News from alpha type Carbonic Anhydrases on the Sea Urchin Embryos

C. Costa1, F. Zito1, K. Karakostis2, R. Bonaventura1, A.Pinsino1, R. Russo1 and V. Matranga1. 1. Institute of Biomedicine and Molecular Immunology "A. Monroy", National Research Council, Via Ugo La Malfa, Palermo 153- 90146, Italy 2. INSERM UMR S 1162, Institut de Génétique Moléculaire, Hôpital Saint-Louis, 27 Rue Juliette Dodu, 75010 Paris, France caterina.costa@ibim.cnr.it Alpha type Carbonic anhydrases (CA) are zinc-containing enzymes and belong to one of the three evolutionarily unrelated CA families (a, ? and gamma). They are found throughout the animal kingdom and play a key regulative role for many important physiological processes, including respiration, pH homeostasis, ion and inorganic carbon transport and skeletogenesis. CAs catalyze the rapid and reversible hydration of CO2, leading to the release of bicarbonate ions and protons from carbon dioxide and water. Drugs, like Acetazolamide (AZ), inhibit specifically CA activity. Previous studies on sea urchin embryo development have reported that the inhibition of CA activity blocks the deposition of CaCO3 and spicule formation, both on whole sea urchin embryos and on isolated and "in vitro" cultured primary mesenchyme cells (PMCs). Recently, we have described new effects caused by the AZ treatment in the embryos of two geographically distant sea urchin species, Paracentrotus lividus and Heliocidaris tuberculata. Based on the new morphotypes observed, we highlight a new role for CA linked to the immune pigment cells of the embryo. Although at least 19 encoding CA genes have been identified in the sea urchin genome, no CAs from sea urchin embryos had been described until now. Here, we report our recent molecular results about: 1) the identification of a new CA mRNA in Paracentotus lividus embryos, referred as Pl-can; 2) the computational characterization of the deduced protein sequence; 3) the temporal and spatial expression profiles throughout embryo development; 4) the production and characterization of a recombinant fusion protein (Pl-CAN).