Project summary This supplement application requests a one-year extension of grant K99AA027835 with additional funds for salary support for Dr. Amanda Barkley-Levenson. This supplement is needed due to the unforeseen and extreme impacts on the funded project created by the COVID-19 pandemic and subsequent restrictions on research activities. The aims of this project have not changed, but additional time is needed to complete the planned work. No additional research funds are requested, and all experimental and animal costs will be paid by the parent grant. During the proposed one-year extension, Dr. Barkley-Levenson will continue follow-up evaluation of novel GWAS hits for problematic alcohol use using mutant mouse lines. She will complete comprehensive behavioral phenotyping of Fut2 knockout mice by measuring ethanol effects on intracranial self-stimulation, and withdrawal-associated escalation of drinking and negative affective changes in the chronic intermittent ethanol exposure model (Aim 1). Dr. Barkley-Levenson will also complete behavioral phenotyping of an initial cohort of AIL mice for preliminary GWAS analysis (Aim 2). These experiments were not possible in the past year due to state and university restrictions on non-essential research and limits on in-person work but are now able to proceed under current guidelines. No further delays are anticipated. During the extension period, Dr. Barkley-Levenson will continue with career development activities including writing and publishing papers, presenting at research conferences, mentoring undergraduate research assistants, applying for faculty jobs, and working towards a timely transition to an independent position.