Exposure to Extrinsic Stressors, Social Defeat or Bisphenol A, Eliminates Sex Differences in DNA methyltransferase expression in the Amygdala

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Chemical and psychological stressors can exert long lasting changes in brain function and behavior. Changes in DNA methylation have been shown to be an important mechanism mediating long lasting changes in neural function and behavior, especially for anxiety-like or stress responses. Here we examined the effects of either a social or chemical stressor on DNA methyltransferase (DNMT) gene expression in the amygdala, an important brain region modulating stress responses and anxiety. In adult California mice (Peromyscus californicus) that were naïve to social defeat, females had higher levels of Dnmt1 expression in punch samples of the central amygdala (CeA) than males. In addition, social defeat stress reduced Dnmt1 and Dnmt3a expression in the CeA of females but not males. A second study using more anatomically specific punch samples replicated these effects for Dnmt1. Perinatal exposure, spanning from periconception through lactation, to bisphenol A or ethinyl estradiol (estrogens in birth control pills) also abolished sex differences in Dnmt1 expression in the CeA but not basolateral amygdala. These findings identify a robust sex difference in Dnmt1 expression in the CeA that is sensitive to both psychological and chemical stressors. Our results suggest that future studies should examine the impact of psychological and chemical stressors on DNA methylation in the CeA and that Dnmt1 may have an underappreciated role in plasticity in behavior.