Protein Synthesis by Day 16 Bovine Conceptuses during the Time of Maternal Recognition of Pregnancy

Abstract

Interferon Tau (IFNT), the conceptus-derived pregnancy recognition signal in cattle, significantly modifies the transcriptome of the endometrium. However, the endometrium also responds to IFNT-independent conceptus-derived products. The aim of this study was to determine what proteins are produced by the bovine conceptus that may facilitate the pregnancy recognition process in cattle. We analysed by mass spectrometry the proteins present in conceptus-conditioned media (CCM) after 6 h culture of Day 16 bovine conceptuses (n = 8) in SILAC media (arginine- and lysine-depleted media supplemented with heavy isotopes) and the protein content of extracellular vesicles (EVs) isolated from uterine luminal fluid (ULF) of Day 16 pregnant (n = 7) and cyclic (n = 6) cross-bred heifers on day 16. In total, 11,122 proteins were identified in the CCM. Of these, 5.95% (662) had peptides with heavy labelled amino acids, i.e., de novo synthesised by the conceptuses. None of these proteins were detected in the EVs isolated from ULF. Pregnancy-associated glycoprotein 11, Trophoblast Kunitz domain protein 1 and DExD-Box Helicase 39A were de novo produced and present in the CCM from all conceptuses and in previously published CCM data following 6 and 24 h. A total of 463 proteins were present in the CCM from all the conceptuses in the present study, and after 6 and 24 h culture in a previous study, while expression of their transcripts was not detected in endometrium indicating that they are likely conceptus-derived. Of the proteins present in the EVs, 67 were uniquely identified in ULF from pregnant heifers; 35 of these had been previously reported in CCM from Day 16 conceptuses. This study has narrowed a set of conceptus-derived proteins that may be involved in EV-mediated IFNT-independent embryo–maternal communication during pregnancy recognition in cattle.

Extracellular vesicles and domestic animal reproduction

“…da Silveira et al (2017) observed that when the culture medium of somatic cell nuclear transfer is supplemented with EVs from the uterus, bovine blastocyst rates and interferon tau (IFNT) expression are improved (Qiao et al, 2018). Protein cargoes in EVs have also been studied, and it seems that maternal-embryonic communication independent of IFNT could be regulated by protein cargoes of EVs secreted by conceptus (Malo Estepa et al, 2020). Ninety-seven proteins are expressed exclusively in EVs of the oviduct in vivo versus in vitro, related to spermatozoa union, fertilization, and embryo development (Almiñana et al, 2017).…”

Embryo–Maternal Interactions Underlying Reproduction in Mammals

“…Despite that the major pregnancy recognition signal in ruminants, interferon-tau, has been discovered long time ago [ 26 ], more and more studies are showing that other embryonic molecules are involved in the establishment of pregnancy, pointing out the high complexity of these interactions. In this line, Malo Estepa et al, examined the protein synthesis by day 16 conceptuses corresponding to the phase of maternal recognition of pregnancy [ 27 ], identifying a set of conceptus-derived proteins that may be involved in EV-mediated IFNT-independent embryo–maternal communication during pregnancy recognition in cattle.…”

Potential ligand-receptor-pathway cascades and a novel non-metabolic function of lactate in remodeling uterine receptivity by inducing endometrial histone lactylation at implantation, revealed by a proteomic atlas of maternal-fetal crosstalk

“…Fine-tuned and reciprocal crosstalk involves secreted ligands, their interacting receptors, and coupled pathways between the conceptus and endometrium. Until now, most research has focused on either the conceptus (23)(24)(25)(26) or the endometrium (20,21,(27)(28)(29) in isolation, the lack of integrated analysis between the paired conceptus and endometrium has made it challenging to advance our understanding of the pathways and functions that govern conceptus-endometrium crosstalk during implantation. More recently, disrupted crosstalk following somatic cell nuclear transfer (SCNT) (30), IVF (31), and fertilityclassi ed animals (32) have been pro led, and revealed important clues to failed implantation and pathological pregnancy induced by impaired conceptus-endometrium crosstalk.…”