Nucleosome release was clearly observed in Sag-/- mice exposed to 2,000 lux for 24 h and Sag-/-, Gnat1-/- and Sag-/-/Gnat1-/- exposed to 6,000 lux for 80 min and dark adaptation for 24 h, indicating high levels of apoptosis. NL, no light; WT, wild type.