Systemic lupus erythematosus is inherited as a complex polygenic trait. Four genomic intervals containing major SLE-susceptibility loci were previously identified by interval mapping in the NZM2410 mouse model. In this paper, we utilized a marker-assisted selection protocol to produce four congenic mouse strains, each carrying an NZM2410-derived SLE-susceptibility interval on a C57BL/6-resistant background. Each strain carries only one susceptibility allele derived from this polygenic model and consequently can be used to characterize the specific component phenotypes contributed by individual SLE-susceptibility genes. We illustrate the efficacy of this approach with phenotypic data for one of our congenic strains, B6.NZMH2z. Our results indicate that this single genomic interval from Chromosome (Chr) 17 of NZM2410 can mediate increased levels of IgG autoantibodies specific for chromatin and that, similar to results obtained in our original genetic cross, B6.NZMH2z/b heterozygotes are more prone than B6.NZMH2z homozygotes to the development of humoral autoimmunity to nuclear antigens. These results illustrate the feasibility of using congenic strains to dissect the complex pathogenic mechanisms that mediate polygenic SLE. These congenic strains will be valuable tools in the genetic analysis of SLE susceptibility. In future studies, these congenic strains will be interbred to produce bi- and tri-congenic strains in order to assess the role of genetic interactions in the expression of specific components of SLE pathogenesis. They will also be instrumental to the positional cloning and identification of the genes responsible for SLE susceptibility, via the production of congenic recombinants.
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