Phosphoinositides,a family of phosphorylated derivatives of phosphatidylinositol (PI),are tightly regulated both temporally and spatially by PI phosphatases and kinases.Mutations in inositol polyphosphate 5-phosphatase E (INPP5E) cause Joubert syndrome,a human disorder associated with numerous ciliopathic defects,including renal cyst formation,linking phosphoinositides to ciliopathies.