PTCH1 and nevoid basal cell carcinoma syndrome: To clarify the mechanism underlying the association between heterozygous PTCH1 mutations/deletions and their associated Gorlin syndrome (GS)-related phenotypic manifestations, two independent lines of Ptch1-deficient mice were constructed: Ptch1+/− (exon 1/2) and Ptch1neo 67/+ mice [40,43].