gp49B1, an inhibitory signaling receptor gene of hematopoietic cells, is induced by leukemia inhibitory factor in the uterine endometrium just before implantation

Abstract

Leukemia inhibitory factor (LIF) is a cytokine involved in hematopoiesis, neuropoiesis, and embryogenesis. Transcriptional activation of various genes occurs subsequent to LIF signal transduction in its target cells. Using the mRNA differential display method, a LIF-inducible gene was isolated from LIF-stimulated M1 murine myeloid leukemia cells. By DNA sequencing, this gene turned out to be gp49B1, which has been reported as an inhibitory signaling receptor to attenuate mast cell activation. Because gp49B1 expression was limited to the uterus of a pregnant mouse, its uterine expression was examined especially in relation to LIF expression during pregnancy gp49B1 was expressed specifically on day 4.0 of pregnancy, as was LIF, and the site of the most abundant expression of LIF and gp49B1 mRNA was the luminal epithelium of the uterine endometrium. These findings suggest that the gp49B1 expression in the uterine endometrium is induced just before implantation by paracrine and/or autocrine effects of LIF. Considering its function as an inhibitory signaling receptor on mast cells, a possible role for gp49B1 on the surface of the uterine endometrium as an immunoreceptor that allows blastocyst attachment is proposed.