Impact of DNA non homologous end joining on stem cell function in vivo. (360G-Wellcome-084704_Z_08_Z)

DNA double strand breaks (DSBs) arise from oxidative damage and following radiation treatment. Their impact on development and particularly on stem cells is unclear but is topical and important. As a result of basic research, an exquisitely sensitive technique to monitor DSB repair in vivo has been recently developed. Additionally, we recently characterised a mouse mutated in DNA ligase IV (LigIVY288C), a component of DNA non-homologous end-joining (NHEJ), the major DSB repair pathway. We showed that haematopoietic stem cell (HSC) numbers and function are diminished in LigIVY288C mice demonstrating that unrepaired DSBs impact on stem cells. Here, we will pursue our analysis by monitoring radiation-induced DSB repair in three stem cell compartments, the HSCs, the ventricular and sub-ventricular zone of the developing embryonic brain, and the intestinal crypt. For this we will use normal mice. We will also exploit LigIVY288C mice to examine the impact of impaired NHEJ in the embryonic br ain and intestinal crypt, where stem cells can be readily identified. Our major focus will be on embryonic neuronal development since microcephaly is a feature of LIG4 syndrome, a disorder caused by mutations in LigIV, and since our preliminary studies have shown abnormalities in the LigIVY288C embryonic brain.