Proteomics of bovine endometrium, oocytes and early embryos

Abstract

Summary. Embryo-maternal communication, as well as recognition and establishment of pregnancy, is predominantly controlled by secretion of hormones and proteins. Furthermore, uterine fluid serves as a histotroph and contains factors essential for embryo development and elongation, making it a meaningful source for proteomic approaches of early embryonic development. The studies included in this review address the analysis of uterine fluid and endometrium during the oestrous cycle, early pregnancy, maternal effects on embryo development and embryo-induced alterations to the maternal environment. Clear differences between the proteome of uterine fluid and blood plasma unravelled the active contribution of the endometrium to the composition of uterine luminal fluid. Proteins were identified which may contribute either to growth enhancement of blastocysts or influence secretion of "Interferon tau". Several studies suggested important roles of intrauterine factors including "Tissue inhibitor of metalloproteinases 2" for pregnancy establishment and "Acyl-CoA-binding protein" for the embryo prior to implantation. A meta-analysis of quantitative proteome studies revealed functional clusters including the terms "degradation of extracellular matrix", "platelet degranulation" and "MHC class II antigen presentation". Proteomic studies targeting oocytes and early embryos provided evidence for the function of "Cyclin B" in mitotic resumption, for "14-3-3 epsilon" to activate "maturation promotion factor" for promotion of mitosis during in vitro maturation, or for the inhibition of proteasomes during the late phase of maturation. Analysis of blastocyst derived trophectoderm cell lines suggested effects of annexin down-regulation on the failure rate of nuclear transfer pregnancies. Finally, absolute quantification of "Y-box-binding protein 2" and "Insulin-like growth factor 2 mRNA-binding protein 3" during early embryogenesis by "selected reaction monitoring" demonstrated the dynamism of proteome alterations during the first embryonic cell divisions.