Pygo1 and Pygo2 targeted mutations
We targeted both the Pygo1 and Pygo2 genes by inserting LoxP sequences to flank critical coding regions including the PHD domains. The resulting targeted mice were mated with transgenic CMV-Cre mice [15] to drive germline LoxP recombination, resulting in the null mutant alleles that were used for this study. PCR confirmed the deletion of the bulk of the coding sequences for both genes, including 89% of coding sequence for Pygo1 and 87% of coding sequence for Pygo2. Previous studies in Drosophila have shown that even a single missense mutation in the PHD domain can eliminate Pygo function in Wnt signaling [8].