Dr. Haj´s laboratory studies the role of tyrosine phosphorylation and dephosphorylation in cell signaling and disease. Research focuses on the function of protein-tyrosine phosphatases (PTPs) in regulating insulin signaling and how deregulation of these pathways leads to diseases such as obesity and type 2 diabetes. This is achieved through the combined use of biochemical, cellular and knockout mouse studies. Collectively, these approaches will enable the dissection of metabolic regulation at the cellular and organism levels.