CFUe development is supported by EE-T-Y343F but is attenuated at a Ter119⁺ stage of differentiation.

(A) Splenocytes were isolated from EE-T-Y343 and EE-T-Y343F mice at 72 hours after exposure to TAP. Cells then were cultured in the presence of EPO (5 U/mL) plus mSCF (150 ng/mL); mSCF with no EPO; or hEGF (5 ng/mL) plus mSCF. At 48 hours of culture, hemoglobinized colonies were stained with benzidine. Results shown are representative of 5 independent experiments (and of all mice assayed). (B) Erythroid splenocytes from TAP-treated EE-T-Y343F mice (upper subpanels) and EE-T-Y343 mice (lower subpanels) were cultured in the presence of mSCF plus EPO or hEGF. Ter119 antigen expression and relative size (FALS, forward angle light scatter) were assayed by flow cytometry. For all EE-T-Y343F mice studied, a defect in the production of more mature, small Ter119⁺ cells in response to hEGF was observed (arrow). No similar defect was observed in the formation of mature Ter119⁺ cells from these mice in the presence of EPO or in cells from EE-T-Y343 mice in the presence of hEGF or EPO. Results shown are representative of 5 independent experiments.