Differential Impact of Mouse Rad9 Deletion on Ionizing Radiation-Induced Bystander Effects

Abstract Zhu, A., Zhou, H., Leloup, C., Marino, S. A., Geard, C. R., Hei, T. K. and Lieberman, H. B. Differential Impact of Mouse Rad9 Deletion on Ionizing Radiation-Induced Bystander Effects. Radiat. Res. 164, 655–661 (2005). The cellular response to ionizing radiation is not limited to cells irradiated directly but can be demonstrated in neighboring “bystander” populations. The ability of mouse embryonic stem (ES) cells to express a bystander effect and the role of the radioresistance gene Rad9 were tested. Mouse ES cells differing in Rad9 status were exposed to broad-beam 125 keV/ μm 3He α particles. All populations, when confluent, demonstrated a dose-independent bystander effect with respect to cell killing, and the Rad9−/− genotype did not selectively alter that response or cell killing after direct exposure to this high-LET radiation. In contrast, relative to Rad9+/+ cells, the homozygous mutant was sensitive to direct exposure to α particles when in log phase, providing evidence of a role for Rad9...