Long non-coding enhancer RNA controls stress-induced changes in reward-related behaviors

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Project Summary/Abstract Chronic stress alters reward-related behavior and this is accompanied by changes in neural circuit function, especially that involving the medial prefrontal cortex (mPFC). However, the molecular mechanisms controlling circuit dysfunction and its effect on associated behaviors remain poorly understood. The Npas4 gene encodes the Neuronal PAS domain protein 4 (NPAS4) transcription factor that functions as a homeostatic regulator of excitatory and inhibitory synaptic connections in response to changes in synaptic activity. Our preliminary findings in mice show that aversive stress experience trigger the transient induction of NPAS4 expression in mPFC and that this is required for chronic social defeat stress (CSDS)-induced reward-related behavior deficit. Furthermore, these studies show that NPAS4 is required for CSDS-induced reduction of mPFC pyramidal neuron excitatory transmission and dendritic spine density. Interestingly, while protein-coding genes (mRNA) are obviously important for functional regulation of brain activity, human and rodent genomes encode a much larger number of long non-coding RNAs (lncRNAs). Emerging evidence demonstrates significant roles for lncRNAs in gene expression, but the physiological and pathological functions of individual lncRNAs are only beginning to be explored. To address this knowledge gap, we will study a novel, non-annotated, lnc-enhancer RNA (lnc-eRNA) transcribed from the enhancer region of Npas4 (Npas4eRNA). We found that Npas4eRNA is required for Npas4mRNA expression and for CSDS-induced deficits in sucrose preference. Npas4eRNA forms an DNA:RNA hybrid R-loop structure that is required for Npas4mRNA expression. We hypothesize that the Npas4eRNA and its R-loop structure directly link the enhancer-associated transcriptional machinery with the Npas4 transcription start site via 3D chromatin loop structure. In this proposal, we will combine innovative molecular and cellular approaches with ethologically relevant models of psychosocial and psychological stressors in both male and female mice and examine the function of Npas4eRNA and R-loop in the PFC for the stress-induced epigenetic gene regulation, functional and morphological synaptic plasticity, and alterations in reward-related behaviors.