The repair of DNA damage is essential for the prevention of disease. The DNA double-strand break (DSB) is a particularly hazardous lesion. DNA DSBs activate a coordinated cellular response involving cell cycle checkpoint activation and repair of the DNA break, or alternatively apoptosis. In the nervous system the inability to respond to DNA DSBs may lead to neurodegenerative disease or brain tumors. Therefore, understanding the DNA DSB response mechanism in the nervous system is of high importance for developing new treatments for neurodegeneration and cancer. In this regard, the use of mouse models represents an important approach for advancing our understanding of the biology of the DNA damage response in the nervous system.