PROJECT SUMMARY/ABSTRACT Recent evidence suggests that paternal drug exposure can affect behavioral and physiological phenotypes in unexposed offspring. In support, preliminary data from my laboratory indicates enhanced contextual fear conditioning and changes in hippocampal functioning in the offspring of nicotine-exposed male mice. This presents a potentially serious issue related to interpretation of data derived from both human and animal populations for which parental nicotine exposure was not taken into account. ?Missing heritability? and discrepancies in heritability estimates between studies may be explained partially by variability in parental exposures. Characterization of mechanisms underlying this mode of inheritance, termed ?multigenerational epigenetic inheritance,? is essential in order to compensate for these effects in experimental design and begin to understand exposure-specific multigenerational consequences. Other models of paternal drug exposure have pointed to inheritance through germline sncRNA expression as a potential underlying mechanism of multigenerational inheritance. In order to identify pathways underlying multigenerational effects of nicotine exposure on contextual fear learning, I will sequence sncRNA derived from sperm of male mice exposed to nicotine (F0) and the hippocampus of their offspring (F1). This data will be analyzed alongside our existing F1 hippocampus DNA methylation and mRNA expression datasets to reveal relationships between sncRNA expression in sperm and pathways underlying expression of multigenerational phenotypes in offspring. The proposed work will provide foundational insight into nicotine?s multigenerational effects, enriching current understanding of addiction heritability.