Nuclear DNA content variation and double-strand DNA breakage in white-footed MICE (Peromyscus leucopus) collected from abandoned strip mines, Oklahoma, USA

Abstract

White-footed mice (Peromyscus leucopus) were collected during the spring, summer, and fall from four metal-polluted abandoned mines and three reference sites in eastern Oklahoma. Two mines in east-central (Okmulgee County) Oklahoma, USA, were matched with a nearby reference site, as were two mines in northeastern Oklahoma (Craig County). A third, remote reference site was located outside the Oklahoma coal belt in north-central Oklahoma (Payne County). Intercellular DNA content variation, measured as a coefficient of variation (CV) of nuclear DNA content among 20,000 cells per animal, was determined for splenocytes of individuals by flow cytometry. Double-strand breakage in liver DNA from the same animals was compared using agarose gel electrophoresis. Mice trapped from mines were expected to have more intercellular DNA content variation and more DNA breakage when compared with mice from the matched and remote reference sites. With one exception, mice from mine sites did not show any significant increase in nuclear DNA content variation during any season. Electrophoresis revealed that mice from both Okmulgee County mines had significantly more DNA breakage compared with the intracounty reference site in the spring. In the summer, mice from one Craig County mine had significantly higher levels of DNA breakage compared with the remote reference.