Accompanying these genetic events, bystander-related tumor induction in the cerebellum of radiosensitive Patched-1 (Ptch1) heterozygous mice after x-ray exposure of the remainder of body, further suggested a mechanism mediated by gap-junctional intercellular communication for transmission of bystander damage to shielded cerebellum. The gene discussed is PTCH1; the disease is neoplasm.