Molecular cloning and characterization of CFT1, a developmentally regulated avian α(1,3)-fucosyltransferase gene

Although coordinate expression of carbohydrate epitopes during development is well described, mechanisms which regulate this expression remain largely unknown. In this study we demonstrate that developing chicken B cells express the Lewis(x) terminal oligosaccharide structure in a stage- specific manner. To examine regulation of this expression, we have cloned and expressed the chicken α(1,3)-fucosyltransferase gene involved in Lewis(x) biosynthesis, naming it chicken fucosyltransferase 1 (CFT1). CFT1 is characterized by a single long open reading frame of 356 amino acids encoding a type II transmembrane glycoprotein. The domain structure and predicted amino acid sequence are highly conserved between CFT1 and mammalian Fuc-TIV genes (52.8% and 46.3% identity to mouse and human respectively). In vitro CFT1 fucosyltransferase activity utilizes LacNAc > 3'sialyl-LacNAc acceptors with almost no utilization of other neutral type II (lactose, 2- fucosyllactose), or type I (lacto-N-biose I) acceptors. CFT1-transfected cells make cell surface Lewis(x) (COS-7) and Lewis(x) + VIM-2 structures (Chinese hamster ovary). CFT1 gene expression is tissue-specific and includes embryonic thymus and bursa. Furthermore, expression of the CFT1 gene and cell surface Lewis(x) structures are closely linked during B cell development. These findings reveal the evolutionary conservation between nonmammalian and mammalian α(1,3)-fucosyltransferase genes and demonstrate a role for fucosyltransferase gene regulation in the developmental expression of oligosaccharide structures.