Amygdalar expression of the microRNA miR‐101a and its target Ezh2 contribute to rodent anxiety‐like behaviour

A greater understanding of neural mechanisms contributing to anxiety is needed in order to develop better therapeutic interventions. The current study interrogates a novel molecular mechanism that shapes anxiety-like behavior, demonstrating that the microRNA miR-101a-3p and its target, enhancer of zeste homolog 2 (Ezh2) in the amygdala, contribute to rodent anxiety-like behavior. We utilized rats that were selectively-bred for differences in emotionality and stress reactivity, showing that high novelty responding (HR) rats, which display low trait anxiety, have lower miR-101a-3p levels in the amygdala compared to low novelty responding (LR) rats that characteristically display high trait anxiety. To determine if there is a causal relationship between amygdalar miR-101a-3p and anxiety behavior, we used a viral approach to over-express miR-101a-3p in the amygdala of HR rats and test whether it would increase their typically low levels of anxiety-like behavior. We found that increasing miR-101a-3p in the amygdala increased HRs’ anxiety-like behavior in the open field test and elevated plus maze. Viral-mediated miR-101a-3p over-expression also reduced expression of the histone methyltransferase Ezh2, which mediates gene silencing via tri-methylation of histone 3 at lysine 27 (H3K27me3). Knockdown of Ezh2 with short-interfering RNA (siRNA) also increased HRs’ anxiety-like behavior, but to a lesser degree than miR-101a-3p over-expression. Overall our data demonstrate that increasing miR-101a-3p expression in the amygdala increases anxiety-like behavior and that this effect is at least partially mediated via repression of Ezh2. This work adds to the growing body of evidence implicating miRNAs and epigenetic regulation as molecular mediators of anxiety behavior. This article is protected by copyright. All rights reserved.