MOLECULAR-CLONING, CHROMOSOMAL ASSIGNMENT AND TISSUE-SPECIFIC EXPRESSION OF A MURINE ALPHA(1,2)FUCOSYLTRANSFERASE EXPRESSED IN THYMIC AND EPIDIDYMAL EPITHELIAL-CELLS

Terminal Fuc alpha(1-2)Gal beta epitopes have been proposed to play si gnificant roles in cell-cell interactions in development, cell adhesio n, and malignant transformation. To begin to investigate the regulatio n and function of alpha(1-2)fucosylated epitopes in an animal model, w e have isolated and characterized a mouse genomic DNA segment encoding a protein orthologous to the human H blood group locus alpha(1,2)fuco syltransferase (FUT1). This segment maintains an open reading frame en coding 376 amino acids sharing 75% sequence identity with the enzyme e ncoded by human FUT1, and 55% sequence identity with the enzyme encode d by the human Secretor blood group locus (FUT2). Expression of the op en reading frame in COS-7 cells yields an alpha(1,2)fucosyltransferase activity with a K-m of 7.6 mM for phenyl-beta-D-galactoside. Southern blotting and interspecific backcross analyses indicate that this muri ne locus represents a single copy sequence mapping to a novel locus 2. 1 centimorgans from the Klk1 locus, in a region of homology between mo use chromosome 7 and the human FUT1 locus on the long arm of chromosom e 19. Mouse FUT1 yields a 2.8 kb mRNA transcript identifiable in many organs, including thymus, lung, stomach, pancreas, small intestine, co lon, uterus and epididymis. Hybridization analyses in situ localize ex pression of FUT1 transcripts to thymic medullary and epididymal epithe lial cells, implying that this gene determines the expression of cell surface Fuc alpha(1-2)Gal beta epitopes in these tissues.