Analysis of mitochondrial DNA variation in the population of Oroks

Mitochondrial DNA (mtDNA) variation was studied in population of Oroks (N = 61), the indigenous inhabitants of Eastern Siberia. Most of the mtDNA types examined fell into five haplogroups (C, D, G, M10, and Y) typical of Eastern Eurasian populations. For three haplogroups (D, C, and M10), the founder effect was established. In one individual, a unique lineage belonging to haplogroup HV and typical of Caucasoids was detected.Translated from Genetika, Vol. 41, No. 1, 2005, pp. 78–84.Original Russian Text Copyright © 2005 by Bermisheva, Kutuev, Spitsyn, Villems, Batyrova, Korshunova, Khusnutdinova.     

Analysis of mitochondrial DNA haplotypes in yakut population

To study the mitochondrial gene pool structure in Yakuts, polymorphism of mtDNA hypervariable segment I (16,024-16,390) was analyzed in 191 people sampled from the indigenous population of the Sakha Republic. In total, 67 haplotypes of 14 haplogroups were detected. Most (91.6%) haplotypes belonged to haplogroups A, B, C, D, F, G, M*, and Y, which are specific for East Eurasian ethnic groups; 8.4% haplotypes represented Caucasian haplogroups H, HV1, J, T, U, and W. A high frequency of mtDNA types belonging to Asian supercluster M was peculiar for Yakuts: mtDNA types belonging to haplogroup C, D, or G and undifferentiated mtDNA types of haplogroup M (M*) accounted for 81% of all haplotypes. The highest diversity was observed for haplogroups C and D, which comprised respectively 22 (44%) and 18 (30%) haplotypes. Yakuts showed the lowest genetic diversity (H = 0.964) among all Turkic ethnic groups. Phylogenetic analysis testified to a common genetic substrate of Yakuts, Mongols, and Central Asian (Kazakh, Kyrgyz, Uigur) populations. Yakuts proved to share 21 (55.5%) mtDNA haplogroups with the Central Asian ethnic groups and Mongols. Comparisons with modern paleo-Asian populations (Chukcha, Itelmen, Koryaks) revealed three (8.9%) haplotypes common for Yakuts and Koryaks. The results of mtDNA analysis disagree with the hypothesis of an appreciable paleo-Asian contribution to the modern Yakut gene pool.     

Minicircle variation in Beta mitochondrial DNA

Summary Mitochondrial DNAs from nine male fertile and eight cytoplasmic male sterile (cms) accessions of wild and cultivated Beta beets were investigated for the presence of low molecular weight DNA molecules. Five different supercoiled DNA molecules were detected, varying in size from 1.33 to 1.63 kb. Southern hybridizations revealed multimeric forms and sequence homologies between the minicircles. The occurrence of the different minicircles among the 17 accessions was investigated by agarose gel electrophoresis and Southern hybridization using minicircle specific probes. The 1.33 and 1.63 kb minicircles were found in most accessions, the other three minicircles were found in one or two of the wild Beta beet accessions. The presence of a low number of small, more or less homologous, minicircles in all investigated plants makes these molecules a general characteristic of Beta mtDNA. No association is found between the presence or absence of specific minicircles and the expression of male sterility. Neither does the distribution of the different minicircles in Beta beets indicate any essential biological role of these minicircles.     

Analysis of the mitochondrial DNA variation in pond smelt Hypomesus olidus (Osmeridae)

Pond smelt Hypomesus olidus (Pallas, 1814), one of the five species of the genus Hypomesus, family Osmeridae, was examined for intraspecific variation of the mitochondrial DNA cytb (1062 bp) and COI (567 bp) genes. Among the ten single substitutions discovered, only one, leading to the substitution of isoleucine by valine, was nonsynonymous, while the remaining substitutions were synonymous. The degree of genetic divergence among pooled nucleotide sequences in H. olidus populations examined constituted 0.4% on average, ranging from 0.2 to 0.6%. These values were not higher than the levels of divergence between the individuals within the populations. Phylogenetic analysis of the populations examined did not reveal their subdivision depending of their geographic location, and pointed to the absence of intraspecific differentiation of the species.     

Phylogeography and population structure of the Japanese wild boar Sus scrofa leucomystax: mitochondrial DNA variation

Phylogeographic characteristics and population structure of Japanese wild boar (Sus scrofa leucomystax) were investigated using mitochondrial DNA (mtDNA) sequence data. Sixteen Japanese wild boar haplotypes detected from partial sequences of the mtDNA control region (574-bp) from 180 Japanese wild boar specimens from 10 local populations on Honshu, Shikoku, and Kyushu islands and 41 haplotypes from other S. scrofa were analyzed using the neighbor-joining method. The Japanese wild boars were more closely related to Northeast Asian wild boars from Mongolia than to the other Asian continental S. scrofa. The Japanese and Northeast Asian wild boars were not significantly distinguished by corrected average pairwise difference analysis. The ancestors of Japanese wild boars are suggested to have been part of the continental S. scrofa population that spread from Southeast to Northeast Asia during the Middle to Late Pleistocene. The Japanese wild boar mtDNA haplotype cladogram shows 95% parsimoniously plausible branch connections supporting three sympatric clades. Nested clade analysis indicates that these three clades are the result of distinct historical events or gene flow. The present population of Japanese wild boars may have been formed by a few independent migrations of distinct clades from the continent with subsequent mixing on the Japanese Islands.     

Genetic variation of the mitochondrial DNA gene encoding cytochrome b in the Magadan population of sable Martes zibellina L

The population of sable Martez zibellina consisting of two subspecies (M. z. kamtschadalica and M. z. jacutensis) on the territory of the Magadan oblast was analyzed for the variation of the 1300-bp mtDNA gene region encoding cytochrome b. Three haplotypes were revealed among the animals studied (n = 52). Six out of nine restriction endonucleases that had recognizable sites within the studied region of mtDNA genome had polymorphic sites. An index of gene diversity h was 0.27. The high level of polymorphism is a result of the fact that the population studied comprised two clearly differentiated subspecies. The ratio of dominating haplotypes corresponds to the percentage of females introduced from Kamchatka and Khabarovsk Krai, which suggests that in the period which has elapsed both maternal lineages remained fairly unchanged.     

The structure of human mitochondrial DNA variation

Summary Restriction analysis of mitochondrial DNA (mtDNA) of 3065 humans from 62 geographic samples identified 149 haplotypes and 81 polymorphic sites. These data were used to test several aspects of the evolutionary past of the human species. A dendrogram depicting the genetic relatedness of all haplotypes shows that the native African populations have the greatest diversity and, consistent with evidence from a variety of sources, suggests an African origin for our species. The data also indicate that two individuals drawn, at random from the entire sample will differ at approximately 0.4% of their mtDNA nucleotide sites, which is somewhat higher than previous estimates. Human mtDNA also exhibits more interpopulation heterogeneity (G_ST=0.351±0.025) than does nuclear DNA (G_ST=0.12). Moreover, the virtual absence of intermediate levels of linkage disequilibrium between pairs of sites is consistent with the absence of genetic recombination and places constraints on the rate of mutation. Tests of the selective neutrality of mtDNA variation, including the Ewens-Watterson and Tajima tests, indicate a departure in the direction consistent with purifying selection, but this departure is more likely due to the rapid growth of the human population and the geographic heterogeneity of the variation. The lack of a good fit to neutrality poses problems for the estimation of times of coalescence from human mtDNA data.     

Genetic diversity and structuring of the grey wolf population from the Central Balkans based on mitochondrial DNA variation

The Dinaric-Balkan grey wolf population used to be at a border between the large remaining Eastern European populations and the largely eradicated Western European populations. During the last few decades we have witnessed the Western European wolf population recovery. Substantial genetic variation has previously been reported in the Balkan wolf population, but rigorous genetic characterization has not been done for its central parts. The aims of this research were to determine genetic diversity based on mtDNA sequence variability, to infer possible population structuring, to find genetic signals of population expansions or bottlenecks and to evaluate phylogenetic position of the grey wolf population from the Central Balkans. Six haplotypes were detected, of which three have only been found in the Balkan region. These haplotypes belong to both haplogroups previously determined in Europe. Based on our mtDNA sequence analyses, the Dinaric-Balkan wolf population is vertically differentiated into “western” (Croatia/Bosnia and Herzegovina) and “eastern” (Serbia/Macedonia) subpopulations. None of the results support assumption of population expansion. Instead, significantly positive values for Tajima's D and Fu's Fs may suggest recent population bottleneck. Obtained data may be helpful in observation to which extent gene pool from the Balkans contribute to newly founded populations in Western Europe.     

Analysis of sequence variation in Gnathostoma spinigerum mitochondrial DNA by single-strand conformation polymorphism analysis and DNA sequence

Morphological variations were observed in the advance third stage larvae of Gnathostoma spinigerum collected from swamp eel (Fluta alba), the second intermediate host. Larvae with typical and three atypical types were chosen for partial cytochrome c oxidase subunit I (COI) gene sequence analysis. A 450 bp polymerase chain reaction product of the COI gene was amplified from mitochondrial DNA. The variations were analyzed by single-strand conformation polymorphism and DNA sequencing. The nucleotide variations of the COI gene in the four types of larvae indicated the presence of an intra-specific variation of mitochondrial DNA in the G. spinigerum population.     

Mitochondrial DNA variation in the Viking age population of Norway

The medieval Norsemen or Vikings had an important biological and cultural impact on many parts of Europe through raids, colonization and trade, from about AD 793 to 1066. To help understand the genetic affinities of the ancient Norsemen, and their genetic contribution to the gene pool of other Europeans, we analysed DNA markers in Late Iron Age skeletal remains from Norway. DNA was extracted from 80 individuals, and mitochondrial DNA polymorphisms were detected by next-generation sequencing. The sequences of 45 ancient Norwegians were verified as genuine through the identification of damage patterns characteristic of ancient DNA. The ancient Norwegians were genetically similar to previously analysed ancient Icelanders, and to present-day Shetland and Orkney Islanders, Norwegians, Swedes, Scots, English, German and French. The Viking Age population had higher frequencies of K*, U*, V* and I* haplogroups than their modern counterparts, but a lower proportion of T* and H* haplogroups. Three individuals carried haplotypes that are rare in Norway today (U5b1b1, Hg A* and an uncommon variant of H*). Our combined analyses indicate that Norse women were important agents in the overseas expansion and settlement of the Vikings, and that women from the Orkneys and Western Isles contributed to the colonization of Iceland.     

Pathogenic mitochondrial DNA mutations are common in the general population

Mitochondrial DNA (mtDNA) mutations are a major cause of genetic disease, but their prevalence in the general population is not known. We determined the frequency of ten mitochondrial point mutations in 3168 neonatal-cord-blood samples from sequential live births, analyzing matched maternal-blood samples to estimate the de novo mutation rate. mtDNA mutations were detected in 15 offspring (0.54%, 95% CI = 0.30–0.89%). Of these live births, 0.00107% (95% CI = 0.00087–0.0127) harbored a mutation not detected in the mother's blood, providing an estimate of the de novo mutation rate. The most common mutation was m.3243A→G. m.14484T→C was only found on sub-branches of mtDNA haplogroup J. In conclusion, at least one in 200 healthy humans harbors a pathogenic mtDNA mutation that potentially causes disease in the offspring of female carriers. The exclusive detection of m.14484T→C on haplogroup J implicates the background mtDNA haplotype in mutagenesis. These findings emphasize the importance of developing new approaches to prevent transmission.     

黄山短尾猴mtDNA控制区序列变异及种群的遗传多样性

短尾猴属灵长目(Primates)猴科(Cercopithecidae)猕猴属(Macaca),是我国特有的国家二级保护动物。为了更有效地保护其野生种群,本文研究了黄山短尾猴种群内的遗传多样性,并对黄山短尾猴与四川短尾猴种群间的遗传差异进行了分析。共测定了黄山短尾猴7个群体中的30个样本的mtDNA控制区5′端493bp的序列,只发现了7个变异位点,定义了3种单倍型,单倍型序列之间缺乏变异,种群中的核苷酸多样性很低(0.006);3种单倍型相应地将黄山种群分为了3个亚群,不同亚群之间呈现出一定的片断化分布,从分子水平上初步揭示了短尾猴黄山种群的遗传多样性。与四川短尾猴的相应序列比较,黄山短尾猴控制区序列存在很大差异,共有59个变异位点,而且存在大片段的碱基插入/缺失,有78%的遗传变异发生在两个种群之间,两个种群间的核苷酸歧异度已达8.21%。进一步分析表明,黄山短尾猴与四川短尾猴之间存在着极显著的遗传分化(FST=0.399,P<0.001),基于最大似然法和邻接法构建的系统发生树均将两者聚为不同的类群,支持将它们归入各自的管理单元。     

Genetic variation in mitochondrial DNA from some aboriginal Australians

Mitochondrial (mt) DNAs from 17 aboriginal Australians, predominantly from the coastal region of the Northern Territory were isolated and digested with four four-base restriction endonucleases, two of which revealed variation between samples. The observed fragment patterns were used directly in parsimony analyses of phylogenetic relationships between the samples, and were also converted to estimates of the number of substitutions per nucleotide position between samples (delta), which estimates were then used in distance analyses of phylogeny. The inferred fragment patterns of the completely sequenced 'Cambridge' human mtDNA were also included in these analyses. No strong evidence of geographic variation was found, consistent with previous findings of Australian aborigines and other humans generally, although the most divergent sample was one of two from Sydney, indicating that further work is desirable. The estimate of mean difference between samples (diversity), 0.0017 +/- 0.0003 (mean +/- 95% confidence interval), is significantly lower than that reported previously for humans generally.     

Parallel variation in mitochondrial DNA type 16278T in genome of the migrant population of Northeast Asia and other caucasoid populations

Types of mtDNA with +16274EcoRV, which had been previously found in East Slavonic residents of Magadan, were identified on the basis of published data on nucleotide sequences of the hypervariable segment I (HVSI) of the mtDNA control region. These mtDNA types occurred in Slavs at a frequency of 7-14% and were assigned to four mitotype groups (1, 2A, 3B, and 5) restricted to Caucasoid populations. Regarding the evolution of mtDNA, this fact indicates that the C-T transition at position 16,278 arose independently in various groups of mtDNA types in Caucasoids. A new subgroup was isolated in Caucasoid group 5. One of the key mutations in this subgroup was variant +16398HaeIII (transition A-G at position 16,399), which was earlier detected in Russian populations at a relatively high frequency.     

Cytoplasmic DNA variation in a potato protoclonal population

Summary Mitochondrial DNA variation was detected in potato plants (protoclones) regenerated from leaf mesophyll protoplasts. Two forms of variation were evident; (1) DNA sequence alterations within the high molecular weight mitochondrial chromosome and (2) the appearance of an additional low molecular weight mitochondrial DNA species. Variation in chloroplast DNA was not detected. The data suggests that protocloning can introduce molecular diversity into mitochondrial genomes and thereby assist in overcoming the cytoplasmic genetic uniformity prevalent in most major crops.     

Structural conservation and variation in the D-loop-containing region of vertebrate mitochondrial DNA

The nucleotide sequences of the D-loop-containing regions of three rat mitochondrial DNAs (mtDNAs), two from the species Rattus norvegicus and one from R. rattus, were determined. Comparisons made among these sequences and with the mouse sequence showed that, on the basis of both base composition and frequency of nucleotide alterations, three domains could be defined within the D-loop-containing region: a central conserved segment, poor in L-strand adenine, flanked by two divergent, adenine-rich regions. Deletions and insertions were found to occur at an unexpectedly high frequency in these sequences and the conserved sequence block called CSB-1 was found not to be intact in the R. rattus sequence. Although in comparisons of more distantly related mtDNAs the D-loop region is the most divergent on the molecule, it does not diverge more than typical protein genes between R. norvegicus and R. rattus, and its central conserved domain appears to be one of the molecule's most conserved regions. The most variable domain borders the tRNAPhe gene and contains the L and H-strand promoters and the 5' terminus for H-strand DNA synthesis. Within this region we have found sequences in all the mtDNAs we have examined, including those of human, two artiodactyls and Xenopus, that are capable of folding into cloverleaf structures. In the other divergent domain of the same mtDNAs, we find sequences capable of assuming similar secondary structural configurations at or near the sites for the termination of D-loop DNA synthesis. The evolutionary preservation of the potential to form such structures despite the high primary-structural divergence of the regions they occur in, suggests the structures are of principal importance for some processes occurring in the D-loop-containing region.     

Regional variation in mitochondrial DNA copy number in mouse brain

Mitochondria have their own DNA (mitochondrial DNA [mtDNA]). Although mtDNA copy number is dependent on tissues and its decrease is associated with various neuromuscular diseases, detailed distribution of mtDNA copies in the brain remains uncertain. Using real-time quantitative PCR assay, we examined regional variation in mtDNA copy number in 39 brain regions of male mice. A significant regional difference in mtDNA copy number was observed (P<4.8×10(-35)). High levels of mtDNA copies were found in the ventral tegmental area and substantia nigra, two major nuclei containing dopaminergic neurons. In contrast, cerebellar vermis and lobes had significantly lower copy numbers than other regions. Hippocampal dentate gyrus also had a relatively low mtDNA copy number. This study is the first quantitative analysis of regional variation in mtDNA copy number in mouse brain. Our findings are important for the physiological and pathophysiological studies of mtDNA in the brain.