EE-T-Y343 and EE-T-Y343F retain high capacities to cosignal in combination with c-Kit.

Erythroid progenitor cells were prepared from TAP-treated mice at 70 hours after TAP withdrawal (c-Kit⁺, EPO receptor⁺, Ter119⁻ stage) and were used in proliferation response assays to assess the abilities of these minimal EPO receptor forms to cosignal with endogenous c-Kit. Specifically, cells at 5 × 10⁶ cells per milliliter were exposed to EPO, hEGF, or SCF at the concentration indexed, and proliferation was assayed based on rates of cytokine-induced methyl–[³H]-thymidine ([³H]dT) incorporation. Stem cell factor (+SCF) was included at a concentration of 50 ng/mL (50% or lower maximum dose as shown in parallel and independent SCF-only response profiles).