Increased proportions of proE and early erythroblasts in the spleens of ERK1^−/− mice. Representative flow cytometric analysis of freshly isolated splenocytes from ERK1^+/+ and ERK1^−/− mice. Ter119^high cells were analyzed for their forward scatter (FSC) and CD71 expression. The number of proE cells is expressed as a percentage of all Ter119⁺ cells, whereas the number of cells in Ery.A (gate A), Ery.B (gate B), and Ery.C (gate C) subsets is expressed as percentages of Ter119^high cells.