Model for the role of mir-196b in hematopoietic cells and MLL fusion-mediated leukemia. MLL regulates expression of mir-196b and MLL fusion proteins cause a block in differentiation of progenitor cells. This effect may be due partially to high levels of mir-196b expression caused by the MLL fusion protein. High levels of mir-196b may also provide a survival advantage to cells expressing the MLL fusion protein.