Zebrafish (Danio rerio) Endomembrane Antiporter Similar to a Yeast Cation/H+ Transporter Is Required for Neural Crest Development+.

CAtiOn/H+ exchangers (CAxs) are integral membrane proteins that transport Ca2+ or other cations by exchange with protons. While several yeast and plant CAX proteins have been characterized, no functional analysis of a vertebrate CAX homologue has yet been reported. In this study, we further characterize a CAX from yeast, VNXl and initiate characterization ofa zebrafish CAX (Cax I). Localization studies indicated that both Vnxl and CaxI proteins are found in endomembrane compartments. Biochemical characterization of endomembrane fractions from vnx I mutant cells and zebrafish Cax I-expressing yeast cells suggested that both yeast and fish CAXs have Ca2+/H+ antiport activities. Additionally, the vnxl mutation was associated with heightened pH-sensitivity. In zebrafish embryos, cax I was specifically expressed in neural crest cells. Morpholino knockdown ofcaxl caused defects in neural crest development, including alterations in pigmentation, defects in jaw development, and reduction in expression of the neural crest marker, Pax7. Collectively, our findings provide insights into Vnxl function and support an unexpected role of CAX transporters in animal growth and development. [ABSTRACT FROM AUTHOR]