Accumulated background variation among H2 mutant congenic strains:: elimination through PCR-based genotyping of F2 segregants

Many commercially and privately available congenic strains of laboratory animals were founded decades ago and are likely to differ from one another by dozens of fixed mutational differences at background loci. This problem is often ignored despite growing evidence that such background variation exists. Eliminating this confounding variation can be largely accomplished by crossing congenic strains to produce F-2 segregants that are homozygous (or heterozygous) for relevant genes. Discriminating F-2 homozygotes can be difficult when strain differences are minor, as are mutant mouse strains differing at single major histocompatibility loci (H2 mutant congenics). Here, we describe a two-step polymerase chain reaction (PCR) method utilizing heteroduplex analysis and sequence specific primers (SSP-PCR) that efficiently discriminates the F-2 progeny of two such H2 mutant congenic mice crosses (bm1 X B6 and bm1 X bm3). A third H2 mutant cross cannot be resolved by heteroduplexing, but is discriminated (albeit less efficiently) with SSP-PCR alone. This sensitive application can be extended to any congenic mutant strains. (C) 2001 Elsevier Science B.V. All rights reserved.