Analysis of DNA fragmentation in 32D cells lines expressing WT or mutant EPORs. Clonal 32D cell lines expressing WT, W282R, YF, or 1–321 EPORs, or 32D cells lacking EPOR, were washed extensively and then cultured in media (A) lacking FCS and exogenous cytokine, (B) containing only FCS, (C) containing only EPO, or (D) containing EPO and FCS for 24 hours. Cells were stained with propidium iodide and the fraction of sub-diploid cells in the population was determined by flow cytometry. Average results from 6 independent experiments are shown.