线粒体肌病和脑肌病患者的肌细胞线粒体DNA突变分析

从１７例原发性线粒体肌病和脑肌病患者骨骼肌活检标本中，经ＤＮＡ抽提，以线粒体ＤＮＡ全长为探针进行了ＤＮＡ杂交，并通过聚合酶链式反应，确认两例慢性进行性眼外肌瘫痪者有线粒体ＤＮＡ改变。其中一例是改变了内切酶ＰｖｕⅡ限制位点的点突变；另一例的线粒体ＤＮＡ存在有约５ｋｂ的“共有缺失”大段。     

线粒体肌病患者线粒体DNA的突变分析

目的分析线粒体肌病患者线粒体DNA的突变情况，为疾病诊断提供依据。方法用常规HE、酶组化染色和电镜检查等病理形态学方法对3例线粒体肌病疑似患者进行诊断，并用聚合酶链反应-单链构象多态和DNA测序等方法对患者线粒体DNA中全部22个tRNA基因进行突变筛查。结果3例患者均被确诊为线粒体肌病，其中例1tRNA—VaI基因发生A1627G纯合突变，例2tRNA—Val基因发生A1627G／A杂合突变，例3tRNA—Trp基因发生T5554C突变、tRNA—Arg基因发生A10412C／A杂合突变。结论线粒体DNA中的tRNA基因突变是线粒体肌病的重要病因之一。     

一例MELAS的线粒体DNA突变

为了检测中国ＭＥＬＡＳ患者的致病因素，采用Ｓｏｕｔｈｅｒｎ印迹杂交、ＰＣＲ、亚克隆及ＤＮＡ测序等技术，对１例中国线粒体脑肌病、乳酸中毒、中风样发作综合征（ｍｉｔｏｃｈｏｎｄｒｉａｌｅｎｃｅｐｈａｌｏｍｙｏｐａｔｈｙｗｉｔｈｌａｃｔｉｃａｃｉｄｏｓｉｓａｎｄｓｔｒｏｋｅ－ｌｉｋｅｅｐｉｓｏｄｅｓ，ＭＥＬＡＳ）患者的线粒体ＤＮＡ（ｍｔＤＮＡ）进行了突变分析。检测到ＭＥＬＡＳ患者特有的Ａ→Ｇ３２４３碱基替换，这一替换导致了一个新的ＡｐａⅠ酶切位点的形成。此突变型ｍｔＤＮＡ在检测的骨骼肌及血液标本中均被发现。突变型ｍｔＤＮＡ在检测的骨骼肌及血液ｍｔＤＮＡ标本中所占的比例分别为８０％和６０％。推测这一影响到ｍｔＤＮＡ中ｔＲＮＡｌｅｕ（ＵＵＲ）基因二氢尿嘧啶环的核苷酸突变是此例ＭＥＬＡＳ的重要致病因素。此外，在所测ｍｔＤＮＡ５６１ｂｐ（２９５０～３５１０）范围内还发现了１个Ｇ→ＴＮＤ１３４２３中性突变。     

慢性进行性眼外肌麻痹2例报道及文献复习

目的 探讨慢性进行性眼外肌麻痹(CPEO)的临床病理特征。方法 应用光镜、电镜和酶组织化学对2例CPEO肌肉活检标本进行形态学观察。结果 HE染色肌组织中见散在分布的，多少不等的嗜盐基性肌纤维。在改良GOMORI三色染色上，这些嗜盐基性肌纤维边缘由于呈现不规则红色，即称不整边红纤维或破碎红纤维。细胞色素氧化酶(CCO)和琥珀酸脱氢酶(SDH)双染色，阳性的蓝色纤维与不整边红纤维的分布一致，数量也较改良GOMORI三色染色增多。结论 改良GOMORI三色染色应作为诊断线粒体疾病的常规染色，CCO／SDH双染色可提高阳性肌纤维的检出率。     

线粒体DNA与人精子活力间的相关性分析

目的 探讨线粒体ＤＮＡ与人精子活力间的关系。方法 用长链ＰＣＲ技术,对６０例精子活力正常和４０例精子活力异常不育患者的精子线粒体ＤＮＡ（ｍｔＤＮＡ）进行了多重缺失的分析。结果 两组不育患者中共有８例具有ｍｔＤＮＡ的多重缺失（其中精子活力正常不育患者６名,精子活力异常不育患者２名）,但缺失型ｍｔＤＮＡ（Ｓ５除外）在总ｍｔＤＮＡ中所占比例很小（０．１６％～１．８５％）,１例精子活力正常的不育患者（Ｓ５     

两个非综合征型耳聋家系中线粒体DNA 12S rRNA基因A827G突变

目的探讨线粒体DNA（mitochondrial DNA，mtDNA）12S rRNA基因与中国人非综合征型遗传性耳聋的关系。方法对两个母系遗传性的非综合征型耳聋家系中20名成员及32例散发耳聋患者外周血DNA进行12S rRNA、tRNA^ser（UCN）以及GJB2基因PCR扩增，产物通过限制性片段多态性分析及基因测序，进行突变检测和分析。结果所有研究对象的基因区域均扩增成功。12S rRNA全序列测定发现两家系中所有受检的母系成员（包括12例耳聋患者）均存在nt827A→G转换，并表现为同质性突变。而非母系成员该位点序列正常。32例散发耳聋中有1例A827G突变阳性。未检测到GJB2基因、tRN^ser（UCN） A7445G及12S rRNA A1555G突变。结论再次验证了mtDNA 12S rRNA基因突变在母系遗传性非综合征型耳聋发病中的重要性。首次发现mt DNA 12S rRNA nt827A→G转换是导致两个中国家系耳聋遗传易感性的分子基础。     

线粒体神经消化道脑肌病家系中线粒体DNA A3243G和PRSS1 IVS3＋75G→A混合突变分析

了解线粒体神经消化道脑肌病（mitochondfial neumgastrointestinal encephalomyopathy,MNGIE）家系中线粒体基因和胰蛋白酶原基因（cationic trypsinogen gene,PRSSl）的突变情况。对一MNGIE家系和60例健康体检者的mtDNA和PRSSl基因进行PCR扩增,产物纯化后直接测序,同时收集患者的一般临床资料。家系中3例糖尿病患者（Ⅰ2、Ⅱ2、Ⅲ1）均发现mtDNAA3243G突变,先证者表现出明显的神经精神症状并伴发慢性胰腺炎和糖尿病,血浆乳酸水平明显高于正常对照;2例胰腺炎患者（I2、112）中发现IVS3＋75G〉A突变     

一个2型糖尿病家系的线粒体基因nt3426 A→G突变分析

目的 了解线粒体DNA NDI nt3426A→G点突变在一个2型糖尿病家系中的发生情况及临床特点。方法 提取家系成员外周血DNA，用聚合酶链反应扩增、限制性内切酶Apa I消化进行点突变筛选，并收集家系的临床资料。结果 21名家系成员中12名母系亲属均存在nt3426A→G突变，而在配偶及父系亲属中未发现该突变。12名突变者中包括2型糖尿病患者7人、糖耐量减低者1人、空腹血糖受损者1人及糖耐量正常者3人。结论 线粒体DNA NDl基因nt3426A→G突变是该家系中糖尿病的易感因素，可协同其他因素(如肥胖、增龄、不良生活习惯等)共同参与糖尿病的发生。     

线粒体脑肌病的影像学表现

线粒体病：是由线粒体DNA（mtDNA）和细胞核DNA（nDNA）编码线粒体相关蛋白的基因突变,导致线粒体的结构及功能异常,而引起细胞呼吸链及能量代谢障碍的一种多系统受累疾病（骨骼肌、脑、心、周围神经）,线粒体几乎存在人体所有细胞内,脑和肌肉组织线粒体含量丰富。病变累及骨骼肌称线粒体肌病,如中枢神经系统同时受累称线粒体脑肌病。线粒体mtDNA的突变（位点突变、缺失、重复及丢失）引起不同类型,临床呈现多个症候群。     

先天性眼外肌纤维化综合征Ⅰ型一家系KIF21A基因突变分析

目的 研究一个先天性眼外肌纤维化综合征Ⅰ型(congenital fibrosis of the extraocular muscles type 1,CFEOM1)家系KIF2lA基因第20、21外显子突变与疾病的关系.方法 收集CFEOM1 一家系共计8个成员,采用测序和等位基因特异性PCR(allele-specific PCR,AS-PCR)方法分别对先证者及家系成员KIF21A第20、21外显子热点突变c.2860C＞T进行分析.选择KIF21A基因两侧4个STR位点(D12S1668、D12S2194、D12S331和D12S1048)进行单倍型分析.结果 先证者和其他两例患者均存在KIF21A c.2860C＞T突变,家系中表型正常的成员均未检出该突变.单倍型分析结果显示该家系突变来源于母源性生殖腺嵌合体.结论 KIF21A基因突变c.2860 C＞T是该CFEOM1家系的致病突变.     

Chronic progressive external ophthalmoplegia with inflammatory myopathy

Chronic progressive external ophthalmoplegia is one of mitochondrial disorders, characterized by ptosis, limitation of eye movement, variably severe bulbar muscle weakness and proximal limb weakness. Chronic progressive external ophthalmoplegia complicated with acquired disease is extremely rare. We report a 44 years old male patient with more than 20 years of chronic progressive bilateral ptosis and limitation of eye movements manifested dysarthria, dysphagia and neck muscle weakness for 3 years. The first muscle biopsy showed red-ragged fibers and cytochrome c oxidase negative fibers as well as inflammatory cells infiltration. Electron microscopy revealed paracrystalline inclusions. Mitochondrial genetic analysis demonstrated a large-scale mtDNA deletion of m.8470_13446del4977. The patient was treated with prednisone. In a three-year follow-up study, the second biopsy was performed. Before the treatment, except bilateral ptosis and external ophthalmopelgia, this patient presented bulbar muscle weakness and neck muscle weakness. After treated with prednisone, the symptoms of dysphagia, dysarthria and neck muscle weakness were significantly improved, and the second biopsy showed only mitochondrial myopathy pathology but the inflammations disappeared. Here, we report a patient with chronic progressive external ophthalmoplegia complicated with inflammatory myopathy and after treated with prednisone as myositis, he had a significant therapeutic effect.     

Homozygous mutations in C1QBP as cause of progressive external ophthalmoplegia (PEO) and mitochondrial myopathy with multiple mtDNA deletions

Biallelic mutations in the C1QBP gene have been associated with mitochondrial cardiomyopathy and combined respiratory‐chain deficiencies, with variable onset (including intrauterine or neonatal forms), phenotypes, and severity. We studied two unrelated adult patients from consanguineous families, presenting with progressive external ophthalmoplegia (PEO), mitochondrial myopathy, and without any heart involvement. Muscle biopsies from both patients showed typical mitochondrial alterations and the presence of multiple mitochondrial DNA deletions, whereas biochemical defects of the respiratory chain were present only in one subject. Using next‐generation sequencing approaches, we identified homozygous mutations in C1QBP. Immunoblot analyses in patients' muscle samples revealed a strong reduction in the amount of the C1QBP protein and varied impairment of respiratory chain complexes, correlating with disease severity. Despite the original study indicated C1QBP mutations as causative for mitochondrial cardiomyopathy, our data indicate that mutations in C1QBP have to be considered in subjects with PEO phenotype or primary mitochondrial myopathy and without cardiomyopathy.     

Humanin expression in skeletal muscles of patients with chronic progressive external ophthalmoplegia

We showed that humanin (HN), an endogenous peptide against Alzheimer disease-related insults, was expressed in muscles of patients with chronic progressive external ophthalmoplegia (CPEO), a major mitochondrial disease. Because HN was recently found to block proapoptotic Bax function and exert its versatile cytoprotective effects in association with an increase in ATP levels, HN expression may thus reflect a physiological response against degenerative changes in the muscles of patients with CPEO. We found HN expression in all four patients examined, each of whom had different mitochondrial DNA mutations including two different single DNA deletions, multiple deletions, and no major mutations detected. We also found that HN expression was not linked to focal cytochrome c deficiency, strongly associated with the subtype of CPEO with single deletions. These results suggest that HN expression is more closely related to degenerative changes in all types of CPEO. Notably, HN was also expressed in non-degenerative muscle fibers of patients with CPEO or Leigh syndrome, who had the 8993T>G mutation in the mitochondrial ATPase 6 gene known to be associated with impaired ATP synthesis. Collectively, our findings suggest that HN may be specifically expressed in response to defects in energy production in muscles with mitochondrial abnormalities.     

Mitochondrial DNA deletions in progressive external ophthalmoplegia and Kearns-Sayre syndrome

We investigated the correlations of deletions of mitochondrial DNA in skeletal muscle with clinical manifestations of mitochondrial myopathies, a group of disorders defined either by biochemical abnormalities of mitochondria or by morphologic changes causing a ragged red appearance of the muscle fibers histochemically. We performed genomic Southern blot analysis of muscle mitochondrial DNA from 123 patients with different mitochondrial myopathies or encephalomyopathies. Deletions were found in the mitochondrial DNA of 32 patients, all of whom had progressive external ophthalmoplegia. Some patients had only ocular myopathy, whereas others had Kearns-Sayre syndrome, a multisystem disorder characterized by ophthalmoplegia, pigmentary retinopathy, heart block, and cerebellar ataxia. The deletions ranged in size from 1.3 to 7.6 kilobases and were mapped to different sites in the mitochondrial DNA, but an identical 4.9-kilobase deletion was found in the same location in 11 patients. Biochemical analysis showed decreased activities of NADH dehydrogenase, rotenone-sensitive NADH-cytochrome c reductase, succinate-cytochrome c reductase, and cytochrome c oxidase, four enzymes of the mitochondrial respiratory chain containing subunits encoded by mitochondrial DNA. We conclude that deletions of muscle mitochondrial DNA are associated with ophthalmoplegia and may result in impaired mitochondrial function. However, the precise relation between clinical and biochemical phenotypes and deletions remains to be defined.     

High proportions of mtDNA duplications in patients with Kearns-Sayre syndrome occur in the heart

Kearns-Sayre syndrome (KSS) is a sporadic multisystem mitochondrial disorder characterized by progressive external ophthalmoplegia, pigmentary retinopathy, onset before age 20, and severe cardiac conduction defects that can lead to death. KSS patients harbor partial deletions of mitochondrial DNA (-mtDNA), sometimes associated with the corresponding mtDNA duplication (dup-mtDNA). As reports on the distribution of dup-mtDNAs among KSS tissues are scarce, we searched for the presence of dup-mtDNAs in different autopsy tissues of two such patients, one of whom carried the so-called “common deletion.” Using a newly developed long polymerase chain reaction (PCR) protocol in conjunction with Southern blot analyses, we found dup-mtDNAs in most of the examined tissues from both patients. The proportion of dup-mtDNA in these tissues was much lower than the proportion of -mtDNA, with one notable exception: in both patients, we found an unusually high level of dup-mtDNA in the heart. These data suggest that dup-mtDNAs may be more stable in heart tissue of KSS patients than in other long-lived postmitotic tissues. Am. J. Med. Genet. 71:443–452, 1997. © 1997 Wiley-Liss, Inc.     

An autopsy case of chronic progressive external ophthalmoplegia with renal insufficiency

An autopsy of a 44-year-old Japanese woman with mitochondrial cytopathy confirmed the presence of chronic progressive external ophthalmoplegia (CPEO). Immunohistochemistry using antimitochondrial antibody was performed to observe the ultrastructure of the skeletal muscle and renal tissues. The patient was born of consanguineous parents, developed normally, and was of average intelligence. At 22 years of age, the patient noticed hearing loss, and subsequently, over time, developed a progressive generalized muscle weakness, which included limitation of eye movement and ptosis. At age 41, a muscle biopsy was performed using the modified Gomori trichrome method and demonstrated the presence of ragged red fibers. After the evaluation of her results in conjunction with her clinical course, she was diagnosed with CPEO. Renal insufficiency was discovered at age 30, and the patient died at the age of 44 of respiratory failure caused by respiratory muscle weakness and pneumonia. The autopsy revealed fiber size variation within the skeletal muscle, and an antimitochondrial antibody analysis demonstrated the accumulation of mitochondria between the bundles of myofibrils, as well as in subsarcolemmal locations. Ultrastructurally, abnormal mitochondria with disoriented cristae and paracrystalline inclusions were seen. Although no remarkable histological changes were noted in the kidneys, tubular epithelial cells exhibited accumulated abnormal mitochondria, similar to those seen in the skeletal muscle. Because mitochondrial diseases can affect other energy-dependent organs in addition to the skeletal muscle, immunohistochemical examina-tions employing an antimitochondrial antibody are useful for obtaining further ultrastructural observations that can assist in making a distinct diagnosis of this systemic disorder.     

Endocrine abnormalities in mitochondrial myopathy with external ophthalmoplegia

Summary Endocrine functions were examined in 21 patients with mitochondrial myopathies presenting with chronic progressive external ophthalmoplegia and other additional neurological and multisystemic symptoms. Ten patients had the features of the Kearns-Sayre syndrome. Deletions of the mitochondrial DNA were found in 4 out of 5 patients examined. Fourteen patients, including 3 with deletions of the mitochondrial DNA, had various and often multiple endocrine abnormalities: 6 patients were of short stature, 3 had irregular menstrual cycles, 3 had undersized testicles, 5 showed an insufficient rise of growth hormone following the administration of growth-hormone-releasing hormone, 4 showed an insufficient rise in FSH after administration of gonadotropin-releasing hormone, 5 had manifest diabetes mellitus, 3 showed an impaired glucose tolerance, and 2 patients had subnormal serum levels of parathormone in combination with hypocalcaemia. One patient additionally had Klinefelter's syndrome with a kariotype 47, XXY and increased levels of FSH and LH, subnormal levels of testosterone and subnormal testicular volume. The occurrence of endocrine defects correlated with the duration of disease. The data demonstrate that endocrine abnormalities are frequently associated with mitochondrial myopathy, indicating that this multisystemic disease also involves various endocrine tissues.Abbreviations ACTH adrenocorticotropic hormone - CoQ coenzyme Q₁₀ - CRH corticotropin-releasing hormone - FSH follicle-stimulating hormone - GH growth hormone - GHRH growth-hormone-releasing hormone - GnRH gonadotropin-releasing hormone - LH luteinizing hormone - mtDNA mitochondrial DNA - PTH parathormone - TRH thyrotropin-releasing hormone - TSH thyroid-stimulating hormone - T₃ triiodothyronine - T₄ thyroxine     

In situ hybridization of mitochondrial DNA in the heart of a patient with Kearns-Sayre syndrome and dilatative cardiomyopathy

Previous studies have revealed cytochrome-c-oxidase-deficient cardiomyocytes and the 4,977 base pair deletion ("common deletion") of mitochondrial DNA (position 8,482-13,459) in the heart of a patient with dilatative cardiomyopathy and Kearns-Sayre syndrome. In the present investigation the co-localization of the enzymatic and genomic defects was studied. In situ hybridization of mitochondrial DNA (mtDNA) revealed different hybridization patterns in the cytochrome-c-oxidase-deficient cells: (1) a selective reduction of the hybridization signal with an mtDNA probe recognizing the common deletion, indicating predominance of the deleted over the nondeleted mtDNA molecules in the cytochrome-c-oxidase-deficient cells; (2) a reduced hybridization signal with different mtDNA probes, indicating depletion of mtDNA; and (3) normal hybridization signals with different probes in single cytochrome-c-oxidase-deficient cardiomyocytes. These results indicate that different mechanisms may co-exist in Kearns-Sayre syndrome and may lead to defective respiratory chain function. The question of the pathogenetic interrelationship is discussed.     

Focal deficiency of cytochrome-c-oxidase in skeletal muscle of patients with progressive external ophthalmoplegia

Summary In skeletal muscle biopsies of 8 patients with progressive external ophthalmoplegia combined light and fine structural cytochemical studies of cytochrome-c-oxidase revealed the absence of the enzyme in single fibres with or without accumulation of abnormal mitochondria. However, some fibres showed abnormal mitochondria without any deficiency of the enzyme. In one case with only slight mitochondrial proliferation the existence of the enzyme defect was the most remarkable finding. The occurence of the enzyme defect obviously does not depend on concominant structural alterations of the chondriom. The results are consistent with an acquired mitochondrial injury leading to a gradual loss of enzyme activity either earlier (with or without a minimal reactive mitochondrial proliferation) or later (after a phase of mitochondrial proliferation) in the course of the disease. Focal lack of cytochrome-c-oxidase activity is apparently a constant feature of the syndrome; it therefore may be not only of pathogenetic but also of diagnostic importance and in this connection cytochemical-fine-structural demonstration of cytochrome-c-oxidase is a valuable method. In contrast to the bio-chemical approach it allows not only the detection but also the exact anatomical localization of single fibre defects.