Mitochondrial DNA A3243G Mutation Research Articles

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.

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.

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: The Clinical Spectrum of MIDD and MELAS in Association With the A3243G Mutation

Abstract Introduction: Maternally inherited diabetes and deafness (MIDD) is a multisystem disorder characterized by insulinopenia and sensorineural hearing loss. This rare form of monogenic diabetes is most commonly associated with the A3243G mutation of mitochondrial DNA (mtDNA). The same mutation is seen in 80 percent of patients with MELAS (Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes). MIDD and MELAS have overlapping features suggesting a continuum of expression for the A3243G mutation. Clinical Case: A 41-year-old male was referred for genetic testing and counseling by his ophthalmologist following detection of bilateral punched-out retinal pigment epithelium (RPE) lesions on routine exam. His medical history was significant for type 1 diabetes mellitus (T1DM) diagnosed at the age of 21 and bilateral sensorineural hearing loss diagnosed at the age of 38. The referral was triggered by patient reported family history of MELAS in two of his brothers who were both diagnosed at the age of 10 and died at the ages of 20 and 27. Whether the patient was previously tested during early childhood remains unclear. His medical history was negative for stroke-like episodes or seizures. Neurologic evaluation revealed mild fluent aphasia with paraphasic errors and some comprehension difficulties. MRI of the brain without contrast showed no focus of restricted diffusion. Mitochondrial DNA sequence analysis was performed. A pathogenic variant (m.3243 A>G) was detected in the MT-TL1 gene at approximately 25% heteroplasmy. The patient was advised to avoid metformin given increased risk for lactic acidosis. He was also instructed against use of statins. At the age of 45, the patient presented to the emergency department (ED) with a complaint of headache, vertigo and incoordination. Physical examination revealed left homonymous hemianopsia, right horizontal nystagmus and bilateral upper extremity dysmetria. MRI of the brain without contrast showed a large area of predominantly cortical restricted diffusion involving the right temporal and occipital region with associated T2/FLAIR hyper-intensity. Cross over between the PCA and MCA territories was suggestive of a stroke-like episode related to MELAS. The patient received a bolus of IV arginine at 0.5 g/kg followed by an IV infusion of 0.5 g/kg/day for 3 days. He was later transitioned to oral arginine 5g three times daily and was discharged to a rehab facility. Clinical Lesson: This case demonstrates the evolution of MIDD to MELAS, supporting the concept that both syndromes represent a spectrum of the same disease. A few case reports describe the progression of MIDD to MELAS. Why some patients develop MELAS and others develop MIDD is unclear but may be related to heteroplasmy. Early identification of MIDD and MELAS is crucial given associated comorbidities and unique management issues.

The Spectrum of Maculopathy in Mitochondrial DNA A3243G Mutation: A Case Series of Six Patients.

The mitochondrial DNA (mtDNA) A3243G point mutation encompasses a heterogenous group of disorders including mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), maternally inherited diabetes and deafness (MIDD), and, rarely, chronic progressive external ophthalmoplegia (CPEO). Regardless of the clinical phenotype, a specific retinopathy has been associated with the presence of this mitochondrial DNA mutation. We present six female patients exhibiting retinopathy of the A3243G point mutation at various stages. Six female patients (37 - 70 years old) with the A3243G point mutation (four MELAS, one MIDD, and oneCPEO) exhibited a maculopathy. Visual acuity ranged from 1/60 to 10/10. Visual field abnormalities varied from minimal decreased sensitivity to absolute central scotomas. They all exhibited, at various degrees, a characteristic pattern of perimacular and peripapillary retinal pigment epithelium (RPE) alterations, with mottled dys-autofluorescence and RPE atrophy and deposits on OCT. The level of visual impairment depended on the foveal involvement and the extension of RPE atrophy. The severity of the maculopathy was not related to age. In the only long-term follow-up (15 years), evolution was slowly progressive. A single mtDNA point mutation at locus 3243 can result in a variety of clinical presentations (MELAS, MIDD, or CPEO). Ocular involvement may manifest as a perimacular/peripapillary RPE atrophy/deposit, which can variably impact central visual function (from asymptomatic to legal blindness). The discovery of such a maculopathy should prompt the ophthalmologist to complete the personal and family history, namely, asking for the presence of diabetes mellitus and/or deafness.

MITOCHONDRIAL DISEASES & METABOLIC MYOPATHIES: P.314 Mitochondrial DNA mutant load in A3243G mutation and clinical correlation

Mitochondrial DNA A3243G mutation is most common in Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). mtDNA heteroplasmy, i.e. mutant load may contribute to clinical disease severity yet not fully understood. We aimed to investigate the level of blood mtDNA A3243G mutant load in MELAS patients and its correlation with functional scale. Total 25 subject were recruited, who met MELAS clinical criteria, positive for mtDNA A3243G mutation and blood mtDNA mutant load analysis.

Mitochondrial A3243G mutation results in corneal endothelial polymegathism.

The mitochondrial DNA point mutation A3243G leads to a spectrum of syndromes ranging from MIDD to MELAS. Ocular manifestations include pattern macular dystrophy and concentric perifoveal atrophy. Given the high metabolic demand of corneal endothelial cells, we performed specular biomicroscopy analysis in patients harboring the mitochondrial DNA point mutation A3243G to assess for the associated presence of corneal endothelial abnormalities. We present a case series with participants from two institutions. Patients diagnosed with macular dystrophy associated with MIDD or MELAS, and the mitochondrial DNA point mutation A3243G were recruited. Exclusion criteria included a prior diagnosis, or a positive family history, of endothelial corneal dystrophy. Slit-lamp corneal examination and specular biomicroscopy were performed. Corneal endothelial cell count, cell size and polymegathism, and central corneal thickness were assessed. Patients diagnosed with MIDD or MELAS based on clinical history and examination were genetically tested for the mitochondrial DNA point mutation A3243G using pyrosequencing. Five patients (two male and three female participants) from five different families, and with different ethnic backgrounds, met the inclusion criteria. Their ages ranged from 41 to 60years. Corneal endothelial changes observed using slit-lamp examination were primarily mild to rare guttata. Specular biomicroscopy displayed mainly polymegathism associated with guttata. The average endothelial cell count was 2358±456 cells per mm2, the average endothelial cell size was 442±103μm2 and the average central corneal thickness (CCT) was 551±33μm. These values were similar to that of the average population. The average coefficient of variation (COV), an index of heterogeneity in cell size, was 42.0 ± 4.1%. When compared to the average population, the average COV was significantly higher than predicted for the patients' age. None of the patients had signs of corneal edema. One patient had a pre-Descemet's opacity. In patients with the mitochondrial DNA point mutation A3243G, corneal endothelial polymegathism is present. This is mainly associated with mild guttata. The findings of corneal endothelial cell polymegathism may be a biomarker of mitochondrial disease, specifically in patients with the mitochondrial DNA A3243G mutation.

Mitochondrial Disorder: Maternally Inherited Diabetes and Deafness.

Patients with maternally inherited diabetes and deafness (MIDD) have insulin-dependent diabetes with relatively low BMI; usually the onset of the diabetes is during the third or fourth decade of life and it is associated with progressive neurosensory deafness. The fundus shows circumferentially oriented but discontinuous patches of RPE and choriocapillaris (CC) atrophy around the macula, within the arcades (Figs. 31.1 and 31.2). Sometimes even hyperpigmentation can be seen, also around the optic nerve, or pattern-like dystrophy may occur. Vision is usually good, about 20/40 or better. Fundus autofluorescence (FAF) shows decreased AF in the areas of RPE atrophy, surrounded by a zone of speckled AF. No generalized retinal dysfunction is seen on full-field electroretinography (ERG), but pattern ERG or multifocal ERG shows abnormal function. Asymptomatic maternal relatives harboring the mutation may show pigmentary changes, hearing loss, and in some, diabetes. Another disorder associated with the same A3243G mitochondrial DNA (mtDNA) mutation as MIDD is Mitochondrial Encephalomyopathy with Lactic Acidosis and Stroke-like episodes (MELAS). The stroke-like episode (such as hemiplegia) occurs at about 5-15 years of age, and severe encephalopathy may cause death at a young age. Patients may also experience headache, vomiting, visual field defects, or cortical blindness.

Inflexibility of AMPK-mediated metabolic reprogramming in mitochondrial disease.

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is most commonly caused by the A3243G mutation of mitochondrial DNA. The capacity to utilize fatty acid or glucose as a fuel source and how such dynamic switches of metabolic fuel preferences and transcriptional modulation of adaptive mechanism in response to energy deficiency in MELAS syndrome have not been fully elucidated. The fibroblasts from patients with MELAS syndrome demonstrated a remarkable deficiency of electron transport chain complexes I and IV, an impaired cellular biogenesis under glucose deprivation, and a decreased ATP synthesis. In situ analysis of the bioenergetic properties of MELAS cells demonstrated an attenuated fatty acid oxidation that concomitantly occurred with impaired mitochondrial respiration, while energy production was mostly dependent on glycolysis. Furthermore, the transcriptional modulation was mediated by the AMP-activated protein kinase (AMPK) signaling pathway, which activated its downstream modulators leading to a subsequent increase in glycolytic flux through activation of pyruvate dehydrogenase. In contrast, the activities of carnitine palmitoyltransferase for fatty acid oxidation and acetyl-CoA carboxylase-1 for fatty acid synthesis were reduced and transcriptional regulation factors for biogenesis were not altered. These results provide novel information that MELAS cells lack the adaptive mechanism to switch fuel source from glucose to fatty acid, as glycolysis rates increase in response to energy deficiency. The aberrant secondary cellular responses to disrupted metabolic homeostasis mediated by AMPK signaling pathway may contribute to the development of the clinical phenotype.

Identification of miRNA, lncRNA and mRNA-associated ceRNA networks and potential biomarker for MELAS with mitochondrial DNA A3243G mutation

Researchers in the field of mitochondrial biology are increasingly unveiling of the complex mechanisms between mitochondrial dysfunction and noncoding RNAs (ncRNAs). However, roles of ncRNAs underlying mitochondrial myopathy remain unexplored. The aim of this study was to elucidate the regulating networks of dysregulated ncRNAs in Mitochondrial myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) with mitochondrial DNA (mtDNA) A3243G mutation, which might make contributions to the unveiling of the complex mechanisms underlying mitochondrial myopathy and, possibly, new tools applicable to clinical practice. Through high-throughput technology followed by quantitative real-time polymerase chain reaction (qRT-PCR) and bioinformatics analyses, for the first time, we found that the dysregulated muscle miRNAs and lncRNAs between 20 MELAS patients with mtDNA A3243G mutation and 20 controls formed complex regulation networks and participated in immune system, signal transduction, translation, muscle contraction and other pathways in discovery and training phase. Then, selected ncRNAs were validated in muscle and serum in independent validation cohorts by qRT-PCR. Finally, ROC curve analysis indicated reduced serum miR-27b-3p had the better diagnosis value than lactate and might serve as a novel, noninvasive biomarker for MELAS. Follow-up investigation is warranted to better understand roles of ncRNAs in mitochondrial myopathy pathogenesis.

Noninvasive Test for Mitochondrial DNA A1555G Mutation Associated with Deafness.

The homoplasmic mitochondrial DNA (mtDNA) A1555G mutation in the highly conserved decoding site of 12S rRNA has been associated with aminoglycoside-induced and nonsyndromic hearing loss in many families worldwide. The A1555G mutation detection is an important part of hearing screening. At present, blood samples are the most common source of genomic DNA. However, drawing blood is invasive for individuals. The whole genomic DNA of samples carrying mitochondrial DNA A1555G mutation (LX010 and LX044) with aminoglycoside-induced and nonsyndromic deafness as well as wild type were used as templates. The PCR products were analyzed by DNA sequencing, PCR-RFLP, dot blot, and southern blot. The DNA sequencing, PCR-RFLP, dot blot, and southern blot demonstrate that buccal cell DNA can be used for the screening and identification of the A1555G mutation as well as peripheral blood DNA. This study established a convenient, noninvasive and suitable for clinical determination of mtDNA A1555G mutation associated with deafness.

Epilepsy Characteristics and Clinical Outcome in Patients With Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes (MELAS)

BackgroundEpileptic seizures in patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) are heterogeneous with no pathognomonic features. We reviewed epilepsy characteristics and clinical outcome exclusively in a pediatric population. MethodsTwenty-two children and adolescents (13 males) with confirmed mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes due to mitochondrial DNA A3243G mutation and epilepsy were recruited. Clinical data including seizure semiology, treatment response, neuroimaging findings, and electroencephalography were analyzed. We also examined the effect of the age at seizure onset and initial symptoms on the clinical variables. ResultsSeizure semiology and electroencephalography abnormalities showed no syndrome-specific findings. Focal seizures occurred in 21 of 22 subjects (95.5%), whereas generalized seizures developed in seven of 22 subjects (31.8%). Twenty of 22 subjects (90.9%) achieved partial to complete reduction of clinical seizures for more than one year with a combination of more than two antiepileptic drugs. The subgroup with earlier seizure onset presented significantly earlier and showed significantly higher rates of drug-resistant epilepsy compared with the late onset group, although there were no significant differences in the initial symptoms. The subjects with severe epileptic conditions tended to have more severe clinical dysfunction and more severe organ involvement. ConclusionsBoth focal and generalized seizures occurred in patients with MELAS. Epilepsy in this population is drug resistant, but a certain degree of clinical seizure reduction was achievable with antiepileptic drugs, with more favorable outcomes than historically expected. Close observation and active epilepsy treatment of individuals with MELAS episodes and earlier seizure onset might improve the prognosis.

Distinctive distribution of brain volume reductions in MELAS and mitochondrial DNA A3243G mutation carriers: A voxel-based morphometric study

ObjectiveThe aim of this study was to investigate the clinically latent brain atrophy of patients with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) harboring a mitochondrial DNA A3243G mutation (A3243G) and A3243G carriers without stroke-like episodes (SEs). MethodsWe used voxel-based morphometry (VBM) with magnetic resonance imaging to investigate gray matter (GM) and white matter (WM) volume reductions in four MELAS patients and in five A3243G carriers compared to 16 healthy controls. In addition, we investigated the regions of previous SEs using conventional MRI. ResultsAll four MELAS patients showed significant GM volume reductions in the left superior parietal lobule (SPL), right precuneus, right middle temporal gyrus (MTG), and bilateral posterior lobes of the cerebellum. These areas of GM volume reduction were beyond the regions of previous SEs. As for A3243G carriers, GM volume reductions in the left SPL, right precuneus, right MTG, and bilateral posterior lobes of the cerebellum were detected in three, one, two, and five subjects, respectively. All four MELAS patients showed significant WM volume reductions in the bilateral or unilateral temporal sub-gyral regions, which were included in the regions of previous SEs. No A3243G carriers showed WM volume reductions. ConclusionThe distribution patterns of GM volume reductions in VBM may reflect a common vulnerability of the brains among MELAS patients and A3243G carriers.

Clinical analysis of three children patients with MELAS

This study aims to investigate the clinical manifestations, laboratory and imaging features, pathological and genetic testing, diagnosis and treatment in 3 children patients with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS). Focal refractory epileptic seizures were the main clinical manifestations of 3 children, at the same time with stroke-like episodes, exercise intolerance, short stature, paroxysmal headache, vomiting, cognitive impairment, visual impairment, increased blood lactic acid (LA) level and metabolic acidosis. Head MRI showed the lesions were located in temporo-parieto-occipital lobes, and EEG showed slow-wave background, bilateral asymmetry and interictal epileptiform discharges of occiput. Mitochondrial DNA (mtDNA) A3243G mutation was found in the peripheral blood samples of 2 cases. The mutation was not detected in the other case, however, the muscle biopsy revealed pathological changes of mitochondrial myopathy. All 3 cases were treated by antiepileptic drugs (AEDs) including topiramate, levetiracetam and oxcarbazepine, and cocktail therapy. One case died of status epilepticus (SE) after 46 months of follow-up, one case had stroke-like episodes for 2-3 times per year during the follow-up of 40 months, and one case was lost. The clinical manifestations, laboratory and imaging characteristics, pathological and genetic testing in children of MELAS have certain features, which will be helpful for early identification and definite diagnosis, and thus may reduce misdiagnosis and mistreatment. DOI: 10.3969/j.issn.1672-6731.2016.05.009

MELAS and Kearns-Sayre overlap syndrome due to the mtDNA m. A3243G mutation and large-scale mtDNA deletions.

This paper reported an unusual manifestation of a 19-year-old Chinese male patient presented with a complex phenotype of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome and Kearns–Sayre syndrome (KSS). He was admitted to our hospital with the chief complaint of “acute fever, headache and slow reaction for 21 days”. He was initially misdiagnosed as “viral encephalitis”. This Chinese man with significant past medical history of intolerating fatigue presented paroxysmal neurobehavioral attacks that started about 10 years ago. During this span, 3 or 4 attack clusters were described during which several attacks occurred over a few days. The further examination found that the hallmark signs of this patient included progressive myoclonus epilepsy, cerebellar ataxia, hearing loss, myopathic weakness, ophthalmoparesis, pigmentary retinopathy and bifascicular heart block (Wolff–Parkinson–White syndrome). By young age the disease progression is characterized by the addition of migraine, vomiting, and stroke-like episodes, symptoms of MELAS expression, which indicated completion of the MELAS/KSS overlap syndrome. The m. A3243G mitochondrial DNA mutation and single large-scale mtDNA deletions were found in this patient. This mutation has been reported with MELAS, KSS, myopathy, deafness and mental disorder with cognitive impairment. This is the first description with a MELAS/KSS syndrome in Chinese.

Oligonucleotide gap-fill ligation for mutation detection and sequencing in situ.

In clinical diagnostics a great need exists for targeted in situ multiplex nucleic acid analysis as the mutational status can offer guidance for effective treatment. One well-established method uses padlock probes for mutation detection and multiplex expression analysis directly in cells and tissues. Here, we use oligonucleotide gap-fill ligation to further increase specificity and to capture molecular substrates for in situ sequencing. Short oligonucleotides are joined at both ends of a padlock gap probe by two ligation events and are then locally amplified by target-primed rolling circle amplification (RCA) preserving spatial information. We demonstrate the specific detection of the A3243G mutation of mitochondrial DNA and we successfully characterize a single nucleotide variant in the ACTB mRNA in cells by in situ sequencing of RCA products generated by padlock gap-fill ligation. To demonstrate the clinical applicability of our assay, we show specific detection of a point mutation in the EGFR gene in fresh frozen and formalin-fixed, paraffin-embedded (FFPE) lung cancer samples and confirm the detected mutation by in situ sequencing. This approach presents several advantages over conventional padlock probes allowing simpler assay design for multiplexed mutation detection to screen for the presence of mutations in clinically relevant mutational hotspots directly in situ.

Severe atrophy of the cerebellum on magnetic resonance imaging in a Chinese patient with maternally inherited diabetes and deafness with the A3243G mitochondrial DNA mutation

Maternally inherited diabetes and deafness (MIDD) is a rare form of diabetes with a maternal transmission and sensorineural hearing loss. Neuroradiological abnormality manifestations have been relatively rarely reported in MIDD patients. In this report, we will describe the clinical features, genetic alterations, and neuroradiological alterations in a Chinese patient with MIDD. We conducted a series of clinical examinations in the patient, including beta cell function, cognitive function tests, and magnetic resonance imaging (MRI) of the brain. The A3243G mitochondrial DNA (mtDNA) mutation in blood cells was assessed by direct sequencing analysis, and the proportions of mutant mtDNA was also analyzed. The patient exhibited the clinical features of early onset of diabetes with progressive insulin secretory defect, sensorineural hearing loss, and maternal history of diabetes and deafness. He had slightly impaired cognitive function. A brain MRI revealed severe atrophy of the cerebellum. Analysis of mtDNA revealed the A3243G mutation, with the proportion of mutant mtDNA of 15 % in leukocytes. This case extends the phenotype of the tRNALeu [UUR] A3243G mtDNA mutation.

Cerebral metabolic abnormalities in A3243G mitochondrial DNA mutation carriers

To establish cerebral metabolic features associated with the A3243G mitochondrial DNA mutation with proton magnetic resonance spectroscopic imaging ((1)H MRSI) and to assess their potential as prognostic biomarkers. In this prospective cohort study, we investigated 135 clinically heterogeneous A3243G mutation carriers and 30 healthy volunteers (HVs) with (1)H MRSI. Mutation carriers included 45 patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS); 11 participants who would develop the MELAS syndrome during follow-up (converters); and 79 participants who would not develop the MELAS syndrome during follow-up (nonconverters). The groups were compared with respect to MRSI metabolic indices of 1) anaerobic energy metabolism (lactate), 2) neuronal integrity (N-acetyl-l-aspartate [NAA]), 3) mitochondrial function (NAA; lactate), 4) cell energetics (total creatine), and 5) membrane biosynthesis and turnover (total choline [tCho]). Consistent with prior studies, the patients with MELAS had higher lactate (p < 0.001) and lower NAA levels (p = 0.01) than HVs. Unexpectedly, converters showed higher NAA (p = 0.042), tCho (p = 0.004), and total creatine (p = 0.002), in addition to higher lactate levels (p = 0.032), compared with HVs. Compared with nonconverters, converters had higher tCho (p = 0.015). Clinically, converters and nonconverters did not differ at baseline. Lactate and tCho levels were reliable biomarkers for predicting the risk of individual mutation carriers to develop the MELAS phenotype. (1)H MRSI assessment of cerebral metabolism in A3243G mutation carriers shows promise in identifying disease biomarkers as well as individuals at risk of developing the MELAS phenotype.

Investigation of the A1555G mutation in mitochondrial DNA (MT-RNR1) in groups of Brazilian individuals with nonsyndromic deafness and normal-hearing

BACKGROUND:Mutations of mitochondrial DNA were described into two genes: The mitochondrially encoded 12S RNA (MT-RNR1) and the mitochondrially encoded tRNA serineucn (MT-TS1). The A1555G mutation in MT-RNR1 gene is a frequent cause of deafness in different countries.AIM:The aim of this work was to investigate the frequency of the A1555G mutation in the MT-RNR1 gene in the mitochondrial DNA in Brazilians individuals with nonsyndromic deafness, and listeners.MATERIALS AND METHODS:DNA samples were submitted to polymerase chain reaction and to posterior digestion with the Hae III enzyme.RESULTS:Seventy eight (78) DNA samples of deaf individuals were analyzed; 75 showed normality in the region investigated, two samples (2.5%) showed the T1291C substitution, which is not related to the cause of deafness, and one sample (1.3%) showed the A1555G mutation. Among the 70 non-impaired individuals no A1555G mutation or T1291C substitution was found.CONCLUSION:We can affirm that A1555G mutation is not prevalent, or it must be very rare in normal-hearing subjects in the State of Paraná, the south region of Brazil. The A1555G mutation frequency (1.3%) found in individual with nonsyndromic deafness is similar to those found in other populations, with nonsyndromic deafness. Consequently, it should be examined in deafness diagnosis. The investigation of the A1555G mutation can contribute towards the determination of the nonsyndromic deafness etiology, hence, contributing to the correct genetic counseling process.

持続する蛋白尿と難聴のみを主症状としたミトコンドリア DNA 3243 変異症例

要旨: 持続する蛋白尿の精査の過程で進行性感音難聴の存在からミトコンドリア DNA3243 変異の診断がついた一例を経験したので報告する。症例は33歳女性。15歳時より難聴, 蛋白尿を指摘され外来にて経過観察されていた。2009年10月, 腎生検目的のため当院内科に入院した。腎生検の結果, 一部に軽度のメサンギウム増殖を認め, 蛍光抗体法では, 係蹄とメサンギウム領域にIgAの顆粒状沈着を認めた。難聴に対する精査目的にて当科受診し, 右42.5dB・左28.8dB (4分法平均聴力レベル) の高音漸傾型の両感音難聴を認めたため, ミトコンドリア遺伝子検査を行ったところ, ミトコンドリア DNA3243 変異を認めた。後日, 電顕にて podocyte や尿細管上皮細胞に腫大した異常ミトコンドリアの集簇を認めた。IgA腎症を合併したミトコンドリア腎症・難聴と診断し, 現在ユビデカレノン投与下で経過観察中である。 感音難聴患者に原因不明の蛋白尿・腎機能異常を認める場合は, 糖尿病がなくともミトコンドリアDNA3243変異を疑い, 内科と連携した診断・治療を行うことが有効だと思われる。