The structurally related KCa3.1 inhibitor TRAM-34, effective in cultured cells (32, 50), also reduced cyst area of Pkd1–/– metanephroi by ~25%–30% at 20 and 40 μM (Figure 4, C and D, and Supplemental Figure 3). The gene discussed is KCNN4; the disease is cyst.