Figure 6.

Increases in histone H3 trimethylation correlate with altered DNA methylation (Zif268 promoter) after fear conditioning. A, Top, Methylation sites within CpG island 1 region of the Zif268 promoter. Sequencing primer pair positions are indicated by the left and right arrows. Methylation levels at the Zif268 promoter increased in area CA1 of hippocampus 30 min following fear conditioning (context plus shock) relative to context exposure (context) or naive animals (2-way ANOVA with Bonferroni's post hoc test; significant effect of behavior condition (F = 18.51, p < 0.0001, n = 4–8/group). B, Average percentage of DNA methylation across the Zif268 promoter (CpG island 1) in area CA1 of hippocampus after fear conditioning (context plus shock) compared with context exposure (context) or naive animals. ***p < 0.001 compared with naive controls. C, Although surprising, after training Zif268 gene expression remained significantly elevated with increased DNA methylation (context plus shock) (1-sample t test, t₍₅₎ = 3.238, p = 0.023, n = 3–6/group). *p < 0.05 compared with naive controls. Error bars are SEM.