Interferon tau-dependent and -independent changes in the bovine corpus luteum of early pregnancy

The effect of interferon tau (IFNT) on the uterus is critical for maternal recognition of pregnancy in ruminants, while its direct role in luteal function is less well understood. To address this, we performed two experiments. In Experiment 1, cattle received intrauterine infusions of either: bovine serum albumin (BSA; vehicle) or vehicle with IFNT from Days 14 to 16 of the estrous cycle or vehicle with IFNT from Days 14 to 19 or vehicle with IFNT from Days 14 to 19 with pregnancy associated glycoprotein (PAG) from Days 17 to 19. Corpora lutea (CL) were collected on Day 17 or 20 and RNAseq was performed. In Experiment 2, cultured luteal steroidogenic cells from cyclic (Days 10-12) cattle were treated with IFNT and RNAseq was performed. Treatment with IFNT resulted in luteal changes (in vivo: 130 transcripts; in vitro: 2981 transcripts), while addition of PAG resulted in 13 changed transcripts. Only 31% of the genes that changed in the CL during early pregnancy (Hughes et al., 2020) were regulated by IFNT; these were antiviral and immune regulators. In contrast, 50% of the genes that changed during early pregnancy were not regulated by IFNT and were associated with cellular proliferation and extracellular matrix organization. The remaining 19% of genes were not conclusively identified as either IFNT regulated or non-regulated. This suggests that the temporal changes in the CL during early pregnancy are only partially regulated by IFNT, drawing into question identities of other luteal regulators or the effect of age of CL.