Experiment
75 female animals from a (C57BL/6 x NZB)F1 x NZB backcross were used to map QTLs involved in splenomegaly and anti-erythrocyte autoantibody (AEA) production. These two phenotypes develop spontaneously in the NZB strain, which is used as a model for autoimmune hemolytic anemia. AEA production and splenomegaly are inherited in a dominant fashion, but wild type alleles contributed by C57BL/6 are shown to have a suppressive affect on these traits. A QTL screen using 63 microsatellite markers mapped these modifying loci, Spm1 (splenomegaly modifer 1; LOD = 3.6), Aem2 (AEA modifier 2; LOD = 3.1), and Aem3 (AEA modifier 3; suggestive) to Chromosome 4 at 45.9 cM in linkage with D4Mit58, Chromosome 7 at 27.8 cM - 37.0 cM in linkage with D7Mit30, and Chromosome 10 at 41.5 cM in linkage with D10Mit42, respectively. Although Aem3 did not reach QTL statistical significance, this locus appears to have an additive affect in the presence of Aem2. Aem1, mapped to Chromosome 4 in a previous study, was not detected in this genome scan.
Analysis Tools