As Nestin-Cre Xrcc4c/−p53+/+, Nestin-Cre Xrcc4c/− p53+/−, Nestin-Cre Xrcc4c/+p53+/−, Nestin-Cre Lig4 p53+/+, and Nestin-Cre Lig4 p53+/− animals do not develop medulloblastomas or gliomas8,9 it is not feasible to address this question in the same genetic background. This evidence concerns the gene NES and medulloblastoma.