 The t(8;21)(q22;q22) translocation, which fuses the ETO gene on human chromosome 8 with the AML1 gene on chromosome 21 (AML1-ETO), is one of the most frequent cytogenetic abnormalities associated with acute myelogenous leukemia (AML).     ///    We have generated a murine model of the t(8;21) translocation by retroviral expression of AML1-ETO in purified hematopoietic stem cells (HSC).     ///    Hematopoietic stem cell expansion and distinct myeloid developmental abnormalities in a murine model of the AML1-ETO translocation..     ///    This suggests that the principal contribution of AML1-ETO to acute myeloid leukemia is the inhibition of multiple developmental pathways..     ///    "HSC numbers in the bone marrow of 10-month-posttransplant animals were 29-fold greater than in transplant-matched control mice, suggesting that AML1-ETO expression overrides the normal genetic control of HSC pool size. "