Histone Arginine Methylation Regulates Neuropeptide Y Expression in the Basolateral Amygdala to Promote Reward-Seeking Behaviour

The basolateral amygdala (BLA) serves in the evaluation of reward. However, the causal molecular substrates in the BLA necessary for reward seeking behaviour are largely unknown. Reward conditioning induces long-lasting changes in epienzymes in limbic areas, including the amygdala. The current study probed the role of histone arginine methylation as a novel epigenetic mechanism in neuropeptide Y (NPY) gene regulation in the BLA during reward and reinforcement. For reward conditioning, adult Wistar rats were trained to self-administer sucrose pellets in a nose-poke operant chamber. Reward conditioning increased protein arginine methyltransferase 4 (PRMT4) and NPY in the BLA. Moreover, after operant conditioning, histone arginine methylation (H3R17me2a) and PRMT4 occupancy at the NPY promoter were heightened. PRMT4 was predominantly colocalised in the nucleus of the NPY-expressing cells in the BLA. Intra-BLA administration of specific siRNA or inhibitor of PRMT4 after conditioning waned the nose-poke activity, which was further reinstated during the subsequent 5 days. These effects of PRMT4 repression were correlated with the NPY expression and H3R17me2a levels at the NPY promoter. Furthermore, NPY peptide administration after PRMT4 siRNA or inhibitor infusion in BLA restored the nose-poke activity. PRMT4 is known to interact with CREB-binding protein (CBP). Therefore, co-occupancy of PRMT4 and CBP resulted in heightened histone acetylation (H3K14ac) in the conditioned rats. The current study suggests a pivotal role of PRMT4-mediated histone arginine methylation in NPY gene expression in the amygdala necessary for the reward-seeking behaviour.