Ramnik Xavier is Associate Professor of Medicine at Harvard Medical School and Associate Physician in the Gastrointestinal Unit at Massachusetts General Hospital. He is a Board Certified physician in medicine and gastroenterology. Ramnik is clinically active, teaching medical students, residents in medicine, and gastroenterology   fellows rotating through the MGH.

Following clinical training, he completed a post-doctoral fellowship with Professor Brian Seed in the Department of Molecular Biology at MGH and the Department of Genetics at the Harvard Medical School. While in the Seed lab, Ramnik and colleagues demonstrated that lipid rafts play an important role in T-cell signaling. Although many important signaling molecules had been found in rafts at the time we began this work, there was little evidence that their localization was important for function, and no work had pointed to a  relevance for rafts in antigen recognition. Using a fractionation scheme that preserves tyrosine phosphorylation, we showed that T-cell activation leads to a striking compartmentation of activated T-cell receptor and associated signal-transducing molecules in rafts. These findings helped focus wider attention on the role of lipid rafts in immune system in the community.

A second area of focus was to develop tools to study in vivo gene activation and develop a high throughput system for identifying novel activators of the serum response element and HIF1a. In the last two years, Dr. Xavier has focused on the role of PDZ domain proteins and PDZ ligands in immune cell signaling

His current research focuses on PDZ proteins in cell signaling and on genomic computational approaches in immunity.