Remote memory and cortical synaptic plasticity require neuronal CCCTC-binding factor (CTCF), a central organizer of 3D chromatin architecture

Molecular mechanism of long-term memory has been extensively studied in the context of hippocampus-dependent recent memory examined within several days; however, months-old remote memory maintained in the cortex for long-term has not much been investigated at molecular levels yet. Various epigenetic mechanisms are known to be important for long-term memory, but how 3D chromatin architecture and its regulator molecules contribute to neuronal plasticity and memory consolidation are still largely unknown. To assess memory upon perturbation of 3D chromatin structure, we chose CCCTC-binding factor (CTCF), a seven-zinc finger protein well known for its role as a transcription factor and a chromatin regulator, and created the conditional knockout (cKO) mice, in which CTCF is lost in neurons during adulthood. Our CTCF cKO mice showed normal recent memory in contextual fear conditioning and spatial water maze task. However, they showed remarkable impairments in remote memory in both tasks. Underlying the remote memory-specific phenotypes, we found that loss of CTCF disrupts cortical long-term potentiation (LTP) but not hippocampal LTP. Through RNA-sequencing, we found that CTCF KD cultured cortical neurons have altered the expression of hundreds of genes, some of which we uncovered to be regulated by neuronal activity. These results suggest that remote memory storage in the cortex requires CTCF-mediated chromatin regulation in neurons while recent memory formation in the hippocampus does not. Primary mouse cortical culture with CTCF knockdown(experimental group) and lacZ knockdown(control group) using adeno-associated virus. Gene expression profile of shCTCF and shLAC were compared