The approximately 30-million-year-old ERVPb1 envelope gene is evolutionarily conserved among hominoids and Old World monkeys.
Most human endogenous retroviruses (HERVs) are ancient and their genes are rendered nonfunctional by debilitating mutations. One exception is a recently discovered envelope gene located on chromosome 14. This envelope protein was also recently shown to be expressed in various human tissues and to mediate cell-cell fusion ex vivo. In this study, we demonstrate that this locus (designated ERVPb1) is preserved in Old World monkeys and that the reading frame is maintained. This is congruent with the entry of the HERV-P(b) group between 27 and 36 million years ago as suggested by long terminal repeat divergence. Although the coding capacity is generally lost in the HERV-IP supergroup, the analysis of nucleotide substitutions, lack of stop codons, and single-nucleotide polymorephisms strongly indicates a selective advantage of the ERVPb1 envelope genes during primate evolution. The purifying selection and tissue-specific expression of the human ERVPb1 envelope gene provide strong evidence of a beneficial role for the host. (+info)
Functional morphology of the first cervical vertebra in humans and nonhuman primates.
The cervical vertebral column bears or balances the weight of the head supported by the nuchal muscles that partly originate from the cervical vertebrae. The position of the head relative to the vertebral column, and consequently locomotion and posture behavior, could thus be associated with the form of the cervical vertebrae. In spite of this assumption and some empirical indications along these lines, primate vertebral morphologies have been reported to be very similar and not clearly related to locomotion. We therefore study the relationship between the morphology of the first cervical vertebra, the atlas, and the locomotion pattern within primates using a geometric morphometric approach. Our analysis is based on a total of 116 vertebrae of adult Homo sapiens, Gorilla gorilla, Pan troglodytes, Pongo pygmaeus, Hylobates lar, Macaca mulatta, Papio hamadryas, Ateles geoffroyi, and Alouatta palliata. On each atlas, 56 landmarks were digitized and superimposed by Procrustes registration. The resulting shape variables were analyzed by principal component analysis, multivariate regression, and partial least-squares analysis. We found that the nine primate species differ clearly in their atlas morphology and that allometric shape change is distinct between the nonhuman primates and Homo sapiens. We could further identify morphological features that relate to the species' locomotion pattern. Human atlas shape, however, cannot be predicted by an extrapolation of the nonhuman primate model. This implies that either the primate atlas is generalized enough to allow bipedal locomotion or else the human atlas morphology is a unique adaptation different from that in the more orthograde nonhuman primates. (+info)
Functionally important glycosyltransferase gain and loss during catarrhine primate emergence.
A glycosyltransferase, alpha1,3galactosyltransferase, catalyzes the terminal step in biosynthesis of Galalpha1,3Galbeta1-4GlcNAc-R (alphaGal), an oligosaccharide cell surface epitope. This epitope or antigenically similar epitopes are widely distributed among the different forms of life. Although abundant in most mammals, alphaGal is not normally found in catarrhine primates (Old World monkeys and apes, including humans), all of which produce anti-alphaGal antibodies from infancy onward. Natural selection favoring enhanced resistance to alphaGal-positive pathogens has been the primary reason offered to account for the loss of alphaGal in catarrhines. Here, we question the primacy of this immune defense hypothesis with results that elucidate the evolutionary history of GGTA1 gene and pseudogene loci. One such locus, GGTA1P, a processed (intronless) pseudogene (PPG), is present in platyrrhines, i.e., New World monkeys, and catarrhines but not in prosimians. PPG arose in an early ancestor of anthropoids (catarrhines and platyrrhines), and GGTA1 itself became an unprocessed pseudogene in the late catarrhine stem lineage. Strong purifying selection, denoted by low nonsynonymous substitutions per nonsynonymous site/synonymous substitutions per synonymous site values, preserved GGTA1 in noncatarrhine mammals, indicating that the functional gene product is subjected to considerable physiological constraint. Thus, we propose that a pattern of alternative and/or more beneficial glycosyltransferase activity had to first evolve in the stem catarrhines before GGTA1 inactivation could occur. Enhanced defense against alphaGal-positive pathogens could then have accelerated the replacement of alphaGal-positive catarrhines by alphaGal-negative catarrhines. However, we emphasize that positively selected regulatory changes in sugar chain metabolism might well have contributed in a major way to catarrhine origins. (+info)
Evolutionary history of chromosome 11 featuring four distinct centromere repositioning events in Catarrhini.
Panels of BAC clones used in FISH experiments allow a detailed definition of chromosomal marker arrangement and orientation during evolution. This approach has disclosed the centromere repositioning phenomenon, consisting in the activation of a novel, fully functional centromere in an ectopic location, concomitant with the inactivation of the old centromere. In this study, appropriate panels of BAC clones were used to track the chromosome 11 evolutionary history in primates and nonprimate boreoeutherian mammals. Chromosome 11 synteny was found to be highly conserved in both primate and boreoeutherian mammalian ancestors. Amazingly, we detected four centromere repositioning events in primates (in Old World monkeys, in gibbons, in orangutans, and in the Homo-Pan-Gorilla (H-P-G) clade ancestor), and one in Equidae. Both H-P-G and Lar gibbon novel centromeres were flanked by large duplicons with high sequence similarity. Outgroup species analysis revealed that this duplicon was absent in phylogenetically more distant primates. The chromosome 11 ancestral centromere was probably located near the HSA11q telomere. The domain of this inactivated centromere, in humans, is almost devoid of segmental duplications. An inversion occurred in chromosome 11 in the common ancestor of H-P-G. A large duplicon, again absent in outgroup species, was found located adjacent to the inversion breakpoints. In Hominoidea, almost all the five largest duplicons of this chromosome appeared involved in significant evolutionary architectural changes. (+info)
Nonhuman anthropoid primate femoral neck trabecular architecture and its relationship to locomotor mode.
Functional analyses of human and nonhuman anthropoid primate femoral neck structure have largely ignored the trabecular bone. We tested hypotheses regarding differences in the relative distribution and structural anisotropy of trabecular bone in the femoral neck of quadrupedal and climbing/suspensory anthropoids. We used high-resolution X-ray computed tomography to analyze quantitatively the femoral neck trabecular structure of Ateles geoffroyi, Symphalangus syndactylus, Alouatta seniculus, Colobus guereza, Macaca fascicularis, and Papio cynocephalus (n = 46). We analyzed a size-scaled superior and inferior volume of interest (VOI) in the femoral neck. The ratio of the superior to inferior VOI bone volume fraction indicated that the distribution of trabecular bone was inferiorly skewed in most (but not all) quadrupeds and evenly distributed the climbing/suspensory species, but interspecific comparisons indicated that all taxa overlapped in these measurements. Degree of anisotropy values were generally higher in the inferior VOI of all species and the results for the two climbing/suspensory taxa, A. geoffroyi (1.71 +/- 0.30) and S. syndactylus (1.55 +/- 0.04), were similar to the results for the quadrupedal anthropoids, C. guereza (male = 1.64 +/- 0.13; female = 1.68 +/- 0.07) and P. cynocephalus (1.47 +/- 0.13). These results suggest strong trabecular architecture similarity across body sizes, anthropoid phylogenetic backgrounds, and locomotor mode. This structural similarity might be explained by greater similarity in anthropoid hip joint loading mechanics than previously considered. It is likely that our current models of anthropoid hip joint mechanics are overly simplistic. (+info)
A remarkable female cranium of the early Oligocene anthropoid Aegyptopithecus zeuxis (Catarrhini, Propliopithecidae).
The most complete and best-preserved cranium of a Paleogene anthropoid ever found, that of a small female of the early Oligocene ( approximately 29-30 Ma) stem catarrhine species Aegyptopithecus zeuxis, was recovered from the Jebel Qatrani Formation (Fayum Depression, Egypt) in 2004. The specimen is that of a subadult and, in craniodental dimensions, is the smallest Aegyptopithecus individual known. High-resolution computed tomographic (microCT) scanning of the specimen's well preserved cranial vault confirms that Aegyptopithecus had relatively unexpanded frontal lobes and a brain-to-body mass ratio lower than those of living anthropoids. MicroCT scans of a male cranium recovered in 1966 [Egyptian Geological Museum, Cairo (CGM) 40237] reveal that previous estimates of its endocranial volume were too large. Thus, some amount of encephalization evolved independently in platyrrhine and catarrhine anthropoids, and the relative brain size of the last common ancestor of crown Anthropoidea was probably strepsirrhine-like or smaller. A. zeuxis shows extreme sexual dimorphism in craniodental morphology (apparently to a degree otherwise seen only in some highly dimorphic Miocene catarrhines), and the crania of female Aegyptopithecus lack a number of morphological features seen in larger males that have been accorded phylogenetic significance in catarrhine systematics (e.g., a well developed rostrum, elongate sagittal crest, and frontal trigon). Although a unique pattern of craniofacial sexual dimorphism may have characterized advanced stem and basal crown catarrhines, expression of various allegedly "discrete" craniofacial features may have been intraspecifically variable in early catarrhine species due to high levels of dimorphism and so should be treated with caution in phylogenetic analyses. (+info)
Mating system and avpr1a promoter variation in primates.