Notch signaling in hematopoiesis. (A) Overview of Notch signaling in hematopoietic cells. Blue gradient represents level of Notch1 expression, red gradient represents level of Notch2 expression, and green gradient represents level of Notch activity as determined using Hes1GFP/WT mice. (B) Notch-deficient hematopoiesis. Genetic inhibition of Notch signaling in HSCs leads to accumulation of GMP, reduction of erythrocyte progenitors, and inhibition of marginal zone B-cell differentiation and T-cell differentiation. CFU-E, colony forming unit-erythrocyte; CLP, common lymphoid progenitors; CMP, common myeloid progenitors; DN3, double-negative 3; ETP, early T-cell progenitors; FoB, follicular B cells; GMP, granulocyte/monocyte progenitors; LMPP, lymphoid-primed multipotent progenitors; LT-HSC, long-term hematopoietic stem cells; MegE, megakaryocyte/erythrocyte progenitors; MkP, megakaryocyte progenitors; MPP, multipotent progenitor; MzB, marginal zone B cell; ProB, pro-B cell; ProE, proerythrocyte.