An important component of Hh signalling required for the release of cholesterol-modified Hh from producing cells is Disp; a 12-span transmembrane protein with a sterol sensing domain (SSD) similar to that of Ptc and proteins involved in sterol homeostasis and transport such as Niemann-Pick disease, type C1 (NPC1) and Sterol regulatory element binding protein cleavage activating protein (SCAP) [105,106]. Here, SCAP is linked to Niemann-Pick disease.