OBJECTIVES/GOALS: 1. Identify candidate AN-SAD-causing variants. 2. Estimate the variant effect size of and genotypic relative risk for arrhythmias and AN-SAD. METHODS/STUDY POPULATION: We performed whole genome sequencing (WGS) on 59 Thoroughbred AN-SAD cases and 58 controls. WGS was mapped and variants identified using a modified version of the Genome Analysis Toolkit best practices. Variants will be selected based on case-control analysis using SnpSift and presence in candidate genes. The top 400 candidate AN-SAD-causing variants will be selected based on being common in cases and rare or absent in controls, and uncommon (allele frequency less than 10%) in a catalog of genetic variation for the horse. The 400 variants will be genotyped in our cohort of 1,200 racehorses to determine variant effect size and genotypic relative risk. RESULTS/ANTICIPATED RESULTS: 17,182,003 variants were identified. 230 variants had significantly different allele frequencies (AF) between cases and controls (SnpSift). 723 high and 4,824 moderate impact variants were identified in 1,072 candidate genes. 3,681 variants were present at an AF 10% in the equine variant catalog. Variant effect prediction is ongoing to select the final 400 variants. Cardiac phenotyping (cardiac auscultation and ECG before, during, and after exercise) was performed on 790 racehorses and we will have 1,200 racehorses with cardiac phenotypes and/or AN-SAD. We will genotype the top 400 candidate AN-SAD-causing variants in these 1,200 horses to identify variants of large effect size. DISCUSSION/SIGNIFICANCE: Identification of candidate AN-SAD variants in a spontaneous animal model can facilitate interpretation of candidate variants in humans and horses. This project will provide further support for the racehorse AN-SAD model and will support future work exploring the genetic and environmental risk factors contributing to AN-SAD in this animal model.