We performed immunohistochemistry staining of paraffin‐embedded kidney sections from two separate mouse models of cystic kidney disease (pcy/pcy and RC/RC mice), along with mice with global OPN deletion (Spp1−/− mice; negative control) and wild‐type controls to determine how the localization of OPN expression in the kidney is altered in cystic kidney disease (Figure 1a–d). This evidence concerns the gene SPP1 and cystic kidney disease.