The RD114/simian type D retrovirus receptor is a neutral amino acid transporter.
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The RD114/simian type D retroviruses, which include the feline endogenous retrovirus RD114, all strains of simian immunosuppressive type D retroviruses, the avian reticuloendotheliosis group including spleen necrosis virus, and baboon endogenous virus, use a common cell-surface receptor for cell entry. We have used a retroviral cDNA library approach, involving transfer and expression of cDNAs from highly infectable HeLa cells to nonpermissive NIH 3T3 mouse cells, to clone and identify this receptor. The cloned cDNA, denoted RDR, is an allele of the previously cloned neutral amino acid transporter ATB0 (SLC1A5). Both RDR and ATB0 serve as retrovirus receptors and both show specific transport of neutral amino acids. We have localized the receptor by radiation hybrid mapping to a region of about 500-kb pairs on the long arm of human chromosome 19 at q13.3. Infection of cells with RD114/type D retroviruses results in impaired amino acid transport, suggesting a mechanism for virus toxicity and immunosuppression. The identification and functional characterization of this retrovirus receptor provide insight into the retrovirus life cycle and pathogenesis and will be an important tool for optimization of gene therapy using vectors derived from RD114/type D retroviruses. (+info)
How clonal are human mitochondria?
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Phylogenetic trees constructed using human mitochondrial sequences contain a large number of homoplasies. These are due either to repeated mutation or to recombination between mitochondrial lineages. We show that a tree constructed using synonymous variation in the protein coding sequences of 29 largely complete human mitochondrial molecules contains 22 homoplasies at 32 phylogenetically informative sites. This level of homoplasy is very unlikely if inheritance is clonal, even if we take into account base composition bias. There must either be 'hypervariable' sites or recombination between mitochondria. We present evidence which suggests that hypervariable sites do not exist in our data. It therefore seems likely that recombination has occurred between mitochondrial lineages in humans. (+info)
A point-mass model of gibbon locomotion.
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In brachiation, an animal uses alternating bimanual support to move beneath an overhead support. Past brachiation models have been based on the oscillations of a simple pendulum over half of a full cycle of oscillation. These models have been unsatisfying because the natural behavior of gibbons and siamangs appears to be far less restricted than so predicted. Cursorial mammals use an inverted pendulum-like energy exchange in walking, but switch to a spring-based energy exchange in running as velocity increases. Brachiating apes do not possess the anatomical springs characteristic of the limbs of terrestrial runners and do not appear to be using a spring-based gait. How do these animals move so easily within the branches of the forest canopy? Are there fundamental mechanical factors responsible for the transition from a continuous-contact gait where at least one hand is on a hand hold at a time, to a ricochetal gait where the animal vaults between hand holds? We present a simple model of ricochetal locomotion based on a combination of parabolic free flight and simple circular pendulum motion of a single point mass on a massless arm. In this simple brachiation model, energy losses due to inelastic collisions of the animal with the support are avoided, either because the collisions occur at zero velocity (continuous-contact brachiation) or by a smooth matching of the circular and parabolic trajectories at the point of contact (ricochetal brachiation). This model predicts that brachiation is possible over a large range of speeds, handhold spacings and gait frequencies with (theoretically) no mechanical energy cost. We then add the further assumption that a brachiator minimizes either its total energy or, equivalently, its peak arm tension, or a peak tension-related measure of muscle contraction metabolic cost. However, near the optimum the model is still rather unrestrictive. We present some comparisons with gibbon brachiation showing that the simple dynamic model presented has predictive value. However, natural gibbon motion is even smoother than the smoothest motions predicted by this primitive model. (+info)
Hepadnavirus infection in captive gibbons.
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The recent isolation of a nonhuman primate hepadnavirus from woolly monkeys prompted an examination of other primates for potentially new hepadnaviruses. A serological analysis of 30 captive gibbons revealed that 47% were positive for at least one marker of ongoing or previous infection with a hepatitis B virus (HBV). The amino acid sequences of the core and surface genes of human and gibbon virus isolates were very similar. Phylogenetic analysis indicated that the gibbon isolates lie within the human HBV family, indicating that these HBV isolates most likely stem from infection of gibbons from a human source. (+info)
How reliable are human phylogenetic hypotheses?
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Cladistic analysis of cranial and dental evidence has been widely used to generate phylogenetic hypotheses about humans and their fossil relatives. However, the reliability of these hypotheses has never been subjected to external validation. To rectify this, we applied identical methods to equivalent evidence from two groups of extant higher primates for whom reliable molecular phylogenies are available, the hominoids and papionins. We found that the phylogenetic hypotheses based on the craniodental data were incompatible with the molecular phylogenies for the groups. Given the robustness of the molecular phylogenies, these results indicate that little confidence can be placed in phylogenies generated solely from higher primate craniodental evidence. The corollary of this is that existing phylogenetic hypotheses about human evolution are unlikely to be reliable. Accordingly, new approaches are required to address the problem of hominin phylogeny. (+info)
Molecular epidemiology of hepatitis B virus variants in nonhuman primates.
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We characterized hepatitis B virus (HBV) isolates from sera of 21 hepatitis B virus surface antigen-positive apes, members of the families Pongidae and Hylobatidae (19 gibbon spp., 1 chimpanzee, and 1 gorilla). Sera originate from German, French, Thai, and Vietnamese primate-keeping institutions. To estimate the phylogenetic relationships, we sequenced two genomic regions, one located within the pre-S1/pre-S2 region and one including parts of the polymerase and the X protein open reading frames. By comparison with published human and ape HBV isolates, the sequences could be classified into six genomic groups. Four of these represented new genomic groups of gibbon HBV variants. The gorilla HBV isolate was distantly related to the chimpanzee isolate described previously. To confirm these findings, the complete HBV genome from representatives of each genomic group was sequenced. The HBV isolates from gibbons living in different regions of Thailand and Vietnam could be classified into four different phylogenetically distinct genomic groups. The same genomic groups were found in animals from European zoos. Therefore, the HBV infections of these apes might have been introduced into European primate-keeping facilities by direct import of already infected animals from different regions in Thailand. Taken together, our data suggest that HBV infections are indigenous in the different apes. One event involving transmission between human and nonhuman primates in the Old World of a common ancestor of human HBV genotypes A to E and the ape HBV variants might have occurred. (+info)
Evolution of the ABO blood group gene in Japanese macaque.
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We determined 5 sequences of Japanese macaque ABO blood group gene exon 7 (ca. 0.5 kb) and 2 sequences for exon 5 and intron 6 (ca. 1.7 kb). We compared those data with published sequences of other Old World monkey species, and the results suggest that alleles A and B were polymorphic in the ancestral species of macaques, and that B type allele evolved independently in macaque and baboon lineages. (+info)
TT virus infection in gibbons.
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TT virus (TTV) is not only an infectious agent of worldwide distribution but has also been demonstrated in various non-human primates in addition to humans. In the present study, we subjected the sera of 67 gibbons to PCR and nucleotide sequencing, with subsequent phylogenetic analysis to determine the nature of the relationship between TTV found in humans and non-human primates. We discovered the virus in 9/67 (13.4%) of the gibbon sera and subjected 6 of those to direct sequencing. The phylogenetic tree constructed encompassed all TTV species known to date, revealing a close proximity between the gibbon virus and those detected in Thai individuals, whereas the chimpanzee strains were phylogenetically more remote. (+info)