Fig. 7: EpoR signaling promotes rapid cycling while maintaining cell size in early erythroblasts.
From: EpoR stimulates rapid cycling and larger red cells during mouse and human erythropoiesis
Proposed model explaining EpoR-dependent functions during ETD. EpoR expression is limited to early erythroblasts, which are sensitive to EpoR signaling. When EpoR signaling is weak or absent, as in late erythroblasts, or in early erythroblasts in the presence of low Epo, cell divisions lead to cell size reductions. In contrast, strong EpoR signaling, as seen in Epo-sensitive early erythroblasts, can override this default state, simultaneously increasing rapid cycling while maintaining cell size. As consequence, high-Epo levels increase the duration of the early ETD phase, increase the relative frequency of early erythroblasts, and also increase erythroblast cell size at every maturation stage, giving rise to larger red cells. In high Epo, red-cell size is also more heterogeneous, a result of the varying sensitivities of early erythroblasts to Epo. Erythroblasts with low sensitivity to Epo, here represented as cells expressing low levels of EpoR, receive only weak EpoR signals even in the presence of high Epo, giving rise to smaller red cells.
