Altered DAPK2 expression and Akt activation in Lyn^-/-erythroblasts. (A) Lyn^-/- and wild-type erythroblasts were expanded from bone marrow preparations in SP34-EX media to yield 90% or more CD71^high populations. Kit^pos erythroblasts were isolated via MACS, washed, deprived of cytokines for 6 hours, and then exposed to SCF plus Epo (150 ng/mL, 5 U/mL) for the indicated intervals. Levels of DAPK2 in Kit^posCD71^high cells then were assayed by Western blotting and quantitatively by densitometry (bottom panels). (B) Lyn^-/- and wild-type erythroblasts were expanded from bone marrow preparations in SP34-EX media, and Kit^posCD71^high erythroblasts were isolated. Cells were then washed and cultured in the absence of SCF and Epo. At the indicated intervals of subsequent exposure to SCF plus Epo (150 ng/mL, 5 U/mL), levels of phospho-Akt were determined. In repeated independent experiments, Kit^negCD71^high erythroblasts also were analyzed (together with Kit^posCD71^high cells) (Figure S4).