My research efforts focus on understanding the pathogenesis of infant and non-infant pediatric leukemia with MLL-gene rearrangements. Infant leukemia is defined by an exceedingly poor prognosis and there is a need for new therapeutic options. We use high-resolution genomic methods to study the landscape of epigenetic and genetic lesions that underlie MLL-R leukemia at diagnosis and at relapse. Pertinent lesions are studies further in murine models to unravel their impact on tumor behavior. These studies will enhance our understanding of the differences between infant and non-infant MLL-R leukemia, and the nature of alterations that drive its development, and will increase our understanding about the genetic basis of relapse. In addition, we are interested in defining how distinct tumor clones cooperate to drive the growth of MLL-R leukemia, and the mechanisms behind clonal cooperation using murine models and in vitro assays to determine its biological significance.