PTGER4 and cyst: However, our data provide compelling evidence (e.g., cilia‐bPAC but not cyto‐bPAC activation induced cyst formation, EP4 localizes predominantly to the cilium, and PGE2‐induced cyst formation is fully abolished under EP4 blockade) that PGE2‐dependent cyst formation predominantly relies on ciliary cAMP signaling.