Reproduction Abstracts

Maternal recognition of pregnancy (MRP) in cattle requires secretion of sufficient interferon tau (IFNT) by the conceptus to prevent luteolysis. However, recent evidence suggests that additional conceptus-derived products may be involved. The aim of this experiment was to identify conceptus-derived proteins in uterine luminal fluid (ULF) during MRP. Following estrous synchronization, the protein content of ULF from cyclic (n=4) and confirmed pregnant (n=4) heifers was analyzed by nano LC MS/MS. In addition, the protein composition of spent culture medium from in vivo derived day 16 conceptuses cultured in vitro for 6 or 24 h (and blank controls) were also analyzed. 305 proteins were identified in the ULF of pregnant heifers while 299 were detected in the ULF of cyclic heifers; 85 proteins were common to both. Analysis of media following culture of day 16 conceptuses for 6 or 24 h (vs blanks) revealed the presence of 1043 and 1020 proteins respectively. Comparison of these proteins to those identified in the ULF of pregnant and cyclic heifers revealed 31 proteins unique to pregnant ULF (i.e. not detected in cyclic heifers) which were also produced in vitro by day 16 conceptus. The transcript abundance of 25 of these 31 proteins was significantly higher in the conceptus (P<0.05, measured by RNA sequencing) compared to endometrial expression and included HSP7C, EF2, CH10, PDIA1, and CYTB. In conclusion, this study provides evidence that the conceptus produces proteins, other than IFNT on day 16 which likely contribute to the process of MRP.