RAC1 and cystic kidney disease: Rac1 suppression at the apical membrane is considered essential for the maintenance of the renal cyst structure, as during the acquisition of cell polarity in Madin–Darby canine kidney (MDCK) cells, Rac1 activity is reportedly homogenous across the plasma membrane in early cystogenesis stages, however, is higher at the lateral membrane than the apical plasma membrane in later stages [35].