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PubMed1996

[Comparative analysis of RFLP of mitochondrial DNA in Eastern Slavic populations in Russia].

Data on restriction fragment length polymorphism (for entire mtDNA molecules--BamHI, DraI, EcoRI, HindIII, PstI, PvuII, ScaI; for the 16,081-16,545 bp segment of mtDNA--AvaII, BamHI, EcoRV, HaeIII, HinfI, KpnI, RsaI, Sau3AI) in eastern Slavs of Magadan is presented. By Sau3AI/BclI digestion analysis, a new polymorphic variant of mtDNA in Caucasoid populations with the C-T nucleotide substitution in position 16147 bp was revealed. The absence of significant differences in mitotypic diversity of Slavic samples from Magadan (h = 0.921 in Russians, h = 0.898 in Ukrainians) was observed. By comparative analysis of mtDNA RFLP, the presence of genetic differences between eastern Slavic populations of Magadan, Tomsk, and the cities of the European region of Russia was demonstrated.

DNA, Mitochondrial↗
PubMed2000

Does a retrograde response in human aging and longevity exist?

The retrograde response (RR) is a compensatory mechanism by which mutant strains of yeast are able to cope with mitochondrial DNA (mtDNA) impairments by up-regulating the expression of the stress-responder nuclear genes and significantly increasing lifespan. Starting from the observation that both mtDNA variability and Tyrosine hydroxylase (THO, stress-responder gene) variability are correlated with human longevity, we asked ourselves whether mechanisms similar to RR may exist in humans. As a first investigative step we have analyzed the distribution of the mtDNA inherited variants (haplogroups) according to THO genotypes in three sample groups of increasing ages (20-49 years; 50-80 years; centenarians). We found that the mtDNA haplogroups and the THO genotypes are associated randomly in the first group, while in the second group, and particularly in the centenarians, a non-random association is observed between the mtDNA and nuclear DNA variability. Moreover, in centenarians the U haplogroup is over-represented (p=0.012) in subjects carrying the THO genotype unfavorable to longevity. On the whole these findings are in line with the hypothesis that longevity requires particular interactions between mtDNA and nuclear DNA and do not exclude the possibility that an RR has been maintained throughout evolution and it is present in higher organisms.

Adult↗
PubMed1992

Heteroplasmy of short tandem repeats in mitochondrial DNA of Atlantic cod, Gadus morhua.

The mitochondrial DNA of the Atlantic cod (Gadus morhua) contains a tandem array of 40-bp repeats in the D-loop region of the molecule. Variation among molecules in the copy number of these repeats results in mtDNA length variation and heteroplasmy (the presence of more than one form of mtDNA in an individual). In a sample of fish collected from different localities around Iceland and off George's Bank, each individual was heteroplasmic for two or more mtDNAs ranging in repeat copy number from two (common) to six (rare). An earlier report on mtDNA heteroplasmy in sturgeon (Acipenser transmontanus) presented a competitive displacement model for length mutations in mtDNAs containing tandem arrays and the cod data deviate from this model. Depending on the nature of putative secondary structures and the location of D-loop strand termination, additional mechanisms of length mutation may be needed to explain the range of mtDNA length variants maintained in these populations. The balance between genetic drift and mutation in maintaining this length polymorphism is estimated through a hierarchical analysis of diversity of mtDNA length variation in the Iceland samples. Eighty percent of the diversity lies within individuals, 8% among individuals and 12% among localities. An estimate of theta = 2N(eo) mu greater than 1 indicates that this system is characterized by a high mutation rate and is governed primarily by deterministic dynamics. The sequences of repeat arrays from fish collected in Norway, Iceland and George's Bank show no nucleotide variation suggesting that there is very little substructuring to the North Atlantic cod population.

Animals↗
PubMed1988

Role of sequence amplification in the generation of nematode mitochondrial DNA polymorphism.

Romanomermis culicivorax, an obligate parasitic nematode of mosquitos, possesses an unusually large mitochondrial genome. Individuals are monomorphic for one of several mitochondrial DNA (mtDNA) size variants ranging from 26-32 kb. In this report, we demonstrate that the mitochondrial genome size differential in three isofemale lineages is due to the presence of mtDNA sequences amplified to different copy numbers within each mtDNA molecule. Restriction enzyme analysis and DNA sequencing studies reveal that each mitochondrial genome contains one of two 3.0 kb repeat types that differ by approximately 30 bp. This difference is primarily due to a short (23 bp) imperfect tandem duplication present within the larger of two polymorphic repeating units. The 3.0 kb reiterated DNA sequences are present as direct, tandem repeats and as inverted portions of the same sequence located elsewhere in the genome. Based on mtDNA analysis of an independently reared R. culicivorax culture, we conclude that events resulting in mitochondrial genome rearrangement occurred in natural field populations prior to propagation within the laboratory.

Animals↗
PubMed2004

Mitochondrial genome size variation in New World and Old World populations of Drosophila melanogaster.

Drosophila melanogaster originated in Africa, spread to Europe and Asia, and is believed to have colonized the New World in the past few hundred years. Levels of genetic variation are typically reduced in New World populations, consistent with a founder event following range expansion out of Africa and the Old World. We describe the patterns of mtDNA length variation within and among several populations of Drosophila melanogaster from the Old and New World. MtDNA length variation is due to insertion and deletion of tandem repeats in the control region (D-loop) of D. melanogaster mitochondrial genome. The distinct mutational dynamics of this system provide an opportunity to compare the patterns of variation in this marker to those of other markers with different mutational pressures and linkage relationships. The data show significantly more length variation in African and Asian samples than in New World samples. New World samples also show more pronounced skew of the length distribution. Our results are distinct from an earlier study that showed significantly higher levels of length variation and heteroplasmy. The level of heteroplasmy is highly correlated with the number of years that samples have been maintained in laboratory culture, suggesting that relaxed selection in small populations permits the accumulation of mtDNA length variation and heteroplasmy. Together, the data indicate that mtDNA length variants retain a signature of founder events and selection, and suggest that further investigation into the mutation-selection dynamics of the D-loop region of mtDNA would provide a distinct and informative marker for analysis of the recent history of populations.

Animals↗
PubMed1993

Significance of mitochondrial DNA deletions in myotonic dystrophy.

Mitochondrial DNA (mtDNA) deletions have been noted in small quantities in a handful of atypical cases of myotonic dystrophy and there are clinical and pathological parallels between this autosomal dominant disease and certain mitochondrial myopathies where such deletions are well recognised. We studied 20 individuals from typical pedigrees of myotonic dystrophy (of whom 19 were clinically affected) with Southern blot analysis, and 2 of the affected individuals with PCR analysis of mtDNA, but were unable to demonstrate the previously noted deletions in any quantity by either method. We conclude that especially in view of known naturally occurring large scale and minor length variants in mtDNA, these previous findings are of dubious relevance to the disease.

Adolescent↗
PubMed2000

A novel method for forensic DNA investigations: repeat-type sequence analysis of tandemly repeated mtDNA in domestic dogs.

A highly variable and heteroplasmic tandem repeat region situated in the mitochondrial mt DNA control region (CR) in domestic dogs and wolves was studied to evaluate its suitability as a forensic genetic marker for analysis of single hairs. The tandem repeat array is composed of three 10-bp repeat types that are distributed so that a secondary DNA sequence is formed. Thus, the region presents two levels of variation: variation in the number of repeats and variation in the secondary DNA sequence of repeat types. Two analysis methods were therefore tested; fragment length analysis and analysis of the sequence of repeat types. Fragment analysis produced unique profiles that could be used to discriminate between blood samples from maternally closely related individuals. However, different hairs from one individual did not have the same fragment profile, and the method is, therefore, not suitable for analysis of single hairs. In contrast, analysis of the repeat type sequences (array types) is highly informative. When different hairs from one individual were studied, identical array types were found. The repeat-type sequence variation was studied among individuals having identical nonrepetitive CR mtDNA sequence variants. Seven, six, and two individuals, representing three different sequence variants, respectively, were analyzed. All these individuals had different array types, which implies a very high genetic variation between individuals in this region. The analysis method considerably improves the exclusion capacity of mtDNA analysis of domestic dogs compared with sequence analysis of non-repetitive DNA.

Animals↗
PubMed2005

Mitochondrial inheritance in depression, dysmotility and migraine?

BACKGROUND: Several studies have reported a high degree of association of the common conditions of depression, bowel dysmotility and migraine. Mitochondrial dysfunction and mitochondrial DNA (mtDNA) sequence variants have been linked individually to each of these three conditions, providing a plausible hypothesis for the reported association. If this hypothesis is correct, the matrilineal relatives (who all share essentially the same mtDNA sequence) of patients with mitochondrial disease secondary to inherited mtDNA mutations would be expected to have an elevated prevalence of each of these three conditions. METHODS: Families were recruited by an advertisement posted on the United Mitochondrial Disease Foundation website and invited to participate in an on-line questionnaire if at least one member was diagnosed with mitochondrial disease by a physician. Based upon the reported family histories, families were assigned by the investigators to either the probable maternal inheritance (PMI) group (55 families) or the probable non-maternal inheritance (PnMI) group (111 families). RESULTS: Bowel disorders, migraine and depression were reported at very high prevalence in the PMI mothers (60%, 54% and 51%, respectively), but were present at significantly lower prevalence rates among the PnMI mothers (16%, 26% and 12%; P<0.0001 for each) and the fathers of both groups (range 9-16%; P < 2 x 10(-6) for each). Similar data was obtained comparing the prevalence rates among maternal and paternal grandmothers, aunts and uncles. LIMITATIONS: Our data was obtained from families ascertained by the presence of a severely affected individual, and may not be applicable to families lacking this proband. CONCLUSIONS: Depression, bowel dysmotility and migraine are common manifestations in individuals with mtDNA sequence-related mitochondrial dysfunction, which supports our hypothesis that mitochondrial dysfunction is a major common factor underlying the association of these three conditions.

Adolescent↗
PubMed2001

Mitochondrial DNA mutations in black Americans with hypertension-associated end-stage renal disease.

For the majority of hypertensive cases, no gene or combination of genes and environmental factors clearly leading to hypertension has been identified. Studies to identify "hypertension" genes have focused on the assessment of markers and candidate genes in the nuclear genome. In this study, we have chosen to assess the mitochondrial genome as a site of mutations possibly contributing to susceptibility to hypertension in black Americans who have progressed to end-stage renal disease (H-ESRD). The mitochondrial genomes of 58 H-ESRD and 58 normotensive individuals were systematically analyzed by means of a high-resolution restriction analysis. After stratification by the presence or absence of an African continent-specific HpaI site gain at bp 3,592, differences in the frequencies of mitochondrial DNA (mtDNA) restriction variants in both groups were examined by chi-square analyses. A total of six variants was identified with significant differences in one or both cohorts. An A10398G DdeI mutation in the ND3 gene was significantly increased in the H-ESRD cohort (H-ESRD, P = 0.048; normotensives, P = 0.20), as was an HaeIII T6620C/G6260A double mutation in the CO1 gene (H-ESRD, P = 0.05; normotensives, P = 0.48). The remaining four variants were a G2758A mutation in the 16SrRNA gene (identified by RsaI), T10810C in the ND4 gene (identified by HinfI), a G7028A/T7055C double mutation in the CO1 gene (identified by AluI), and finally, a A10086G mutation in the ND3 gene (identified by TaqI; also causing an Asn-->Asp amino acid change). The RsaI and HinfI variants were in strong linkage disequilibrium with the HpaI site and not amenable to further analysis. After correction of all P values for multiple comparisons, the ND3 A10086G (Asn-->Asp) mutation shown by TaqI remained statistically significant (P = 0.0036) in the H-ESRD cohort, not in the normotensive cohort. To the best of our knowledge, this is the first report of an increased prevalence of mitochondrial gene variants in hypertensive individuals. In addition, we have identified single-nucleotide polymorphisms in flanking regions of these genes. Although replication and further assessment are necessary, the current results support our hypothesis that mtDNA may account for a portion of hypertensive cases in black Americans with ESRD.

Black or African American↗
PubMed1989

[Family study on mitochondrial DNA polymorphism].

Mitochondrial DNA restriction fragment length polymorphisms (mtDNA RFLPs) were surveyed among 19 Japanese families with 67 individuals including twins. A mother and children, and siblings of each family showed the same pattern of mtDNA RFLPs. Samples from Japanese war orphans remained in China and their probable relatives were also surveyed and one pair indicating a high probability to be siblings using other genetic markers possessed the same variant of mtDNA. Moreover mtDNA RFLPs was applied for maternity test among two families. The data suggested that parents mistook their children for each other at birth.

Adult↗
PubMed2005

[Association of mitochondrial DNA variation with type 2 diabetes mellitus].

OBJECTIVE: To explore the prevalence of mitochondrial DNA (mtDNA) mutations in patients with type 2 diabetes mellitus in Hubei. METHODS: A total of 184 cases of type 2 diabetes mellitus and 210 matched healthy controls with normal glucose tolerance were recruited for the study. The variants of mtDNA, including MIND13316 (G-->A), MIND13394 (T-->C), MTTE14693 (A-->G), MTTL1 3243 (A-->G), MTRNA1310 (C-->T) and 16189 (T-->C), were screened using PCR-restriction fragment length polymorphism (PCR-RFLP) analysis and DNA sequencing. The mutations were analyzed by mfold or tRNAscan-SE softwares. RESULTS: The mutation rates of 3316 (G-->A), 3394 (T-->C), 14693 (A-->G) were 3.26%, 2.72% and 2.17% respectively in type 2 diabetes group, whereas in the control group, the point mutations of 3394 (T-->C) and 14693 (A-->G) were not detected, but two subjects with 3316 (G-->A) were found (0.99%). There were significant differences in mutation rates of 3394 (T-->C) and 14693 (A-->G) between the two groups (P<0.05). In 4 of 184 cases, a T to C transition at nucleotide position 14693 was uncovered for the first time. The prevalence of 16189 variant among type 2 diabetes was significantly higher that of the controls (36.9% vs 26.6%, P=0.03). Moreover, the type 2 diabetes with 16189 variant showed higher fasting serum insulin level and higher HOMA-IR level than those without 16189 variant; stepwise multiple regression analysis showed the 16189 variant was an independent factor contributing to HOMA-IR (R(2)=0.043, P=0.037). Secondary structure prediction revealed that there were differences in 3394 T-->C vs wild-type ND1 protein and in 14693 A-->G vs wild-type tRNA(Glu) protein. CONCLUSION: The mutations of 3394 (T-->C) and 14693 (A-->G) may contribute to the genetic predisposition to type 2 diabetes; 16189 (T-->C) variant is associated with insulin resistance and risk factor of diabetes.

Aged↗
PubMed2006

Mitochondrial mutations in cancer.

The metabolism of solid tumors is associated with high lactate production while growing in oxygen (aerobic glycolysis) suggesting that tumors may have defects in mitochondrial function. The mitochondria produce cellular energy by oxidative phosphorylation (OXPHOS), generate reactive oxygen species (ROS) as a by-product, and regulate apoptosis via the mitochondrial permeability transition pore (mtPTP). The mitochondria are assembled from both nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) genes. The mtDNA codes for 37 genes essential of OXPHOS, is present in thousands of copies per cell, and has a very high mutations rate. In humans, severe mtDNA mutations result in multisystem disease, while some functional population-specific polymorphisms appear to have permitted humans to adapt to new environments. Mutations in the nDNA-encoded mitochondrial genes for fumarate hydratase and succinate dehydrogenase have been linked to uterine leiomyomas and paragangliomas, and cancer cells have been shown to induce hexokinase II which harnesses OXPHOS adenosine triphosphate (ATP) production to drive glycolysis. Germline mtDNA mutations at nucleotides 10398 and 16189 have been associated with breast cancer and endometrial cancer. Tumor mtDNA somatic mutations range from severe insertion-deletion and chain termination mutations to mild missense mutations. Surprisingly, of the 190 tumor-specific somatic mtDNA mutations reported, 72% are also mtDNA sequence variants found in the general population. These include 52% of the tumor somatic mRNA missense mutations, 83% of the tRNA mutations, 38% of the rRNA mutations, and 85% of the control region mutations. Some associations might reflect mtDNA sequencing errors, but analysis of several of the tumor-specific somatic missense mutations with population counterparts appear legitimate. Therefore, mtDNA mutations in tumors may fall into two main classes: (1) severe mutations that inhibit OXPHOS, increase ROS production and promote tumor cell proliferation and (2) milder mutations that may permit tumors to adapt to new environments. The former may be lost during subsequent tumor oxygenation while the latter may become fixed. Hence, mitochondrial dysfunction does appear to be a factor in cancer etiology, an insight that may suggest new approaches for diagnosis and treatment.

Cell Nucleus↗
PubMed1995

mtDNA deletion in a patient with symptoms of mitochondrial cytopathy but without ragged red fibers.

We describe a heteroplasmic 4237-bp mitochondrial DNA (mtDNA) deletion in an 11-year-old girl who has suffered from progressive illness since birth. Her clinical features include global developmental delay with regression, brainstem dysfunction, lactic acidosis, and a history of pancytopenia and failure to thrive. The deletion spanned nt 9498 to nt 13734 and was flanked by a 12-bp direct repeat. Southern blot analysis also revealed an altered ApaI restriction site caused by a G --> A nucleotide substitution at nt 1462 in the 12S rRNA gene. This homoplasmic nucleotide change was presumed to be a mtDNA nucleotide variant. No abnormalities of mitochondrial ultrastructure or distribution were observed, although mild deficiencies were noted for complexes IV, II + III, and I of the mitochondrial respiratory chain. The absence of ragged red fibers and COX-negative fibers in this patient shows that mtDNA deletions do not always result in these classical hallmarks of mitochondrial cytopathies.

Base Sequence↗
PubMed1986

Mitochondrial DNA transmission genetics in crickets.

This paper presents the results of a single generation study of the transmission genetics of mitochondrial DNA in the field cricket Gryllus firmus. In this species, individuals heteroplasmic for at least two different-sized mitochondrial genomes can be collected easily from natural populations. The frequencies of mtDNA size variants in heteroplasmic females and samples of their offspring were estimated by densitometry of autoradiographs. The variance in mitochondrial genotype frequencies among the offspring of heteroplasmic females indicates that, through genetic drift, fixation would take several hundred animal generations. Differences between the observations and data on mtDNA transmission in yeast and cows are discussed in light of the differences in organelle sampling regime and early developmental events in these species. Our data also show shifts in genotype frequencies in the transmission from mother to offspring that suggest a bias in favor of smaller genomes. The nature of mtDNA size variation in natural populations of crickets is discussed in reference to a mutation-selection balance.

Animals↗
PubMed2005

Maternal inheritance in cyclic vomiting syndrome.

Cyclic vomiting syndrome (CVS), characterized by severe discrete episodes of nausea, vomiting, and lethargy, is a fairly common, disabling, predominately-childhood condition most often associated with migraine and dysautonomic features. Our group recently reported that children with CVS and additional neuromuscular disease manifestations demonstrate strong maternal inheritance of multiple disease manifestations and abnormal urine organic acids, suggesting the presence of predisposing mitochondrial DNA (mtDNA) sequence variants. In order to determine if maternal inheritance is present in CVS in general, a clinical interview was administered regarding 80 unrelated individuals with CVS ascertained randomly from the database of the Cyclic Vomiting Syndrome Association (CVSA). Disease manifestations consistent with potential mitochondrial dysfunction were far more common in matrilineal (sharing the same mtDNA sequence) versus in non-matrilineal relatives, including mothers versus fathers (P = 3 x 10(-9)) and maternal versus paternal grandmothers (P = 2 x 10(-6)). Maternal inheritance is suggested in 52% of the 23 subjects with two or more neuromuscular abnormalities ("CVS+") and in 54% of the 44 subjects without any neuromuscular abnormalities ("CVS-"). In both the CVS+ and CVS- sub-groups, subjects, and affected matrilineal relatives of all ages suffer at a far higher incidence from several dysautonomic-related conditions, including migraine and irritable bowel, as well as depression and hypothyroidism, while neuromuscular and cognitive disorders such as hypotonia and ADHD are common only in affected children. We conclude that mtDNA sequences predispose towards the development of protean disease manifestations in CVS patients ascertained through a disease-specific association, as well as among their matrilineal relatives, whether or not neuromuscular disease is present in the proband. Since CVS was absent in all but one matrilineal relative of our probands, CVS is apparently a rare clinical presentation in individuals carrying the predisposing mtDNA sequences. The four conditions reported most frequently among the matrilineal relatives of our cases, migraine, depression, irritable bowel, and hypothyroidism, are known to segregate together in families, and our findings suggest that a common predisposing genetic factor is likely present on the mtDNA.

DNA, Mitochondrial↗
PubMed1996

Phylogeography and population structure of the Atlantic and Mediterranean green turtle Chelonia mydas: a mitochondrial DNA control region sequence assessment.

Mitochondrial (mt) DNA sequences were analysed to resolve the phylogeography and population genetic structure of Atlantic and Mediterranean populations of green turtles (Chelonia mydas). Analysis of sequence variation over 487 base pairs of the control (D-loop) region identified 18 haplotypes among 147 individuals from nine nesting populations. Pairwise comparisons of haplotype frequencies distinguished most nesting colonies, indicating significant genetic differentiation among rookeries and a strong propensity for natal homing behaviour by nesting females. Comparison of control region sequence data to earlier restriction fragment length polymorphism (RFLP) data for the same individuals demonstrates approximately a sixfold higher substitution rate in the 5' end of the control region. The sequence data provide higher resolution both in terms of the number of mtDNA genotype variants and the phylogeographic relationships detected within the Atlantic region, and reveal a gene genealogy that distinguishes two groups of haplotypes corresponding to (i) the western Caribbean and Mediterranean, and (ii) eastern Caribbean, South Atlantic and West Africa. The data suggest that phylogeographic patterns in the Atlantic Ocean may be interpreted in terms of female nest site fidelity and episodic dispersal events. The distribution of mtDNA haplotypes within the region is thus explained by the geological and climatic alternations (glacial and interglacial) over the last million years.

Animals↗
PubMed2005

Rapid deployment of the five founding Amerind mtDNA haplogroups via coastal and riverine colonization.

Numerous studies of variation in mtDNA in Amerindian populations established that four haplogroups are present throughout both North and South America. These four haplogroups (A, B, C, and D) and perhaps a fifth (X) in North America are postulated to be present in the initial founding migration to the Americas. Furthermore, studies of ancient mtDNA in North America suggested long-term regional continuity of the frequencies of these founding haplogroups. Present-day tribal groups possess high frequencies of private mtDNA haplotypes (variants within the major haplogroups), consistent with early establishment of local isolation of regional populations. Clearly these patterns have implications for the mode of colonization of the hemisphere. Recently, the earlier consensus among archaeologists for an initial colonization by Clovis hunters arriving through an ice-free corridor and expanding in a "blitzkrieg " wave was shown to be inconsistent with extensive genetic variability in Native Americans; a coastal migration route avoids this problem. The present paper demonstrates through a computer simulation model how colonization along coasts and rivers could have rapidly spread the founding lineages widely through North America.

Computer Simulation↗
PubMed1990

Cytoplasmic male sterility in beta is associated with structural rearrangements of the mitochondrial DNA and is not due to interspecific organelle transfer.

Chloroplast (ct) and mitochondrial (mt) DNAs from four cytoplasmic male sterile (cms) and 22 normal fertile sugar beet lines and accessions of wild beets from the genus Beta have been compared with restriction analyses and Southern hybridizations. We have used restriction analyses of ctDNA as a phylogenetic marker to confirm the taxonomic relationships between the different cytoplasms. According to the ctDNA data, all four cms cytoplasms belong to the same taxonomic section, Beta. Restriction patterns of ct and mtDNA from fertile accessions produced analogous trees of similarity and showed a close correlation between the organellar DNA diversity and the accepted taxonomic classification of the species studied. However, the mt-DNA restriction profiles of the four cms types differed dramatically from each other and from those of all fertile accessions from the genus. No indication of cytoplasmic introgression was found in any of the four investigated cms types. Southern hybridization to mtDNA revealed variant genomic arrangements in the different fertile and cms cytoplasms, indicating that rearrangement of the mitochondrial genome is a common denominator to the different cms systems in Beta. It may, indeed, be a common property to spontaneously occurring cms in all or most species.

Chloroplasts↗