Figure 3.

iESREs Terminally Mature into Reticulocytes In Vitro

(A) Almost all of the Bmi-1-induced ESREs (iESREs) in expansion cultures lack detectable hemoglobin (black line). Transfer of iESREs and ESREs into maturation media on day 0 resulted in rapid accumulation of hemoglobin (red and blue lines, respectively), quantified by benzidine staining. (Mean ± SEM; N = 6 independent replicates for iESRE self-renewing cultures; N = 7 and 3 independent replicates for iESRE and ESRE maturation cultures, respectively.)

(B) Morphology of self-renewing (upper panel) and maturing (lower panels) iESREs stained with Wright-Giemsa. iESREs differentiated in vitro into reticulocytes and pyrenocytes (arrow). One representative image of more than three independent experiments is shown.

(C) In vitro maturation of iESREs is characterized by the progressive downregulation of KIT (CD117) and transferrin receptor (CD71). Representative data from one of three independent experiments are shown.