Figure 1 depicts double immunofluorescence labeling with H+-ATPase and AQP-2 in kidney cysts of mice with principal cell inactivation of Tsc1 (top panel), kidney-specific inactivation of Pkd1 (middle panel), and Tsc2 haploinsufficiency (Tsc2+/−). The gene discussed is TSC2; the disease is Kidney Cyst.