Prenatal Δ9-Tetrahydrocannabinol Exposure in Males Leads to Motivational Disturbances Related to Striatal Epigenetic Dysregulation

Background Cannabis remains one of the most widely abused drugs during pregnancy. In utero exposure to its principal psychoactive component, Δ9-tetrahydrocannabinol (THC), can result in long-term neuropsychiatric risk for the progeny. The current study investigated epigenetic signatures underlying these enduring consequences. Methods Rat dams were exposed daily to THC (0.15mg/kg) during pregnancy and adult male offspring were examined for reward and depressive-like behavioral endophenotypes. Using unbiased sequencing approaches, we explored transcriptional and epigenetic profiles in the nucleus accumbens (NAc), a brain area central to reward and emotional processing. An in vitro CRISPRa model coupled with RNA-sequencing was also applied to study specific consequences of epigenetic dysregulation and altered molecular signatures were compared to human major depressive disorder (MDD) transcriptome datasets. Results Prenatal THC-exposure induced increased motivation for food, heightened learned helplessness and anhedonia, and altered stress sensitivity. We identified a robust increase specific to males in the expression of Histone-Lysine N-Methyltransferase 2A (Kmt2a) that targets lysine 4 on histone H3 (H3K4me) in cellular chromatin. Normalizing Kmt2a in the NAc restored the motivational phenotype of prenatally THC-exposed animals. Comparison of RNA and H3K4me3 sequencing datasets from the NAc of rat offspring with the in vitro model of Kmt2a upregulation revealed overlapping, significant disturbances in pathways that mediate synaptic plasticity. Similar epigenetic alterations were detected in human MDD. Conclusions These studies provide direct evidence for the persistent effects of prenatal cannabis exposure on transcriptional and epigenetic deviations in the NAc via Kmt2a dysregulation and associated psychiatric vulnerability.