Sustained CaMKII Delta Gene Expression Is Specifically Required for Long-Lasting Memories in Mice.

Although important information is available on the molecular mechanisms of long-term memory formation, little is known about the processes underlying memory persistence in the brain. Here, we report that persistent gene expression of CaMKIIδ isoform participates in object recognition long-lasting memory storage in mice hippocampus. We found that CaMKIIδ mRNA expression was sustained up to one week after training and paralleled memory retention. Antisense DNA infusion in the hippocampus during consolidation or even after consolidation impairs 7-day- but not 1-day-long memory, supporting a role of CaMKIIδ in memory persistence. CaMKIIδ gene expression was accompanied by long-lasting nucleosome occupancy changes at its promoter. This epigenetic mechanism is described for the first time in a memory process and offers a novel mechanism for persistent gene expression in neurons. CaMKIIδ protein is mainly present in nucleus and presynaptic terminals, suggesting a role in these subcellular compartments for memory persistence. All these results point to a key function of the sustained gene expression of this overlooked CaMKII isoform in long-lasting memories.