Comprehensive Analysis of sialyltransferases in vertebrate genomes.

Sialyltransferases are a subset of glycosyltransferases involved in the biosynthesis of sialylated glycolipids or/and glycoproteins. The aim of this review is to provide a comprehensive review and analysis of vertebrate sialyltransferase genes. Primary structure/ function relationships have been explored through the use of molecular phylogeny and phylogenomic approaches. Several animal sialyltransferase sequences have been identified in genomic databases on the basis of the presence of sialylmotifs. Depending on the glycosidic linkage formed and their monosaccharide acceptor, vertebrate sialyltransferases are arranged in four families of proteins (ST3Gal, ST6Gal, ST6GalNAc and ST8Sia), which are characterized by consensus peptides called family-motifs. Sialyltransferases families are further subdivided into 20 sub-families in mammals and more than 25 sub-families in lower vertebrates, each of them being characterized by conserved amino acid positions. From an evolutionary point of view, the genomic organization of the coding region of these sialyltransferase genes is highly conserved across vertebrate species suggesting that they evolved from common ancestral genes through multiple duplication events. Finally, comparative analysis of the sialyltransferase gene expression evolution in vertebrate adult tissues and during embryonic development have shown marked differences suggesting the influence of genetic and tissue specific factors.