New directions to understand and learn from embryonic diapause in mammals

Embryonic diapause is a key strategy to extend pregnancy until conditions are ideal for birth and postnatal survival. There is still a lot to discover about this unique phenomenon observed in more than 130 mammalian species. The present review aims at complementing existing research efforts by (1) identifying new directions for a better understanding of embryonic diapause in mammals and (2) considering this complex mechanism as a source of inspiration for other areas in cellular biology. Comparative explorations in different species of new molecular players associated with the use of emerging technologies in the study of embryos (epigenetics for instance), the uterus (immune cells, microbiota, cell-free DNA), and the whole organism (remote sensing, systems biology) will shed some new lights on embryonic diapause characterizations. Collective results of advanced studies should be integrated into the measurement of climate and environmental changes potentially influencing the physiology of females and their arrested embryos. Interestingly, lessons from nonmammalian species using similar strategies (killifish for instance) could also improve our understanding of this unique phenomenon. Furthermore, studying embryonic diapause offers a great opportunity to decipher other cellular mechanisms and develop new applications (stem cell technologies, cancer treatments, contraceptive methods, short-term storage of embryos, or early fetal loss prevention). Overall, these new ideas and directions should define some themes for a future International Symposium on Embryonic Diapause.