Fig. 6: Graphical summary of the contribution of epigenetic mechanisms to hippocampal engram stability.

Reinforcing DNA methylation-related mechanisms through Dnmt3a2 overexpression within memory encoding DG neuronal ensembles (engram) during consolidation was sufficient to strengthen contextual fear memory and engram stability. This manipulation improved the reactivation of the encoding ensembles upon memory retrieval without altering the size of the neuronal population activated by recall. Whereas reinforcing DNA methylation-related mechanisms by overexpression of Dnmt3a2 in a similarly sized, but random subset of DG neurons (non-engram) during the consolidation window did not alter memory strength. Spheres represent DG neurons. Red color gradient in Me-labeled spheres represent the magnitude of DNA methylation-related changes. Me: DNA methylation-related changes.