Emerging role of N6-methyladenosine (m6A) epitranscriptomic changes in adult anxiety after adolescent alcohol exposure

Adolescent intermittent ethanol (AIE) exposure affects multiple brain regions by producing long-lasting effects on epigenetic mechanisms and behavioral phenotypes later in life. Recently, it has been shown that epigenetic switches can control epitranscriptomics, or RNA modifications. Specifically, the most abundant RNA modification, known as N6-methyladenosine (m6A), has been the subject of intense investigation in brain plasticity; however, little is known about its role in adult psychopathology after AIE. Herein, we investigated whether changes in m6A modifiers (writers, erasers, and readers) after AIE regulate phenotypes of anxiety in adulthood using an animal model. We characterized m6A regulators in the amygdala, hippocampus, medial prefrontal cortex, and the nucleus accumbens of rats after AIE in adolescence and adulthood. AIE induces differential gene expression of m6A modifiers, with some brain regions being more affected during adolescence, while other limbic brain regions show long-lasting changes in adulthood. We observed that Mettl3 mRNA levels were significantly increased in the amygdala and medial prefrontal cortex in adulthood after AIE, as measured by real-time polymerase chain reaction. We further evaluated changes in METTL3 expression and global m6A methylation in amygdala nuclei using a histochemical procedure. Indeed, protein and mRNA levels of METTL3, as well as m6A levels, were upregulated in the central and medial nucleus of the amygdala after AIE in adulthood. We pharmacologically inhibited METTL3 activity using STM2457, which significantly attenuated AIE-induced anxiety-like behaviors in adulthood. These results suggest that m6A epitranscriptomics can serve as a novel avenue in the exploration of therapeutics for AIE-induced adult psychopathology.