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The Chillingham herd of wild Northumbrian cattle remains viable despite over 300 years of in-breeding and a near-homozygous nuclear genome. Here we report the complete mitochondrial DNA sequence using ultra-deep next generation sequencing. Random population sampling of ~10% of the extant herd identified a single mtDNA haplotype harbouring a unique bovine variant present in all other higher mammals (m.11789C/Y421H) which may contribute to their survival.
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Short communication
Unique mitochondrial DNA in highly inbred feral cattle
Gavin Hudson
, Ian Wilson
, Brendan I.A. Payne
, Joanna Elson
, David C. Samuels
Mauro Santibanez-Korev
, Stephen J.G. Hall
, Patrick F. Chinnery
Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
Vanderbilt University Medical Centre, Nashville, TN, United States
Department of Biological Sciences, University of Lincoln, UK
abstractarticle info
Article history:
Received 2 February 2012
Received in revised form 23 April 2012
Accepted 10 May 2012
Available online 17 May 2012
The Chillingham herd of wild Northumbrian cattle remains viable despite over 300 years of in-breeding and a
near-homozygous nuclear genome. Here we report the complete mitochondrial DNA sequence using ultra-
deep next generation sequencing. Random population sampling of ~ 10% of the extant herd identied a single
mtDNA haplotype harbouring a unique bovine variant present in all other higher mammals (m.11789C/
Y421H) which may contribute to their survival.
© 2012 Elsevier B.V. and Mitochondria Research Society. All rights reserved.
The Chillingham herd of wild cattle (Fig. 1a) has been inbred for over
300 years (67 generations), and has passed through at least one popu-
lation genetic bottleneck (reduction to 5 males and 8 females in
1947). Apparently in consequence, the microsatellite genome is almost
homozygous, and it is argued that the continuing viability of the herd
(which now numbers 97) is due to the loss of deleterious nuclear alleles
since isolation (Visscher et al., 2001). This affords a unique opportunity
to study a mammalian population in the wild, where the mitochondrial
genome is operating against a background of near-uniform nuclear
Multiplexed next-generation sequencing, at great depth (mean
coverage 2935 fold, SD =2676), of eight randomly selected, distinct,
Chillingham cattle from the extant population of 93, revealed no
inter-sample sequence variation, with all carrying the same twelve
mtDNA variants (m.169G; m.352G; m.2501A; m.2536A; m.2568C;
m.7851C; m.8346T; m.9682C; m.11476A; m.11789C; m.13310C and
16264A), and no detectable evidence of mtDNA heteroplasmy
(>10% (He et al., 2010)). From these eight samples we can estimate
that 100% of the current population has descended from a single
recent female founder (ClopperPearson binomial 95% condence in-
terval=63% to 100%).
Phylogenetic network-analysis of 256 complete mtDNA se-
quences, rooted with Bos grunniens (Yak), indicates that Chillingham
cattle are related to modern cattle, and belong to the T3 sub-
haplogroup (Fig. 1b). Bootstrap values indicate poor tree placement
(51%, 1000 replicates, Supplementary Fig. 1), likely due to the poor
resolution of haplogroup T3, which has a star-like phylogeny
(Achilli et al., 2008). There was evidence of ancient extant bovine
variation (Aurochs, Bos primigenius: m.2536A, m.9682C m.13310C,
and m.16264A), inherited down the Bos taurus maternal lineage, and
two rare variants (m.2568C and m.11476A, 5.8% and 2.9% of modern
taurine mtDNAs) previously seen only in Italian cattle (Bonglio
et al., 2010).
The Chillingham herd was stated by Darwin (1868, revised 1905)
to be a semi-wild, though much degenerated in size descendant of
the ancestor of domestic cattle, the aurochs Bos primigenius. Aurochs
remains later than 1500 BC are not known in Britain and although
there are reports of wild cattle from medieval Britain these were
probably escapes from husbandry, and were not in districts near
Chillingham. The earliest record of the Chillingham herd is dated
1646 and the most likely origin of the herd is by selection from
local husbanded cattle. The idea of a connection with Roman cattle
has also been advanced, but again there is no evidence that the
Romans brought cattle to Britain, nor that Italian cattle were
subsequently imported, so m.2568C and m.11476A are either recur-
rent mutations, or are more widely distributed amongst European
cattle lineages.
Despite sampling ~10% of the extant Chillingham herd, the lack of
heteroplasmy is not surprising, given the rapid shifts observed in a
single maternal lineage of the Holstein cow, leading to xation within
2 generations (Olivo et al., 1983).
All eight Chillingham cattle harboured three unique mtDNA
substitutions (m.2501A in 16s rRNA; m.8346T, a synonymous variant
in ATP6; and m.11789C, a non-synonymous variant in URF4) not
found in other modern taurine lineages (Supplementary Table 1).
m.7851C is also found in
Bos indicus and the modern Yak, B. grunniens.
Mitochondrion 12 (2012) 438440
Corresponding author at: Institute of Genetic Medicine, Central Parkway, Newcastle
upon Tyne, NE1 3BZ, UK. Tel.: +44 191 5101; fax: +44 191 222 8553.
E-mail address: (P.F. Chinnery).
1567-7249/$ see front matter © 2012 Elsevier B.V. and Mitochondria Research Society. All rights reserved.
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Given the phylogenetic relationship between these different species
(Fig. 1b), m.7851C is likely to be a recurrent mutation. This is similar
to other B. taurus breeds, which harbour 5 +/ 1.06 unique mtDNA
variants (Achilli et al., 2008). Based on a phylogenetic mutation rate
of 2.043 ± 0.099 ×10
/base-pair/year for the mtDNA coding region
(15,247 bp) (Achilli et al., 2008), the herd is predicted to have a
Fig. 1. (a) The Chillingham wild cattle, Bos taurus. (b) Phylogenetic network of 256 complete Bovine mitochondrial DNA sequences based on coding-region variations relative to the
bovine reference sequences (BRS, GenBank accession no. V00654). The relative positions and population frequencies of Chillingham cattle, Asian Auroch (Bos indicus), European
Auroch (Bos primigenius) and Banteng wild cattle (Bos javanicus ) are shown for reference. The network is shown rooted to the Yak (Bos grunniens) and indicates the major taurine
haplogroups (Supplementary Fig. 1). Node sizes are proportional frequency and all variant weights were considered equal.
439G. Hudson et al. / Mitochondrion 12 (2012) 438 440
common maternal T3 ancestor ~12,000 years ago, in keeping with the
Neolithic domestication of European founder cattle in the Fertile
Inbreeding is generally found to reduce tness in both farmed and
wild animals (Visscher et al., 2001), so the continued survival of the
isolated Chillingham herd suggests that deleterious alleles have
been purged from the population. It is conceivable that the diver-
gence of the Chillingham mtDNA genome contributes to the herd vi-
ability. This could, in part, be due the presence of m.11789C (Y421H),
which resides in a highly conserved region of the complex I ND4
respiratory chain subunit. The histidine residue found in the
Chillingham cattle is the sole allele in almost all other higher
mammals (including domesticated sheep and horses), but not in
modern bovine lineages (Supplementary Fig. 2), and is in a region
sensitive to pathogenic mtDNA variation in humans (Taylor and
Turnbull, 2005). Thus, m.11789C is likely to have a functional effect.
This could occur directly through complex I activity, or indirectly
though the nuclear genome, given evidence that mtDNA substitution
drives the adaption in nuclear-encoded respiratory chain proteins in
other species (Blier et al., 2001). Whichever is the case, since that
all are healthy, the Chillingham-specic variant could optimize the
aerobic synthesis of adenosine triphosphate, and thus promote herd
viability in the context of an otherwise invariant nuclear genome.
PFC is a Wellcome Trust Senior Fellow in Clinical Science
(WT084980/Z/08/Z) and an NIHR Senior Investigator, who is also
supported through the Wellcome Trust Centre for Mitochondrial Re-
search (WT096919Z/11/Z), the Medical Research Council (UK) Trans-
lational Neuromuscular Centre, and the UK NIHR Biomedical Research
Centre for Ageing and Age-related Disease award to the Newcastle
upon Tyne Foundation Hospitals NHS Trust.
Appendix A. Supplementary data
Supplementary data to this article can be found online at http://
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Pala, M., Kashani, B.H., Perego, U.A., Battaglia, V., Fornarino, S., Kalamati, J.,
Houshmand, M., Negrini, R., Semino, O., Richards, M., Macaulay, V., Ferretti, L.,
Bandelt, H.J., Ajmone-Marsan, P., Torroni, A., 2008. Mitochondrial genomes of ex-
tinct aurochs survive in domestic cattle. Curr. Biol. 18, R157R158.
Blier, P.U., Dufresne, F., Burton, R.S., 2001. Natural selection and the evolution of
mtDNA-encoded peptides: evidence for intergenomic co-adaptation. Trends
Genet. 17, 400406.
Bonglio, S., Achilli, A., Olivieri, A., Negrini, R., Colli, L., Liotta, L., Ajmone-Marsan, P.,
Torroni, A., Ferretti, L., 2010. The enigmatic origin of bovine mtDNA haplogroup
R: sporadic interbreeding or an independent event of Bos primigenius domestica-
tion in Italy? PLoS One 5, e15760.
Darwin, C., 1868. The Variation of Animals and Plants under Domestication. J. Murray,
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He, Y., Wu, J., Dressman, D.C., Iacobuzio-Donahue, C., Markowitz, S.D., Velculescu, V.E.,
Diaz L.A. Jr., Kinzler, K.W., Vogelstein, B., Papadopoulos, N., 2010. Heteroplasmic
mitochondrial DNA mutations in normal and tumour cells. Nature 464, 610614.
Olivo, P.D., Van de Walle, M.J., Laipis, P.J., Hauswirth, W.W., 1983. Nucleotide sequence
evidence for rapid genotypic shifts in the bovine mitochondrial DNA D-loop. Na-
ture 306, 400402.
Taylor, R.W., Turnbull, D.M., 2005. Mitochondrial DNA mutations in human disease.
Nat. Rev. Genet. 6, 389402.
Visscher, P.M., Smith, D., Hall, S.J., Williams, J.L., 2001. A viable herd of genetically
uniform cattle. Nature 409, 303.
440 G. Hudson et al. / Mitochondrion 12 (2012) 438 440
... Although there is circumstantial evidence that selection was practised in the 19 th century (a substantial proportion of bulls were castrated: Hall and Hall 1988), and the herd was reduced by about 50% around 1918, selective breeding has been avoided since then. For the present discussion the most interesting feature of the breed is its continued viability in spite of the genetic uniformity attributable to bottlenecks in its history (Ballingall et al. 2012;Hudson et al. 2012;Visscher et al. 2001), though this is probably not of relevance to the design of conservation strategies for FAnGR generally. ...
... The Enderby Island cattle of New Zealand are a prime example; this vanishingly rare breed was rescued through a very early application of cloning (Wells et al. 1998). In the UK fundamental research on immunology and mitochondrial genetics, using the Chillingham cattle (Ballingall et al. 2012;Hudson et al. 2012), has led to the cryopreservation of cell cultures of possible use in cloning. ...
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Report commissioned by Defra, UK
... This is not caused by isolation of the site as the material culture support contact to northern Italy and to a lesser extend to the north-west [33]. Could it be a disease, selection, or inbreeding within a small population kept in one area, as seen in Chillingham cattle today [54]? Archaeozoological data support the use of cattle for meat at Nössingbühel where it was well possible to farm and pasture [33]. ...
The Bronze Age in Europe is characterized by major socio-economic changes, including certain aspects of animal husbandry. In the Alpine region archaeozoological data, though not very abundant, reveal that cattle were the most important domestic animals in this time period. They were probably used differently in the lowlands than at higher altitude, traction became more important and people increasingly exploited them for dairy products rather than for meat. Thus, a crucial question in this context is whether these major events are accompanied by changes in genetic diversity of cattle. Here we report partial mtDNA d-loop data (320 bp) obtained by PCR from 40 alpine cattle excavated at different sites in South Tyrol, Italy, and Grisons, Switzerland. Most cattle belong to the main European taurine T3 haplogroup, but a few members of T2 and Q haplogroups were identified. Moreover, genetic diversity measures and population genetic statistics indicate different cattle histories at different sites, including bottlenecks and potential admixture. However, Bronze Age Alpine cattle appear to be linked to modern rural cattle mainly from Italy.
... The validation of our primary hypothesis leads us to propose a novel hypothesis, namely a Scandinavian affiliation for the Chillingham cattle. The earliest record of the Chillingham herd is from 1645 (Hall & Clutton-Brock, 1988), and mitochondrial DNA studies indicate that the breed as it exists today is descended from a single cow (Hudson et al., 2012). In the absence of historical evidence of Chillingham cattle having influenced the White Galloway, the most parsimonious explanation for the occurrence of the same gene in both these breeds is that the Chillingham herd was assembled some time before 1645 from cattle selected in the England-Scotland border region. ...
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Coat colour patterns are important characteristics of many cattle breeds and in some are determined by a chromosomal translocation, which can have the pleiotropic effect of testicular hypoplasia. We test the hypothesis that this variant, known as the Cs29 allele, is prevalent in the ancient Chillingham White Cattle (Bos taurus) of north‐east England. Its distribution may provide insights into breed history, and as it is associated with reproductive anomalies, we investigated the issues of subfertility in this cattle herd which are of clear relevance to its conservation. We report that the cattle are homozygous for the translocation. As it is also known in other breeds of the England‐Scotland border and northern Irish area, namely the White Galloway and Irish Moiled, and in the Northern Finncattle and Swedish Mountain, we further hypothesize a Scandinavian connection for White Galloway, Irish Moiled and Chillingham cattle. We present unpublished data showing testicular hypoplasia to be present at Chillingham. Sperm quality is also known to be very low, and the question arises as to how the highly inbred (Fis = 0.92) Chillingham cattle have continued to survive in spite of these reproductive anomalies. Surprisingly, herd fertility has not declined over the last 160 years, and in the light of behavioural data, we propose this is probably because of multiple mating, there being no castration and only welfare culling in this herd. These findings have wide relevance, particularly for breeds of conservation importance and probably for other bovine species, because male subfertility, frequent in cattle generally, could restrict the choice of bulls for representation in gene banks with consequent risk of loss of lineages. Research on heterospermic insemination or multiple mating of cattle could, therefore, be a useful complement to the development of assisted reproduction technologies for cryoconservation. The distinctive colour pattern of the Chillingham White Cattle is determined by a gene also found in Scandinavian cattle. It is also associated with a reproductive anomaly, but it appears multiple mating can overcome this. There are lessons for gene bank management – rare breed bulls that appear subfertile should not automatically be excluded from representation.
... The roosting habits of P. hypomelanus on the islands had increased the possibility for the occurrence of inbreeding between the individuals in a population. Thus, small populations are generally considered to be susceptible to a number of genetic problems like low level of variability, inbreeding depression, and the ability to overcome disease agents [16].The impact of the inbreeding process had caused a reduction in fitness for each population [17]. Genetic diversity, the primary component of adaptive evolution, is essential for the long-term survival probability of a population [16]. ...
Conference Paper
The study was conducted to determine phylogenetic relationships of Island Flying Fox (Pteropus hypomelanus) along the East and West Coast of the Peninsular Malaysia based on Cytochrome b sequences of mitochondrial DNA and to see the effectiveness of using this region in explaining the relationships among them. There are 29 genetic samples were collected from the several islands includes Dangli Island (Langkawi), Tioman Island (Johor), Tinggi Island (Johor), Redang Island (Terengganu) and Pangkor Island (Perak). Meanwhile, one sequences from the GeneBank represent as outgroup, Pteropus vampyrus to construct a complete phylogenetic tree. Tree topologies were built using the Neighbour Joining (NJ) and Maximum Parsimony (MP) methods. The resulting phylogenetic tree showed a clear separation between (North-West) and (South-East) population supported with 100% bootstrap value. The effectiveness of Cytochrome b has successfully resolved the phylogenetic tree when separating individuals between the populations. This study can contribute to the resolution of taxonomic and systematic problems of Island Flying Fox in Peninsular Malaysia by looking at the effectiveness of Cytochrome b region in explaining the phylogenetic relationships between the populations.
...  Hindmarch and Hall (2012) General review in context of European pastoralist systems.  Hudson et al. (2012) Mitochondrial DNA genotype of Chillingham cattle.  Brenig et al. (2013) Genetic mechanism of coat coloration in some British white breeds, possibly similar to situation in Chillingham cattle, though this is yet to be studied formally. ...
Technical Report
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Bibliography on Chillingham Wild Cattle and on Chillingham Park
...  Hindmarch and Hall (2012) General review in context of European pastoralist systems.  Hudson et al. (2012) Mitochondrial DNA genotype of Chillingham cattle.  Brenig et al. (2013) Genetic mechanism of coat coloration in some British white breeds, possibly similar to situation in Chillingham cattle, though this is yet to be studied formally. ...
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Chillingham: an academic bibliography on the wild cattle and Chillingham Park
... Previous analysis of genetic variation using 25 microsatellites identified only one marker with polymorphism (Visscher et al., 2001). Additionally, sequences of the full mitochondria of eight animals (sequencing depth ∼2935x using next generation sequencing) revealed a single haplotype in the herd that differentiated them from other taurine breeds by three mutations, and one mutation (likely to be a recurrent mutation) that related them to indicine breeds and yak (Hudson et al., 2012). These studies suggest that Chillingham probably survives because the population has purged most deleterious mutations. ...
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The domestication of the aurochs took place approximately 10,000 years ago giving rise to the two main types of domestic cattle known today, taurine (Bos taurus) domesticated somewhere on or near the Fertile Crescent, and indicine (Bos indicus) domesticated in the Indus Valley. However, although cattle have historically played a prominent role in human society the exact origin of many extant breeds is not well known. Here we used a combination of medium and high-density Illumina Bovine SNP arrays (i.e., ~54,000 and ~770,000 SNPs, respectively), genotyped for over 1300 animals representing 56 cattle breeds, to describe the relationships among major European cattle breeds and detect patterns of admixture among them. Our results suggest modern cross-breeding and ancient hybridisation events have both played an important role, including with animals of indicine origin. We use these data to identify signatures of selection reflecting both domestication (hypothesized to produce a common signature across breeds) and local adaptation (predicted to exhibit a signature of selection unique to a single breed or group of related breeds with a common history) to uncover additional demographic complexity of modern European cattle.
... Phylogenetic reconstructions based on neighbour joining, including representatives of all bovine haplogroups, showed that all mitogenomes of the WPC belong to the haplogroup T, main subgroup T3. However, WPC1, WPC23 and the Chillingham cattle (Hudson et al. 2012) were grouped together with EU177840 (Cabannina breed) representing a T1/2/3 haplotype (Achilli et al. 2008). This group has a basal position to T3 and T4 in the phylogenetic reconstruction (Fig. 1) and is discussed as primitive within domestic cattle (Achilli et al. 2008). ...
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The White Park Cattle (WPC) is an indigenous ancient breed from the British Isles which has a long-standing history in heroic sagas and documents. The WPC has retained many primitive traits, especially in their grazing behaviour and preferences. Altogether, the aura of this breed has led to much speculation surrounding its origin. In this study, we sequenced the mitogenomes from 27 WPC and three intronic fragments of genes from the Y chromosome of three bulls. We observed six novel mitogenomic lineages that have not been found in any other cattle breed so far. We found no evidence that the WPC is a descendant of a particular North or West European branch of aurochs. The WPC mitogenomes are grouped in the T3 cluster together with most other domestic breeds. Nevertheless, both molecular markers support the primitive position of the WPC within the taurine breeds.
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Current concerns about food security highlight the importance of maintaining productive and disease-resistant livestock populations. Major histocompatibility complex (MHC) class I genes have a central role in immunity. A high level of diversity in these genes allows populations to survive despite exposure to rapidly evolving pathogens. This review aims to describe the key features of MHC class I genetic diversity in cattle and to discuss their role in disease resistance. Discussion centers on data derived from the cattle genome sequence and studies addressing MHC class I gene expression and function. The impact of intensive selection on MHC diversity is also considered. A high level of complexity in MHC class I genes and functionally related gene families is revealed. This highlights the need for increased efforts to determine key genetic components that govern cattle immune responses to disease, which is increasingly important in the face of changing human and environmental demands.
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Background: When domestic taurine cattle diffused from the Fertile Crescent, local wild aurochsen (Bos primigenius) were still numerous. Moreover, aurochsen and introduced cattle often coexisted for millennia, thus providing potential conditions not only for spontaneous interbreeding, but also for pastoralists to create secondary domestication centers involving local aurochs populations. Recent mitochondrial genomes analyses revealed that not all modern taurine mtDNAs belong to the shallow macro-haplogroup T of Near Eastern origin, as demonstrated by the detection of three branches (P, Q and R) radiating prior to the T node in the bovine phylogeny. These uncommon haplogroups represent excellent tools to evaluate if sporadic interbreeding or even additional events of cattle domestication occurred. Methodology: The survey of the mitochondrial DNA (mtDNA) control-region variation of 1,747 bovine samples (1,128 new and 619 from previous studies) belonging to 37 European breeds allowed the identification of 16 novel non-T mtDNAs, which after complete genome sequencing were confirmed as members of haplogroups Q and R. These mtDNAs were then integrated in a phylogenetic tree encompassing all available P, Q and R complete mtDNA sequences. Conclusions: Phylogenetic analyses of 28 mitochondrial genomes belonging to haplogroups P (N = 2), Q (N = 16) and R (N = 10) together with an extensive survey of all previously published mtDNA datasets revealed major similarities between haplogroups Q and T. Therefore, Q most likely represents an additional minor lineage domesticated in the Near East together with the founders of the T subhaplogroups. Whereas, haplogroup R is found, at least for the moment, only in Italy and nowhere else, either in modern or ancient samples, thus supporting an origin from European aurochsen. Haplogroup R could have been acquired through sporadic interbreeding of wild and domestic animals, but our data do not rule out the possibility of a local and secondary event of B. primigenius domestication in Italy.
Using the housefly, Musca domestica (L.), as a model system, we tested the ability of two extremes in the range of possible captive breeding protocols to yield sustainable populations following founding with low founder numbers. The protocols tested included two levels of migration as well as inbreeding followed by selection, each with appropriate controls. Each low-founder-number population was founded with two pairs of flies. The maximum migration scheme had 50% migration per generation, and the minimum migration populations experienced a migration rate of 2.5% per generation. The control level of migration was 0%. A fourth low-founder-number treatment was designed to test the effect of inbreeding followed by selection. Two sets of high-founder-number control groups were also derived from the stock population. Two fitness measures, viability and productivity of the populations, were recorded at the fifth generation. Populations in the minimum-migration and zero migration treatment groups had lower fitness than populations in any other treatment for both measures. Populations that experienced inbreeding and selection for high fitness levels high levels of migration, or large high-founder-number populations were equally fit. These results demonstrate that a captive-breeding scheme that contains substantial levels of migration or inbreeding followed by selection can yield highly adapted populations.
The presence of hundreds of copies of mitochondrial DNA (mtDNA) in each human cell poses a challenge for the complete characterization of mtDNA genomes by conventional sequencing technologies. Here we describe digital sequencing of mtDNA genomes with the use of massively parallel sequencing-by-synthesis approaches. Although the mtDNA of human cells is considered to be homogeneous, we found widespread heterogeneity (heteroplasmy) in the mtDNA of normal human cells. Moreover, the frequency of heteroplasmic variants varied considerably between different tissues in the same individual. In addition to the variants identified in normal tissues, cancer cells harboured further homoplasmic and heteroplasmic mutations that could also be detected in patient plasma. These studies provide insights into the nature and variability of mtDNA sequences and have implications for mitochondrial processes during embryogenesis, cancer biomarker development and forensic analysis. In particular, they demonstrate that individual humans are characterized by a complex mixture of related mitochondrial genotypes rather than a single genotype.
Mitochondrial DNA (mtDNA) is unusual in its rapid rate of evolution and high level of intraspecies sequence variation. The latter is thought to be related to the strict maternal inheritance of mtDNA, which effectively isolates within a species mitochondrial gene pools that accumulate mutations and vary independently. A fundamental and as yet unexplained aspect of this process is how, in the face of somatic and germ-line mtDNA ploidy of 10(3) to 10(5) (refs 4, 5), individual variant mtDNA molecules resulting from mutational events can come to dominate the large intracellular mtDNA population so rapidly. To help answer this question, we have determined here the nucleotide sequence of all or part of the D-loop region in 14 maternally related Holstein cows. Four different D-loop sequences can be distinguished in the mtDNA of these animals. One explanation is that multiple mitochondrial genotypes existed in the maternal germ line and that expansion or segregation of one of these genotypes during oogenesis or early development led to the rapid genotypic shifts observed.
Inbreeding, which can lead to the loss of genetic variation or the accumulation of deleterious alleles, has been shown to reduce fitness in wild, zoo, laboratory and farmed animals. But it has been proposed that when combined with selection, inbreeding may purge deleterious alleles. Here we provide support for this hypothesis in a study of the Chillingham cattle, which shows that this viable herd is almost genetically uniform. The homozygosity of this herd far exceeds that of other cattle and that found in wild populations of other mammalian species.
Mitochondrial DNA (mtDNA) variation is an important tool for the investigation of the population genetics of animal species. Recently, recognition of the role of mtDNA mutations in human disease has spurred increasing interest in the function and evolution of mtDNA and the 13 polypeptides it encodes. These proteins interact with a large number of peptides encoded in the nucleus to form the mitochondrial electron transport system (ETS). As the ETS is the primary energy generation system in aerobic metazoans, natural selection would be expected to favor mutations that enhance ETS function. Such mutations could occur in either the mitochondrial or nuclear genes encoding ETS proteins and would lead to positive intergenomic interactions, or co-adaptation. Direct evidence for intergenomic co-adaptation comes from functional studies of systems where nuclear-mitochondrial DNA combinations vary naturally or can be manipulated experimentally.
The human mitochondrial genome is extremely small compared with the nuclear genome, and mitochondrial genetics presents unique clinical and experimental challenges. Despite the diminutive size of the mitochondrial genome, mitochondrial DNA (mtDNA) mutations are an important cause of inherited disease. Recent years have witnessed considerable progress in understanding basic mitochondrial genetics and the relationship between inherited mutations and disease phenotypes, and in identifying acquired mtDNA mutations in both ageing and cancer. However, many challenges remain, including the prevention and treatment of these diseases. This review explores the advances that have been made and the areas in which future progress is likely.
Archaeological and genetic evidence suggest that modern cattle might result from two domestication events of aurochs (Bos primigenius) in southwest Asia, which gave rise to taurine (Bos taurus) and zebuine (Bos indicus) cattle, respectively [1,2,3]. However, independent domestication in Africa [4,5] and East Asia [6] has also been postulated and ancient DNA data raise the possibility of local introgression from wild aurochs [7,8,9]. Here, we show by sequencing entire mitochondrial genomes from modern cattle that extinct wild aurochsen from Europe occasionally transmitted their mitochondrial DNA (mtDNA) to domesticated taurine breeds. However, the vast majority of mtDNAs belong either to haplogroup I (B. indicus) or T (B. taurus). The sequence divergence within haplogroup T is extremely low (eight-fold less than in the human mtDNA phylogeny [10]), indicating a narrow bottleneck in the recent evolutionary history of B. taurus. MtDNAs of haplotype T fall into subclades whose ages support a single Neolithic domestication event for B. taurus in the Near East, 911 thousand years ago (kya).