Regulation of interferon-tau gene expression and the maternal recognition of pregnancy

In order for pregnancy to be established, the maternal system must recognize the presence of a conceptus(es) within the uterus. This physiological phenomenon, which subsequently causes the extension of the corpus luteum (CL) life-span, is known as maternal recognition of pregnancy. In ruminant ungulates, interferon-tau (IFN tau), produced by the conceptus, binds to the receptor located in the maternal endometrium in a paracrine manner. Its binding then affects levels of endometrial oxytocin receptor and estrogen receptor, which reduces pulsatile secretion of a luteolysin, prostaglandin F sub(2alpha), resulting in the extension of CL function. Production of IFN tau seems to parallel the degree of trophoblast elongation and as the conceptus begins its attachment to the endometrium, IFN tau levels decline rapidly. Involvement of IFN tau in the process of implantation has long been suspected, but a role for IFN tau other than CL extension or transcriptional regulation of IFN tau genes has not been elucidated. In fact, several transcription factors that regulate the expression of IFN tau have been found, but none could explain its unique regulation. Recent findings related to maternal recognition of pregnancy are presented herein and a new insight into the potential regulation of IFN tau is discussed.