PTCH1 and hydrops fetalis: In contrast, DMBA/TPA-treated R26-LacZ Ptchf/f CD4Cre skin shows Ptch mutant LacZ+ HF (Figure 6B) but at much lower numbers compared to the skin of age-matched untreated CD4Cre R26-tdT mice, which show numerous wildtype Ptch tdT+ HF (Figure 6A).