RAR-β occupies a novel RARE on the Lingo-1 promoter and represses Lingo-1 expression. (A) Real-time RT-PCR gene expression analysis of Lingo-1 in wild-type CGNs transfected with RAR-β2 plated on myelin versus PDL with vehicle or RA. RA represses Lingo-1 gene expression with a similar pattern to that observed with both RA and RAR-β2, whereas RAR-β2 alone has a more modest repression. (B) Real-time RT-PCR gene expression analysis of Lingo-1 in RAR-β^−/− CGNs transfected with RAR-β2 plated on myelin versus PDL revealed a rescue of Lingo-1 inhibition and was further inhibited in combination with RA. (A and B) The dashed lines represent the level of no change (onefold). (C) A diagram of two newly discovered RAREs (bold letters) in the Lingo-1 promoter. Small arrows indicate primer sets used for ChIP assays. (D) A ChIP assay shows a significant decrease in the occupancy of the Lingo-1 RARE1 by RAR-β on myelin in comparison with PDL in wild-type (WT) CGNs and a significant increase in occupancy with RA on myelin versus myelin with vehicle. (E) A ChIP assay shows no significant change in the occupancy of either the Lingo-1 RAREs by RXR on myelin in comparison with PDL or with RA treatment on myelin in wild-type CGNs. Unpaired two-tailed t test: *, P < 0.05; ***, P < 0.001. (F) A diagram of the Lingo-1 luciferase construct. CMV, cytomegalovirus. (G) Transfection of SH-SY5Y cells with RAR-β2 in combination with the Lingo-1 promoter or mutant Lingo-1 promoter luciferase expression plasmid with or without RA (24 h) revealed an increase in both luciferase expression plasmids on myelin versus PDL, but only the Lingo-1 promoter luciferase expression plasmid was attenuated by RA treatment (n = 3). RLU, relative light unit. One-way ANOVA Bonferroni posttests: *, P < 0.05; ***, P < 0.001. Data are plotted as the mean ± SEM.