a Normally, STIL binds SUFU, releases SUFU’s suppression on GLI1, then GLI1 can be translocated to the nucleus for gene transcription. b When STIL is mutated, Shh down-stream signaling transduction cannot be completed because the SUFU-GLI1 heterodimers cannot enter the nucleus for gene transcription. (Modified from reference¹⁵)

a, b Wild-type retinas that received sham or sub-toxic 6-OHDA treatment. No differences in the number of DA cells were observed. c, d Mutant retinas that received sham or sub-toxic 6-OHDA treatment. The number of DA cells was decreased after drug treatment. e, f Wild-type and mutant retinas that received sub-toxic 6-OHDA injections, but previously treated with Stil- and Sufu-specific MOs, respectively. Note the increase of drug susceptibility (decreases in cell survival) in wild-type fish and the decrease of drug susceptibility (increases in cell survival) in mutant fish. Scale bar, 100 μm. (Modified from reference¹⁷)

a, b Sections from wild-type and nbb retinas. Note the decrease of PCNA labeling in the mutant. c A section from cyclopamine-treated wild-type fish. Note the decrease in the number of PCNA-positive cells. d A section from nbb fish that received Sufu-MO injection. Note the increase in the number of PCNA-positive cells. Scale bar, 100 μm. (Modified from reference³²)

The rate of survival under control conditions (treated with vehicle solution) is normalized to 100%. a, b Percentage of cell survival after 6-OHDA treatment in proliferating cells. Note the increase of drug susceptibility after the overexpression of Stil (red circle). c, d Percentage of cell survival after 6-OHDA treatment in mature cells. Note the increase of drug susceptibility when the expression Stil is down regulated (red circle). Asterisks indicate statistical differences, p < 0.05; ns, not significant (Modified from reference⁵⁶)