PROJECT SUMMARY/ABSTRACT– OVERALL PPG This new Program Project Grant (PPG) utilizes recent advances in transcriptional biology to fundamentally increase our knowledge of the long-lasting abnormalities in brain that underlie stimulant and opiate addiction. Our work focuses on several specific cell types in key addiction-related brain regions: nucleus accumbens, dorsal striatum, and prefrontal cortex. The PPG is composed of four Projects and three Cores all at Mount Sinai. The PIs are leaders in their fields who have an established history of effective collaboration and use their complementary expertise and approaches to chart a multidisciplinary course in the proposed research. Project 1 (Eric Nestler) focuses on novel transcription factors induced in brain reward regions by self-administered stimulants and opiates. Project 2 (Paul Kenny) mines the PPG’s complex datasets to understand the role played by circular RNAs in addiction; these are a newly discovered class of non-coding RNAs some of which, within brain, are concentrated at synapses. Project 3 (Anne Schaefer) focuses on the influence of microglia in controlling transcriptional responses to drugs of abuse within brain reward neurons and their behavioral consequences. Project 4 (Yasmin Hurd) concentrates on the influence of enhancer regions, and their transcriptional and chromatin mediators, in controlling molecular and behavioral adaptations to drugs of abuse. All four projects validate findings from animals in human postmortem brain tissue, while discoveries in human substance use disorders are fed back to animal models to explicate the underlying mechanisms involved. The PPG is supported by three Cores, an Administrative Core (Eric Nestler) to oversee and coordinate PPG operations; an Animal Models Core (Vanna Zachariou) to provide animal models of addiction and other advanced tools (e.g., viral gene transfer, inducible mutant mice) to manipulate individual genes of interest in specific cell types of the targeted brain regions and thereby provide causal evidence linking molecular-cellular plasticity to addiction-related phenomena; and a Gene and Chromatin Analysis Core (Li Shen) to provide state- of-the-art methods and bioinformatics to characterize genome-wide regulation of gene expression and chromatin modifications in addiction. This pioneering investigation of transcriptional mechanisms of drug addiction will help drive major advances in the field.