4种昆虫基因组中的线粒体假基因

为了进一步了解昆虫核基因组中线粒体假基因(Numts)序列分布情况,避免Numts序列对基于线粒体DNA(mtDNA)进行系统发育关系研究结果的误导,利用Blast N对GenBank中已完成核基因组和mtDNA测序的4种昆虫核基因组中的Numts序列进行检索,结果表明:冈比亚按蚊Anopheles gambiae中没有Numts序列;黑腹果蝇Drosophila melanogaster中仅有少量Numts序列;赤拟谷盗Tribolium castaneum和意大利蜜蜂Apis melliera基因组中Numts序列超过100条,尤其是意大利蜜蜂中的Numts序列涵盖全部mtDNA.ND2,ND4,ND5,COⅠ与lrRNA向核内转移频率高于其他mtDNA基因片段,因此,在使用其进行系统发育关系研究时需加倍谨慎.     

Premature ageing in mice expressing defective mitochondrial DNA polymerase

Point mutations and deletions of mitochondrial DNA (mtDNA) accumulate in a variety of tissues during ageing in humans, monkeys and rodents. These mutations are unevenly distributed and can accumulate clonally in certain cells, causing a mosaic pattern of respiratory chain deficiency in tissues such as heart, skeletal muscle and brain. In terms of the ageing process, their possible causative effects have been intensely debated because of their low abundance and purely correlative connection with ageing. We have now addressed this question experimentally by creating homozygous knock-in mice that express a proof-reading-deficient version of PolgA, the nucleus-encoded catalytic subunit of mtDNA polymerase. Here we show that the knock-in mice develop an mtDNA mutator phenotype with a threefold to fivefold increase in the levels of point mutations, as well as increased amounts of deleted mtDNA. This increase in somatic mtDNA mutations is associated with reduced lifespan and premature onset of ageing-related phenotypes such as weight loss, reduced subcutaneous fat, alopecia (hair loss), kyphosis (curvature of the spine), osteoporosis, anaemia, reduced fertility and heart enlargement. Our results thus provide a causative link between mtDNA mutations and ageing phenotypes in mammals.     

Mitochondrial genome variation and the origin of modern humans

The analysis of mitochondrial DNA (mtDNA) has been a potent tool in our understanding of human evolution, owing to characteristics such as high copy number, apparent lack of recombination, high substitution rate and maternal mode of inheritance. However, almost all studies of human evolution based on mtDNA sequencing have been confined to the control region, which constitutes less than 7% of the mitochondrial genome. These studies are complicated by the extreme variation in substitution rate between sites, and the consequence of parallel mutations causing difficulties in the estimation of genetic distance and making phylogenetic inferences questionable. Most comprehensive studies of the human mitochondrial molecule have been carried out through restriction-fragment length polymorphism analysis, providing data that are ill suited to estimations of mutation rate and therefore the timing of evolutionary events. Here, to improve the information obtained from the mitochondrial molecule for studies of human evolution, we describe the global mtDNA diversity in humans based on analyses of the complete mtDNA sequence of 53 humans of diverse origins. Our mtDNA data, in comparison with those of a parallel study of the Xq13.3 region in the same individuals, provide a concurrent view on human evolution with respect to the age of modern humans.     

应用PCR－SSCP银染技术检测消化系统肿瘤的P53基因突变

应用ＰＣＲ－ＳＳＣＰ银染技术，初步研究了肝细胞癌、胃癌和大肠癌中Ｐ５３基因的第６和第７外显子的分子结构改变。对来自癌组织ＤＮＡ和正常组织ＤＮＡ的ＰＣＲ－ＳＳＣＰ电泳带迁移作对比分析，发现３０例肝癌病人中，６例肝癌样品电泳带迁移异常；２６例胃癌病人中，４例胃癌样品电泳带迁移异常；２９例大肠癌病人中，６例大肠癌样品电泳带迁移异常。依据ＤＮＡ单链构象与分子电泳迁移的关系，研究结果表明：该三组病人中，Ｐ５３基因第６、７外显子的突变率分别为２０．０％，１５．４％和２５．０％。同时，也间接提示了Ｐ５３基因突变可能是肝细胞癌、胃癌和大肠癌中一种较多见的分子结构改变。     

Deletions of muscle mitochondrial DNA in patients with mitochondrial myopathies

In vitro studies of muscle mitochondrial metabolism in patients with mitochondrial myopathy have identified a variety of functional defects of the mitochondrial respiratory chain, predominantly affecting complex I (NADH-CoQ reductase) or complex III (ubiquinol-cytochrome c reductase) in adult cases. These two enzymes consist of approximately 36 subunits, eight of which are encoded by mitochondrial DNA (mtDNA). The increased incidence of maternal, as opposed to paternal, transmission in familial mitochondrial myopathy suggests that these disorders may be caused by mutations of mtDNA. Multiple restriction endonuclease analysis of leukocyte mtDNA from patients with the disease, and their relatives, showed no differences in cleavage patterns between affected and unaffected individuals in any single maternal line. When muscle mtDNA was studied, nine of 25 patients were found to have two populations of muscle mtDNA, one of which had deletions of up to 7 kilobases in length. These observations demonstrate that mtDNA heteroplasmy can occur in man and that human disease may be associated with defects of the mitochondrial genome.     

DNA甲基化在肿瘤形成中的作用（综述）

DNA甲基化改变是肿瘤细胞中常见的现象,DNA甲基化与肿瘤的发生有密切关系。从以下几方面对此做一综述。（1）简介哺乳动物细胞的DNA甲基化;（2）DNA甲基化与肿瘤基因突变;（3）肿瘤DNA甲基化的基因外作用,其中包括：原癌基因的低甲基化和抑癌基因的高甲基化。     

p53、Rb、p16抑癌基因在胃粘膜上皮异型增生病变中表达的意义

目的：研究p53、Rb和P16 3个抑癌基因在正常胃粘膜→异型增生粘膜→胃癌发展过程中的表达状态及相互关系。方法：收集胃手术及胃镜活检标本共60例,镜下观察胃粘膜并选取不增生病灶、35例胃腺癌和32例正常胃粘膜中的表达情况。应用聚合酶链反应单链构象多态性分析技术（PCR-SSCP）对35例胃腺癌进行p16基因点突变检测。结果：p53阳性率在轻、中、重度异型增生病灶的分别为7.5%、35.1%、59.1%,胃癌组为68.6%,正常对照组中无表达。Rb蛋白阳性率在轻、中、重度异型增生病灶中分别为80.0%、89.3%、81.8%,胃癌组为57.1%,正常对照组为90.6%。p16蛋白在正常胃粘膜、异型增生粘膜和胃癌中普遍表达,3组间阳性率比较无显著性差异。p16基因PCR-SSCP分析示只有1例低分化腺癌出现异常单链泳动带。不同类型（隐窝型、腺瘤型、再生型）异型增生病灶组间、位于癌旁和良性病变旁的异型增生病组间p53、Rb和p16蛋白的阳性率无显著性差异。高-中分化、低分化、未分化胃癌组p53、Rb和p16蛋白的阳性率无显著性差异。结论：突变型p53蛋白的积聚在胃粘膜异型增生阶段已经开始,随着异型增生程度的加重逐渐增加,重度病变中p53表达率与胃癌组相似,提示p53基因突变是胃癌发生过程中的早期事件。Rb蛋白在癌变组中缺失率较异型增生显著,可能是胃癌发生过程中的较晚事件。推测在p53基因突变的基础上加以Rb蛋白的缺失最终导致胃粘膜上皮癌变。p16蛋白的表达在胃癌发生过程的3个阶段病变中无显著的变化,可能不起要作用。不同类型（隐窝型、腺瘤型、再生型）异型增生间、癌旁或良性病变旁的异型增生间,不同分化程度的胃腺癌组间这3种抑癌基因蛋白表达状态基本相同。     

饮牛沟墓地古人骨线粒体DNA的研究

对内蒙古饮牛沟战国时期墓地的古代人群（Yng古代人群）进行分子生物学研究, 获得了线粒体高可变一区DNA序列, 初步确定了单倍型归属并搜寻其共享序列, 与现代人群对比构建系统发育树和多维尺度分析. 结果表明, 饮牛沟古代人群与现代东亚人群在母系遗传关系上较近.     

De novo mutations revealed by whole-exome sequencing are strongly associated with autism

Multiple studies have confirmed the contribution of rare de novo copy number variations to the risk for autism spectrum disorders. But whereas de novo single nucleotide variants have been identified in affected individuals, their contribution to risk has yet to be clarified. Specifically, the frequency and distribution of these mutations have not been well characterized in matched unaffected controls, and such data are vital to the interpretation of de novo coding mutations observed in probands. Here we show, using whole-exome sequencing of 928 individuals, including 200 phenotypically discordant sibling pairs, that highly disruptive (nonsense and splice-site) de novo mutations in brain-expressed genes are associated with autism spectrum disorders and carry large effects. On the basis of mutation rates in unaffected individuals, we demonstrate that multiple independent de novo single nucleotide variants in the same gene among unrelated probands reliably identifies risk alleles, providing a clear path forward for gene discovery. Among a total of 279 identified de novo coding mutations, there is a single instance in probands, and none in siblings, in which two independent nonsense variants disrupt the same gene, SCN2A (sodium channel, voltage-gated, type II, α subunit), a result that is highly unlikely by chance.     

P73蛋白在胃炎、不典型增生和胃癌中的表达及意义

目的探讨p73基因在胃癌发生、发展中的作用和意义。方法采用免疫组化技术检测胃炎、轻度不典型增生、中重度不典型增生和胃癌（均为外科手术患者）各30例组织中p73蛋白的表达。结果p73蛋白在胃癌组和不典型增生组中表达高于胃炎组,胃癌组中表达高于不典型增生组（P〈0．05）;p73蛋白的阳性表达率在胃癌的不同的分化度之间有差异,低分化腺癌组织中的阳性表达强度高于高、中分化腺癌（P〈0．05）,p73蛋白在中、重度不典型增生组的阳性表达率与轻度不典型增生组无显著差异（P〉0．05）;在胃癌的不同TNM分期之间也有差异（P〈0．05）,并且TNM分期越高,阳性表达率越高;均与淋巴结转移、肿瘤部位、胃癌侵及层次、肿瘤大小无关（P〉0．05）。结论p73的高表达可能参与了胃癌发生、发展,作为胃癌发生、发展及预后的肿瘤指标物。     

Conformational mutations in human mitochondrial DNA

Variation in the human mitochondrial DNA (mtDNA) sequence has been extensively analysed using restriction fragment length polymorphisms (RFLPs). MtDNA RFLPs have previously been attributed to nucleotide changes within restriction endonuclease recognition sites or to small insertion-deletion mutations. We now report that RFLPs detected by polyacrylamide gel electrophoresis can also result from single nucleotide substitutions which alter the mobility of small- to medium-sized restriction fragments that incorporate the sequence. We have defined the mutation responsible at two loci and have identified several possible additional loci. When screening human mtDNAs with multiple restriction endonucleases, such mutations can be misidentified as insertion-deletion mutations or counted as multiple polymorphic restriction sites. This can lead to errors in constructing restriction maps and estimating sequence diversity.     

胃液成分多参数逐步判别在胃病判别中的意义

根据胃液成分的6项参数,用POMS程序,就6种(510例)慢性胃病,按3种组合进行Bayes准则逐步判别。结果显示:1.胃癌、胃溃疡和萎缩性胃炎之间具有十分显著的差异,有判别作用的参数依次为DNA、胆汁酸以及蛋白酶和游离酸;其判别距阵示萎缩性胃炎的符合率达78％。2.胃癌、胃溃疡和十二指肠溃疡3种病之间,胃液参数判别的差异亦十分显著;粘液、DNA、胆汁酸及pH值的判别效果有显著性;胃癌和十二指肠溃疡的判别符合率分别为63.3％及92％。3.浅表性、浅表-萎缩性和萎缩性胃炎进行判别时差异有显著意义,本组有判别作用的参数则依次为粘液、胆汁酸以及蛋白酶和pH值4项;判别距阵显示的符合率,萎缩性胃炎为51％,浅表性胃炎为75.8％,而浅表-萎缩性仅13％,表明后者具有很高的重叠性。     

Conservation and rearrangement of mitochondrial structural gene sequences

Mitochondria contain the simplest DNA molecules that are present in eukaryotes. Mitochondrial DNA (mtDNA) is easily purified, and is an important model system for studying eukaryote gene structure and basic molecular processes. The protein sequences of mitochondrial gene products have been shown to be conserved from yeast to man, and there are definite similarities at the DNA sequence level. In contrast, the overall organization of the mitochondrial genome is drastically different in these organisms. To understand this, we need to extend work on mtDNA to a wider range of species. We have chosen to study the mtDNA of Aspergillus nidulans because a particularly comprehensive analysis of this system can be achieved using genetics as well as biochemistry, and like most eukaryotes it is an obligate aerobe, whereas Saccharomyces cerevisiae is not. We have investigated whether defined pieces of particular yeast mitochondrial genes show enough homology to Aspergillus mtDNA fragments to enable the corresponding Aspergillus genes to be located on the physical map. The results reported here show that this is the case for all five genes tested, and present the first data on the physical organization of the structural genes in the mitochondrial genome of A. nidulans.     

Somatic mutations affect key pathways in lung adenocarcinoma

Determining the genetic basis of cancer requires comprehensive analyses of large collections of histopathologically well-classified primary tumours. Here we report the results of a collaborative study to discover somatic mutations in 188 human lung adenocarcinomas. DNA sequencing of 623 genes with known or potential relationships to cancer revealed more than 1,000 somatic mutations across the samples. Our analysis identified 26 genes that are mutated at significantly high frequencies and thus are probably involved in carcinogenesis. The frequently mutated genes include tyrosine kinases, among them the EGFR homologue ERBB4; multiple ephrin receptor genes, notably EPHA3; vascular endothelial growth factor receptor KDR; and NTRK genes. These data provide evidence of somatic mutations in primary lung adenocarcinoma for several tumour suppressor genes involved in other cancers--including NF1, APC, RB1 and ATM--and for sequence changes in PTPRD as well as the frequently deleted gene LRP1B. The observed mutational profiles correlate with clinical features, smoking status and DNA repair defects. These results are reinforced by data integration including single nucleotide polymorphism array and gene expression array. Our findings shed further light on several important signalling pathways involved in lung adenocarcinoma, and suggest new molecular targets for treatment.     

Somatic variants of murine immunoglobulin lambda light chains

Studies of the murine lambda light chains produced by myeloma cells provided the first evidence for somatic point mutation of germ-line variable (V) region genes. An examination of the variable regions of 19 lambda 1 chains revealed seven which differed from a common sequence by one to three amino acid substitutions. Subsequently, one of these presumed somatic variants of the single lambda 1 V gene was characterized by DNA sequence analysis of the rearranged functional gene. The predicted DNA sequence alteration was observed and no silent mutation was evident. These studies of lambda chain variants suggested that the hypervariable, complementarity-determining regions (CDRs) ht be a preferred site of somatic mutation because all seven characterized variants contained substitutions only in these regions. By contrast, comparisons of closely related kappa chain variable region amino acid sequences, and more recently VK and VH genes, have suggested that somatic mutation probably occurs in codons for both framework and CDR residues. To examine this apparent discrepancy between the sites of somatic mutations in lambda and kappa genes, we have determined the nucleotide sequence of two lambda 1 gene from hybridomas and a lambda 2 gene from a myeloma. These sequences demonstrate that somatic mutation in lambda genes can occur in both the framework and CDR residues.     

Paternal inheritance of mitochondrial DNA in mice.

For nearly 20 years it has been assumed on the basis of low-resolution experiments that mitochondrial (mt)DNA, in contrast to the genes in the nucleus, has an exclusively maternal mode of inheritance in animals. Using the polymerase chain reaction, paternally inherited mtDNA molecules have now been detected in mice at a frequency of 10(-4), relative to the maternal contributions. These mice were hybrids between two inbred strains (C57BL/6J and Mus spretus) whose mtDNAs can be distinguished easily. This new mode of inheritance provides a mechanism for generating heteroplasmy and may explain mitochondrial disorders exhibiting biparental transmission.     

An autosomal dominant disorder with multiple deletions of mitochondrial DNA starting at the D-loop region

Deletions of muscle mitochondrial DNA (mtDNA) have recently been found in patients with mitochondrial myopathy. However, as most of the described cases were sporadic, and individual deletions involved different portions of mtDNA, the mechanism(s) producing the molecular lesions, as well as their mode of transmission, remain unclear. By studying families with mtDNA heteroplasmy, valuable information can be obtained about the role of inheritable factors in the pathogenesis of these disorders. We have studied four members of a family with autosomal dominant mitochondrial myopathy. Multiple deletions, involving the same portion of muscle mtDNA, were identified in all patients. Sequence analysis of the mutant mtDNAs, performed after DNA amplification by the polymerase-chain reaction showed that all the deletions start within a 12-nucleotide stretch at the 5' end of the D-loop region, a site of active communication between the nucleus and the mtDNA. The data indicate that a mutation of a nuclear-coded protein can destroy the integrity of the mitochondrial genome in a specific, heritable way.     

幽门螺杆菌感染与胃癌的关系

目的 :探讨幽门螺杆菌 (简称 Hp)感染与胃癌的关系。方法 :43例胃癌患者的新鲜癌手术标本及血清标本、36例十二提肠溃疡患者 (对照组 )的胃窦粘膜组织及血清标本入本组研究。分别采用 PCR及血清学试验检测其 Hp感染状况 ,两项检测均为阳性者即确立为 Hp感染。结果 :(1) 4 3例胃癌中 ,Hp阳性 30例 ,阳性率 6 9.77% ;36例十二指肠溃疡中 ,Hp阳性 30例 ,阳性率 83.33% ,两组阳性率相比差异无显著性。Hp阳性患者中 ,胃癌及对照组 cag A基因阳性分别为 2 4例、2 5例 ,阳性率分别为 80 .0 0 %、83.33% ,两组阳性率相比差异无显著性。(2 ) 4 3例胃癌中 ,高中分化腺癌组 Hp及 cag A检出率分别为 6 2 .5 0 %及 70 .0 0 % ,低未分化癌组 Hp及 cag A检出率分别为 74.0 7%及 85 .0 0 % ,但两组 Hp及 cag A检出率统计学上均无显著性差异。结论 :(1) Hp感染及 cag A+ 菌株感染不是胃癌发生的唯一或必须因素。 (2 )胃癌的分化程度与 Hp及cag A+菌株感染无明显相关性。