CM-expressing CD34⁺ cells retain progenitor activity but are inefficient in erythroid differentiation. (A-B) Five thousand magnetically selected CD34⁺ cells were plated to methylcellulose. (A) Total colony number was determined after 14 days. W indicates weeks in culture at the start of the assay. (B) Colony type frequency was scored as myeloid or erythroid for CD34⁺ cells from independent CB (n = 2), AE (n = 4), and CM (n = 4) cultures. Averages and SDs are shown. (C-D) Similarly, CD34⁺ cells from CM cultures were grown in methylcellulose assays with cytokines promoting red cell differentiation. After 14 days, (C) total cells or (D) pooled red cell colonies were stained for erythroid differentiation markers. Photographs show a representative red cell colony expressing GFP that was plucked and pooled for the CD71/CD235a stain in panel D.