Expression and regulation of fucosyltransferase 4 in human endometrium

It has been suggested that selectin ligands expressed by the endometrial epithelium are essential for the initial adhesion of the blastocyst to the luminal epithelium of human endometrium. One of the enzymes responsible for the production of selectin ligands is fucosyltransferase 4 (FUT4), a member of alpha1,3 fucosyltransferases. The aims of the present study were to characterize FUT4 mRNA and protein in human endometrium during the menstrual cycle and to investigate the hormonal regulation of FUT4 whose mRNA expression was quantified by real-time PCR in fresh endometrial tissue from cycling women and protein expression was analyzed by immunohistochemistry and Western blotting. Hormonal regulation of FUT4 transcription was investigated using an endometrial explant system. FUT4 mRNA was significantly upregulated in fresh tissues during early and mid-secretory phases when compared with other phases of the menstrual cycle. FUT4 protein was localized to glandular and luminal epithelium and the expression levels followed the same pattern as for FUT4 mRNA. Our data also show that, in proliferative explants, progesterone significantly increased FUT4 transcription and translation after 24 h in culture. The inductive effect of progesterone on FUT4 transcription was lost after 48 h of treatment. Estrogen did not have any significant effects. These data suggest that the upregulation of selectin ligands in the human endometrium at the time of implantation may be mediated, at least in part, by the regulation of FUT4 expression.