Differentiation of cultured erythroid progenitors derived from fetal liver
(a) Morphological studies, second phase. The graphs represent the number of cells per 2 × 106 nucleated cells harvested at each time point after the addition of EPO on Day 0. ○, nonhemoglobinized erythroid cells (pronormoblasts and basophilic normoblasts); ●, Partially hemoglobinized erythroid cells (polychromatophilic normoblasts); ▲, Fully hemoglobinized cells (orthochromatic normoblasts). (b and c) RNA analyses of first and second phase of the fetal liver culture, respectively. Total cytoplasmic RNA was harvested and aliquots of the same RNA samples were analyzed by RT-PCR for either γ-globin mRNA (210 bp amplification product) or for β-globin mRNA (297 bp). The numbers represent days in culture. K562 RNA served as a positive control for γ-mRNA; adult culture-derived RNA, purified from a sample harvested on Day 5, served as a positive control for β-mRNA. M, DNA size marker.