线粒体脑肌病伴高乳酸血症和卒中样发作综合征的线粒体DNA突变特点

目的探讨线粒体脑肌病伴高乳酸血症和卒中样发作(MELAS综合征)的分子遗传学特点.方法用聚合酶链反应-限制片段长度多态性(PCR-RFLP)方法检测来自7个家庭的9例MELAS患者及其部分母系亲属的肌肉和(或)外周血细胞的mtDNA的A3243G和T3271C点突变,并进行突变型mtDNA的定量.结果在9例患者和1例亲属的肌肉和(或)外周血细胞中检测到A3243G点突变,未检测到T3271C突变.在这10例A3243G阳性标本中,外周血细胞(9例)的突变型mtDNA的比例为26.8%～50.3%;肌肉组织(4例)的突变型mtDNA的比例为46.8%～61.0%;对3例患者同时进行了肌肉和血细胞标本的检测,突变型mtDNA的比例肌肉组织均高于血细胞.对6个家庭的部分母系亲属的血细胞研究表明:只有1例先证者的同胞有此突变;另外3例先证者的母亲及2例先证者的同胞均未检测到此突变.另外有2例先证者的儿子临床表现符合MELAS,血中也检测到此突变.结论 mtDNA A3243G突变在本组MELAS综合征中的发生率较高,并且可在不同组织中检测到此突变,与国外文献报道一致;但国外报道多为母系遗传,而我们的病例以散发的居多,推测是由于新生突变所致.     

线粒体脑肌病伴高乳酸血症和卒中样发作综合征的线粒体DNA突变特点

目的 探讨线粒体脑肌病伴高乳酸血症和卒中样发作（MELAS综合征）的分子遗传学特点。方法 用聚合酶链反应-限制片段长度多态性（PCR-RFLP）方法检测来自7个家庭的9例MELAS患者及其部分母系亲属的肌肉和（或）外周血细胞的mtDNA的A3243G和T3271C点突变,并进行突变型mtDNA的定量。结果 在9例患者和1例亲属的肌肉和（或）外周血细胞中检测到A3243G点突变,未检测到T3271C突变。在这10例A3243G阳性标本中,外周血细胞（9例）的突变型mtDNA的比例为26.8%-50.3%;肌肉组织（4例）的突变型mtDNA的比例为46.8%-61.0%;对3例患者同时进行了肌肉和血细胞标本的检测,突变型mtDNA的比例肌肉组织均高于血细胞。对6个家庭的部分母系亲属的血细胞研究表明：只有1例先证者的同胞有此突变;另外3例先证者的母亲及2例先证者的同胞均未检测到此突变。另外有2例先证者的儿子临床表现符合MELAS,血中也检测到此突变。结论 mtDNA A3243G突变在本组MELAS综合征中的发生率较高,并且可在不同组织中检测到此突变,与国外文献报道一致;但国外报道多为母系遗传,而我们的病例以散发的居多,推测是由于新生突变所致。     

线粒体DNA A3243G点突变在成年患者中的临床特点

目的 探讨mtDNA A3243G点突变在成年患者的临床表现特点.方法 对发病年龄在18岁以上的36例患者的临床资料进行分析(5个家系28例,散发8例),其中23例行mtDNAA3243G点突变检查(5个家系15例,散发8例),14例行头颅影像学检查,10例进行了骨骼肌病理检查.结果 5个家系的28例患者中出现糖尿病17例(60.7%)、耳聋16例(57.1%)、卒中样发作9例(32.1%),三者可以并存或单独出现,少见表现包括心肌病和肾脏损害.23例mtDNA A3243G点突变患者中线粒体脑肌病伴随乳酸血症和卒中样发作(MELAS)14例(61.0%),其主要表现为认知功能障碍、言语障碍和头痛;其余9例包括无症状的基因突变携带者3例(13.0%)、线粒体糖尿病和(或)神经性耳聋2例(8.7%)、自主神经功能异常2例(8.7%)、糖尿病伴不孕症1例(4.3%)和心肌病1例(4.3%).14例MELAS患者的头颅影像学检查显示以枕叶和颞叶受累为主,额叶最少;10例肌肉病理检查发现9例存在不整红边纤维.mtDNA A3243G点突变比例均值在MELAS患者为28.75%±13.69%,非MELAS患者为25.08%±11.54%,两者差异没有统计学意义.结论 mtDNAA3243G点突变在成年患者主要累及中枢神经、胰岛以及听神经.认知功能障碍、言语障碍和头痛是成年MELAS的主要临床表现.家族中多例患者出现糖尿病和耳聋,提示该突变并非MELAS突变,应当关注mtDNA A3243G点突变家系中非MELAS患者的存在.     

遗传性共济失调线粒体DNA 3243、8993点突变的研究

目的研究线粒体DNA点突变与遗传性共济失调(HA)的关系。方法采用聚合酶链反应方法,扩增26例HA患者和35例健康对照者的外周血白细胞线粒体DNA,用限制片断长度多态性分析法检测有无A3243G、T8993G或T8993C点突变。结果所有HA患者和健康对照者均未检测到线粒体DNA点A3243G、T8993G或T8993C点突变。结论线粒体DNAA3243G、T8993G或T8993C基因突变导致HA的可能性不大。     

DNA A3243G突变相关MELAS综合征4例临床特点及治疗

目的探讨DNA A3243G突变相关的线粒体脑肌病伴乳酸血症与卒中样发作综合征(Mitochondrial encephalomyopathy,lactic acidosis,and stroke-like episodes,MELAS)的临床特点及基因学表型,提高临床医生对该病的认识及诊断。方法回顾性分析2017年6月—2018年6月于河南省人民医院小儿神经内科门诊及住院诊治的4例DNA A3243G突变相关MELAS综合征患儿的临床资料及影像学特征,并复习相关文献。结果 4例患儿中3例因抽搐、1例因头晕起病,经基因检测证实均为线粒体DNA A3243G突变引起的MELAS综合征,予以抗癫痫治疗,随访1年,4例患者中2例患儿病情稳定,1例患儿仍有发作,1例患儿病情无好转。结论 DNA A3243G突变相关MELAS综合征患者的临床表型异质性多因DNA突变的"异质性"和"阈效应"所致,DNA A3243G突变率高达80%,在提倡精准医疗的时代,基因检查有助于MELAS综合征的早期确诊和治疗,提高患者的生活质量,改善预后。     

线粒体脑肌病伴高乳酸血症和脑卒中样发作综合征一家系临床特征及线粒体基因A3243G位点点突变异质性水平

目的 调查1个疑似患有母系遗传性线粒体脑肌病伴高乳酸血症和脑卒中样发作(MELAS)综合征家系的临床表现、生物化学检测数据和影像学资料,并探索其与血细胞线粒体基因突变异质性水平的关联性.方法 收集先证者和11位其母系家系成员的一般情况、抽搐及脑卒中样发作等病史,检测家系成员的血常规和运动前后血浆乳酸水平等生化指标,并做头颅磁共振检查.用聚合酶链反应(PCR)-限制性内切酶片段长度多态和DNA测序法检测其成员是否存在线粒体基因组A3243G点突变,并用荧光实时定量PCR定量该突变的水平.结果 该家系部分成员存在抽搐、脑卒中样发作和高乳酸血症等MELAS综合征典型症状,以及身材矮小、运动不耐受和发热、偏头痛等非典型症状.发作期头颅磁共振成像符合MELAS综合征的典型特点,且普遍存在小脑萎缩.母系亲属均存在线粒体基因的A3243G位点点突变,突变异质性水平越高,症状越典型且严重.结论 该调查家系确诊母系遗传性MELAS综合征,其致病基因为线粒体A3243G点突变.外周血血细胞线粒体基因突变异质性水平与亲缘关系、抽搐早现性和血乳酸值等临床表型存在相关性.     

线粒体3243位点基因点突变异质性水平与MELAS病临床特征的家系分析

背景 线粒体脑肌病伴高乳酸血症及卒中样发作（MELAS）是线粒体疾病中最常见的一种,它主要由线粒体基因组第3243号位点的腺嘌呤突变为鸟嘌呤所导致的。本研究的目的即是调查一个疑似患有母系遗传性MELAS病家系的临床表现、生化学检测数据和影像学资料,并探索其与血细胞线粒体基因突变异质性水平的关联性。 方法 收集先征者和其母系家系12人的自然情况、抽搐及卒中样发作等病史,检测家系成员的血常规和运动前后血浆乳酸水平等生化指标,并做头部磁共振检查。之后用聚合酶链反应-限制性内切酶片段长度多态性（PCR-RFLP）法和DNA测序法检测并验证其成员存在线粒体基因组的m.3243A>G点突变,并用荧光实时定量PCR法（Real-time PCR）来定量m.3243A>G的水平。 结果 该家系部分成员存在抽搐、卒中样发作和高乳酸血症等MELAS病典型症状和身材矮小、运动不耐受和发热、偏头痛等非典型症状。发作期头磁共振符合MEALS病影像学资料的典型特点,且普遍存在小脑萎缩表现。母系亲属均存在线粒体基因的3243位点点突变,同时突变异质性水平越高,症状越典型且严重。 结论 该调查家系确诊母系遗传性MELAS病,其致病因素为线粒体A3243G点突变。突变异质性水平与亲缘关系、抽搐早现性和血乳酸值等临床表型存在相关性。     

线粒体脑肌病伴有高乳酸血症和卒中样发作综合征的临床及基因突变分析

目的 探讨线粒体脑肌病伴有高乳酸血症和卒中样发作综合征(MELAS)的临床及基因突变特征. 方法 对1例MELAS患者的临床表现、影像学、肌肉病理特点进行分析,并用PCR-RFLP结合基因测序方法进行线粒体基因突变分析. 结果 患者主要临床表现为发作性头痛和呕吐、反复卒中样发作、癫痫、运动不耐受、身材矮小、神经性耳聋、乳酸水平升高等.脑CT见双侧基底节多个钙化灶,MRI见枕叶异常信号,1H-MRS见T2WI异常信号区域有明显的乳酸峰,在T2正常信号区域也有小的乳酸峰.光镜及电镜肌肉病理检查未见明显的线粒体异常,基因检测显示mtDNA A3243G杂合突变. 结论 MELAS的诊断必须结合临床表现、影像学、病理学和基因突变检测等结果进行综合分析,病理学检查阴性不能否定MELAS的诊断,诊断MELAS应常规进行mtDNA突变分析.     

线粒体脑肌病患者的基因突变研究

目的 探讨线粒体脑肌病患者骨骼肌细胞线粒体DNA基因突变情况及发病机制。方法 观察总结5例线粒体脑肌病患者的临床表现,影像学变化特点,并应用PCR、限制性内切酶BglⅠ、ApaⅠ酶切,PAGE电泳鉴定DNA片段长度的方法,检测5例患者骨骼肌细胞中mtDNA是否发生nt3243和8344位点A→G突变。结果 5例患者（3例MELAS和2例MERRF）在临床表现和影像学改变等方面均与国外学者的研究结果相符。1例MELAS患者仅存在3243A→G点突变,1例MERRF患者存在8344A→G点突变,1例MERRF上述2个位点均存在突变。另2例呈家系起病的MELAS患者这2个位点都无突变。结论 3243及8344位点突变分别与MELAS和MERRF的发病有关,MERRF患者可以同时存在上述2个位点的突变。临床表现仍是确诊和分类的主要依据。Ⅰ     

家族性线粒体脑肌病并乳酸血症与卒中样发作的临床特点

正线粒体病是一组由于线粒体结构功能异常所导致的脑和肌肉受累为主的多系统遗传代谢性疾病。线粒体脑肌病伴高乳酸血症和卒中样发作(MELAS)是最常见的类型,其中80%MELAS患者的致病基因和mt DNA A3243G点突变有关~([1])。本文报道一对MELAS母女,对比两者临床特点结合文献,旨在对该病的临床与分子遗传学特征进一步认识。     

Clinical and genetic features in two families with MELAS and the T3271C mutation in mitochondrial DNA

The majority of patients with MELAS (mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes) have the A3243G point mutation. The much rarer T3271C mutation has been reported predominantly in Japanese subjects. Our objective was to better define the clinical phenotype and mutation load in patients with MELAS and the T3271C mutation in mitochondrial DNA. We present clinical and molecular genetic data in two pedigrees with the T3271C mutation. The age at onset was 8 years in one proband and 14 years in the other. Both patients had migrainelike headache, seizures, and strokelike episodes. Mutation loads were quantified in multiple tissues from the patients and from family members by polymerase chain reaction-restriction fragment length polymorphism analysis. The symptoms in both probands were typical of MELAS, and, contrary to previous reports, onset was early. Hearing loss was less common than in typical MELAS, and ragged red fibers were absent. The proportion of mutant genomes was consistently and markedly greater in DNA from urinary sediment than from blood. In the mother of one proband, mutant genomes were detected only in DNA from hair follicles and cheek mucosa The phenotype of patients with the T3271C mutation might not be as distinct as that of the A3243G mutation, as previously described. Our data also suggest that urine is a better source of DNA than blood for diagnosis and that multiple tissues should be studied in maternal relatives, especially when the mutation cannot be detected in blood.     

MELAS syndrome with mitochondrial tRNA(Leu(UUR)) gene mutation in a Chinese family.

The clinical features of a patient in a Chinese family with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS syndrome) are reported. The study revealed that hearing and visual impairments and miscarriages may be early clinical presentations in MELAS. A heteroplasmic A to G transition in the tRNA(Leu(UUR)) gene was noted at the nucleotide pair 3243 in the mitochondrial DNA of muscle, blood, and hair follicles of the proband and his maternal relatives. Quantitative analysis of the mutated mitochondrial DNA revealed variable proportions in different tissues and subjects of maternal lineage in the family. Muscle tissue contained a higher proportion of the mutant mitochondria than other tissues examined. The function of the reproductive system of the proband seems to be impaired. In one clinically healthy sibling, the 3243rd point mutation was found in sperm mitochondrial DNA, although sperm motility was not affected. It seems that biochemical defects in mitochondrial respiration and oxidative phosphorylation are tissue specific expressions of the 3243rd point mutation in the mitochondrial DNA of the affected target tissues.     

Clinical and genetic features in a MELAS child with a 3271T>C mutation

A mitochondrial DNA 3271T>C point mutation was reported to be the second most common mutation (following the mutation 3243A>G) in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) in Japan. This mutation has rarely been reported in other countries. We present an 11-year-old Taiwanese girl with MELAS, who harbored the 3271T>C mutation and had manifested short stature, epilepsia partialis continua, and recurrent basal ganglia infarctions since age 6 years, and rapid intellectual regression, dysarthria, and unsteady gait since age 10 years. The proportion of 3271T>C mutant genomes in various tissues, including urinary sediments, hair follicles, blood leukocytes, and buccal mucosa cells from the patient and her mother, was analyzed by polymerase chain reaction-restriction fragment length polymorphism analysis and quantitative real-time polymerase chain reaction. The proportion of mutant load in the patient's muscles was near 100%. Except for muscle, the highest mutation load was detected in urinary sediments of the patient by both methods. This is the first report involving mutant load analysis with quantitative real-time polymerase chain reaction in the 3271T>C mutation. The results suggest that urinary sediments may be an alternative tissue of choice which can be obtained noninvasively in the diagnosis of mitochondrial DNA 3271T>C mutations.     

Absence of maternal A3243G mtDNA mutation and reversible hyperglycemia in a patient with MELAS syndrome

We report the unusual features of a female patient who had MELAS-specific A3243G mutation in mitochondrial DNA (mtDNA) and diabetes mellitus (DM). The patient showed mitochondrial myopathy, encephalopathy, lactic acidosis, and deafness but lacked the stroke-like episode. Acute hyperglycemia was noted after one attack of status epilepticus. Molecular genetic analysis demonstrated a heteroplasmic A3243G point mutation in the mtDNAs of muscle, blood cells and hair follicles. Glucagon stimulation test exhibited marked depression of pancreatic beta-cell function. However, in a further study neither this mutation, nor MELAS syndrome or DM, was found in all of her maternal relatives. A series of follow-up studies for beta-cell function also showed gradual improvement. The pedigree study led us to believe that this A3243G mutation arose from the germ line cells or occurred later in somatic tissues of the patient. We also suggest that the A3243G mutation of mtDNA may elicit the pathogenesis of a subtype of DM. Nevertheless, environmental stress may be another important factor for provocation of the disease.     

Association of the MELAS m.3243A>G mutation with myositis and the superiority of urine over muscle,blood and hair for mutation detection

A patient with a known family history of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) due to the MT-TL1 m.3243A>G mutation presented with mild myalgia and very minor upper limb proximal muscle weakness. Muscle histology revealed low levels of cytochrome oxidase-negative fibres and non-specific myositis. Using the last “hot cycle” polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP), the MELAS MT-TL1 m.3243A>G mutation was only detected in urine, and not in hair, blood or skeletal muscle. This report highlights the need to screen various tissues to achieve an accurate mitochondrial genetic diagnosis and suggests the likelihood of myositis arising secondary to the MELAS MT-TL1 m.3243A>G mutation.     

MERRF/MELAS overlap syndrome in a family with A3243G mtDNA mutation

Four members of a family were found to carry the A3243G mtDNA mutation. Clinical features varied from typical MELAS to myoclonic epilepsy to simple deafness without neurological signs. Several other members of the family had symptoms consistent with a mitochondrial disease. Muscle biopsy in 3 of the 4 patients showed the most prominent mitochondrial alterations with partial deficiency of cytochrome c oxidase in the case with the mildest phenotype. Mitochondrial DNA analysis detected a variable percentage of A3243G mutation, roughly correlating with the phenotype. The interesting feature of the family lies in the great intrafamilial variability of the severity of clinical expression, encompassing MELAS and MERRF features, associated with the A3243G mtDNA mutation. A search for the most common mtDNA mutations is recommended in all patients featuring incomplete MELAS or MERRF syndromes and in all familial cases presenting minimal clinical signs.     

Mitochondrial 3243 A-->G mutation (MELAS mutation) associated with painful muscle stiffness.

The mitochondrial mutation A-->G at nucleotide position 3243 is associated with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and other mitochondrial encephalomyopathies. We found this mutation in a 61-year-old patient who developed at the age of 54 a myopathy with painful muscle stiffness as the predominant symptom. Additionally hypacusis, a mild hemisensory syndrome and impaired glucose tolerance were present. Muscle histopathology showed few ragged red fibers. The mutation was detected heteroplasmatically in DNA from muscle and blood. So far painful muscle stiffness has not been a known phenotype of the 3243 mutation.     

Nerve conduction abnormalities in patients with MELAS and the A3243G mutation

BACKGROUND: Mitochondrial DNA point mutations are especially deleterious to tissues with high energy demand, including the peripheral nervous system. Neuropathy has been associated with several mitochondrial diseases, including MELAS (mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes). OBJECTIVE: To evaluate nerve conduction in a genotypically and phenotypically homogeneous group of patients with MELAS and the A3243G mutation. DESIGN: We studied 30 patients with MELAS and the A3243G mutation using neurophysiological techniques, medical history questionnaires, laboratory tests, and a standardized neurological examination. RESULTS: Twenty-three subjects (77%) had abnormal nerve conduction measures. Symptoms suggestive of neuropathy were present in only half of the patients, but almost all had decreased reflexes or distal sensory findings on examination. Nerve conduction abnormalities were predominantly axonal and sensory and mainly present in the legs. Patients with nerve conduction abnormalities tended to be older and were more likely male. CONCLUSIONS: Peripheral nerve impairment is common in those with MELAS and the A3243G mutation, and may be subclinical. Male sex and older age may add to the genetic disposition to develop neuropathy.     

MELAS mitochondrial DNA mutation A3243G reduces glutamate transport in cybrids cell lines

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.