Nucleotide sequences of chimpanzee MHC class I alleles: evidence for trans-species mode of evolution

To obtain an insight into the evolutionary origin of the major histocompatibility complex (MHC) class I polymorphism, a cDNA library was prepared from a heterozygous chimpanzee cell line expressing MHC class I molecules crossreacting with allele-specific HLA-A11 antibodies. The library was screened with human class I locus-specific DNA probes, and clones encoding both alleles at the A and B loci have been identified and sequenced. In addition, the sequences of two HLA-A11 subtypes differing by a single nucleotide substitution have been obtained. The comparison of chimpanzee and human sequences revealed a close similarity (up to 98.5%). The chimpanzee A locus alleles showed greatest similarity to the human HLA-A11/A3 family of alleles, one of them being very close to HLA-A11. Similarly, segments of the ChLA-B alleles displayed greatest similarity to certain HLA-B alleles. The calculated evolutionary branch point for the A11-like alleles is 7 x 10(6) to 9 x 10(6) years, whereas the other A locus alleles diverged between 12 x 10(6) and 17 x 10(6) years ago. Since the human and chimpanzee lineages separated 5 x 10(6) to 7 x 10(6) years ago, our data support the notion that during evolution, MHC alleles are transmitted from one species to the next.     

Primate comparative genomics: lemur biology and evolution

Comparative genome sequencing projects are providing insight into aspects of genome biology that raise new questions and challenge existing paradigms. Placement in the phylogenetic tree can often be a major determinant of which organism to choose for study. Lemurs hold a key position at the base of the primate evolutionary tree and will be highly informative for the genomics community by offering comparisons of primate-specific characteristics and processes. Combining research in chromosome evolution, genome evolution and behavior with lemur comparative genomic sequencing will offer insights into many levels of primate evolution. We discuss the current state of lemur cytogenetic and phylogenetic analyses, and suggest how focusing more genomic efforts on lemurs will be beneficial to understanding human and primate evolution, as well as disease, and will contribute to conservation efforts.     

Evidence for glycosyltransferases in trout liver microsomes (Salmo gairdneri).

1. Trout (Salmo gairdneri) serum is rich in glycoproteins which are synthetized in liver. 2. An attempt to localize glycosyltransferases in hepatocytes is described, using cellular fractionation and marker enzyme determination. 3. Galactosyltransferase, mannosyltransferase, N-acetyl-glucosaminyl transferase, glucosyltransferase, sialyltransferase (on exogenous acceptor) are found in a microsomal fraction obtained by centrifugation at 117 X 10(5) g min of the post-mitochondrial supernatant. 4. Mannose is transferred to endogenous lipids and proteins.     

Primate origins and the evolution of angiosperms

Traditionally, the morphological traits of primates were assumed to be adaptations to an arboreal way of life. However, Cartmill [1972] pointed out that a number of morphological traits characteristic of primates are not found in many other arboreal mammals. He contends that orbital convergence and grasping extremities indicate that the initial divergence of primates involved visual predation on insects in the lower canopy and undergrowth of the tropical forest. However, recent research on nocturnal primates does not support the visually-oriented predation theory. Although insects were most likely important components of the diets of the earliest euprimates, it is argued here that visual predation was not the major impetus for the evolution of the adaptive traits of primates. Recent paleobotanical research has yielded evidence that a major evolutionary event occurred during the Eocene, involving the angiosperms and their dispersal agents. As a result of long-term diffuse coevolutionary interactions with flowering plants, modern primates, bats, and plant-feeding birds all first arose around the Paleocene-Eocene boundary and became the major seed dispersers of modern tropical flora during the Eocene. Thus, it is suggested here that the multitude of resources available on the terminal branches of the newly evolved angiosperm, rain forest trees led to the morphological adaptations of primates of modern aspect.     

Avoiding Predators: Expectations and Evidence in Primate Antipredator Behavior

Predation and antipredator behavior are important but poorly studied influences on the evolution of primate societies. I review recent evidence of predation and antipredator strategies among primates. I describe patterns of antipredator behavior and attempt to explain the variation among primate taxa and among antipredator strategies. I use predation by chimpanzees on red colobus and antipredator strategies by the colobus as a case study of how a primate prey species may respond to the threat of predation.     

Primate chromosome evolution: with reference to marker order and neocentromeres

Establishing chromosomal homology in comparative cytogenetics remained speculative until the advent of molecular cytogenetics. Chromosome sorting by flow cytometry and degenerate oligonucleotide primed-PCR (DOP-PCR) brought a significant simplification and impetus to chromosome painting. Comparative chromosome painting has permitted reasonable hypotheses for ancestral karyotypes at many points on the phylogenetic tree of mammals. Derived associations often provided landmarks that showed the route evolution took. More recently hybridization with cloned DNA has provided information on intrachromosomal rearrangements. BAC-FISH allows marker order, in addition to syntenies and associations, to be added to the ancestral karyotypes. Comparisons of marker order across species revealed that centromere shifts (evolutionary new centromeres) are frequent and important phenomena of chromosome evolution. Further comparison between evolutionary new centromeres and clinical neocentromeres shows that an evolutionary perspective can provide compelling, underlying, explicative grounds for contemporary genomic phenomena.     

Primate segmental duplications: crucibles of evolution, diversity and disease

Compared with other mammals, the genomes of humans and other primates show an enrichment of large, interspersed segmental duplications (SDs) with high levels of sequence identity. Recent evidence has begun to shed light on the origin of primate SDs, pointing to a complex interplay of mechanisms and indicating that distinct waves of duplication took place during primate evolution. There is also evidence for a strong association between duplication, genomic instability and large-scale chromosomal rearrangements. Exciting new findings suggest that SDs have not only created novel primate gene families, but might have also influenced current human genic and phenotypic variation on a previously unappreciated scale. A growing number of examples link natural human genetic variation of these regions to susceptibility to common disease.     

Primate foot evolution: a new approach to the old problem

Functional reasons for specific changes in mammal foot skeleton occurring in course of formation and progressive evolution of locomotion on the parasagittal extremities are formulated for the first time. The paper establishes the base of the study of highly parasagittal forms (terrestrial catarhine monkeys, man and his ancestors), that evolved in primate history much later then their counterparts in other orders. The foot of primitive primate (Lemur catta) is scrutinized as a model of a primitive foot structure, that determined the peculiarities of foot evolution in higher forms. Primate foot traits as elements of general mammal foot evolution are described. Some specializations of the primate foot to the arboreal habitats are concluded to preclude the primate foot from progressing to the state inherent in highly advanced parasagittal members of other mammalian orders.     

Primate brain evolution: Integrating comparative,neurophysiological, and ethological data

“Undoubtedly the most distinctive trait of the Primates, wherein this order contrasts with all other mammalian orders in its evolutionary history, is the tendency towards the development of a brain which is large in proportion to the total body weight, and which is particularly characterized by a relatively extensive and often richly convoluted cerebral cortex (p. 228).” 1 While this statement is generally true, primate brains vary in size nearly one thousand‐fold, from a mass of 1.8 g in the tiny mouse lemur to 1,300 g in modern humans. Many attempts have been made to understand both the distinctiveness of primate brains and the variation observed within the order: How did such variation evolve and why, and what are its cognitive implications? Following Jerison's 2 masterly review thirty years ago, comparative studies have highlighted suggestive correlations of brain size. However, the meaning and validity of these correlations have been vigorously debated. It has become clear that progress depends on taking great care in the use of comparative methods and in finding multiple converging strands of comparative evidence as opposed to making speculative interpretations of single correlations. In particular, recent work demonstrates the value of examining how evolutionary changes at different anatomical levels interrelate.     

Evidence for male-driven evolution in Drosophila

In several vertebrate taxa studied to date, mutation rates arehigher in males than females (male-driven evolution). The male-to-femalemutation rate () can be estimated by contrasting DNA divergencedata at X-linked, Y-linked, and autosomal loci. Previous studiesin Drosophila, comparing X-linked and autosomal divergence,have found no evidence for male-driven evolution in this genus.Here, I compare levels of nucleotide divergence between homologousX- and Y-linked loci in Drosophila miranda. Using divergenceat both synonymous sites and at short introns, I estimate tobe approximately 2. This study thus provides the first evidencefor male-biased mutation rates outside vertebrates, supportingthe view that DNA sequence evolution is male driven in a widevariety of taxa.     

Common origin and evolution of glycosyltransferases using Dol-P-monosaccharides as donor substrate

On the basis of the analysis of 64 glycosyltransferases from 14 species we propose that several successive duplications of a common ancestral gene, followed by divergent evolution, have generated the mannosyltransferases and the glucosyltransferases involved in asparagine-linked glycosylation (ALG) and phosphatidyl-inositol glycan anchor (PIG or GPI), which use lipid-related donor and acceptor substrates. Long and short conserved peptide motifs were found in all enzymes. Conserved and identical amino acid positions were found for the alpha 2/6- and the alpha 3/4-mannosyltransferases and for the alpha 2/3-glucosyltransferases, suggesting unique ancestors for these three superfamilies. The three members of the alpha 2-mannosyltransferase family (ALG9, PIG-B, and SMP3) and the two members of the alpha 3-glucosyltransferase family (ALG6 and ALG8) shared 11 and 30 identical amino acid positions, respectively, suggesting that these enzymes have also originated by duplication and divergent evolution. This model predicts a common genetic origin for ALG and PIG enzymes using dolichyl-phospho-monosaccharide (Dol-P-monosaccharide) donors, which might be related to similar spatial orientation of the hydroxyl acceptors. On the basis of the multiple sequence analysis and the prediction of transmembrane topology we propose that the endoplasmic reticulum glycosyltransferases using Dol-P-monosaccharides as donor substrate have a multispan transmembrane topology with a first large luminal conserved loop containing the long motif and a small cytosolic conserved loop containing the short motif, different from the classical type II glycosyltransferases, which are anchored in the Golgi by a single transmembrane domain.     

Primate evolution of a dispersed human repetitive DNA sequence

A dispersed middle repetitive DNA sequence isolated originally from human chromosome 12 did not show homology with rodent DNA under standard conditions of Southern DNA blot analysis. The evolutionary relationship of this human repetitive DNA to that of other primates was investigated using three hybridization methods: DNA dot blot, Southern DNA blot analysis, and chromosome in situ hybridization. Homology with the human repetitive DNA was found throughout the suborder Anthropoidea, in fourteen ape and New and Old World monkey species. In addition, the human pattern of hybridization to noncentromeric regions of all chromosomes was seen. No hybridization by any of the three techniques was found in five species of the suborder Prosimii. The phenomenon of marked differences in sequence homology and copy number of dispersed repetitive DNA from closely related species has been observed in protozoans (Plasmodia), Drosophila, sea urchins, mice and the great apes (Hominoidea). We report here a similar phenomenon that may have occurred at an early stage in primate evolution.     

ABO(H) blood group A and B glycosyltransferases recognize substrate via specific conformational changes

The final step in the enzymatic synthesis of the ABO(H) blood group A and B antigens is catalyzed by two closely related glycosyltransferases, an alpha-(1-->3)-N-acetylgalactosaminyltransferase (GTA) and an alpha-(1-->3)-galactosyltransferase (GTB). Of their 354 amino acid residues, GTA and GTB differ by only four "critical" residues. High resolution structures for GTB and the GTA/GTB chimeric enzymes GTB/G176R and GTB/G176R/G235S bound to a panel of donor and acceptor analog substrates reveal "open," "semi-closed," and "closed" conformations as the enzymes go from the unliganded to the liganded states. In the open form the internal polypeptide loop (amino acid residues 177-195) adjacent to the active site in the unliganded or H antigen-bound enzymes is composed of two alpha-helices spanning Arg(180)-Met(186) and Arg(188)-Asp(194), respectively. The semi-closed and closed forms of the enzymes are generated by binding of UDP or of UDP and H antigen analogs, respectively, and show that these helices merge to form a single distorted helical structure with alternating alpha-3(10)-alpha character that partially occludes the active site. The closed form is distinguished from the semi-closed form by the ordering of the final nine C-terminal residues through the formation of hydrogen bonds to both UDP and H antigen analogs. The semi-closed forms for various mutants generally show significantly more disorder than the open forms, whereas the closed forms display little or no disorder depending strongly on the identity of residue 176. Finally, the use of synthetic analogs reveals how H antigen acceptor binding can be critical in stabilizing the closed conformation. These structures demonstrate a delicately balanced substrate recognition mechanism and give insight on critical aspects of donor and acceptor specificity, on the order of substrate binding, and on the requirements for catalysis.