RNA expression (RT-PCR) of myeloid lineage–associated antigens (CD45, CD115, and CD11b) and GAPDH (internal control). Lane 1, peripheral blood mononuclear cells (positive control); lane 2, CFU-ECs from healthy control; lanes 3-5, E-CFCs at passages I obtained in 3 different patients with JAK2^V617F E-CFCs; lane 6-8, E-CFCs at passages IV obtained from the same 3 patients. MW indicates molecular weight marker (50 base pair); GAPDH, glyceraldehyde-3-phosphate dehydrogenase.