Project Summary Alcohol-related liver disease (ALD) is a very common health problem among alcohol drinkers. Multiple genome-wide association studies have reproducibly identified a single nucleotide polymorphism (rs738409, C→G) in the human patatin-like phospholipase domain containing 3 (PNPLA3) gene, which results in isoleucine (I) to methionine (M) substitution at amino acid 148, as the most significant gene variant associated with a broad spectrum of ALD ranging from steatosis, hepatitis, to cirrhosis to date. PNPLA3 is a lipid droplet-associated protein that is most abundantly expressed in human liver, which has been shown to have triglyceride lipase and retinyl palmitate hydrolase activities. However, the pathophysiology of the 148M variant of PNPLA3 in the liver remains largely unclear. In this project, we have developed transgenic mouse models for both variants of human PNPLA3 and validated the key features of human ALD in the 148M mouse model. We aim to further address the molecular underpinning of the 148M mutation in the alcohol-induced hepatic inflammation and fibrosis using both cell and animal models. It is expected that the mechanistic investigation in this application will provide direct evidence of the causal relationship between the 148M variant and the associated liver pathology. Altogether, we believe that this project is highly significant and innovative.