PROJECT SUMMARY There is a growing appreciation that a father’s preconception stress, diet, or drug use can directly affect the development of his children via epigenetic mechanisms in the germline. Accordingly, recent findings from our lab revealed that parental (mother and father) exposure to 9-tetrahydrocannabinol (THC) increased drug- seeking behavior in male offspring. Suggesting a significant role for the father, I found that THC significantly alters an epigenetic mechanism in sperm known to play a causal role in heritable neurobehavioral phenotypes. Given the progressive legalization of recreational cannabis use, it is imperative that the associated reproductive and intergenerational health risks become better defined. Therefore, I will examine the heritable epigenetic effects of paternal THC exposure on the sperm, developing embryo, and fetal brain. In Aim 1, I will examine the effects of THC on sperm small noncoding RNAs across three translationally- relevant doses. Subsequently, in Aim 2a, I will characterize the effects of paternal THC exposure on gene expression in the early embryo. Moreover, Aim 2b will follow-up on preliminary experiments showing that a low dose THC exposure reduces sperm-borne microRNA-34c by examining the effects of microRNA-34c inhibition on early embryonic gene expression programming. Finally, in Aim 3, I will determine the heritable epigenetic effects of paternal THC exposure on prenatal neurodevelopment by examining genome-wide chromatin accessibility in embryonic striatal neurons. This project represents an important advancement in our understanding of the intergenerational effects of THC exposure, aiming to identify novel mechanisms of epigenetic inheritance through the male germline. The findings will help determine potential health risks associated with the cannabis use of fathers-to-be.