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。     

线粒体基因G13513A突变导致的线粒体脑肌病六例临床表型分析

目的 报告6例mtDNA G13513A点突变引起的线粒体脑肌病患者的临床、影像学特点,总结mtDNA G13513A突变所致的线粒体病的临床表型.方法 对35例mtDNA常见突变(包括大片段缺失及A3243G、T3271C、A8344G、T8993G/C点突变)检查为阴性的线粒体脑肌病患者,用线粒体DNA全长测序和(或)聚合酶链反应-限制性片段长度多态法检测mtDNA G13513A点突变,分析阳性患者的临床特点,复习文献报道的mtDNA G13513A所致线粒体病的病例.结果 35例患者中有6例存在mtDNA G13513A突变.该6例患者均出现偏盲、轻偏瘫或偏身感觉障碍等卒中样发作表现,其中3例成人发病者以卒中样发作为主要症状,伴随癫痫、头痛、身材矮小、神经性耳聋等,头颅MRI显示以顶-枕-颢叶受累为主的大片病灶,符合成人型线粒体脑肌病伴高乳酸血症和卒中样发作(MELAS)的临床和影像学特点;3例青少年发病者除卒中样发作外,还有构音障碍、共济失调、眼外肌瘫痪等脑干受累的症状,MRI检查可见枕-颞叶大脑皮质非对称性病灶,以及双侧基底节和脑干的对称性病灶,符合青少年型MELAS-Leigh叠加综合征的临床和影像学特点.肌肉病理检查在5例患者发现不整红边纤维.经复习文献,发现mtDNA G13513A突变患者还存在婴幼儿型Leigh或Leigh样综合征表型.结论 mtDNA G13513A点突变是线粒体脑肌病较常见的致病性突变,主要导致Leigh综合征、MELAS-Leigh叠加综合征或MELAS综合征,其临床表型具有年龄依赖性.

Abstract：

Objective To report 6 Chinese patients with mitochondrial encephalomyopathy caused by mitochondrial DNA(mtDNA)G13513A mutation and discuss the mitochondrial phenotype associated with this mutation based on the data of our patient series as well as the reports by others.Methods Direct sequencing of polymerase chain reaction(PCR)products or PCR-RFLP analysis Was performed to screen mtDNA G13513A mutation in 35 cases with mitoehondrial encephalomyopathy.who carried no mtDNA common mutations(1arge 8eale deletion,A3243G,T3271 C,A8344G,or T8993G/C).The clinical features,MRI changes were retrospectively collected and analyzed.Published studies of all patients with mtDNA G13513A mutation were also reviewed.Results Six patients were identified carrying mtDNA G13513A mutation.All patients presented stroke-like episodes with hemianopsia.hemiparesis or hemiparesthesia.Three adult patients presented clinical and radiological features of adult-onset mitochondrial myopathy,encephalopathy,lactic acidosis,and stroke-like episodes(MELAS),including stroke-like episodes,epilepsy,headache,short stature,sensorineural deafness,multifocal lesions on parietal,occipital and temporal lobes on cranial MRI scans.Three iuvenile.onset patients presented the clinical and brain MRI features of MELAS-Leigh syndrome(LS)overlap syndrome.In addition to the stroke-like episodes,they also showed brain stem lesions with dysarthria,ataxia,and ophthalmopJegia. Brain MRI revealed asymmetrical lesions in the cortex of the oecipital and temporal lobes,as well as symmetrical lesions in the bilateral basal ganglia and brainstem.Muslce biopsy showed ragged redfibem in 5 patients.The infant-onset LS or Leigh-like syndrome with mtDNA G135 13A was described in the English literature.Conclusions mtDNA G13513A mutation is a common pathogenic mutmion for mitochondrial encephalomyopathy,which can result in Leigh syndrome,MELAS-LS overlap syndrome and adult MELAS.The onset of various phenotypes is relatively age-dependent.     

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     

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.     

母女线粒体DNA突变位点不同线粒体脑病1例报道并文献复方

目的 报道线粒体脑病mtDNA多突变位点遗传1例,母女mtDNA突变位点不同,并结合相关文献探讨线粒体脑病遗传特点、基因型和表型的相关性。方法 回顾线粒体脑病的遗传特点,对患者家系进行基因检测。结果 本例患者急性起病,以感觉性失语为首发症状,而后癫痫间发作,血生化示CK、LDH升高,肌电图示左上肢肌源性损害可疑,头颅MRI示双侧颞叶皮层和左侧小脑半球片状异常信号,脑室扩大和脑萎缩; 磁共振波谱见右颞叶病灶区NAA峰降低,NAA/Cr降低,双乳酸峰升高; 基因检测发现mtDNA上存在T14484C的点突变,符合线粒体脑病诊断。对患者亲属进行基因检测,发现患者母亲存在T14484C和A3243G位点突变。结论 mtDNA单突变基因遗传极少子代可出现突变位点丢失,多突变基因遗传可以出现部分位点遗传丢失现象。     

8例肢带型线粒体肌病患者的临床、病理特点和线粒体基因突变分析

目的分析肢带型线粒体肌病患者的临床、病理特点及线粒体基因突变情况。方法回顾分析8例肢带型线粒体肌病患者的临床特征及肌肉病理改变,并进行线粒体DNA(mtDNA)突变分析。结果 8例患者发病年龄为5～30岁,病程2～36年,主要表现为四肢近端肌无力和运动耐力下降,仅1例有双下肢肌痛。血肌酸激酶水平呈轻中度升高。电生理检查结果最示骨骼肌呈肌源性或神经源性损害。骨骼肌病理检查结果显示所有患者存在破碎红纤维(RRF),细胞色素C氧化酶染色可见深染的RRF,也可见阴性的RRF。4例患者存在tRNAleu~(UUR)A3243G突变,1例为tRNAlys A8344G突变,1例同时存在tRNAleu~(UUR)A3276G和ATP酶6编码基因G9196A(D224N)突变,1例为细胞色素b编码基因G15221A(D159N)突变,1例则为细胞色素C氧化酶亚单位Ⅲ的编码基因A9567G(I121V)突变。结论肢带型线粒体肌病主要表现为四肢肌无力和运动耐力下降。骨骼肌病理改变存在一定的异质性。mtDNA的tRNA基因可能是家族性肢带型线粒体肌病的热点突变区。     

肌肉活检未见显著异常的MELAS综合征：3例病理病例分析

目的：探讨肌肉活检未见显著线粒体异常病理改变的MELAS综合征的临床、神经影像及分子病理学特点。方法：3例患者（1男,2女）,发病年龄13-18岁,1例以癫痫首发,2例以头痛呕吐首发。3例均有家族史,符合母系遗传方式。主要临床表现包括：癫痫发作(3/3例),视物下降(3/3例),发作性头痛(2/3例),听力减退 (2/3例),身材矮小（2/3例）,智能减退 (2/3例),精神异常(1/3例)。3例患者均进行肱二头肌活检。应用限制性片段长度多态方法对患者尿液mtDNA A3243G位点突变进行分析。结果：3例患者血清肌酸激酶正常,空腹血乳酸增高。肌电图检查正常。头颅MRI示T2异常高信号,枕叶3例,颞叶2例,顶叶2例,动态检查卒中样病灶呈迁徙样改变者1例。肌活检在3例患者均可见个别SDH深染的肌间小血管,未见破碎红肌纤维和COX阴性肌纤维。3例患者mtDNA基因突变分析发现均存在A3243G点突变。结论：MELAS综合征的临床异质性明显,肌无力症状可以不突出,而且肌肉活检可以没有破碎红肌纤维和COX阴性肌纤维,SDH深染的小血管可能有重要提示价值。     

线粒体脑肌病伴高乳酸血症和卒中样发作综合征与一种新的线粒体DNA基因突变

目的 检测1例线粒体脑肌病伴高乳酸血症和卒中样发作综合征(MELAS)患者脑组织和外周血线粒体DNA(mtDNA)的基因突变类型。方法 应用聚合酶链反应-限制性片段长度多态性(PCR—RFLP)方法对这例MELAS患者脑组织和外周血mtDNA的A3243G点突变进行检测，对检测过程中发现的异常扩增产物进行DNA测序分析。结果 该例MELAS患者脑组织和外周血白细胞PCR扩增产物行聚丙烯酰胺凝胶电泳时产生了两条带，一条为494bp，另一条为218bp。494bp的扩增产物是目的片段，而218bp的片段是一种异常扩增产物。我们对218bp的PCR扩增产物进行测序，发现在mtDNA3314—3589之间有276bp的碱基缺失。结论 mtDNA3314-3589位点之间276bp的碱基缺失可能是导致MELAs的一种新的基因突变类型。     

Common mitochondrial DNA and POLG1 mutations are rare in the Chinese patients with adult-onset ataxia on Taiwan

BACKGROUND AND PURPOSE: Spinocerebellar ataxia (SCA) is a heterogeneous group of neurodegenerative disorders with common features of adult-onset cerebellar ataxia. Many patients with clinically suspected SCA are subsequently diagnosed with common SCA gene mutations. Previous reports suggest some common mitochondrial DNA (mtDNA) point mutations and mitochondrial DNA polymerase gene (POLG1) mutations might be additional underlying genetic causes of cerebellar ataxia. We tested whether mtDNA point mutations A3243G, A8344G, T8993G, and T8993C, or POLG1 mutations W748S and A467T are found in patients with adult-onset ataxia who did not have common SCA mutations. METHODS: Four hundred seventy-six unrelated patients with suspected SCA underwent genetic testing for SCA 1, 2, 3, 6, 7, 8, 10, 12, 17, and DRPLA gene mutations. After excluding these SCA mutations and patients with paternal transmission history, 265 patients were tested for mtDNA mutations A3243G, A8344G, T8993G, T8993C, and POLG1 W748S and A467T mutations. RESULTS: No mtDNA A3243G, A8344G, T8993G, T8993C, or POLG1 W748S and A467T mutation was detected in any of the 265 ataxia patients, suggesting that the upper limit of the 95% confidence interval for the prevalence of these mitochondrial mutations in Chinese patients with adult-onset non-SCA ataxia is no higher than 1.1%. CONCLUSIONS: The mtDNA mutations A3243G, A8344G, T8993G, T8993C, or POLG1 W748S and A467T are very rare causes of adult-onset ataxia in Taiwan. Routine screening for these mutations in ataxia patients with Chinese origin is of limited clinical value.     

Leigh syndrome: Clinical features and biochemical and DNA abnormalities

We investigated the etiology of Leigh syndrome in 67 Australian cases from 56 pedigrees, 35 with a firm diagnosis and 32 with some atypical features. Biochemical or DNA defects were determined in both groups, ie, 80% in the tightly defined group and 41% in the “Leigh-like” group. Eleven patients had mitochondrial DNA point mutations (nucleotide [nt] 8993 T to G, nt 8993 T to C, or nt 8344 A to G) and 1 Leigh-like patient had a heteroplasmic deletion. Twenty-nine patients had enzyme defects, ie, 13 respiratory chain complex I, 9 complex IV, and 7 pyruvate dehydrogenase complex (PDHC). Complex I deficiency is more common than recognized previously. Six PDHC-deficient patients had mutations in the X-chromosomal gene encoding the Elα subunit of PDHC. Parental consanguinity suggested autosomal recessive inheritance in two complex IV-deficient sibships. We found no strong correlation between the clinical features and basic defects. An assumption of autosomal recessive inheritance (frequently made in the past) would have been wrong in nearly one-half (1 1 of 28 tightly defined and 18 of 41 total patients) of those in whom a cause was found. A specific defect must be identified if reliable genetic counseling is to be provided.     

A point mutation of mitochondrial ATPase 6 gene in Leigh syndrome.

A T-to-G transition at nucleotide 9176 (T9176G) in the mitochondrial adenosine triphosphate 6 gene (MTATP6) was detected in two siblings with Leigh syndrome. Heteroplasmy was observed in the mother's leukocytes. The T9176G mutation changes a highly conserved leucine residue to an arginine in subunit 6 of ATPase and is maternally inherited like mutations in the other mitochondrial genes. Another mutation in the same codon (T9176C) has been previously reported in Leigh syndrome. This gives strong support to the relevance of MTATP6 dysfunction in Leigh syndrome and the importance of leucine at that position.     

The T9176G mtDNA mutation severely affects ATP production and results in Leigh syndrome

The authors identified a novel mtDNA mutation (T9176G) in the ATPase 6 gene in a family in which a 10-year-old girl had a severe neurodegenerative disorder, her elder sister had died of Leigh syndrome (LS), and a maternal uncle had a spinocerebellar disorder. Biochemical studies disclosed a reduced rate of ATP synthesis in skin fibroblast cultures from the proposita as the likely explanation of her severe illness. The findings expand the genetic variants associated with LS.     

Biochemical and genetic analysis of Leigh syndrome patients in Korea

Sixteen Korean patients with Leigh syndrome were identified at the Seoul National University Children’s Hospital in 2001–2006. Biochemical or molecular defects were identified in 14 patients (87.5%). Thirteen patients had respiratory chain enzyme defects; 9 had complex I deficiency, and 4 had combined defects of complex I + III + IV. Based on the biochemical defects, targeted genetic studies in 4 patients with complex I deficiency revealed two heteroplasmic mitochondrial DNA mutations in ND genes. One patient had the mitochondrial DNA T8993G point mutation. No mitochondrial DNA defects were identified in 11 (68.7%) of our LS patients, who probably have mutations in nuclear DNA. Although a limited study based in a single tertiary medical center, our findings suggest that isolated complex I deficiency may be the most common cause of Leigh syndrome in Korea.     

The mutation at nt 8993 of mitochondrial DNA is a common cause of Leigh's syndrome

Twelve patients with Leigh's syndrome from 10 families harbored a T > G point mutation at nt 8993 of mtDNA. This mutation, initially associated with neurogenic weakness, ataxia, and retinitis pigmentosa, was later found to result in the Leigh phenotype when present in a high percentage. In our patients, the mutation was heteroplasmic, maternally inherited, and appeared to segregate rapidly within the pedigrees. Quantitative analysis revealed a good correlation between percentage of mutant mitochondrial genomes and severity of the clinical phenotype. The mutation was not found in > 200 patients with other mitochondrial encephalomyopathies or in controls. Mitochondrial enzyme activities were normal in all but 1 patient, and there were no ragged-red fibers in the muscle biopsy. Lactic acidosis was present in 92% of patients. Our findings suggest that the mtDNA nt 8993 mutation is a relatively common cause of Leigh's syndrome.     

Adult Leigh syndrome with mitochondrial DNA mutation at 8993

Adult onset Leigh syndrome with a nucleotide (nt) 8993 mutation in mitochondrial (mt) DNA is reported. A 43-year-old woman with a 6-year-history of insulin-resistant diabetes mellitus developed muscular weakness, intractable nausea and vomiting, and anemia. These were followed vertigo, blindness, and deafness with nystagmus. Magnetic resonance imaging (MRI) revealed abnormal high intensities in the bilateral medial regions of the thalamus and periaqueductal gray matters. Autopsy disclosed well-demarcated necrotizing lesions with prominent capillaries in the areas detected by MRI, which were sufficiently diagnostic for Leigh syndrome. MtDNA analysis performed on DNAs extracted from formalin-fixed tissues including liver, heart, brain, muscle, kidney and pancreas showed a T→G mutation at nt 8993. This is the first case of adult Leigh syndrome demonstrating on mtDNA mutations. Received: 24 August 1998 / Revised, accepted: 21 October 1998     

Adult onset Leigh syndrome with mitochondrial DNA 8344 A>G mutation

We report a pedigree of adult-onset Leigh syndrome (LS) with mitochondrial mutation 8344 A>G. A 38-year-old woman presented with optic neuropathy, weakness and cognitive impairment. Family history of optic neuropathy and systemic involvement was suggestive of mitochondrial encephalopathy. Genetic and radiologic studies showed m.8344 A>G mutation with characteristics of LS. To our knowledge this is the first case of adult-onset LS demonstrating the m.8344 A>G mutation.