Dickkopf (DKK) is a family of proteins consisting of five members as of 2020.
[1] DKK proteins inhibit the Wnt signaling pathway coreceptors LRP5 and LRP6.
[2] DKK proteins have important roles in the development of vertebrates.
[2] Dickkopf is a German word meaning "stubborn person", or literally, "thick head".
It was coined as the name for these proteins in a 1998 Nature paper by Glinka et al.[3] in reference to the discovery that DKK1 induces head formation in the embryogenesis of Xenopus.