Figure 9.

Correct control of c-Myb levels is required to maintain the haematopoietic hierarchy. The diagram summarises the ways in which disrupted loss of normal (A) control of c-Myb expression has been shown to lead to expansion of cells with stem-cell characteristics at different points in the haematopoietic hierarchy, resulting in (B) myeloid and (C) lymphoid leukaemia or, as described here, myeloproliferation (D). The highly simplified representation of haematopoiesis is divided on the basis of cells being in the KSL stem cell compartment (purple) or committed towards myeloid (green) or lymphoid (blue) differentiation. The approximate range of expression of crucial markers is indicated at the bottom (SP, side population). Circular arrows are used to depict self-renewal, the extent of which is related to the size. Vertical bars indicate blocks to further differentiation. The dotted arrow and cell in (D) represent a putative new pathway of dedifferentiation seen in the c-myb knockdown.