Deficiency of Bax and Bak protects photoreceptors from light damage in vivo

Photoreceptors of bax −/− bak −/− but neither bax −/− mice nor bak −/− mice are protected from developmental apoptosis, suggesting that bax −/− bak −/− photoreceptors may also be protected from pathologic apoptosis. To test this possibility, we exposed bax −/− bak −/− and bax −/− mice to bright light, which normally induces photoreceptor death. Photoreceptors in bax −/− bak −/− mice were protected from death compared to bax −/− mice as indicated by a reduction in the number of TUNEL-positive photoreceptor nuclei 24 h following light damage and almost complete preservation of photoreceptors 7 days following light damage. These results provide the first in vivo evidence that combined deficiency of Bax and Bak can rescue cells from a pathologic stimulus more effectively than Bax deficiency and suggest that combined deficiency of Bax and Bak may also protect cells from other insults.