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Here, we used RNA capture-seq to identify a large population of lncRNAs that are expressed in the infralimbic prefrontal cortex of adult male mice in response to fear-related learning. Combining these data with cell-type-specific ATAC-seq on neurons that had been selectively activated by fear extinction learning, we find inducible 434 lncRNAs that are derived from enhancer regions in the vicinity of protein-coding genes. In particular, we discover an experience-induced lncRNA we call ADRAM (activity-dependent lncRNA associated with memory) that acts as both a scaffold and a combinatorial guide to recruit the brain-enriched chaperone protein 14-3-3 to the promoter of the memory-associated immediate-early gene Nr4a2 and is required fear extinction memory. This study expands the lexicon of experience-dependent lncRNA activity in the brain and highlights enhancer-derived RNAs (eRNAs) as key players in the epigenomic regulation of gene expression associated with the formation of fear extinction memory.

DNA modification is known to regulate experience-dependent gene expression. However, beyond cytosine methylation and its oxidated derivatives, very little is known about the functional importance of chemical modifications on other nucleobases in the brain. Here we report that in adult mice trained in fear extinction, the DNA modification N6-methyl-2'-deoxyadenosine (m6dA) accumulates along promoters and coding sequences in activated prefrontal cortical neurons. The deposition of m6dA is associated with increased genome-wide occupancy of the mammalian m6dA methyltransferase, N6amt1, and this correlates with extinction-induced gene expression. The accumulation of m6dA is associated with transcriptional activation at the brain-derived neurotrophic factor (Bdnf) P4 promoter, which is required for Bdnf exon IV messenger RNA expression and for the extinction of conditioned fear. These results expand the scope of DNA modifications in the adult brain and highlight changes in m6dA as an epigenetic mechanism associated with activity-induced gene expression and the formation of fear extinction memory.

The RNA modification N6 -methyladenosine (m6 A) regulates the interaction between RNA and various RNA binding proteins within the nucleus and other subcellular compartments and has recently been shown to be involved in experience-dependent plasticity, learning, and memory. Using m6 A RNA-sequencing, we have discovered a distinct population of learning-related m6 A- modified RNAs at the synapse, which includes the long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 (Malat1). RNA immunoprecipitation and mass spectrometry revealed 12 new synapse-specific learning-induced m6 A readers in the mPFC of male C57/BL6 mice, with m6 A-modified Malat1 binding to a subset of these, including CYFIP2 and DPYSL2. In addition, a cell type- and synapse-specific, and state-dependent, reduction of m6 A on Malat1 impairs fear-extinction memory; an effect that likely occurs through a disruption in the interaction between Malat1 and DPYSL2 and an associated decrease in dendritic spine formation. These findings high-light the critical role of m6 A in regulating the functional state of RNA during the consolidation of fear-extinction memory, and expand the repertoire of experience-dependent m6 A readers in the synaptic compartment. [ABSTRACT FROM AUTHOR]

We have identified a member of the growth arrest and DNA damage (Gadd45) protein family, Gadd45y, which is known to be critically involved in DNA repair, as a key player in the regulation of immediate early gene (IEG) expression underlying the consolidation of associative fear memory in adult male C57BL/6 mice. Gadd45y temporally influences learning-induced IEG expression in the prelimbic prefrontal cortex (PLPFC) through its interaction with DNA double-strand break (DSB)-mediated changes in DNA methylation. Our findings suggest a two-hit model of experience-dependent IEG activity and learning that comprises (1) a first wave of IEG expression governed by DSBs and followed by a rapid increase in DNA methylation, and (2) a second wave of IEG expression associated with the recruitment of Gadd45y and active DNA demethylation at the same site, which is necessary for memory consolidation. [ABSTRACT FROM AUTHOR]

The RNA modification N 6 -methyladenosine (m 6 A) regulates the interaction between RNA and various RNA binding proteins within the nucleus and other subcellular compartments and has recently been shown to be involved in experience-dependent plasticity, learning, and memory. Using m 6 A RNA-sequencing, we have discovered a distinct population of learning-related m 6 A- modified RNAs at the synapse, which includes the long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 ( Malat1 ). RNA immunoprecipitation and mass spectrometry revealed 12 new synapse-specific learning-induced m 6 A readers in the mPFC of male C57/BL6 mice, with m 6 A-modified Malat1 binding to a subset of these, including CYFIP2 and DPYSL2. In addition, a cell type- and synapse-specific, and state-dependent, reduction of m 6 A on Malat1 impairs fear-extinction memory; an effect that likely occurs through a disruption in the interaction between Malat1 and DPYSL2 and an associated decrease in dendritic spine formation. These findings highlight the critical role of m 6 A in regulating the functional state of RNA during the consolidation of fear-extinction memory, and expand the repertoire of experience-dependent m 6 A readers in the synaptic compartment. SIGNIFICANCE STATEMENT We have discovered that learning-induced m 6 A-modified RNA (including the long noncoding RNA, Malat1 ) accumulates in the synaptic compartment. We have identified several new m 6 A readers that are associated with fear extinction learning and demonstrate a causal relationship between m 6 A-modified Malat1 and the formation of fear-extinction memory. These findings highlight the role of m 6 A in regulating the functional state of an RNA during memory formation and expand the repertoire of experience-dependent m 6 A readers in the synaptic compartment., (Copyright © 2023 the authors.)

A major challenge in neurobiology in the 21st century is to understand how the brain adapts with experience. Activity-dependent gene expression is integral to the synaptic plasticity underlying learning and memory; however, this process cannot be explained by a simple linear trajectory of transcription to translation within a specific neuronal population. Many other regulatory mechanisms can influence RNA metabolism and the capacity of neurons to adapt. In particular, the RNA modification N 6 -methyladenosine (m 6 A) has recently been shown to regulate RNA processing through alternative splicing, RNA stability, and translation. Here, we discuss the emerging idea that m 6 A could also coordinate the transport, localization, and local translation of key mRNAs in learning and memory and expand on the notion of dynamic functional RNA states in the brain., (Crown Copyright © 2020. Published by Elsevier Ltd. All rights reserved.)

We have identified a member of the growth arrest and DNA damage (Gadd45) protein family, Gadd45γ, which is known to be critically involved in DNA repair, as a key player in the regulation of immediate early gene (IEG) expression underlying the consolidation of associative fear memory in adult male C57BL/6 mice. Gadd45γ temporally influences learning-induced IEG expression in the prelimbic prefrontal cortex (PLPFC) through its interaction with DNA double-strand break (DSB)-mediated changes in DNA methylation. Our findings suggest a two-hit model of experience-dependent IEG activity and learning that comprises (1) a first wave of IEG expression governed by DSBs and followed by a rapid increase in DNA methylation, and (2) a second wave of IEG expression associated with the recruitment of Gadd45γ and active DNA demethylation at the same site, which is necessary for memory consolidation. SIGNIFICANCE STATEMENT How does the pattern of immediate early gene transcription in the brain relate to the storage and accession of information, and what controls these patterns? This paper explores how Gadd45γ, a gene that is known to be involved with DNA modification and repair, regulates the temporal coding of IEGs underlying associative learning and memory. We reveal that, during fear learning, Gadd45γ serves to act as a coordinator of IEG expression and subsequent memory consolidation by directing temporally specific changes in active DNA demethylation at the promoter of plasticity-related IEGs., (Copyright © 2019 the authors 0270-6474/19/390970-14$15.00/0.)