Cytogenetics, conserved synteny and evolution of chicken fucosyltransferase genes compared to human.

Fucosyltransferases appeared early in evolution, since they are present from bacteria to primates and the genes are well conserved. The aim of this work was to study these genes in the bird group, which is particularly attractive for the comprehension of the evolution of the vertebrate genome. Twelve fucosyltransferase genes have been identified in man. The orthologues of theses genes were looked for in the chicken genome and cytogenetically localized by FISH. Three families of fucosyltransferases: alpha6-fucosyltransferases, alpha3/4-fucosyltransferases, and protein-O-fucosyltransferases, were identified in the chicken with their associated genes. The alpha2-fucosyltransferase family, although present in some invertebrates and amphibians was not found in birds. This absence, also observed in Drosophila, may correspond to a loss of these genes by negative selection. Of the eight chicken genes assigned, six fell on chromosome segments where conservation of synteny between human and chicken was already described. For the two remaining loci, FUT9 and FUT3/5/6, the location may correspond to a new small syntenic area or to an insertion. FUT4 and FUT3/5/6 were found on the same chicken chromosome. These results suggest a duplication of an ancestral gene, initially present on the same chromosome before separation during evolution. By extension, the results are in favour of a common ancestor for the alpha3-fucosyltransferase and the alpha4-fucosyltransferase activities. These observations suggest a general mechanism for the evolution of fucosyltransferase genes in vertebrates by duplication followed by divergent evolution.