Identification of a genetic contamination in a commercial mouse strain using two panels of polymorphic markers

Rapid detection of genetic contamination is critical in mouse studies involving inbred strains. During a Quantitative Trait Locus (QTL) study using simple sequence length polymorphism (SSLP) markers, we noticed heterozygosity at some loci of a commercially available inbred C57BL/6N mouse strain, suggesting a contamination by another mouse strain. A panel of 100 single-nucleotide polymorphism (SNP) markers was used to confirm and specify the genetic contamination suspected. Retrospective analyses demonstrated that the contamination took place as early as autumn 2003 and has persisted ever since at a fairly constant level. Contaminating alleles most probably originated from a DBA strain. Our data demonstrate the suitability of SNP markers for rapid detection and identification of the source of genetic contamination. Further, our results show the importance of a state-of-the art genetic monitoring of the authenticity of murine inbred strains.