a–f, Sca-1Low (Low, black), Sca-1Mid (Mid, grey), and Sca-1High (High, white) fractions (a) stimulated by Epo (b) and GM-CSF (f) immediately after isolation showed variable differentiation rates into the erythroid and myeloid lineages, respectively. Upon 7, 14, and 21 days (d) of post-sort culture, Epo- treated cells showed convergence in both pre-stimulation, baseline Sca-1 expression () and relative differentiation rates (b–e). Asterisk, p < 0.001 (two-tailed normal-theory test). g, h, qRT-PCR analysis of GATA1 (g) and PU.1 (h) mRNA levels in Sca-1 sorted fractions. Means ± s.e.m. of triplicates shown; triple asterisk p < 10−5, double asterisk p < 0.0002, asterisk p < 0.003 (one-tail Student’s t-test). i, j, Western blot analysis of GATA1 (i) and PU.1 (j) protein levels in Sca-1 fractions (lanes 3–5) and mock-sorted cells (lane 6). MEL cell line (lane 1), positive control; G1E and 503 (lane 2) cell lines, negative controls for GATA1 and PU.1, respectively. GAPDH, loading control.