Substance use disorder (SUD) is a debilitating condition characterized by compulsive use of a substance, in spite of the subjective recognition of the drawbacks associated with its use. Chronic use of the substance leads to the development of withdrawal and dependence, hindering intentional controls over its use. Among all substances, opioids are among the ones that pose the greatest negative impact on our society. Animal and human studies have implicated several brain regions involved in opioid use disorder (OUD), in particular various components of the dopamine system. Major dopamine-containing neurons are clustered in regions of the midbrain called the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA). Classically, their activities correlate with valence, e.g., promoting approach behavior to rewarding stimuli. Upstream of them, two major circuits are involved: one including the nucleus accumbens projecting onto the VTA, and the other including the dorsal striatum projecting onto the SNc. The scope of this study is thus to conduct in-depth transcriptomics across the cells of these two circuits to dissect genes, pathways, and cell types mediating opioid action in the mouse brain. We will use these data to predict driver genes, regulatory regions, pathways, and cell types involved in the emergence of opioid addiction behaviors. Finally, to test the causal role of these predicted drivers, we will use opioid self-administration, a classical paradigm used in the field of addiction. By combining a rich set of behavioral protocols with state-of-the-art transcriptomics, epigenomics, and computational data analysis, we aim to obtain multi-modal data with an unprecedented level of single-cell resolution for identifying genes, pathways, and cell types affected in mouse models of OUD.

Opioid Use Disorder (OUD) is a debilitating condition for which we have an incomplete knowledge of pathobiological processes. A better understanding of these processes in key affected cell types will lead to the development of better therapeutic targets. The goals of this project are to perform single cell studies across OUD-relevant mouse brain regions under various opioid exposure paradigms, in order to identify candidate OUD driver genes, pathways and cell types, and to test the causal involvement in OUD of the candidates identified.