Prof. Maxwell Hincke
In residence at
Dr Sophie Rehault-Godbert
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 solubilisation 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. The highly vascularized CAM occupies a strategic position, as it forms a lining under the eggshell and totally surrounds the embryo by the end of incubation. To date, the cellular and genetic basis for its protective mechanisms remains to be fully elucidated. Application of cutting-edge transcriptomics, proteomics and microbiology approaches, where the INRAE team "Défenses de l’Oeuf, Valorisation, Evolution" is an international centre of excellence, will be a fertile location for the STUDIUM experience of Professor Maxwell Hincke. Given the overlap in the research interests of Hincke with the INRAE team, and their remarkable potential to develop a new productive interaction together, there is tremendous potential for synergy and successful outcome of this project. Studying the role and the dynamics of the CAM in interaction with its surrounding tissues/structures throughout embryonic development is an ideal model for identification of novel bio-active molecules for biomedical and other non-food applications. These scientists will decipher the molecular mechanisms underlying innate immunity in the context of a model of decalcification of a biomineralized tissue (eggshell decalcification during embryonic development).
Publications in relation with the research project
Amorphous calcium carbonate (ACC) is an unstable mineral phase, which is progressively transformed into aragonite or calcite in biomineralization of marine invertebrate shells or avian eggshells, respectively. We have previously proposed a model of vesicular transport to provide stabilized ACC in chicken uterine fluid where eggshell mineralization takes place. Herein, we report further experimental support for this model. We confirmed the presence of extracellular vesicles (EVs) using transmission EM and showed high levels of mRNA of vesicular markers in the oviduct segments where eggshell mineralization occurs. We also demonstrate that EVs contain ACC in uterine fluid using spectroscopic analysis. Moreover, proteomics and immunofluorescence confirmed the presence of major vesicular, mineralization-specific and eggshell matrix proteins in the uterus and in purified EVs. We propose a comprehensive role for EVs in eggshell mineralization, in which annexins transfer calcium into vesicles and carbonic anhydrase 4 catalyzes the formation of bicarbonate ions (HCO[Formula: see text]), for accumulation of ACC in vesicles. We hypothesize that ACC is stabilized by ovalbumin and/or lysozyme or additional vesicle proteins identified in this study. Finally, EDIL3 and MFGE8 are proposed to serve as guidance molecules to target EVs to the mineralization site. We therefore report for the first-time experimental evidence for the components of vesicular transport to supply ACC in a vertebrate model of biomineralization.