HUMAN ENDOMETRIAL MUC1 CARRIES KERATAN SULFATE - CHARACTERISTIC GLYCOFORMS IN THE LUMINAL EPITHELIUM AT RECEPTIVITY

MUC1 is a high molecular mass, highly glycosylated epithelial apical g lycoprotein that has been shown to exhibit both adhesive and anti-adhe sive properties. Its expression in human glandular endometrial epithel ium is transcriptionally regulated with the highest levels in the mid secretory phase, the ''receptive'' period during which implantation oc curs. We demonstrate that endometrial MUC1 carries highly sulfated lac tosaminoglycan chains recognized by monoclonal antibody (Mab) 5D4, and the sialokeratan sulfate epitope recognized by Mab D9B1. These glycan s are hormonally regulated in endometrium, and show increased abundanc e in the secretory phase, but detailed evaluation of their distributio n shows important differences. The 5D4 epitope is abundant at the lumi nal epithelial surface until the implantation phase, when it disappear s, first from patches of cells, then altogether, D9B1 binding sites ar e retained in the luminal epithelium at receptivity, These data show t hat endometrial MUC1 carries sulfated lactosaminoglycans. They identif y the luminal epithelial compartment as a site of unique MUC1 glycosyl ation and independent regulation. Glycosylation and the negative charg e associated with sialo-and sulfoglycans may be important in the regul ation of embryo attachment.