation across a subset of the mitochondrial tRNA maturation pathway. We conclude by discussing the potential application of CIU for the development of RNA-based biotherapeutics and, more broadly, transcriptomic characterization.

Assessment of the risk of hearing loss in children with cystic fibrosis

Cystic fibrosis (CF) is a severe hereditary disease with a multisystem lesion. Manifestations of CF include severe infectious purulent lesions of all parts of the respiratory tract, including purulent rhinosinusitis with nasal polyps. The involvement of the sinonasal region and the need for systemic use of ototoxic drugs (primarily aminoglycosides to treat resistant bacterial infection) potentially create a risk of both conductive and sensorineural hearing loss (SNHL). The available data on the epidemiology of hearing disorders in CF is contradictory. Currently, genetic determinants of the development of aminoglycoside SNHL have been identified. For 136 CF patients (75 girls, 61 boys) aged 3 to 17 (9.4±3.9) years were performed audiological examination: tympanometry, transient-evoked otoacoustic emission and the pure tone threshold audiometry (standard frequency range) (n=126). History of systemic therapy with aminoglycosides was evaluated for each patient. Sequencing of c.35delG mutations in the GJB2 gene (nuclear DNA) and A1555G in the 12S rRNA gene (mitochondrial DNA) was performed in 215 patients with cystic fibrosis (the group partially overlaps with the audiological group), and as a control - 106 children with bronchial asthma and 103 healthy children, their age ranged from 3 to 17 (8.8±3.8) years. Audiological examination of CF children reveled a prevalence of conductive hearing loss comparable to the general population (2.4%). The frequency of SNHL was 1.6%, wich exceeds that of non-CF children. A genetic study revealed one case of heterozygous carriage of the c.35delG mutation in the GJB2 gene in a patient with bronchial asthma. In the group of patients with CF (n=215), mutations in the connexin 26 gene were not detected. No A1555G mutation was detected either in the group of patients with CF or in the control groups. Children with CF are at risk for the development of sensorineural, but not conductive hearing loss. Routine total screening for A1555G and c.35delG mutations probably seems not to be recommended.

Epilepsy and MELAS syndrome: literature review and clinical observation

MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes) belongs to the group of mitochondrial diseases. Most MELAS syndrome cases are associated with the A3243G mutation in the MTTL1 gene. A common clinical manifestation of the syndrome is presented by epileptic seizures (ES) characterized by phenotypic polymorphism and resistance to antiepileptic therapy. Diagnosis and treatment of epilepsy in patients with MELAS syndrome often poses difficulties. We present a clinical case of adult patient with MELAS syndrome with identified A3243G mutation and epilepsy. The disease course developed to severe cognitive impairment. The first focal ES occurred during stroke-like episode. Further seizures were observed spontaneously, with high frequency, often manifested as a series. Focal ES often had blurred polymorphic manifestations. The choice of drug therapy took into account the side effects of antiepileptic drugs (AEDs) including potentially mitochondria-related negative effects. While diagnosing EP in MELAS syndrome, it should be considered that seizures often occur during stroke-like episodes and may have blurred polymorphic clinical manifestations. Cognitive impairment in patients complicates ES detection. First-line drugs should be presented by AEDs with low mitochondrial toxicity.

Detection of mtDNA Mutations Using the Amplification Refractory Mutation System-Polymerase Chain Reaction Method in Type II Diabetes Mellitus Patients in Publich Health Center Poasia

Background: Diabetes Mellitus (DM) is a heterogeneous disease caused by hereditary and ecological factors. One form of diabetes mellitus that is related to genetic factors is type 2 DM. type 2 diabetec melitus caused by dysfunction of insulin secretion, due to the presence of inhibition in the production of Adenosine Triphosphate (ATP) necessary in the process of its secretion by cells β glands of the pancreas. The dysfunction is related to the mutation of A to G at the 3243rd nucleotide position of the mitochondrial DNA tRNA gene. The purpose of the study was to find out whether there was a heteroplasmic mtDNA mutation in the genes of respondents to type 2 diabetes mellitus using the ARMS-PCR method. Methods: The type of research used is descriptive research, the sample used in this study is a blood sample in respondents of type 2 diabetes mellitus. The method chosen in this study is the Amplification Refractory Mutation System (ARMS)-PCR Method which is a PCR application that uses a specific primer. Results: According to this study, 20 of the 20 samples evaluated using the ARMS-PCR method were positive for the heteroplasmic A3243G mutation, which is defined by the presence of DNA bands measuring 200 bp on both tubes. These pathogenic mutations are inherited maternally and can cause a variety of disorders. Conclusion: After analyzing all samples, this study has concluded that they all contain hetero plasma mutations. The suggestions provided in this study are expected to be useful for future researchers who employ samples from other public health centers and hospitals.

Simulation Modeling of A3243g Mutations on tRNALeu (UUR) against Type 2 Diabetes Mellitus using In Silico Method

Mitochondrial disease is a disease that affects the genetic condition of mitochondrial DNA. One of the causes of this disease is the mutation of nucleotide bases A to G at the 3243 nucleotide position of the mtDNA tRNALeu (UUR) gene. The characteristic of the mutation A3243G mtDNA is a heteroplasmic mutation with a relatively low amount of mutant DNA. The mutants that occur can undergo a dimerization process which can reduce aminoacylation. The purpose of this study was to prove in silico the effect of mitochondrial DNA mutation A3243G tRNA leucine on type 2 diabetes mellitus. The stages of the research carried out included structural modeling of tRNALeu and Protein tRNA Synthetase using the homology method, then a native and mutant leucine tRNA model was made. The results of the modeling were assessed and validated. The next step is the dimerization process between mutant tRNAs to see the binding of structures to the tRNA. The next process is docking between the tRNA and protein models. The final step is to simulate molecular dynamics in the native tRNA model, mutants and dimer structures to see the differences in aminoacylation reactions in the three models in mitochondria. This study is expected to provide information about the effect of the A3243G mutation on the causes of type 2 diabetes in mitochondria.

Development of a sensitive double TaqMan Probe-based qPCR Angle-Degree method to detect mutation frequencies

We designed a method to examine the mutation frequencies of the A3243G mutation of mitochondrial DNA (mtDNA) in patients with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome. We performed a qPCR assay using the FAM and VIC TaqMan probes, which detect the 3243G (mutated) and 3243A (wild-type) sequences of mtDNA, respectively. The results obtained by “degree” in a series of differential mutation frequencies were used to plot a standard curve of the mutation frequency. The standard curve was then applied for qPCR assays of the desired samples. The standard deviation (%) of the samples calculated using the standard curve for the TaqMan probe was 2.4 ± 1.5%. This method could be used to examine mutation frequencies in the context of diabetes, aging, cancer, and neurodegenerative diseases.

Leber's Hereditary Optic Neuropathy with Mitochondrial DNA Mutation G11778A: A Systematic Literature Review and Meta-Analysis.

LHON is a progressive disease with early disease onset and male predominance, usually causing devastating visual loss to patients. These systematic review and meta-analysis are aimed at summarizing epidemiology, disease onset and progression, visual recovery, risk factors, and treatment options of Leber's hereditary optic neuropathy (LHON) with mitochondrial DNA mutation G11778A from current evidence. The PubMed database was examined from its inception date to November 2021. Data from included studies were pooled with either a fixed-effects model or a random-effects model, depending on the results of heterogeneity tests. Sensitivity analysis was conducted to test the robustness of results. A total of 41 articles were included in the systematic review for qualitative analysis, and 34 articles were included for quantitative meta-analysis. The pooled estimate of proportion of G11778A mutation among the three primary mutations of mitochondrial DNA (G11778A, G3460A, and T14484C) for LHON was 73% (95% CI: 67% and 79%), and the LHON patients with G11778A mutation included the pooled male ratio estimate of 77% (76% and 79%), the pooled age estimate of 35.3 years (33.2 years and 37.3 years), the pooled onset age estimate of 22.1 years (19.7 years and 24.6 years), the pooled visual acuity estimate of 1.4 LogMAR (1.2 LogMAR and 1.6 LogMAR), and the pooled estimate of spontaneous visual recovery rate (in either 1 eye) of 20% (15% and 27%). The G11778A mutation is a prevalent mitochondrial DNA mutation accounting for over half of LHON cases with three primary mutations. Spontaneous visual recovery is rare, and no effective treatment is currently available.

Clinical Profile of Patients with Leber Hereditary Optic Neuropathy (LHON): An Ambispective Study of North Indian Cohorts.

Leber hereditary optic neuropathy (LHON) is a maternally inherited disease resulting in irreversible visual loss usually in patients belonging to the age group of 15-35 years. Clinically, the patients present with sequential or bilateral, painless, progressive visual loss with central (or ceco-central) scotomas. Although the three mutations, namely, G11778A, T14484C, and G3460A contribute to >95% of LHON cases globally, the relative frequency of each mutation varies. We aimed to assess the clinical and genetic profile of patients with mutation-positive LHON at a north Indian tertiary care center. One hundred sixty-one patients (61 prospective and 100 retrospective) presenting with the clinical diagnosis of LHON were screened for the three known mitochondrial mutations (G1178A, G3460A, T14448C). Patients were assessed for detailed clinical, ophthalmological, and neurological examinations. Five milliliter of blood sample was taken to assess the three known mutations using DNA isolation and Sanger sequencing. Clinical profile of 83 patients with both positive and negative mutations was analyzed. Twenty-three out of 161 patients (14.3%) tested positive for either of the three mutations. The majority of the patients harbored G11778A mutation (56.52%) followed by T14484C (34.78%) and G3460A (8.69%). No statistical difference could be noted between the clinical profiles of mutation-negative and -positive patients.

Clinical and laboratory polymorphism of mitochondrial diseases by the example of A3243G mutation in mitochondrial DNA

The article is devoted to the clinical polymorphism of mitochondrial diseases by the example of A3243G mutation in mitochondrial DNA. The article also discusses clinical criteria and an algorithm for the diagnosis of mitochondrial diseases.Material and methods. Тhree families with A3243G mutation in mitochondrial DNA are presented. All patients underwent clinical neurological examination, instrumental examination (ECG, Echo-CG, MRI and CT of the brain, EEG, needle and stimulation electromyography, audiometry), biochemical study of the level of lactic and pyruvic acids in the blood before and after exercise, muscle biopsy.Results. Аll patients had myopathy, exercise intolerance, sensorineural hearing loss, short stature; other symptoms varied. According to the results of muscle biopsy, the phenomenon of «ragged red fibers» was found in two patients. The diagnosis was confirmed by molecular genetic examination. Conclusion. Мitochondrial diseases with the same mutation are characterized by significant variability of clinical symptoms. The identification of clinician traits characteristic of a group of mitochondrial diseases should alert the doctors to this pathology.

Mitochondrial Diabetes is Associated with tRNALeu(UUR) A3243G and ND6 T14502C Mutations.

BackgroundMutations in mitochondrial DNA (mtDNA) are associated with type 2 diabetes mellitus (T2DM). In particular, m.A3243G is the most common T2DM-related mtDNA mutation in many families worldwide. However, the clinical features and pathophysiology of m.A3243G-induced T2DM are largely undefined.MethodsTwo pedigrees with maternally inherited T2DM were underwent clinical, molecular and biochemical assessments. The mtDNA genes were PCR amplified and sequenced. Mitochondrial adenosine triphosphate (ATP) and reactive oxygen species (ROS) were measured in polymononuclear leukocytes derived from three patients with both the m.A3243G and m.T14502C mutations, three patients with only the m.A3243G mutation and three controls without these mutations. Moreover, GJB2, GJB3 and GJB6 mutations were screened by PCR-Sanger sequencing.ResultsMembers of the two pedigrees manifestated variable clinical phenotypes including diabetes and hearing and vision impairments. The age at onset of T2DM varied from 31 to 66 years, with an average of 41 years. Mutational analysis of mitochondrial genomes indicated the presence of the m.A3243G mutation in both pedigrees. Matrilineal relatives in one of the pedigrees harbored the coexisting of m.A3243G and m.T14502C mutations. Remarkably, the m.T14502C mutation, which causes the substitution of a conserved isoleucine for valine at position 58 in ND6 mRNA, may affect the mitochondrial respiratory chain functions. Biochemical analysis revealed that cell lines bearing both the m.A3243G and m.T14502C mutations exhibited greater reductions in ATP levels and increased ROS production compared with those carrying only the m.A3243G mutation. However, we did not find any mutations in the GJB2, GJB3 and GJB6 genes.ConclusionOur study indicated that mitochondrial diabetes is associated with the tRNALeu(UUR) A3243G and ND6 T14502C mutations.

Clinical and molecular findings in a Chinese family with a de novo mitochondrial A1555G mutation

BackgroundThe mitochondrial 12S rRNA A1555G mutation is the most prevalent deafness-causing mitochondrial DNA (mtDNA) mutation and is inherited maternally. Studies have suggested that A1555G mutations have multiple origins, although there is no direct evidence of this. Here, we identified a family with a de novo A1555G mutation.MethodBased on detailed mtDNA analyses of the family members using next-generation sequencing with 1% sensitivity to mutated mtDNA, the level of heteroplasmy in terms of the A1555G mutation in blood DNA samples was quantified.ResultsAn individual harbored a heterogeneous A1555G mutation, at 28.68% heteroplasmy. The individual’s son was also a heterogeneous carrier, with 7.25% heteroplasmy. The individual’s brother and mother did not carry the A1555G mutation, and both had less than 1% mitochondrial 12S rRNA A1555G heteroplasmy.ConclusionThe A1555G mutation arose de novo in this family. This is the first report of a family with a de novo A1555G mutation, providing direct evidence of its multipoint origin. This is important for both diagnostic investigations and genetic counselling.

Clinical observations of Leber hereditary optic neuropathy with and without neurological symptoms

Three case studies of adults with Leber hereditary optic neuropathy with and without neurological symptoms are presented. An elevated blood lactate level and changes in the activity of the mitochondrial enzymes in peripheral blood lymphocytes were noted. Mutations in the mitochondrial DNA (G3460A in one patient and G11778A in two patients) were found. The patient with a G3460A mutation, in addition to reduced visual acuity, was diagnosed with a cerebellar disorder due to cerebellar vermis hypoplasia. These changes are indications for prescribing energotropic drugs (idebenone, carnitine); carnosine can also be prescribed. These case studies show that patients with optic nerve atrophy should be assessed for Leber hereditary optic neuropathy. Differential diagnosis with multiple sclerosis should be performed, since this condition often presents as optic neuropathy.

Development of Real-time PCR Kit for Detection and Quantitation of Six Common Mutations A3243G, G3380A, A8344G, T8993G, T8993C, G11778A of Human Mitochondrial Genome

A procedure for production of a real-time PCR kit for detection and quantitation of 6 common mitochondrial genome mutations including A3243G, G3380A, A8344G, T8993G, T8993C, G11778A using fluorescent locked nucleic acid (LNA) Taqman probes was reported. The procedure consists of designing of specific primers and LNA probes, selection of master mixture components and real-time PCR thermal conditions. The produced kit had specificity of 100% and sensitivity ≥ 1% and remained fully active after 7 days of storage at 25 oC or 20 days at 4 oC or 6 months at -20 oC. The kit was used to analyze A3243G, G3380A, A8344G, T8993G, T8993C, G11778A mutations from 69 patients tentatively diagnosed with mitochondrial diseases and 3 cases of A3243G carriers (4.34%) was found. In these cases, the A3243G mutation was heteroplasmic, maternally inherited, and the heteroplasmy level was shown to be related to the symptome expression.tome expression.