MOLECULAR-CLONING AND CHARACTERIZATION OF CFT1, A DEVELOPMENTALLY-REGULATED AVIAN ALPHA(1,3)-FUCOSYL-TRANSFERASE GENE

Although coordinate expression of carbohydrate epitopes during develop ment is well described, mechanisms which regulate this expression rema in largely unknown. In this study we demonstrate that developing chick en 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 alpha(1,3)-fucosyltransferase ge ne involved in Lewis(x) biosynthesis, naming it chicken fucosyltransfe rase 1 (CFT1), CFT1 is characterized by a single long open reading fra me of 356 amino acids encoding a type II transmembrane glycoprotein. T he domain structure and predicted amino acid sequence are highly conse rved between CFT1 and mammalian Fuc-TIV genes (52.8% and 46.3% identit y to mouse and human respectively). In vitro CFT1 fucosyltransferase a ctivity utilizes LacNAc > 3'sialyl-LacNAc accepters with almost no uti lization of other neutral type II (lactose, 2-fucosyllactose), or type I (lacto-N-biose I) accepters, CFT1-transfected cells make cell surfa ce Lewis(x) (COS-7) and Lewis(x) + VIM-2 structures (Chinese hamster o vary). CFT1 gene expression is tissue-specific and includes embryonic thymus and bursa. Furthermore, expression of the CFT1 gene and cell su rface Lewis(x) structures are closely linked during B cell development . These findings reveal the evolutionary conservation between nonmamma lian and mammalian alpha(1,3)-fucosyltransferase genes and demonstrate a role for fucosyltransferase gene regulation in the developmental ex pression of oligosaccharide structures.