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Molecular phylogenetic inference from saber-toothed cat fossils of Rancho La Brea.

A method for the successful extraction of sequestered cellular DNA from 14,000-year-old fossil bones was developed and applied to asphalt-preserved specimens of the extinct saber-toothed cat, Smilodon fatalis. Two distinct gene segments, the mitochondrial gene for 12S rRNA and nuclear FLA-I (the feline class I major histocompatibility complex gene), from three different individual fossil specimens were cloned and sequenced after PCR amplification. Comparison of fossil-derived DNA sequences to homologous regions in 15 living carnivorous species, including 9 species of Felidae and 6 nonfelids, affirmed the phylogenetic placement of Smilodon within the modern radiation of Felidae distinct from the Miocene paleofelid (Nimravidae) saber-toothed "cat" species. These results raise the prospect of obtaining genetically informative DNA from preserved bones of extinct fossil species, particularly among the 2 million specimens excavated from the asphaltic sediments at Rancho La Brea in metropolitan Los Angeles.

Animals↗

Structure of the mitochondrial control region of the Eurasian otter (Lutra lutra; Carnivora, Mustelidae): patterns of genetic heterogeneity and implications for conservation of the species in Italy.

In this study we determined the complete sequence of the mitochondrial DNA (mtDNA) control region of the Eurasian otter (Lutra lutra). We then compared these new sequences with orthologues of nine carnivores belonging to six families (Mustelidae, Mephitidae, Canidae, Hyaenidae, Ursidae, and Felidae). The comparative analyses identified all the conserved regions previously found in mammals. The Eurasian otter and seven other species have a single location with tandem repeats in the right domain, while the spotted hyena (Hyaenidae) and the tiger (Felidae) have repeated sequences in both the right and left domains. To assess the degree of genetic heterogeneity of the Eurasian otter in Italy we sequenced two fragments of the gene and analyzed length polymorphisms of repeated sequences and heteroplasmy in 32 specimens. The study includes 23 museum specimens collected in northern, central, and southern Italy; most of these specimens are from extinct populations, while the southern Italian samples belong to the sole extant Italian population of the Eurasian otter. The study also includes all the captive-reared animals living in the colony "Centro Lontra, Caramanico Terme" (Pescara, central Italy). The colony is maintained for reintroduction of the species. We found a low level of genetic polymorphism; a single haplotype is dominant, but our data indicate the presence in central and southern Italy of two slightly divergent haplotypes. One haplotype belongs to an extinct population, the other is present in the single extant Italian population. Analyses of length polymorphisms and heteroplasmy indicate that the autochthonous Italian samples are characterized by a distinct array of repeated sequences from captive-reared animals.

Animals↗

Immunogenetic evidence for the phylogenetic sister group relationship of dogs and bears (Mammalia, Carnivora: Canidae and Crsidae). a comparative determinant analysis of carnivoran albumin, c3 complement and immunoglobulin micro-chain.

Thirty-seven antigenic determinants were identified in the albumins, the immunoglobulin micro- and IgG(Fc) chains, and the C3 proteins of 51 carnivoran (sub)species from 31 genera, and in 12 noncarnivoran mammals. In addition to 19 determinants plesiomorphic for Carnivora as an order, 18 synapomorphic epitopes of carnivoran families revealed nine phylogenetic reaction groups: (1) canids, (2) ursids, (3) the racoon, (4) the Weddell seal, (5) the lesser panda, (6) the harbour seal, (7) mustelids, (8) viverrids and hyaenas, and (9) felids. These data identify Canoidea (Canidae, Ursidae, Phocidae, Procyonidae, Ailuridae, Mustelidae) and Feloidea (Viverridae, Hyaenidae, Felidae) as two fundamentally differentiated lineages of Carnivora, and confirm the inclusion of seals among the former. The Ursidae are the sister group of the Canidae. The antigenic determinants in the studied proteins do not subdivide the Canidae, Ursidae and Felidae into immunologically differentiated lineages.

Albumins↗

Morphological integration in the carnivoran skull.

The correlated evolution of traits may be a principal factor in morphological evolution, but it is typically studied in genetic or developmental systems. Most studies examining phenotypic trait correlations, through analysis of morphological integration, consider only few taxa, with limited ability to test hypotheses of the influence of trait integration on morphological variation and diversity. The few comparative studies in less inclusive groups have yielded varying relationships of integration to the key factors of phylogeny and diet. In this paper, I present analyses of cranial morphological integration in 30 species from the mammalian order Carnivora, spanning eight extant families and a wide range of ecological and morphological diversity. Fifty-five cranial landmarks were captured through three-dimensional digitization of 15-22 specimens for each species. Using a node-based phylogenetic distance matrix, a significant correlation was found between similarity in patterns of integration and phylogenetic relatedness within Felidae (cats) and Canidae (dogs), but not within more inclusive clades, when size-related variation was removed. When size was included, significant correlations were found across all Caniformia, Musteloidea, Mustelidae, and Felidae. There was a significant correlation between phylogeny and morphological integration only within the higher-level clade Feliformia (cats, civets, mongooses, and hyaenas) when a branch-length-based phylogenetic distance matrix was analyzed, with and without size. In contrast, diet was significantly correlated with similarity in morphological integration in arctoid carnivorans (bears, raccoons, and weasels), but had no significant relationship with integration in feliforms or canids. These results support the proposition that evolutionary history is correlated with cranial integration across large clades, although in some smaller clades diet also exerts significant influence on the correlated evolution of traits.

Animals↗

General introduction and epidemiology of trichinellosis.

All studies on trichinellosis have been based on the assumption that there is only one cosmopolitan agent of human and animal trichinellosis; Trichinella spiralis (Owen, 1835). In the past, swine and only a few synanthropic animals were considered reservoirs, and the presence of the parasite in sylvatic animals was considered rare. Breeding experiments before, and then biochemical approaches (isoenzymes and DNA analysis), showed the presence of a high genetic variability inside this genus, suggesting it be considered as polyspecific. At present, eight gene pools, named from T1 to T8, have been identified in the genus Trichinella. T1 (T. spiralis s str) is the etiological agent for the domestic cycle, with a cosmopolitan distribution related to swine breeding and human habits. However, in some areas this parasite passes from domestic to sylvatic animals and vice versa. Six gene pools are the agents for the sylvatic cycle at different latitudes, mainly in carnivores. T2 (T. nativa) is present in terrestrial mammals and seldom in sea mammals of arctic and subarctic regions. T3, T5, and T8 are present mainly in Canidae (T3), Ursidae (T5), Hyaenidae and Felidae (T8) of temperate-subtropical areas of Palearctic, Nearctic and South African regions, respectively. T6 is present in carnivores in the subarctic-temperate area of the Nearctic region; and T7 (T. nelsoni) in Hyaenidae and Felidae of Equatorial Africa. Only T4 (T. pseudospiralis) can infect both mammals and birds, and it shows a cosmopolitan distribution. Probably trichinellosis is present world-wide, but unknown in those areas where it has not been sought.

Animals↗

Characterization of MHC cDNA clones in the domestic cat. Diversity and evolution of class I genes.

The abundant functional polymorphism and evolutionary divergence of mammalian MHC class I genes has been affirmed recently by sequence analysis of more than 40 mouse H-2 and human HLA transcripts. In a comparative approach to the evolution of the MHC, we isolated eight molecular clones of feline MHC (termed FLA for feline leukocyte antigen) class I genes from a cDNA library of a cat T cell lymphoma line. DNA sequence analysis of eight clones revealed that they all fell into one of two internally identical allelic groups which differed by 9% of their nucleotide sequences. The occurrence of only two allelic cDNA clones is consistent with the expression of a single heterozygous functional class I gene in the studied cell line despite the occurrence of more than 20 class I copies estimated to be present in the cat genome. Comparison of the FLA class I coding sequence with other class I genes from other species revealed that the domestic cat genes display 81 to 82% sequence identity with human, and 73 to 79% sequence identity with mouse class I genes. Feline and human class I genes have similar sequences and protein structures, with three (alpha) extracellular domains, one transmembrane domain, and one cytoplasmic domain. Variable codons detected in FLA class I alleles were, in most cases, in positions which were also variable in humans and mice, whereas invariant positions with defined functional constraints were generally conserved and invariant between the three species as well. Southern analysis of DNA from diverse species of Felidae revealed a similar numerosity and restriction pattern indicating conservation of the organization of class I genes during the Felidae radiation.

Alleles↗

Regulation of sperm function by protein tyrosine phosphorylation in diverse wild felid species.

Protein tyrosine phosphorylation is associated with sperm capacitation and the acrosome reaction in several mammalian species. Changes in phosphorylation of a 95-kDa protein in human, mouse, and domestic cat spermatozoa are known to be influenced by capacitation and exposure to zona pellucida (ZP) proteins. We previously reported diminished phosphorylation of 95- and 160-kDa proteins in spermatozoa from teratospermic cats, compared with normospermic domestic cats. To determine if these proteins and mechanisms are present in other species in the phenotypically diverse Felidae family, we examined the relationship between tyrosine-phosphorylated sperm proteins and sperm morphology in the leopard cat (approximately 65% normal sperm/ejaculate), tiger (approximately 65%), clouded leopard (approximately 15%), and cheetah (approximately 30%). Furthermore, we investigated the involvement of cyclic adenosine monophosphate (cAMP) in the regulation of sperm protein tyrosine phosphorylation. Specifically, we assessed the following: 1) presence of tyrosine-phosphorylated proteins in sperm extracts; 2) changes in protein tyrosine phosphorylation after sperm capacitation and swim-up separation; 3) impact of tyrosine kinase inhibition on leopard cat sperm protein phosphorylation and ZP penetration; and 4) involvement of a cAMP-dependent pathway in the regulation of protein tyrosine phosphorylation. Immunoblotting analysis with anti-phosphotyrosine antibody (PY20) indicated that a 95-kDa protein was present in all four species. Additional phosphorylated proteins were detected in the leopard cat (145- and 175-kDa proteins), tiger (185-kDa protein), clouded leopard (160- and 190-kDa proteins), and cheetah (115- and 155-kDa proteins). Sperm capacitation in vitro increased phosphorylation of one or more proteins in the leopard cat, tiger and clouded leopard, but not in the cheetah. Although swim-up separation increased the proportion of morphologically normal spermatozoa in the clouded leopard and cheetah, no changes were observed in phosphorylation of the 95-kDa sperm protein. Thus, phosphorylation of the 95-kDa protein appeared to be related to the condition of teratospermia. Exposing leopard cat spermatozoa to the tyrosine kinase inhibitor, tyrphostin, reduced (P < 0.05) phosphorylation of the 95- and 145-kDa proteins, as well as ZP penetration, without affecting sperm motility. Similarly, when spermatozoa were incubated in the presence of cAMP analogs or active and inactive stereoisomers of cAMP, phosphorylation of sperm proteins was either stimulated or inhibited. Together, these data suggest that protein tyrosine kinase mechanisms appear conserved within the family Felidae and are regulated by a cAMP/protein kinase A pathway.

Animals↗

Nuclear and microtubule remodeling and in vitro development of nuclear transferred cat oocytes with skin fibroblasts of the domestic cat (Felis silvestris catus) and leopard cat (Prionailurus bengalensis).

The leopard cat (Prionailurus bengalensis), a member of the felidae family, is a threatened animal in South Korea. In terms of protecting endangered felids, nuclear transfer (NT) is a potentially valuable technique for assuring the continuation of species with dwindling numbers. In the present experiment, nuclear and microtubule remodeling and the in vitro developmental potential of enucleated domestic cat oocytes reconstructed with nuclei of somatic cells from either domestic cat fibroblast (DCF) or leopard cat fibroblast (LCF) were evaluated. Microtubule aster is allocated to de-condensed chromatin following nuclear transfer (3h after activation) of fibroblast cells from both domestic and leopard cats, suggesting the introduction of a somatic cell centrosome. The transferred fibroblast nuclei formed a large, swollen, pronuclear-like structure in most reconstructed oocytes, in the cat or leopard cat. At 18h following nuclear transfer, mitosis occurred, and according to the photo (F) it appears that spindle microtubules and two asters were observed. The percentages of blastocyst formation from nuclear transfer embryos derived from domestic cat fibroblasts (4/46, 8.6%) were not significantly different than those for nuclear transfer embryos constructed with leopard cat fibroblasts (4/52, 7.6%). These results indicate that nuclear and microtubule remodeling processes and in vitro developmental ability are similar in reconstructed cat oocytes following transfer of nuclei from either domestic or leopard cats.

Animals↗

Species-, sex-, and age-dependent urinary excretion of cauxin, a mammalian carboxylesterase.

Domestic cats exhibit physiological proteinuria due to the excretion of cauxin, a carboxylesterase, into the urine. In the present report, we demonstrate that cauxin is excreted in a species-, sex-, and age-dependent manner. Although the cauxin gene is conserved in mammals, including human, mouse, and dog, urinary cauxin was found only in member of the genus Felis and lynx (bobcat, and lynx) and not in other Felidae (genus: Panthera and puma) tested. In mature cats, cauxin excretion was higher in intact males than in castrated males or in intact or spayed females. Daily cauxin excretion decreased immediately after castration. Immunohistochemistry confirmed that cauxin expression in the kidney proximal straight tubules was higher in intact males than in castrated males. Urinary cauxin was detectable by Western blotting in cats older than about 3 months, and its excretion increased with age. In a zymographic esterase assay, urine contained a major cauxin band; by contrast, kidney homogenates contained three major bands, comprising two carboxylesterases and an unidentified esterase, and one minor cauxin band. These results suggest that 1. cauxin excretion is regulated by sex hormones, such as testosterone, 2. cauxin functions as an esterase in the urine rather than in kidney cells, and 3. the decomposition products by cauxin are excreted in a species-, sex-, and age-dependent manner, as is cauxin itself.

Aging↗

Molecular evidence for species-level distinctions in clouded leopards.

Among the 37 living species of Felidae, the clouded leopard (Neofelis nebulosa) is generally classified as a monotypic genus basal to the Panthera lineage of great cats. This secretive, mid-sized (16-23 kg) carnivore, now severely endangered, is traditionally subdivided into four southeast Asian subspecies (Figure 1A). We used molecular genetic methods to re-evaluate subspecies partitions and to quantify patterns of population genetic variation among 109 clouded leopards of known geographic origin (Figure 1A, Tables S1 ans S2 in the Supplemental Data available online). We found strong phylogeographic monophyly and large genetic distances between N. n. nebulosa (mainland) and N. n. diardi (Borneo; n = 3 individuals) with mtDNA (771 bp), nuclear DNA (3100 bp), and 51 microsatellite loci. Thirty-six fixed mitochondrial and nuclear nucleotide differences and 20 microsatellite loci with nonoverlapping allele-size ranges distinguished N. n. nebulosa from N. n. diardi. Along with fixed subspecies-specific chromosomal differences, this degree of differentiation is equivalent to, or greater than, comparable measures among five recognized Panthera species (lion, tiger, leopard, jaguar, and snow leopard). These distinctions increase the urgency of clouded leopard conservation efforts, and if affirmed by morphological analysis and wider sampling of N. n. diardi in Borneo and Sumatra, would support reclassification of N. n. diardi as a new species (Neofelis diardi).

Animals↗

In vitro production and initiation of pregnancies in inter-genus nuclear transfer embryos derived from leopard cat (Prionailurus bengalensis) nuclei fused with domestic cat (Felis silverstris catus) enucleated oocytes.

The leopard cat (Prionailurus bengalensis), a member of the felidae family, is currently listed as threatened by the Ministry of Environment in South Korea. In exotic or endangered species, the lack of oocytes and recipients precludes the use of traditional somatic cell nuclear transfer, and an approach such as inter-genus nuclear transfer may be the only alternative for producing embryos and offspring. In the present study, we used the leopard cat as a somatic cell donor to evaluate the in vivo developmental competence, after transfer into domestic cat recipients, of cloned embryos produced by the fusion of leopard cat fibroblast cell nuclei with domestic cat cytoplasts. A total of 412 enucleated domestic cat oocytes were reconstructed with either male (Group A) or female (Group B) adult leopard cat fibroblasts. There was no significant difference in fusion rate (60.4% versus 56.9%) between Groups A and B. Of the cultured embryos, the cleavage and blastocyst developmental rate were not significantly different between Groups A and B (69.5% versus 60.8%; 7.2% versus 7.8%, P > 0.05). In Group A, in vivo developmental studies at 30-45 days postimplantation demonstrated 4.8% (21/435) of reconstructed embryos (n = 435) had entered into the uterine lining of recipients, while 1.4% (6/435) formed fetuses. However, all of the reconstructed embryos failed to develop to term (65 days). Microsatellite analyses confirmed that the nuclear genome of the cloned fetus were leopard cat in origin.

Animals↗

Follicle-stimulating hormone receptor in felids: intra- and interspecies variation.

Assisted reproductive technologies are increasingly applied to support breeding efforts for many endangered felids. To explain the highly variable responses among felids to exogenous gonadotropins (FSH, eCG), we analyzed a 567bp fragment spanning a hyper-variable region of the FSH receptor in the domestic cat (catFSHR) and nine wild felid species/subspecies (felFSHR). Phylogenetic analysis indicated that the newly sequenced felFSHRs, together with the bear FSHR, belong to the carnivore group closely related to the ungulate clade. Within Felidae, genetic distances were 0.0089 +/- 0.0018 for nucleotide and 0.0183 +/- 0.0044 for amino acid (aa) sequences. In pairwise comparisons among catFSHR and all new felFSHRs, similarity ranged from 98.6 to 99.5% for nucleotides and from 97.4 to 98.9% for aa. Besides interspecies variability, intraspecies variation was also detected on both the cDNA and the protein level. There were no indications for an expression of tissue-specific isoforms of FSHR in testis and ovary.

Amino Acid Sequence↗

Comparative endocrinology of domestic and nondomestic felids.

The ability to track gonadal and adrenal activity via hormones is key to optimizing health and reproduction. Through decades of study, a great deal has been learned about the biology of female domestic cats, including endocrine function. More recently, comparative endocrine studies have greatly expanded our knowledge base of nondomestic felids as well. The latter has been possible largely through the development of noninvasive fecal steroid metabolite analysis techniques, which currently is the method of choice for monitoring endocrine function in wildlife species, including felids. It now is well-recognized that a range in endocrine patterns exists among Felidae, with many traits and mechanisms being uncommon, if not unique. There is a high degree of variability in the type of ovulation (spontaneous versus induced) expressed across the taxon. Even within species, some individuals exhibit ovulation that is only induced, whereas others ovulate spontaneously as well. Steroid metabolism also differs in that metabolites are excreted almost exclusively in feces, with very little steroid found in urine. Across species there are marked differences in seasonal and social influences on reproduction, adrenal responses to husbandry practices, and ovarian responses to assisted reproductive procedures. This means that developing strategies to improve health and reproduction of felids must be done on a species by species basis. This paper summarizes current knowledge on the reproductive endocrinology of female domestic and nondomestic cats, and describes how the rapidly growing endocrine database is aiding ex situ management efforts.

Animals↗

The impact and potential etiology of teratospermia in the domestic cat and its wild relatives.

Teratospermia (production of >60% morphologically abnormal sperm/ejaculate) is relatively common among various species in the family Felidae, which is comprised of 37 species. Over two decades of research in this area have produced a significant understanding of the phenotypic expression, its impacts on sperm function and etiology. There is good evidence suggesting that a reduction in genetic diversity contributes to this phenomenon. Results to date demonstrate that spermatozoa from teratospermic donors are compromised in the ability to undergo capacitation and the acrosome reaction, penetrate the zona-pellucida, fertilize conspecific oocytes and survive cryopreservation. Recent studies also reveal abnormalities in chromatin integrity in sperm from teratospermic donors, which, interestingly, fails to impact fertilization or embryo development after intracytoplasmic sperm injection. Through planned inbreeding studies, we now have established that teratospermic cats also produce more spermatozoa by virtue of more sperm producing tissue, more germ cells per Sertoli cell and reduced germ cell loss during spermatogenesis. Overall, it now is clear that gain in sperm quantity is achieved at the expense of sperm quality, suggesting an extensive disruption of normal testicular function in teratospermic donors. Preliminary studies on testicular gene expression in teratospermic cats have also revealed abnormal expression patterns. These findings have markedly increased our understanding of testis biology in the teratospermic donor and reaffirm the value of cats, including wild species, as models for studying novel regulatory mechanisms controlling spermatogenesis and spermiogenesis.

Animals↗

Mitochondrial Impostors: Prevalence and Impacts of NUMTs on Genetic and Evolutionary Studies in Carnivora.

Nuclear mitochondrial pseudogenes are mitochondria-derived DNA sequences integrated into the nuclear genome, which can introduce errors in species identification, phylogenetic inference, and population genetics. Although nuclear mitochondrial pseudogene contamination has been reported in some Carnivora species, a systematic investigation into the prevalence and impacts of nuclear mitochondrial pseudogenes across an order is still lacking. In this study, 22,102 mitochondrial DNA sequences of 80 Carnivora species from 14 families and 54 genera were retrieved from the public National Center for Biotechnology Information database and further analyzed. Using alignment-based methods, 158 problematic sequences/sequence groups were identified and categorized into four types: nuclear mitochondrial pseudogenes, species misidentification or mislabeling, sequence errors, and anomalous sites. Among families, Felidae exhibited the highest rate of nuclear mitochondrial pseudogene contamination, particularly in species of the genus Panthera. In contrast, no nuclear mitochondrial pseudogene contamination was detected in members of Ursidae and Ailuridae. Phylogenetic analysis revealed multiple independent origins of nuclear mitochondrial pseudogene, with some tracing back to the common ancestor of Carnivora. To mitigate nuclear mitochondrial pseudogene-related errors, rigorous sequence verification strategies, such as sequence alignment and phylogenetic validation, should be implemented. In conclusion, our findings highlight the necessity of nuclear mitochondrial pseudogene awareness in genetic and evolutionary studies of Carnivora and other taxa.

Animals↗

In vitro fertilization of gonadotropin-stimulated leopard cat (Felis bengalensis) follicular oocytes.

Based on techniques developed for the domestic cat, in vitro fertilization (IVF) studies were conducted in the taxonomically related leopard cat (Felis bengalensis). Adult females received pregnant mares' serum gonadotropin (PMSG) followed 80 or 84 h later by human chorionic gonadotropin (hCG) on two to four occasions over a 40-day to 27-month interval. Oocytes were collected laparoscopically from ovarian follicles 25-27 h after hCG and co-cultured with processed, homologous spermatozoa (37 degrees C, 5% CO2 in air, humidified atmosphere) for 30-36 h. There was no apparent ovarian refractoriness to repeated treatments with exogenous gonadotropins. Overall, the mean number of mature follicles present and the total number of oocytes and proportion of immature oocytes collected did not differ (P greater than 0.05) between the 80 h (4.9 +/- 0.9; 4.7 +/- 1.2; 14.9%, respectively) and 84 h (5.6 +/- 1.4; 5.4 +/- 1.7; 22.2%, respectively) gonadotropin interval groups. However, the proportion of mature leopard cat oocytes fertilized in vitro, as determined by embryonic cleavage, was increased (P less than 0.005) by extending the interval between PMSG and hCG from 80 (17.5%) to 84 (52.4%) h. These data 1) demonstrate that, compared to the domestic cat, the ovaries of the leopard cat are less responsive to a given PMSG/hCG treatment; 2) indicate that leopard cat follicular oocytes can be recovered readily by laparoscopy and are capable of becoming fertilized in vitro; and 3) suggest that IVF may be a viable approach for producing embryos and perhaps enhancing captive propagation of rare Felidae.

Animals↗

Cloning and genomic characterization of Felis domesticus papillomavirus type 1.

A novel papillomavirus was cloned from hyperkeratotic cutaneous lesions of a Persian domestic cat. The Felis domesticus papillomavirus (FdPV-1) genome counts 8300 bp and has a typical genome structure with an early region (E1, E2, E4, E6, E7), a late region (L1, L2), and a noncoding upstream regulatory region (URR or NCR1) between the end of L1 and the beginning of E6. The FdPV-1 also shows an unusual second noncoding region (NCR2) of 1.3 kb, situated between the end of E2 and the beginning of L2. This NCR2 is uniquely related to a similar region in the canine oral papillomavirus (COPV). Phylogenetic analysis places FdPV-1 together with COPV, the cottontail rabbit papillomavirus, human papillomavirus type 1 (HPV-1), and HPV-63 in the group of the benign cutaneous papillomaviruses. The position of FdPV-1 in the phylogenetic tree allows us to hypothesize that already in an early phase of the papillomavirus molecular evolution, a split occurred into viruses with a dual tropism primarily for cutaneous epithelia but also secondarily for mucosal surfaces, and viruses with a specific monotropism for mucosal surfaces. The close relationship between FdPV-1 and COPV, and between their Canidae and Felidae hosts, supports the hypothesis that papillomaviruses have speciated and coevolved together with their hosts throughout vertebrate evolution. A papillomavirus mutation rate of 0.73 to 0.96 x 10(-8) nucleotide substitutions per base per year was calculated.

Animals↗

Numt, a recent transfer and tandem amplification of mitochondrial DNA to the nuclear genome of the domestic cat.

The mitochondrial DNA of plant and animal cells is a transcriptionally active genome that traces its origins to a symbiotic infection of eucaryotic cells by bacterial progenitors. As prescribed by the Serial Endosymbiosis Theory, symbiotic organelles have gradually transferred their genes to the eucaryotic genome, producing a functional interaction of nuclear and mitochondrial genes in organelle function. We report here a recent remarkable transposition of 7.9 kb of a typically 17.0-kb mitochondrial genome to a specific nuclear chromosomal position in the domestic cat. The intergrated segment has subsequently become amplified 38-76 times and now occurs as a tandem repeat macrosatellite with multiple-length alleles resolved by pulse-field gel electrophoresis (PFGE) segregating in cat populations. Sequence determination of the nuclear mitochondrial DNA segment, Numt, revealed a d(CA)-rich 8-bp motif [ACACACGT] repeated imperfectly five times at the deletion junction that is a likely target for recombination. The extent and pattern of sequence divergence of Numt genes from the cytoplasmic mtDNA homologues plus the occurrence of Numt in other species of the family Felidae allowed an estimate for the origins of Numt at 1.8-2.0 million years ago in an ancestor of four modern species in the genus Felis. Numt genes do not function in cats; rather, the locus combines properties of nuclear minisatellites and pseudogenes. These observations provide an empirical glimpse of historic genomic events that may parallel the accommodation of organelles in eucaryotes.

Animals↗