Analysis of cell surface galactosyltransferase activity during mouse trophectodermal differentiation.
The ectoplacental cone (EPC) of the Day 7.5 mouse embryo consists of a core of adhesive, proliferating trophoblast cells which transform to invasive trophoblast giant cells during implantation. Adhesive trophoblast cell types express monoclonally defined lactosaminoglycans (LAGs) at the cell surface; transformation to giant cells results in a loss of LAG cell surface expression (H. J. Hathaway and B. S. Babiarz, 1988, Cell Differ. 24, 55-66). LAGs can serve as substrates for cell surface galactosyltransferase (GalTase), providing an adhesive mechanism between a number of different cell types (B. D. Shur, 1984, Mol. Cell. Biochem. 61, 143-158). It was hypothesized that the LAGs in the EPC represented a substrate for a similar GalTase-mediated cell:cell adhesion system. Cell surface GalTase activity was demonstrated on EPC trophoblast on Day 7.5 of development by the incorporation of galactose from exogenous radiolabeled substrate. In 24- to 48-hr EPC trophoblast cultures the enzyme was localized by immunofluorescence to areas of cell:cell contact. Monolayers of differentiated trophoblast giant cells lacked this labeling pattern. The cell surface glycopeptide substrate for GalTase eluted as a single peak with an apparent molecular mass of 15,000 Da. A portion of this material was sensitive to endo-beta-galactosidase digestion, indicating that it contained a LAG structure. Perturbation of the enzyme:substrate complex in 24- to 48-hr EPC outgrowths, with alpha-lactalbumin, uridine 5'-diphosphogalactose, or anti-GalTase antibody, resulted in the disruption of cell:cell contacts. Differentiation to trophoblast giant cells resulted in a loss of sensitivity to surface GalTase perturbation. The results suggest that adhesive EPC trophoblast cells possess a GalTase-mediated cell:cell adhesion system which is downregulated upon differentiation to invasive trophoblast giant cells.
Hathaway
H J
HJ
Department of Biological Sciences, Rutgers University, Piscataway, New Jersey 08855-1059.
Romagnano
L C
LC
Babiarz
B S
BS
D000818:Animals; D001345:Autoradiography; D002454:Cell Differentiation; D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured; D004247:DNA / Q000032:analysis; D004261:DNA Replication; D004475:Ectoderm / Q000166:cytology* / Q000201:enzymology; D005700:Galactosyltransferases / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D010920:Placenta / Q000166:cytology / Q000201:enzymology; D014316:Tritium; D014327:Trophoblasts / Q000166:cytology* / Q000201:enzymology; D014531:Uridine Diphosphate Galactose / Q000378:metabolism
D014316:Tritium; D014531:Uridine Diphosphate Galactose; D004247:DNA; D005700:Galactosyltransferases