Non-major histocompatibility complex-linked diabetes susceptibility loci on chromosomes 4 and 13 in a backcross of the DP-BB/Wor rat to the WF rat

BB rats are used as models of autoimmune human IDDM. Genetic control of IDDM in both species is complex, including both major histocompatibility complex (MHC)-linked and non-MHC-linked genes, DP-RR rats develop IDDM spontaneously Expression of disease in these animals requires homozygosity at the lyp locus, which causes lymphopenia, All genetic analyses of BE rat diabetes to date have backcrossed to the DP-BB strain or used (DP-BB x non-BB)F2 animals to ensure that a fraction of progeny are homozygous for lyp. Here we report the analysis of a back,cross of the DP-BB rat to the histocompatible WF rat, Neither NF nor (WF x DP-BB)F1 animals develop spontaneous EI)DM. lion-ever, 9.5% of(WF x DP-BB)F1 rats and a fraction of (WF x DP-BB) x WF backcross animals readily develop IDDM Liter treatment with polyinosinic:polycytidylic acid and a cytotoxic anti-RT6.1 monoclonal antibody, Using simple sequence length polymorphism analysis, we have mapped loci on chromosomes 4 and 13 that show significant linkage to IDDM expression and insulitis, The susceptibility locus on chromosome 4 is linked to, hut nut identical to, lyp. We propose a disease model for the EE rat that requires 1) the RT1(u) MHC haplotype for disease susceptibility; 2) a new locus on chromosome ii for disease initiation (as measured by insulitis), 3) a new locus on chromosome 13 for disease progression in response to environmental perturbation, and 4) lyp, for spontaneous expression of disease.