The GenBank ((http://www.ncbi.nlm.nih.gov/Genbank) accession numbers for the genes and gene products discussed in this paper are Apc (NM_007462), β-catenin (NM_007614), AXIN 2 (NM_004655), plakoglobin (NM_002230), Asef (NM_015320), kinesin superfamily–associated protein 3 (NM_014970), EB1 (NM_012325), human homolog of Drosophila Discs large (U13897), Lef1 (NM_010703), Dkk1 (NM_010051), K1 (NM_008473), K5 (NM_027011), K6 (NM_008476), K8 (NM_031170), K14 (NM_016958), involucrin (NM_008412), loricrin (NM_008508), and Shh (NM_009170).