ADAMTS9 and ADAMTS20 are necessary for formation of the primary cilium (11), a cellular organelle of postmitotic cells that transmits signaling by hedgehog proteins and other morphogens, and recessive ADAMTS9 mutations were found in the human ciliopathies nephronophthisis and Joubert syndrome (24, 25). Here, ADAMTS9 is linked to nephronophthisis.