Loss of and Impairs the Maintenance of the Hematopoietic Stem Cell Pool Size.

A germ line copy number duplication of chromosome 14q32, which contains and , was identified in families with myeloproliferative neoplasm (MPN). Here, we show that mice lacking both and , but not either alone, exhibited decreased hematopoiesis, resulting in death accompanied by anemia. In marked contrast to MPN patients with duplication of and , the number of hematopoietic stem cells (HSCs), in particular long-term HSCs, in double-knockout fetal livers was significantly decreased due to increased cell death.