Primary keratinocytes were culture in low-calcium medium as previously described [4]. Transient transfections were carried out with FuGENE6 reagent (Roche, Indianapolis, Indiana, United States) according to the manufacturer's protocol. Measurement of β-galactosidase or luciferase levels in promoter activity studies were carried out with the Galacto-Lite assay kit (TROPIX, Bedford, Massachusetts, United States) and the Dual luciferase (Promega, Madison, Wisconsin, United States), respectively. Runella luciferase was cotransfected into cells to correct for transfection efficiency. Experiments were done in triplicate and repeated at least three times. Measurements were done on a luminometer (MGM Instruments, Hamden, Connecticut, United States). For experiments measuring phosphorylation of MAPK, keratinocytes were serum starved for 3 h prior to harvesting of cells by incubation in medium lacking serum. Treatment of cells with Wnt- and noggin-conditioned medium was previously described [4].