ABSTRACT High-throughput functional genomics of variants in genes linked to substance use disorders Understanding of the genetic basis of substance use disorders has advanced significantly in the recent past; the generation of a reference human sequence in the early 2000’s enabled Genome Wide Association Studies (GWAS), which in turn led to the identification of thousands of genetic variants that are statistically significantly associated with substance use and substance use disorders. The number of these clinically relevant variants continues to grow proportionally with the increase in sample sizes for GWAS and genome sequencing studies of substance use disorders. Model organism studies have also led to the identification of genes and pathways that are linked to these phenotypes. However, one persistent bottleneck in this field has been the lack of experimental testing of nearly all (>99%) of these variants in genes and regulatory regions to determine which are functionally significant. Determining the functional effects of genetic variants is crucial to acquiring a molecular understanding of the basis of substance use disorders, and this deeper understanding will enable future development and testing of targeted and rationally designed therapeutic interventions. This forward- thinking application proposes to address this gap by applying highly innovative high-throughput functional genomics approaches, including Massively Parallel Reporter Assays (MPRAs) and Deep Mutational Scan (DMS) techniques, that were recently deployed for the study of rare Mendelian disorders, to the study thousands of both noncoding and coding variants associated with substance use disorders. These approaches have not previously been applied to the genetics of substance use disorders, although they have enabled significant advancements in other fields, such as the genetics of neurodevelopmental and neuropsychiatric disorders. Furthermore, this early-stage investigator’s multidisciplinary training, including MD/PhD degrees, Pediatrics residency, a postdoctoral fellowship, and four years of dedicated K08 Early Career Development work that was focused on acquiring expertise in the use of functional genomics techniques, has established him as a rising leader in the field of human genetics. His prior paradigm-altering and team-based accomplishments include establishment of an exome sequencing testing pipeline for children with autism in 2015, ongoing coordination of the Model Organism Screening Center for the NIH-funded Undiagnosed Diseases Network, and leadership of a $1.5 million institutionally-funded, multi- investigator functional genomics project that resulted in deployment of critical infrastructure and delivered a 10:1 return on investment in subsequent grant funding. Although this talented investigator has not previously focused on substance use disorders, he has established a collaboration with a world expert in this field, Dr. Laura Bierut, who has agreed to advise ...