A 3:1 stoichiometry between PKD2 and MST3:SIP would explain why each PKD channel is only associated with a single mastigoneme.16 It would also match the stoichiometry observed for the human PKD1-PKD2 channel, 49,50 mutations in which are a major cause of autosomal dominant polycystic kidney disease. The gene discussed is PKD2; the disease is autosomal dominant polycystic kidney disease.