Fluorescent light-induced DNA crosslinkage and chromatid breaks in mouse cells in culture

A single 20-hr exposure of mouse cells derived from embryonic or lung tissue to cool-white fluorescent light (4.6 W/m2) causes both DNA damage and chromosome aberrations including chromatid breaks, exchanges, and minutes. In Kohn's alkaline elution technique, the DNA from exposed cells elutes more slowly than that from shielded cells. Because larger molecular weight DNA elutes slower than smaller, we interpret these results to mean that the DNA in cells exposed to light is crosslinked. The estimated frequency of crosslinks is sufficient to account for the number of chromatid breaks observed. The types of chromosome aberrations produced by light indicate that the primary lesion results in chromatid rather than chromosome breaks, and the results suggest an influence of cell density in that cells in densely populated cultures showed few or no chromatid breaks after irradiation. The present results, together with observations from the literature, suggest that the DNA crosslinkage and the chromosome aberrations produced by light may be related.