C. elegans patched-3 is an essential gene implicated in osmoregulation and requiring an intact permease transporter domain

► C. elegans lacks conventional Hedgehog signalling, yet ptc-3 is an essential gene. ► Deletion of ptc-3 causes a lethal defect in osmoregulation. ► ptc-3 epidermal expression is necessary and sufficient for viability. ► An intact sterol sensing domain is dispensable for ptc-3 activity. ► Missense mutations highlight the importance of the ptc-3 transporter domain.