Integral Proteomic Analysis of Blastocysts Reveals Key Molecular Machinery Governing Embryonic Diapause and Reactivation for Implantation in Mice1

Abstract

Among nearly 100 mammalian species, implantation can be suspended at blastocyst stage for a certain time and reactivated under favorable conditions, a phenomenon known as embryonic diapause. Until now, the underlying molecular mechanism governing embryonic diapause and reactivation for implantation remained largely unknown. Here we conducted the first integral proteomic analysis of blastocysts from diapause to reactivation by using a physiologically relevant mouse delayed implantation model. More than 6000 dormant and reactivated blastocysts were used for the proteomic analysis. A total of 2255 proteins were detected. Various cellular and molecular processes, including protein translation, aerobic glycolysis, pentose phosphate pathway, purine nucleotide biosynthesis, glutathione metabolism, and chromatin organization were identified as differentially regulated. In particular, we demonstrated a remarkable activation of mitochondria in blastocysts upon reactivation from dormancy, highlighting their essential physiological significance. Moreover, the activities of the endosome-lysosome system were prominently enhanced in the mural trophectoderm of reactivated blastocysts, accompanied by active phagocytosis at the fetal-maternal interface, suggesting a critical role in promoting trophoblast invasion. Collectively, we provided an integral proteomic view upon the regulatory network of blastocyst reactivation from diapause, which will help to better interpret the nature of embryonic diapause and reactivation in wild animals and to identify molecular indicators for selecting blastocysts with high implantation competency.

Embryonic diapause: development on hold

“…A recent proteomic analysis, remarkable in its investigation of 6000 embryos, identified numerous factors that were differentially expressed between the diapause and activated blastocyst (Fu et al, 2014). Not unexpectedly, elements essential to aerobic glycolysis and a wide range of factors related to chromatin remodeling and proliferation were upregulated with reactivation.…”

Reflections on Rodent Implantation

“…Global gene expression and proteomics analysis have identifi ed molecular pathways distinguishing blastocyst dormancy and activation in mice, identifying alterations in major functional categories of cell cycle, calcium signaling, adhesion molecules, mitochondrial, and energy metabolic pathways (Hamatani et al 2004 ;Fu et al 2014 ). An intriguing feature of dormant blastocysts is their activation of autophagy ("self-eating") (Lee et al 2011 ), a major cellular catabolic pathway by which macromolecules and organelles are recycled (Mizushima 2007 ).…”

Embryonic Diapause and Maternal Recognition of Pregnancy in Diapausing Mammals

“…Let 7 inhibits attachment, and its targets include genes that regulate cell proliferation (Gurtan et al 2013 ). The gene data set has now been extended by a proteomic analysis of mouse blastocysts during diapause and after activation (Fu et al 2014 ). This study of 6000 mouse blastocysts identifi ed 2255 proteins that have differential regulation of the protein translation, aerobic glycolysis, pentose phosphate pathway, purine nucleotide biosynthesis, glutathione metabolism and chromatin remodelling.…”

“…This study of 6000 mouse blastocysts identifi ed 2255 proteins that have differential regulation of the protein translation, aerobic glycolysis, pentose phosphate pathway, purine nucleotide biosynthesis, glutathione metabolism and chromatin remodelling. Interestingly, reactivation is accompanied by activation of mitochondria and of the endosome-lysosome system (Fu et al 2014 ).…”