PKD2 and polycystic kidney disease: To investigate whether the two-cilia phenotype is observed in other conditions, we chose to investigate cilia in mouse primary brain ECs from polycystic kidney disease (Pkd2) knockout mouse, a ciliopathic condition associated with an abnormal primary ciliary function that causes phenotype of polyploidy and a defective cell cycle (AbouAlaiwi et al., 2011).