Evolution of innate immunity at biomineralized barriers

In oviparous animals such as birds, embryonic development occurs in the egg, and after oviposition there is no further possibility of material exchange with the hen to fulfill the needs of the embryo. In such a context, the egg must contain all systems required for proper development of a living organism. Among these, the chorioallantoic membrane (CAM) is a novel placenta-like structure which is the nexus for many different physiological and metabolic processes including acid-base balance, breathing and calcium solubilization from the eggshell that is re-allocated to assist bone and tissue formation in the embryo. Moreover, it is believed to play a pivotal role in innate immunity to protect the embryo, in close interaction with the eggshell and the eggshell membranes. Therefore, weakening of the eggshell during CAM-mediated decalcification is hypothesized to be compensated by upregulation of innate immune mechanisms. In order to characterize this role of the CAM during embryonic development, we performed transcriptomics, proteomics and bioinformatics analyses. This residence was also the opportunity to stimulate a new international dynamic collaboration towards investigating innate immunity in diverse biomineralized structures (shells, bone, corals).