Sticky cells in a prickly system

The olfactomedin (OLF) protein domain appears in a strange assortment of places: its namesake, olfactomedin, is found in the mucous covering the bullfrog olfactory neuroepithelium, while mutations in the OLF domain of human myocilin/TIGR protein are associated with a form of familial glaucoma, and the OLF-containing protein noelin appears to be involved in neural crest formation in vertebrates. But what does this conserved domain do? On page 597, Hillier and Vacquier identify another OLF-containing protein, show that it mediates a novel form of intercellular adhesion, and describe a simple but powerful model system for future work in this area.

The authors set out to understand how cells in the coelom of a sea urchin clot in response to an injury. In contrast to vertebrate or arthropod blood clotting, sea urchin clotting involves rapid aggregation of phagocytic...