Advance Access publication June 9, 2011 Manganese Interferes with Calcium, Perturbs ERK Signaling, and Produces Embryos with No Skeleton

Manganese (Mn) has been associated with embryo toxicity as it impairs differentiation of neural and skeletogenic cells in vertebrates. Nevertheless, information on the mechanisms oper-ating at the cellular level remains scant. We took advantage of an amenable embryonic model to investigate the effects of Mn in biomineral formation. Sea urchin (Paracentrotus lividus) embryos were exposed to Mn from fertilization, harvested at different developmental stages, and analyzed for their content in calcium (Ca), expression of skeletogenic genes, localization of germ layer markers, and activation of the extracellular signal-regulated kinase (ERK). By optical and immunofluorescence microscopy, we found that Mn exposure produced embryos with no skeleton, by preventing the deposition of the triradiate calcitic spicules usually produced only by specialized mesoderm cells. On the contrary, ectoderm and endoderm differentiation was not impaired. Endog