To confirm that the observed anemia in the Wt1+/R394W mice was of a purely hematologic etiology and not due to renal disease, we measured erythropoietin levels in these mice and did not observe a difference when comparing wild type and Wt1+/R394W mice, but did observe an appropriate increase in erythropoietin in anemic mice, regardless of genotype (Supplementary Figure 1). This evidence concerns the gene WT1 and anemia.