Senescence-Accelerated Mouse (SAM) strains have a spontaneous mutation in the Abcb1a gene

Senescence-Accelerated Mouse (SAM) strains are used as animal models for gerontological research. Here, we report that the SAMR1 strain, which shows a high sensitivity to toxicity of the parasiticide ivermectin, has a spontaneous retroviral insertional mutation in the ATP-binding cassette, sub-family B (MDR/TAP), member 1A (Abcb1a) gene. This mutation is identical to that found in Crl:CF1-Abcb1a mice, which are also highly sensitive to ivermectin due to the mutation. The mutant Abcb1a allele was found in SAMR4, SAMR5, SAMP1, SAMP6, SAMP7, and SAMP9, but not in SAMP3, SAMP8, SAMP10, SAMP11, and other outbred and inbred strains, including 129/SvJ strains. These results impart both caution and promise in the use of SAM strains in studies of biological processes in which P-glycoprotein participates.