WNTs: Multiple Genes, Multiple Functions

The development of ectodermal appendages such as hair, feathers and teeth has long fascinated biologists, who have attempted to understand how cells of different types interact with each other to induce the coordinated changes in cell shape, proliferation, adhesion and movement required for the formation of these intricate three-dimensional structures. Classical experiments involving recombination of ectodermal and mesenchymal cells from different sources revealed that, for each of these types of appendage, reciprocal communication between the epithelium and mesenchyme is essential at each stage of development (Hardy, 1992;Jernvall and Thesleff, 2000).