PROJECT SUMMARY Marijuana is now the most commonly used illicit drug in pregnancy. The main psychoactive compound of marijuana, delta-9-tetrahydrocannabinol (THC), can access and bind to cannabinoid receptors in the placenta and fetal brain. Preliminary data suggest that prenatal cannabinoid exposure results in epigenetic changes in the placenta and brains of exposed offspring. This is concerning because the placenta plays a key role in fetal growth and development by mediating fetal nutrition, oxygenation, inflammatory signaling, and transmission of maternal environmental exposures. Compromises to placental function can adversely affect brain development. Epigenetic responses to maternal marijuana use likely result in molecular alterations in gene regulation of offspring developmental trajectories towards neurodevelopmental morbidity, including addiction, autism spectrum disorder, attention deficit hyperactivity disorder, and cognitive disabilities. Specifically, prenatal THC exposure is known to alter reward processing, by histone modification of ventral striatal dopaminergic signaling, affecting addiction vulnerability. However, a mechanistic link between maternal THC use and its impact on offspring epigenetic regulation of neurodevelopment is impeded by the lack of in vivo longitudinal assessment secondary to the limitations of current imaging capabilities and feasibility of tissue sampling. We propose to address this problem by defining a trajectory of perturbed epigenetic regulation following in utero THC exposure across fetal and early childhood brain and behavioral development. To this end, we will employ three innovative and complementary approaches using our novel, non-human primate model of chronic maternal THC use: 1) first-in-kind, longitudinal in vivo imaging of placental and fetal epigenetic regulation and development, 2) extensive postnatal assessment of infant cognition and behavior, and 3) sophisticated tissue studies confirming the role of epigenetic modifications in the imaging and behavioral studies. In summary, our study will interrogate the previously inaccessible mechanistic links underlying the impact of maternal marijuana use on fetal origins of health, disease and addiction risk. The successful completion of our study will result in 1) new insights into the impact of maternal THC use on the developing fetal and infant brain, 2) the impact of THC-induced epigenetic alterations on trajectories of offspring neurodevelopment and behavioral regulation 3) the creation of a comprehensive, longitudinal in vivo map of offspring epigenetic regulation of neurodevelopment from fetal life to early childhood, and 4) characterization of ex vivo epigenetic and transcriptomic assessments that can be used as a reference for other drugs of abuse and environmental exposures. This study has the potential for immediate translational impact, given the high prevalence of prenatal and postnatal marijuana use and limited data on longer-term off...