In our experiments, while heterozygous Pkd1+/- cells mostly behaved like WT PCT cells in 2D or 3D (not shown), homozygous PCT Pkd1-/- cells, lacking the functional Pkd1 gene on both chromosomes, exhibited hallmarks characteristic for ADPKD, including an increased proliferation rate (∼1.8-fold, Supplementary Figure 4) (Wei et al., 2008) and an increased extrusion in confluent cultures (not shown). Here, PKD1 is linked to autosomal dominant polycystic kidney disease.