Mice and phenotype characterization

All protocols were approved by the Brigham and Women’s and the Seattle Children’s Research Institute Animal Care and Use Committees. The Brigham and Women’s and the Seattle Children’s Research Institute are fully accredited by the American Association of the Accreditation of Laboratory Animal Care. B6 jck/+ and jck/jck mice are maintained in our mouse colony. The lines we designated as “P”, “M-C” and “M-A” were obtained from Iakoubova and West, and correspond to the lines they designated as BDChr4P, BDChr4M, and BDVhr4D, respectively (Iakoubova et al. 2001). To test these congenic lines, female B6 jck/+ mice were crossed with males of the imported strains and jck/+ progeny were identified by genotyping for the mutation. These were intercrossed and homozygotes identified by genotype analysis. These were sacrificed at 7 weeks of age and scored for the presence of abnormal kidneys, which were removed, weighed, and fixed.

We obtained 15 homozygous mice from Line P, 13 from line M-C, and 11 from line M-A. Given these modest numbers, we elected to analyze the combined cohort. All homozygous mice were typed for 10 microsatellite markers distributed along Chr 4 (Fig. 2).

For high resolution analysis we employed a two-step strategy whereby we generated three separate jck/+ lines that were homozygous for a sub-congenic region defined by analysis of 21 SNP markers on Chr 4 (Fig. 3), and intercrossed these. Thus all tested mice were homozygous for the sub-congenic region. Progeny homozygous for jck were identified by genotype analysis, and kidneys assessed as described above. The numbers of mice analyzed, separated by gender, is shown in Fig. 3.