Project Summary Osteoarthritis (OA) is a prevalent joint disease that affects over 250 million individuals globally. Despite extensive research, there are no known cures or therapies to prevent the disease's progression. Understanding the complex molecular mechanisms responsible for its development and progression is crucial. Genome-wide association studies (GWAS) have identified over 100 loci associated with OA disease risk; however, identifying the putative causal variants and the affected genes has been challenging due to the non-coding nature of most OA risk variants and the linkage disequilibrium between nearby variants. Alternative mRNA splicing can alter transcript and protein function, and its dysregulation has been implicated in a wide variety of human diseases. Previous studies have found differentially spliced transcripts in OA tissue, suggesting it may play a role in OA pathogenesis; however, the genetic causes and OA-related impacts of alternative splicing in human chondrocytes have not yet been explored. The overall objective is to identify genetic variants that alter OA risk by influencing RNA splicing in either resting or stimulated chondrocytes. The project will identify differential splicing events in chondrocytes responding to cartilage matrix damage (Aim 1), identify genetic variants that influence splicing patterns (i.e., splicing QTLs) in both resting and activated chondrocytes (Aim 2), and integrate these results with OA GWAS data to identify putative disease-relevant variants and genes, followed by experimental validation. (Aim 3). The findings from this research will pave the way for developing new treatments and drug targets for OA.