Wnt genes have been identified in vertebrates and invertebrates but not in plants, unicellular eukaryotes or prokaryotes. In humans, 19 WNT proteins are known. Because of their insolubility little is known about Wnt protein structure, but all have 23 or 24 Cys residues whose spacing is highly conserved. Signal transduction by Wnt proteins (including the Wnt/beta-catenin, the Wnt/Ca++, and the Wnt/polarity pathway) is mediated by receptors of the Frizzled and LDL-receptor-related protein (LRP) families [1].

1: The Wnts. Miller JR; Genome Biol 2002;3:REVIEWS3001. PMID:11806834