OBJECTIVES/GOALS: Our long-term goal is to understand how both genetic and environmental (GxE) factors contribute to neurodevelopmental disorders (NDDs) so that we may potentially intervene in disease pathogenesis and design therapies to address functional deficiencies. METHODS/STUDY POPULATION: Our studies use a novel GxE model to determine how cephalosporin antibiotic exposure alters the gut microbiome, hippocampal neurogenesis, and behavior in the genetically vulnerable 16p11.2 microdeletion (16pDel) mouse. This mouse models one of the most frequently observed genetic risk variants implicated in NDDs, including ~1% of autism diagnoses. Wildtype and 16pDel littermates were exposed to saline or the cephalosporin, cefdinir, from postnatal days 5-9. We quantified changes in gut microbiota composition using 16S rRNA gene sequencing and utilized immunoblotting, immunohistochemistry, and bulk RNA gene sequencing to assess changes in hippocampal neurogenesis. An additional cohort of saline or cefdinir-exposed mice were subjected to a behavioral battery to assess changes in sociability and anxiety. RESULTS/ANTICIPATED RESULTS: We leveraged the next-generation microbiome bioinformatics platform, Quantitative Insights Into Microbial Ecology 2 (QIIME2) to analyze 16S rRNA gene sequencing datasets of P13 cecal samples from saline- and cefdinir-exposed mice. We found successful perturbations to the gut microbiome following early life cefdinir exposure. Further, we found a robust 50% reduction in hippocampal cyclin E protein in cefdinir-exposed 16pDel male mice, which was replicated in a second independent experiment. This reduction extended to the S-phase cell entry and general stem cell population, quantified by EdU+ and Ki67+ cell numbers, respectively. Lastly, in our first cohort of mice for behavioral studies, we found reduced sociability and increased anxiety-like behaviors in cefdinir-exposed mice. DISCUSSION/SIGNIFICANCE: The findings from this GxE model will provide mechanistic insights into the causes of NDDs; they may inform practice guidelines so as to reduce this environmental exposure; and may suggest interventions like probiotics for those at risk in order to overcome altered gut microbiome composition and restore hippocampal neurogenesis defects.