PROJECT SUMMARY Gout is prevalent in the US (3.9% of the adult population) and not only directly impacts peoples’ lives but is also co-morbid with cardiometabolic disease. Gout consists of unpredictable episodes of acute inflammation or flares resulting from monocyte NLRP3 inflammasome activation by monosodium urate (MSU) crystals in people with hyperuricemia, the subsequent production of IL-1, and recruitment of large numbers of inflammatory cells into the affected joint. Altered gene expression and DNA methylation in response to MSU crystals in immune cells (neutrophils, macrophages and monocytes) are key mechanisms underpinning this immune response. In the parent grant to this supplement we ask two questions: 1) Do neutrophils and/or monocytes, upon ex vivo activation by MSU crystals, exhibit gene expression and DNA methylation differences between gout patients with recurrent gout flares compared to those that do not? 2) Among gout patients from a clinical trial setting, where treat-to-target urate lowering therapy (ULT) is administered, are there gene expression and DNA methylation differences from the peripheral blood between individuals with or without recurrent flares? Here, in this diversity supplement, we will link these expression and methylation differences in immune cells and whole blood to genetic variants (quantitative trait loci (QTL)) and assign regulatory function to these genetic variants and their target genes causal in the gout-flare and MSU crystal response. In Aim 1 RNA-sequencing and whole genome genotyping and methylation data from two datasets (Gout Registry and Stop Gout) will be used to identify gout-specific blood and immune-cell gene expression QTL (eQTL) and methylation QTL (meQTL). In Aim 2 we will use experimental systems, including a zebrafish model of gene regulation, to understand where gout-relevant gene regulatory regions are expressed, if the genetic variants alter regulatory function and how the target genes might influence the MSU-induced immune response. Our studies will deepen our knowledge of the mechanisms of gout flares and its genetic basis, and ultimately point to areas of research that may allow for novel treatments in gout.