WNT5a in tongue and fungiform Papilla development.

Fungiform papillae are complex taste organs that develop in a pattern on anterior tongue in rodent embryos. Several intrinsic secreted molecules are important for papilla development and patterning, including sonic hedgehog, bone morphogenetic proteins, Noggin, epidermal growth factor, and WNTs. Recent data about roles of WNTs in regulation of tongue and fungiform papilla development lead to new insights about the importance of tissue and timing contexts when studying the effects of morphogenetic proteins. WNT/beta-catenin signaling is required for formation of fungiform papillae, but not for determining tongue size and shape. In contrast, WNT5a apparently is important for tongue outgrowth, but not papilla development. Preliminary data from WNT5a mutant mice separate genetic programs for papilla number from those for tongue shape and size.