CD34 is detected on cells from both wild-type and scl-null EBs but only wild-type EBs contain cells positive for globin or GATA-1. Indirect immunofluorescence of cells from disaggregated day-12 scl^+/+ (A, C, E, and F ) and scl-null (B, D, F, and H) EBs stained with antibodies to globin (A and B), GATA-1 (C and D), and CD34 (E through H).