DNA ligase IV suppresses medulloblastoma formation.

Substantial neural defects are often present in mice with targeted inactivation of DNA repair factors such as DNA ligase IV (Lig4). Whereas Lig4(-/-) mice undergo widespread neural apoptosis and die during development, p53 deficiency rescues this death. We found that all Lig4(-/-)p53(-/-) mice developed medulloblastoma, but did not develop other tumors of the nervous system. Lig4(-/-)p53(-/-) medulloblastoma occurred as early as 21 days of age, originated in the external granule layer of the developing cerebellum, and was synaptophysin immunoreactive. These data reveal a pronounced susceptibility of the cerebellum to the effects of chronic DNA damage and provide a direct link between genotoxic stress and medulloblastoma formation.