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  • 1
    Electronic Resource
    Electronic Resource
    MOLECULAR TRANS-SPECIES POLYMORPHISM (1998)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 29 (1998), S. 1-21 
    Details
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Trans-species polymorphism (TSP) is the occurrence of similar alleles in related species. Excluding instances in which the similarity arose by convergent evolution, TSP is generated by the passage of alleles from ancestral to descendant species. Closely related, recently diverged species, such as those of the Lake Victoria cichlid flock, may share neutral alleles, but long-lasting TSPs occur only in genetic systems evolving under balancing selection. Two such systems have been studied extensively, the major histocompatibility complex (Mhc) of jawed vertebrates and the self-incompatibility (SI) system of flowering plants. Allelic lineages that diverged many millions of years ago and passed through numerous speciation events have been described in both systems. The lineages may differ at up to 50% of their coding sites, both synonymous and nonsynonymous. The differences arise by the process of incorporation of mutations, which is different from the process of fixation. TSP, on the one hand, complicates phylogenetic analysis, but on the other, it is a useful tool for the study of speciation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ecolsys.29.1.1
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  • 2
    Electronic Resource
    Electronic Resource
    Expression of the Dentin Matrix Protein 1 Gene in Birds (2000)
    Springer
    Journal of molecular evolution 50 (2000), S. 31-38 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Tooth formation — Dentin matrix protein 1 —DMP1— Hen's tooth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The emergence of jawed vertebrates was predicated on the appearance of several innovations, including tooth formation. The development of teeth requires the participation of several specialized genes, in particular, those necessary for the formation of hard tissues—dentin, enamel, and cementum. Some vertebrates, most conspicuously birds, secondarily lost the tooth-forming ability. To determine the fate of some of the tooth-forming genes in the birds, we tested a domestic fowl cDNA library for the expression of the dentin matrix protein 1 (DMP1) gene. The library was prepared from the poly(A+) RNA isolated from the jaws of 11- to 13-day-old embryos and the testing was carried out by the polymerase chain reaction with degenerate primers designed on the basis of the available mammalian and reptile sequences. A chicken homologue of the DMP1 gene identified by this approach was shown to be expressed in the jaws and long bones, the same two tissues as in mammals. The chicken DMP1 gene has an exon/intron organization similar to that of its mammalian and reptile counterparts. The chicken gene contains three short highly conserved segments, the rest of the gene being poorly alignable or not alignable with its mammalian or reptilian homologues. The distribution of similarities and dissimilarities along the gene is indicative of a mode of evolution in which only short segments are kept constant, while the rest of the gene is relatively free to vary as long as the proportion of certain amino acid residues is retained in the encoded polypeptide. The DMP1 gene may have been retained in birds because of its involvement in bone formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002399910004
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  • 3
    Electronic Resource
    Electronic Resource
    Biglycan-Like Extracellular Matrix Genes of Agnathans and Teleosts (2000)
    Springer
    Journal of molecular evolution 51 (2000), S. 363-373 
    Details
    ISSN: 1432-1432
    Keywords: Key words:Petromyzon—Oreochromis— Zebrafish — Biglycan — Decorin — Proteoglycans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Biglycan and decorin are two members of a family of small extracellular matrix proteoglycans characterized by the presence of 10 leucine-rich repeats and one or two attachment sites for glucosaminoglycans. Both have thus far been described only from tetrapod species, mainly mammals. Because the extracellular matrix has played an important part in the evolution of Metazoa, the phylogeny of its components is of considerable interest. In this study, biglycan-like (BGL) cDNA sequences have been obtained from two teleost (Oreochromis cichlid and zebrafish) and two lamprey species. The analysis of the sequences suggests that, like tetrapods, the lampreys possess two types of proteoglycans, both of which are biglycan-like; decorin-like proteoglycans could not be identified in these species. The genes specifying these two types apparently arose by duplication in the lamprey lineage after its divergence from gnathostomes. The two teleost species possess a BGL proteoglycan and a bona fide decorin. The BGL proteoglycan is highly divergent from the tetrapod biglycan and related to the BGL proteoglycans of the lamprey. Hence, although the duplication generating the ancestors of biglycan and decorin genes occurred after the divergence of agnathans but before the emergence of teleosts, only decorin acquired its characteristic properties in the bony fishes. The BGL gene presumably turned into a typical biglycan only in the tetrapod lineages. The presumed acquisitions of new functions appear to have been accompanied by changes in the evolutionary rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002390010098
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence for convergent evolution of A and B blood group antigens in primates (1997)
    Springer
    Human genetics 〈Berlin〉 101 (1997), S. 141-148 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract To determine whether convergent or trans-specific evolution is responsible for the persistence of the ABO polymorphism in apes, we have sequenced segments of introns 5 and 6 of the ABO gene. Four substitutions and one insertion or deletion group human A, B, and O alleles together, separate from their chimpanzee A and gorilla B counterparts. No shared substitutions support a trans-species mode of evolution for any of the alleles examined. We conclude that the A and B antigens of the chimpanzee and gorilla, respectively, have arisen by convergent evolution. Phylogenetic analysis suggests that the human A and B alleles are ancient, having diverged at least 3 million years ago. These alleles must have therefore been trans-specifically inherited within the genus Homo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004390050603
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  • 5
    Electronic Resource
    Electronic Resource
    Identification of major histocompatibility complex genes in the guppy, Poecilia reticulata (1995)
    Springer
    Immunogenetics 43 (1995), S. 38-49 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The guppy, Poecilia reticulata, a teleostean fish of the order Cyprinodontiformes, has been used extensively in studies of host-parasite interactions, courtship behavior, and mating preference, as well as in ecological and evolutionary genetics. A related species was among the first poikilotherm vertebrates to be used in the study of histocompatibility genes. All these studies could benefit from the identification and characterization of the guppy major histocompatibility complex (Mhc) genes. Here, both class I and class II genes of the guppy are described. The number of expressed loci, as determined by representation of clones in a cDNA library, sequencing, and Southern blot analysis, may be low in both Mhc classes: combined evidence suggests that there may be one expressed class II locus only and one or two expressed class I loci. The variability of aquaristic guppy stocks is very low: only three and two genes have been detected at the class I and class II loci, respectively, in the stocks examined. This genetic paucity is most likely the consequence of breeding practices employed by aquarists and commercial establishments. Limited sampling of wild guppy populations revealed extensive Mhc polymorphism at loci of both classes in nature. Comparison of guppy Mhc sequences with those of other vertebrates has revealed the existence of a set of insertions/deletions which can be used as characters in cladistic analysis to infer phylogenetic relationships among vertebrate taxa and the Mhc genes themselves. These indels are particularly frequent in the regions coding for the loops of α1 and α2 domains of class I proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00186602
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  • 6
    Electronic Resource
    Electronic Resource
    Class I Mhc genes of cichlid fishes: identification, expression, and polymorphism (1997)
    Springer
    Immunogenetics 46 (1997), S. 63-72 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Cichlid fishes of the East African Rift Valley lakes constitute an important model of adaptive radiation. Explosive speciation in the Great Lakes, in some cases as recently as 12 400 years ago, generated large species flocks that have been the focus of evolutionary studies for some time. The studies have, however, been hampered by the paucity of biochemical markers for phylogenetic reconstruction. Here, we describe a set of markers which should help to alleviate this problem. They are the class I genes of the major histocompatibility complex. We provide evidence for the existence of at least 17 class I loci in cichlid fishes, and for extensive polymorphism of three of these loci. Since the polymorphism has a trans-species character, it will be possible to use it in investigating the founding events of the individual species. The sequences of the cichlid class I fishes support the monophyly of actinopterygian fish on the one hand, and of tetrapods on the other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050243
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  • 7
    Electronic Resource
    Electronic Resource
    Mapping of Mhc class I and class II regions to different linkage groups in the zebrafish, Danio rerio (1997)
    Springer
    Immunogenetics 46 (1997), S. 129-134 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The mammalian major histocompatibility complex (Mhc) consists of three closely linked regions, I, II, and III, occupying a single chromosomal segment. The class I loci in region I and the class II loci in region II are related in their structure, function, and evolution. Region III, which is intercalated between regions I and II, contains loci unrelated to the class I and II loci, and to one another. There are indications that a similar Mhc organization exists in birds and amphibians. Here, we demonstrate that in the zebrafish (Danio rerio), a representative of the teleost fishes, the class II loci are divided between two linkage groups which are distinct from the linkage group containing the class I loci. The β2-microglobulin-encoding gene is loosely linked to one of the class II loci. The gene coding for complement factor B, which is one of the region III genes in mammals, is linked neither to the class I nor to the class II loci in the zebrafish. These results, combined with preliminary data suggesting that the class I and class II regions in another order of teleost fish are also in different linkage groups, indicate that close linkage of the two regions is not necessary either for regulation of expression or for co-evolution of the class I and class II loci. They also raise the question of whether linkage of the class I and class II loci in tetrapods is a primitive or derived character.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050251
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