Myeloid and erythroid defects in

eng^−/− cells. (A) Sorted Flk1⁺ cells from day-6 ES-cell/OP9 cocultures were reseeded onto OP9 cells, and analyzed at days 9 and 12 for cell surface expression of CD45, TER119, and CD11b by flow cytometry. (B) Total cellularity from cocultures, as indicated, was determined for erythroid and myeloid lineages for the experiment represented in panel A. (C) Total cellularity from separate experiments with aneng^+/− ES clone and a secondeng^−/− ES clone are shown. (D) Expression of embryonic-type ζ-globin and adult-typeβ-globin transcripts identifying primitive or definitive erythropoiesis, respectively, was analyzed from day-12 cocultures, OP9 cells, and E13 FL by RT-PCR.