PTCH1 and glioma: In humans, the Hh pathway has several main components: (1) three Hh homologs, (2) Patched1 (PTCH1 in humans, Ptch1 in mice, and Ptc in Drosophila), (3) a G-protein-coupled receptor (GPCR)-like receptor Smoothened (SMO in humans and Smo in mice/Drosophila), and (4) three transcription factors (GLI1, GLI2, and GLI3) named from the correlation of GLI1 and glioma [25].