Abstract
Terminal Fuc alpha 1-3GlcNAc moieties are displayed by mammalian cell surface glycoconjugates in a tissue-specific manner. These oligosaccharides participate in selectin-dependent leukocyte adhesion and have been implicated in adhesive events during murine embryogenesis. Other functions for these molecules remain to be defined, as do the tissue-specific expression patterns of the corresponding alpha-(1-3)-fucosyltransferase (alpha 1-3FT) genes. This report characterizes a murine alpha 1-3FT that shares 77% amino acid sequence identity with human ELAM ligand fucosyltransferase (ELFT, also termed Fuc-TIV). The corresponding gene maps to mouse chromosome 9 in a region of homology with the Fuc-TIV locus on human chromosome 11q. In vitro, the murine alpha 1-3FT can efficiently fucosylate the trisaccharide Gal alpha 1-3Gal beta 1-4GlcNAc (apparent Km of 0.71 mM) to form an unusual tetrasaccharide (Gal alpha 1-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc) described in periimplantation mouse tissues. The enzyme can also form the Lewis x determinant from Gal beta 1-4GlcNAc (Km = 2.05 mM), and the sialyl Lewis x determinant from NeuNAc alpha 2-3Gal beta 1-4GlcNAc (Km = 1.78mM). However, it does not yield sialyl Lewis x determinants when expressed in a mammalian 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 intestine, 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.
Highlights
Terminal Fuc␣1–3GlcNAc moieties are displayed by mammalian cell surface glycoconjugates in a tissue-specific manner
Molecular Cloning of a Murine ␣1–3FT Gene—A hybridization screen for a murine ␣1–3FT gene yielded numerous phages that cross-hybridize with probes derived from human ␣1–3FT genes
Sequence analysis of the insert in a representative of a group of phages with similar restriction maps identified a region with a substantial amount of primary sequence similarity to the coding portion of the human Fuc-TIII gene (62% sequence identity; data not shown; sequence deposited in GenBank, accession number U33458)
Summary
Vol 270, No 42, Issue of October 20, pp. 25047–25056, 1995 Printed in U.S.A. Molecular Cloning, Expression, Chromosomal Assignment, and Tissue-specific Expression of a Murine ␣-(1,3)-Fucosyltransferase Locus Corresponding to the Human ELAM-1 Ligand Fucosyl Transferase*. These oligosaccharides participate in selectin-dependent leukocyte adhesion and have been implicated in adhesive events during murine embryogenesis Other functions for these molecules remain to be defined, as do the tissue-specific expression patterns of the corresponding ␣-(1–3)-fucosyltransferase (␣1– 3FT) genes. In detail, the enzymes and mechanisms that determine expression of Fuc␣1–3GlcNAc linkages in murine cell surface oligosaccharides, we have isolated and characterized a murine gene that corresponds to a human ␣1–3FT gene termed Fuc-TIV Northern blot analyses confirm that transcripts corresponding to this gene accumulate in leukocytic cell lines and in leukocyte-rich tissues in the mouse These analyses, and companion in situ hybridization studies, demonstrate that Fuc-TIV/ELFT transcripts are unexpectedly abundant in epithelial cells lining the gastrointestinal and reproductive tracts and suggest that this sequence, and the cognate Fuc␣1–3GlcNAc linkages whose expression it determines may have unexpected functions in these tissues
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