An evolutionary conserved developmental program is carefully maintained in hematopoietic stem cells (HSCs). Genetic alterations and epigenetic mechanisms can alter the balance of normal blood development resulting in hematological malignancies. Our recent studies have identified MUSASHI (MSI2), as an RNA binding protein that controls normal and leukemia self-renewal. Moreover, the MSI family is highly expressed in the most aggressive solid tumors and we have demonstrated that MSI2 expression predicts a worse clinical prognosis in acute myeloid leukemia (AML). We hypothesize that the RNA binding proteins MSI2 controls leukemic stem cell self-renewal and elucidating the mechanism of action for MSI2 in LSCs may provide novel therapeutic strategies in myeloid leukemia. This proposal utilizes Msi2 conditional knockouts and patient samples with AML to dissect the requirement for MSI2 in leukemia self-renewal. Furthermore, our global genetic approaches have already uncovered how regulation of translation alters several epigenetic pathways that are controlled by the MLL-AF9 oncogene. Our studies will examine the direct mRNA targets of MSI2 that control LSC function. Additionally, we will stratify patients based on their MSI2 expression and determine how cytotoxic agents, molecular targeted and epigenetic therapies can be used to improve therapeutic outcomes in AML.