Sea urchin eggs in the acid reign

Sea urchin eggs have been an indispensable model system for studying egg activation and ionic signalling for at least a century. Instrumental in the discovery of two Ca2+-mobilizing second messengers, cyclic ADP-ribose and NAADP, the sea urchin has revolutionized cell biology for all phyla. This review attempts to summarize what we currently know about egg acidic vesicles in the context of Ca2+ signalling. The dynamics of Ca2+ storage, Ca2+ mobilization, proton fluxes and two-pore channels will be discussed.