Dr. Ellen Rothenberg's group works at the interface of developmental biology, immunology, genomics, and systems biology, focusing on gene networks that control early T-cell development. Their goal is to generate a comprehensive explanation at the molecular level for the process of T-lymphocyte development from mouse hematopoietic stem/progenitor cells. Of greatest interest are the lineage choice events through which cells select the T-cell fate and exclude other developmental pathways. Rothenberg’s group has optimized in vitro differentiation technology to determine the sequence of changes in the cells and generated detailed gene expression profiles for transitions from stage to stage. This system also makes possible detailed gain and loss of function experiments to test the roles of important transcription factors which turn out to have sharply delineated effects on stage to stage progression. Recently, her group's analysis of the T-cell specification process has been extended to a genome-wide scale. This work is now providing a comprehensive picture of the stepwise transcriptional and epigenetic changes brought about by altered transcription factor activity, and thus how transcription factors sequentially control acquisition of T-cell identity.