Fig. 7. Model of Hh movement. The orange arrow indicates that Disp releases Hh proteins from the cell membrane of the Hh-producing cells. The purple arrow indicates that glypicans can present Hh to Ptc. The thin black arrows at the top of this diagram indicate the displacement of Hh from one GAG chain to another GAG chain. The double-headed arrow indicates the lateral movement of glypicans on cell membrane.