Gender-associated mitochondrial DNA heteroplasmy in the venerid clam Tapes philippinarum (Mollusca Bivalvia)

This paper provides evidence of a gender-associated mitochondrial DNA (mtDNA) heteroplasmy in the clam Tapes philippinarum. The pattern of tissue distribution of the two observed mtDNA types (referred to as M and F) parallels that of the doubly uniparental inheritance system of Mytilus. The mitochondrial genetic features of the clam are related to a different rate of evolution of the M- and F-type mtDNAs. Since clams are known to be phylogenetically very distant from mussels, the present findings support the hypothesis that the mechanism producing gender-associated heteroplasmy should be considered an ancestral character in the Bivalvia. Received: 2 August 2000 / Accepted: 3 December 2000     

Sex-biased heteroplasmy and mitochondrial DNA inheritance in the musselMytilus galloprovincialis Lmk.

An exceptional mode of mtDNA inheritance involving separate maternal and paternal transmission routes has been reported recently in the musselMytilus edulis. This mode of inheritance provides an explanation for the high levels of heteroplasmy for two highly diverged genomes observed in males of this species. Here we provide evidence for a similar pattern of heteroplasmy in Atlantic and Mediterranean forms of the related musselM. galloprovincialis. The results support the hypothesis that this mode of mtDNA inheritance has an ancient origin. In addition, the detection of some heteroplasmic females suggests preferential, rather than exclusive, transmission within male and female lines of descent. We also present evidence that the two highly diverged genomes dislay a parallel split between the Atlantic and Mediterranean forms, consistent with neutral evolution.     

Molecular interactions of mussel protective coating protein, mcfp-1, from Mytilus californianus

Protective coating of the byssus of mussels (Mytilus sp.) has been suggested as a new paradigm of medical coating due to its high extensibility and hardness co-existence without their mutual detriment. The only known biomacromolecule in the extensible and tough coating on the byssus is mussel foot protein-1 (mfp-1), which is made up with positively charged residues (∼20 mol%) and lack of negatively charged residues. Here, adhesion and molecular interaction mechanisms of Mytilus californianus foot protein-1 (mcfp-1) from California blue mussel were investigated using a surface forces apparatus (SFA) in buffer solutions of different ionic concentrations (0.2-0.7 M) and pHs (3.0-5.5). Strong and reversible cohesion between opposed positively charged mcfp-1 films was measured in 0.1 M sodium acetate buffer with 0.1 M KNO₃. Cohesion of mcfp-1 was gradually reduced with increasing the ionic strength, but was not changed with pH variations. Oxidation of 3,4-dihydroxyphenylalanine (DOPA) residues of mcfp-1, a key residue for adhesive and coating proteins of mussel, didn’t change the cohesion strength of mcfp-1 films, but the addition of chemicals with aromatic groups (i.e., aspirin and 4-methylcatechol) increased the cohesion. These results suggest that the cohesion of mcfp-1 films is mainly mediated by cation-π interactions between the positively charged residues and benzene rings of DOPA and other aromatic amino acids (∼20 mol% of total amino acids of mcfp-1), and π-π interactions between the phenyl groups in mcfp-1. The adhesion mechanism obtained for the mcfp-1 proteins provides important insight into the design and development of functional biomaterials and coatings mimicking the extensible and robust mussel cuticle coating.     

An inherited mitochondrial DNA disruptive mutation shifts to homoplasmy in oncocytic tumor cells

A disruptive frameshift mtDNA mutation affecting the ND5 subunit of complex I is present in homoplasmy in a nasopharyngeal oncocytic tumor and inherited as a heteroplasmic germline mutation recurring in two of the patient's siblings. Homoplasmic ND5 mutation in the tumor correlates with lack of the ND6 subunit, suggesting complex I disassembly. A few oncocytic areas, expressing ND6 and heteroplasmic for the ND5 mutation, harbor a de novo homoplasmic ND1 mutation. Since shift to homoplasmy of ND1 and ND5 mutations occurs exclusively in tumor cells, we conclude that complex I mutations may have a selective advantage and accompany oncocytic transformation. Hum Mutat 0, 1–6, 2008. © 2008 Wiley‐Liss, Inc.     

Leigh syndrome caused by mitochondrial DNA G13513A mutation: frequency and clinical features in Japan

The mitochondrial DNA (mtDNA) G13513A mutation in the ND5 subunit gene has been recently reported as a common cause of some phenotypes of mitochondrial myopathy. Until now, the prevalence and characteristics of this mutation in Leigh syndrome (LS) has not been determined. We screened 84 patients with Leigh syndrome (LS) and found the mutation in six (7%) of them. The proportions of mutant mtDNA in muscles were relatively low (42–70%). The onset of symptoms for patients with this mutation was from 9 months to 5 years. It should be noted that five patients had cardiac conduction abnormalities, particularly Wolff-Parkinson-White (WPW) syndrome (three patients). This study suggests that G13513A mutation is a frequent cause of LS and that patients with this mutation may have a characteristic clinical course.     

Transfer of paternal mitochondrial DNA during fertilization of honeybee (Apis mellifera L.) eggs

Strict maternal inheritance of mitochondrial (mt) DNA is believed to be the rule in most eukaryotic organisms because of exclusion of paternal mitochondria from the egg cytoplasm during fertilization. In honeybees, polyspermic fertilization occurs, and many spermatozoa, including their mitochondria-rich flagellum, can completely penetrate the egg, thus allowing for a possibly high paternal leakage. In order to identify paternal mtDNA in honeybee eggs, restriction fragment length polymorphisms (RFLP) of different subspecies were used. Total DNA extracts of different developmental stages of an Apis mellifera carnica x Apis mellifera capensis hybrid brood were tested with a radioactively-labelled diagnostic mtDNA probe. Densitograms of autoradiographs indicated that the male contribution represents up to 27% of the total mitochondrial DNA in the fertilized eggs 12 h after oviposition. In subsequent developmental stages the portion of paternal mtDNA slowly decreased until hatching of the larvae when only traces were found. Although rapid disintegration of paternal mtDNA does not occur, the initially high paternal mitochondrial contribution is not maintained in the adult animal.     

线粒体DNA母系遗传机制的研究进展

线粒体DNA一般只通过母系遗传,是人们探索母系遗传的绝佳工具。本文简要地介绍了线粒体DNA的遗传学特性及其为母系遗传的必要性,进而以对动物精子线粒体DNA在精子发生时及受精后发生降解的机制的阐述为基础,对国内外关于动物线粒体DNA母系遗传机制的研究进展作一综述。     

The detectioon of genotoxin-induced DNA adducts in the common mussel Mytilus edulis

In order to establish the capacity of Mytilus spp. to form genotoxin–DNAadducts, a series of in vitro and in vivo studies were conductedin which tissue samples and animals were exposed to five modelgenotoxins. Following the in vitro characterization of the majoradducts induced by the compounds, a series of in vivo studieswere conducted to determine if the levels of genotoxin–DNAadduct formation followed a dose response. The results of thesestudies suggested that under appropriate conditions, DNA adductsin the hepatopancreas could be used as molecular dosimetersof exposure to genotoxic compounds in the species. However,these studies also revealed that the successful detection ofsuch genotoxin-DNA adducts depends largely upon their chromatographicproperties and thus the vigour of the characterization undertaken. ¹To whom correspondence should be addressed     

128例Ⅱ型糖尿病患者线粒体ND1基因突变位点的研究

目的通过对128例Ⅱ型糖尿病(Type 2 diabetes mellitus,T2DM)患者线粒体DNA ND1基因进行突变位点筛查,探索ND1基因点突变与山西人群T2DM的相关性。方法 PCR扩增患者ND1基因所在区段,PCR产物直接测序分析。结果128例患者共有38例患者检测到基因点突变,突变检出率为29.7%。38例患者共筛出22个突变位点,2种突变类型。其中31例存在单个位点突变,5例存在2个位点突变,2例存在3个位点突变。22个突变位点中,3552(T→A)突变频率最高,为40.9%(9/22);3394(T→C)、3435(C→T)、3497(C→T)、3316(G→A)、3571(C→T)、3537(A→G)的突变频率分别为22.7%(5/22)、22.7%(5/22)、18.2%(4/22)、13.6%(3/22)、13.6%(3/22)和10.1%(2/22);其余突变位点的突变率均为4.5%(1/22)。在所有突变位点中,除3688(G→C)为异质性突变外,其余突变均为同质性。此外,22个突变位点中存在一个新的突变位点3499(A→T),属首次报道。结论 3552(T→A)和3394(T→C)突变频率最高,可能与山西地区T2DM发病相关;新发现的突变位点3499A→T(Thr→Ser),其致病性需要进一步研究。     

线粒体ND5基因13513G＞A突变导致Leigh综合征

目的 分析1个母系遗传的Leigh综合征家系的线粒体突变.方法 描述该家系患者的临床和实验室特点,应用DNA芯片结合直接测序对该家系患者进行全线粒体DNA测序.结果 该Leigh综合征家系患者临床以生长发育延迟、精神运动迟滞、呼吸节律异常、颅神经麻痹、小脑共济失调、抽搐为主要特征.神经影像学显示中脑、双侧大脑脚、导水管周围灰质、小脑齿状核及双侧丘脑受累.伴乳酸、丙酮酸代谢异常.突变分析证实该Leigh综合征家系由线粒体ND5*13513G＞A突变所致.结论 ND5突变导致的母系遗传的Leigh综合征有某些特点,ND5*13513G＞A突变可作为Leigh综合征患者的高频候选位点.     

Involvement of pore-forming molecules in immune defense and development of the Mediterranean mussel (Mytilus galloprovincialis)

The membrane attack complex and perforin (MACPF) superfamily is one of the largest families of pore-forming molecules. Although MACPF proteins are able to destruct invading microbes, several MACPF proteins play roles in embryonic development, neural migration or tumor suppression. We describe two apextrin-like proteins (ApelB and ApelP) and one MACPF-domain-containing protein (Macp) in Mytilus galloprovincialis. The two apextrin-like proteins did not present any conserved domain. The Macp protein contained the membrane/attack complex domain and its signature motif. Gene expression during larval development was analyzed by RT-PCR. There was a stage-specific up-regulation of the three proteins, suggesting that they play a role in development. Apextrin-like proteins were highly expressed at blastula and trochophore stage, whereas Macp was expressed at veliger stage. RT-PCR revealed up-regulation of the three genes in tissues and hemocytes from adults treated with bacteria and pathogen-associated molecular patterns, suggesting that they may be involved in the immune response.     

非综合征型遗传性耳聋两家系线粒体基因突变分析

目的 探讨母系遗传非综合征型耳聋发病机理及7445^G点突变在这类家系及散发感音神经性耳聋病例中的发生率，为建立相应的基因诊断方法提供依据。方法 收集两个母系遗传非综合征型耳聋家系和14个感音神经性耳聋散发病例；抽外周血标本，从白细胞中提取DNA；聚合酶链反应扩增线粒体DNA（mitochondrial DNA,mtDNA）目的片段，分别以Alw 26Ⅰ、ApaⅠ及XbaⅠ限制性内切酶检测1555^G、3243^G及7445^G点突变；行mtDNA 12S r RNA、tRNA^Leu(UUR)、tRNA^Ser(UCN)基因测序。结果 经酶切检测，两家系中12例为7445^G点突变阳性，其余6例及14例散发病例均为阴性，所有病例1555^G、3243^G点突变均阴性；7445^G点突变呈母系遗传。mtDNA测序显示，所有病例1555^G、3243^G点突变均阴性；酶切显示为7445^G突变阳性病例经基因测序均发现有（nt)7445A→G替换。结论 7445^G点突变在母系遗传非综合征型耳聋家系中有较高的发生率，而在散发病例中发生率很低；7445^G结合1555^G点7突变筛查对这类耳聋的诊断有重要意义。     

家族性糖尿病人群中线粒体ND4基因12026 A→G突变的分析研究

目的了解线粒体ND4基因mt12026A→G变异在中国人家族性糖尿病人群中的发生率及其临床特点。方法应用PCR-限制性片段长度多态性技术结合直接测序方法对随机抽取的无亲缘关系的770个糖尿病家系的先证者及309名非糖尿病对照者进行线粒体基因mt12026A→G变异的筛查。结果在糖尿病先证者组中发现28例（3．63％）mt12026A→G变异，而在正常对照组中发现9例（2．91％），两组间变异的发生率差异无统计学意义。伴mt12026A→G的糖尿病组与无该变异的糖尿病组之间的临床特点（年龄、体重指数、胰岛素抵抗指数）比较差异无统计学意义。结论线粒体ND4基因mt12026A→G变异可能不是中国人线粒体糖尿病发病的致病原因，而是中国人线粒体的一种基因多态。     

Phylogeographic analysis of mitochondrial DNA haplogroup F2 in China reveals T12338C in the initiation codon of the ND5 gene not to be pathogenic

In this report, we studied on a homoplasmic T12338C change in mitochondrial DNA (mtDNA), which substituted methionine in the translational initiation codon of the NADH dehydrogenase subunit 5 gene (ND5) with threonine. This nucleotide change was originally identified in two mtDNAs belonging to haplogroup F2 by our previous complete sequencing of 48 mtDNAs. Since then, a total of 76 F2 mtDNAs have been identified by the variations occurring in the hypervariable segments and coding regions among more than 3,000 individuals across China. As the T12338C change was detected in 32 samples representing various sub-clades of the F2 haplogroup while not in 14 non-F2 controls, we believe that the T12338C change is specific to the F2 haplogroup. As F2 and its sub-clades were widely distributed in normal individuals of various Chinese populations, we conclude that T12338C is not pathogenic. In addition, based on the average distribution frequency, haplotype diversity and nucleotide diversity of haplogroup F2 in the populations across China, the T12338C nucleotide substitution seems to have been occurred in north China about 42,000 years ago. Our results provided a good paradigm for distinguishing a polymorphic change from a pathogenic mutation based on mtDNA phylogeny.Accession numbers and URLs for the sequence data of mtDNA control region (including HVS-I and HVS-II) of F2 types in this article are as follows: GenBank, (accession numbers: AY522667–AY522718).     

虫卵基因序列分析鉴定斯氏并殖吸虫病

目的探索运用分子生物学技术分析虫卵基因序列鉴定并殖吸虫病。方法从云南省的并殖吸虫病流行区采集溪蟹,常规分离囊蚴,经形态学鉴定后感染实验终宿主家猫,从猫粪便中分离虫卵,对虫卵进行详细的形态学观察和鉴定。用匀浆器研磨虫卵提取基因组DNA,PCR扩增出虫卵中完整的核糖体基因第二间隔区（ITS2）和部分线粒体细胞色素C氧化酶亚单位I基因（COI）,测序获得该基因的核苷酸序列。将核苷酸序列输入GenBank中进行Blast比较,通过ITS2和COI的同源性来判断所感染的并殖吸虫种类。结果取自猫粪便中的虫卵形态符合并殖吸虫卵的形态特征。该虫卵的ITS2基因序列与GenBank中的斯氏并殖吸虫的基因序列同源性为99%,COI基因序列的同源性也高达98%。结果鉴定为斯氏并殖吸虫虫卵,证明家猫感染的是斯氏并殖吸虫病。结论通过并殖吸虫卵的基因序列分析,不仅可以快速诊断并殖吸虫病,而且还能准确地鉴定感染者所感染的并殖吸虫虫种。     

Influence of the SCGE protocol on the amount of basal DNA damage detected in the Mediterranean mussel, Mytilus galloprovincialis

Genotoxicity studies using the single cell gel electrophoresis (SCGE) assay indicate that basal levels of DNA strand breaks (SBs) in marine invertebrates are higher and more variable than those in marine vertebrates. This elevated level of DNA damage was attributed to a large number of alkali-labile sites, which are characteristic of the tightly-packaged DNA in invertebrate cells. To investigate if altering the SCGE protocol can artificially modulate high levels of SBs, SCGE experiments were performed on haemocytes from the Mediterranean mussel (Mytilus galloprovincialis) using proteinase K (PK) digestion in combination with assay buffers containing various concentrations of EDTA. In addition, the effects of Trolox (soluble antioxidant) and aurintricarboxylic acid (ATA; inhibitor of Ca(2+)/Mg(2+)-dependent nucleases) also were tested. The levels of SBs in M. galloprovincialis cells were compared with SBs in cells from a terrestrial mollusk (the snail Helix aspersa), and a teleost fish (the seabass Dicentrarchus labrax). The integrity of M. galloprovincialis DNA isolated with phenol extractions using EDTA, Trolox, and ATA was further assayed by gel electrophoresis. High SBs in mussel cells were reduced by combining EDTA with PK digestion, or using Trolox or ATA during cell processing for the SCGE assay. Snails and seabass had lower levels of SBs in the SCGE assay, and the levels were not affected by the protocol modifications. Adding EDTA, Trolox, or ATA to phenol extractions of M. galloprovincialis genomic DNA also reduced the extent of DNA fragmentation. These results suggest that the internal fluids of M. galloprovincialis may increase the basal levels of DNA SBs through oxidative and/or enzyme-mediated pathways. M. galloprovincialis is used extensively as a sentinel species for assessing the genotoxic hazard of marine pollutants. Our data suggest that the SCGE protocol should be carefully considered when assessing DNA damage in these species.     

Maternal transmission of mitochondrial DNA in interspecific hybrids of Populus

Summary Restriction fragment analysis was conducted to investigate the mode of inheritance of mitochondrial (mt) DNA in F₁ progeny of two P. deltoides x P. deltoides, three P. deltoides x P. nigra, and two P. deltoides x P. maximowiczii controlled crosses, and in Populus x canadensis by using 16 restriction endonucleases and two heterologous probes of cloned mtDNA fragments of maize. Five restriction fragment length polymorphisms (RFLPs) of mtDNA differentiated P. deltoides from P. nigra, whereas three RFLPs of mtDNA separated P. deltoides from P. maximowiczii. In all cases, F₁ progeny of P. deltoides x P. nigra, and P. deltoides x P. maximowiczii, crosses had mtDNA restriction fragments of only their maternal P. deltoides parents. P. x canadensis had mtDNA restriction fragments of only P. deltoides. F₁ progeny of intraspecific P. deltoides crosses also had the same mtDNA fragments as their maternal parent. The results clearly demonstrate uniparental-maternal inheritance of the mitochondrial genome in F₁ interspecific hybrids of P. deltoides with P. nigra and P. maximowiczii.     

Maternal inheritance of mitochondrial DNA in sexual crosses of Pythium sylvaticumm

Summary Fifty single oospore progeny from crosses between opposite mating types of Pythium sylvaticum that contained polymorphisms in mitochondrial DNA (mtDNA) for HindIII restriction sites were analyzed for patterns of mitochondrial inheritance. All progeny retained the morphological form of the oogonial parental type; the antheridial form or recombinant forms of parental mtDNA were not detected. With the techniques used, other forms of mtDNA would have been detected it they had comprised 8% or more of the mitochondrial population.     

Analysis of mitochondrial DNA and its inheritance in Populus

Summary The mitochondrial genome of several poplar clones has been characterized by restriction analysis and hybridization with gene probes from Oenothera. The mitochondrial (mt) DNA of Populus has a complex restriction fragment pattern and its genome size was estimated to be about 450 kilobase pairs (kb). Restriction fragment length polymorphisms (RFLPs) could be detected only between, and not within, species of Populus and were used as genetic markers to follow mitochondrial inheritance. Location of the apocytochrome b (cob) gene on different Eco RI or Hin dIII fragments in Muhle Larsen (P. trichocarpa) and Androscoggin (P. maximowiczii × P. trichocarpa) has been used for analysis of mitochondrial inheritance. All hybrids investigated exhibit a fragment pattern identical to that of the female parent. Hybridization with other gene probes (coxIII/HindIII, coxIII/SalI, coxIII/Xho I, atp6/Bgl1, atp6/Hco RI, atp6/Hin dIII, nad1/Hin dIII, nad1/Sal I, nad1/Xba I) showed the same results as given by cob hybridization. Thus, mtDNA seems to be inherited maternally in Populus.