Our research focuses on the development of T lymphocytes from hematopoietic stem cells. T cells are a population of immune cells that play key roles in self vs. non-self determination in almost all vertebrates. Adaptive immune responses to foreign invasion and tumors are orchestrated by a diverse array of effector T lymphocyte subsets, all of which arise from a small number of common precursor cells that enter the thymus from the bone marrow. Once in the thymus these progenitor cells are induced by the thymic microenvironment to begin the long process of T cell differentiation. We study gene regulatory network changes and checkpoint control in the earliest stages of T cell development and our current goal is to understand the mechanisms through which precursor cells relinquish their multi-potential stem cell-like properties and commit to the T cell lineage. We use genetic analysis, in vitro cell culture techniques, transcriptome analysis, and imaging to accomplish this goal and we are currently developing single cell methods towards generating kinetic models of T cell development. In addition, we investigate how errors in early T cell development can lead to altered lineage decisions, leukemia initiation, and even autoimmune diseases like Type 1 diabetes.