Genetic loci controlling susceptibility to gamma-ray-induced thymic lymphoma

BALB/c is a susceptible strain for the development of gamma -ray induced mo use thymic lymphoma whereas MSM shows resistance. Association analysis of 2 20 backcross mice between the two strains using 67 markers was carried out to identify loci involved in the control of susceptibility. The genotype of mice with lymphoma showed excess heterozygosity relative to MSM homozygosi ty at D2Mit15 and D4Mit12 and was skewed toward MSM-derived alleles at D5Mi t5. The P values in Mantel-Cox test were 0.0048 (D2Mit15), 0.0034 (D4Mit12) and 0.0048 (D5Mit5), suggesting association at the three loci in the susce ptibility. Cooperative effect on lymphomagenesis was also observed among th e three loci. To obtain independent evidence for linkage at D4Mit12, we mad e partially congenic mice in which a D4Mit12 region in BALB/c was replaced by MSM-derived homolog. Examination for the lymphoma susceptibility in 78 p rogeny of the congenic mice confirmed the effect of the locus near D4Mit12 (P=0.0037). The result, together with the linkage analysis, shows that the locus near D4Mit12 is regarded as a confirmed linkage but the other two loc i as marginally suggestive.