Wnt-β-catenin signaling initiates taste papilla development

Fungiform taste papillae form a regular array on the dorsal tongue. Taste buds arise from papilla epithelium 1 and, unusually for epithelial derivatives, synapse with neurons, release neurotransmitters and generate receptor and action potentials 2,3 . Despite the importance of taste as one of our five senses, genetic analyses of taste papilla and bud development are lacking. We demonstrate that Wnt-p-catenin signaling is activated in developing fungiform placodes and taste bud cells. A dominant stabilizing mutation of epithelial β-catenin causes massive overproduction of enlarged fungiform papillae and taste buds. Likewise, genetic deletion of epithelial β-catenin or inhibition of Wnt-p-catenin signaling by ectopic dickkopf1 (Dkk1) 4-6 blocks initiation of fungiform papilla morphogenesis. Ectopic papillae are innervated in the stabilizing β-catenin mutant, whereas ectopic Dkk1 causes absence of lingual epithelial innervation. Thus, Wnt-p-catenin signaling is critical for fungiform papilla and taste bud development. Altered regulation of this pathway may underlie evolutionary changes in taste papilla patterning.