PTCH1 and cerebellar neoplasm: Finally, no significant differences were observed for the main downstream Shh-responsive genes, namely, Gli1, Gli2, Ptch1, and N-Myc, in Ptch1+/−/Btg1KO MBs relative to Ptch1+/−/Btg1WT MBs (data not shown), indicating that the deletion of Btg1 does not interfere with Shh signaling in cerebellar tumors.