Thirty years of interferon-tau research; Past, present and future perspective

The year 2017 marks the 30th year since the discovery was made of amino acid and complementary DNA sequences of ovine trophoblast protein-1 (oTP-1), later renamed as interferon-tau (IFNτ). Ovine TP-1 was originally found as a secretory product of sheep conceptuses that rescues maternal corpus luteum (CL) and in fact, the uterine infusion of oTP-1 extended inter-estrous intervals. Finding this signaling molecule as an IFN-like sequence was surprising to the scientific community in reproduction because a homologous molecule in humans possesses anti-viral and anti-prolific activity and is often used in human medicines. However, since its discovery was made, large efforts have been made in the elucidation of transcriptional regulation and functions of bovine and ovine IFNτs, more importantly, the improvement of pregnancy rates in sheep and cattle, most of which resulted in unsuccessful outcomes. In this review, physiological, cellular and molecular events associated with continued secretion of progesterone, maternal recognition of pregnancy, identification, transcriptional regulation and function of IFNτ, and its future perspectives will be discussed.