We thank Peter Vize and Erik Segerdell at Xenbase (www.xenbase.org) for providing access to the Xenopus anatomy ontology; Julie Moss (MRC Human Genetics Unit, Edinburgh, UK) for generating movies of Xenopus embryos stained for slc12a1 expression; and Monika Hebeisen (Institute of Pharmaceutical Sciences, ETH Zürich) for assistance with sequencing of Xenopus EST clones
