PTCHassociateswiththesmoothenedprotein(SMO)totransducethehedgehogsproteinssignal.PTCHhasatumorsuppressorfunction,asinactivationofthisproteinisprobablyanecessary,ifnotsufficientstepfortumorigenesis.PTCHisexpressedintheadultbrain,lung,liver,heart,placenta,skeletalmuscle,pancreasandkidney.Itisalsoexpressedintumorcellsbutnotinnormalskin.DuringdevelopmentPTCHisfoundinallmajortargettissuesofsonichedgehog,suchastheventralneuraltube,somites,andtissuessurroundingthezoneofpolarizingactivityofthelimbbud.