MOLECULAR-CLONING, EXPRESSION, CHROMOSOMAL ASSIGNMENT, AND TISSUE-SPECIFIC EXPRESSION OF A MURINE ALPHA-(1,3)-FUCOSYL-TRANSFERASE LOCUS CORRESPONDING TO THE HUMAN ELAM-1 LIGAND FUCOSYL-TRANSFERASE

Terminal Fuc alpha 1-3GlcNAc moieties are displayed by mammalian cell surface glycoconjugates in a tissue-specific manner. These oligosaccha rides participate in selectin-dependent leukocyte adhesion and have be en implicated in adhesive events during murine embryogenesis. Other fu nctions for these molecules remain to be defined, as do the tissue-spe cific expression patterns of the corresponding alpha-(1-3)-fucosyltran sferase (alpha 1-3FT) genes. This report characterizes a murine alpha 1-3FT that shares 77% amino acid sequence identity with human ELAM lig and fucosyltransferase (ELFT, also termed Fuc-TIV). The corresponding gene maps to mouse chromosome 9 in a region of homology with the Fuc-T IV locus on human chromosome 11q. In vitro, the murine (alpha 1-3FT ca n efficiently fucosylate the trisaccharide Gal alpha 1-3Gal beta 1-4Gl cNAc (apparent K-m of 0.71 mM) to form an unusual tetrasaccharide (Gal alpha 1-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc) described in periimplanta tion mouse tissues. The enzyme can also form the Lewis x determinant f rom Gal beta 1-4GlcNAc (K-m = 2.05 mM), and the sialyl Lewis x determi nant from NeuNAc alpha 2-3Gal beta 1-4GlcNAc (K-m = 1.78 mM). However, it does not yield sialyl Lewis x determinants when expressed in a mam malian cell line that maintains sialyl Lewis x precursors. Transcripts from this gene accumulate to low levels in hematopoietic organs, but are unexpectedly abundant in epithelia that line the stomach, small in testine, colon, and epididymus. Epithelial cell-specific expression of this gene suggests function(s) in addition to, and distinct from, its proposed role in selectin ligand synthesis.