Identification and Characterization of the V(D)J Recombination Activating Gene 1 in Long-Term Memory of Context Fear Conditioning

Abstract

An increasing body of evidence suggests that mechanisms related to the introduction and repair of DNA double strand breaks (DSBs) may be associated with long-term memory (LTM) processes. Previous studies from our group suggested that factors known to function in DNA recombination/repair machineries, such as DNA ligases, polymerases, and DNA endonucleases, play a role in LTM. Here we report data using C57BL/6 mice showing that the V(D)J recombination-activating gene 1 (RAG1), which encodes a factor that introduces DSBs in immunoglobulin and T-cell receptor genes, is induced in the amygdala, but not in the hippocampus, after context fear conditioning. Amygdalar induction of RAG1 mRNA, measured by real-time PCR, was not observed in context-only or shock-only controls, suggesting that the context fear conditioning response is related to associative learning processes. Furthermore, double immunofluorescence studies demonstrated the neuronal localization of RAG1 protein in amygdalar sections prepared after perfusion and fixation. In functional studies, intra-amygdalar injections of RAG1 gapmer antisense oligonucleotides, given 1 h prior to conditioning, resulted in amygdalar knockdown of RAG1 mRNA and a significant impairment in LTM, tested 24 h after training. Overall, these findings suggest that the V(D)J recombination-activating gene 1, RAG1, may play a role in LTM consolidation.

The Role of DNA Damage in Neural Plasticity in Physiology and Neurodegeneration

“…Furthermore, knock down of RAG1 using antisense oligonucleotides significantly impaired LTM. This study, therefore, implies the existence of a link between RAG1 and DSBs with associative learning processes and in the consolidation of LTMs (Castro-Perez et al, 2016 ).…”

“…LTM requires the establishment, maintenance, and rearrangement of specific neural networks, within specific brain areas involved in learning and memory. This was recently shown to involve recombination-activating genes (RAGs) that encode components of the protein complex that mediates the rearrangement and recombination of genes of the adaptive immune system (Castro-Perez et al, 2016 ). V(D)J recombination is a somatic process that occurs in developing lymphocytes during the early stages of T and B cell maturation.…”

“…This is a tightly regulated process involving the generation of DNA DSBs, and activation of DNA ligases and DNA repair proteins for re-joining the new gene segments. Expression of RAG1 was induced in the amygdala of C57BL/6 mice after context fear conditioning, but not after context-only or shock-only conditioning (Castro-Perez et al, 2016 ). Furthermore, knock down of RAG1 using antisense oligonucleotides significantly impaired LTM.…”

Therapeutic effects of stress-programmed lymphocytes transferred to chronically stressed mice

“…Although both Rag1 and Rag2 proteins are required for lymphocyte maturation (McBlane et al, 1995), and therefore knockout of either gene is sufficient for lymphocyte depletion, we did not use the Rag 1 −/− mouse for study because the Rag1 gene but not the Rag2 gene is expressed in the brain, strongly in the hippocampus (Chun et al, 1991), which may lead to altered cognitive behavior in this mouse (Castro-Pérez et al, 2016, Cushman et al, 2003, McGowan et al, 2011, Rattazzi, Piras, 2013). The Rag1 −/− mouse also shows reduced adult hippocampal neurogenesis compared to wildtype (Huang et al, 2010, Wolf, Steiner, 2009).…”