Seawater carbonate chemistry and otop2l expression of sea urchins (Stongylocentrotus purpuratus)

• Main Authors: Chang, William Weijen, Matt, Ann-Sophie, Schewe, Marcus, Musinszki, Marianne, Grüssel, Sandra, Brandenburg, Jonas, Garfield, David, Bleich, Markus, Baukrowitz, Thomas, Hu, Marian Y
• Format: Dataset
• Language: English
• Published: PANGAEA 2021
• Subjects: Alkalinity; total; Animalia; Aragonite saturation state; Bicarbonate ion; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coast and continental shelf; Echinodermata; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gene expression; Gene expression (incl. proteomics); Laboratory experiment; North Atlantic; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Registration number of species; Replicate; Salinity; Single species; Species; Strongylocentrotus purpuratus; Temperate; Temperature; water; Time in days; Treatment; Type; Uniform resource locator/link to reference; Zooplankton
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.939436; https://doi.org/10.1594/PANGAEA.939436

Otopetrins comprise a family of proton-selective channels that are critically important for the mineralization of otoliths and statoconia in vertebrates but whose underlying cellular mechanisms remain largely unknown. Here, we demonstrate that otopetrins are critically involved in the calcification process by providing an exit route for protons liberated by the formation of CaCO3. Using the sea urchin larva, we examined the otopetrin ortholog otop2l, which is exclusively expressed in the calcifying primary mesenchymal cells (PMCs) that generate the calcitic larval skeleton. otop2l expression is stimulated during skeletogenesis, and knockdown of otop2l impairs spicule formation. Intracellular pH measurements demonstrated Zn2+-sensitive H+ fluxes in PMCs that regulate intracellular pH in a Na+/HCO3−-independent manner, while Otop2l knockdown reduced membrane proton permeability. Furthermore, Otop2l displays unique features, including strong activation by high extracellular pH (>8.0) and check-valve–like outwardly rectifying H+ flux properties, making it into a cellular proton extrusion machine adapted to oceanic living conditions. Our results provide evidence that otopetrin family proton channels are a central component of the cellular pH regulatory machinery in biomineralizing cells. Their ubiquitous occurrence in calcifying systems across the animal kingdom suggest a conserved physiological function by mediating pH at the site of mineralization. This important role of otopetrin family proton channels has strong implications for our view on the cellular mechanisms of biomineralization and their response to changes in oceanic pH.