Scl is a critical regulator of early myeloid development. (A-E) Whole-mount embryos (13 × magnification); anterior views; dorsal, top; numbers of embryos represented in gray. Pu.1 expression in the ALM initiated weakly in morphants and 1 somite later than wt (A, arrows), remaining weak until 10 somites (14 hpf) (A). dra was expressed normally in Scl-depleted embryos until 6 somites (12 hpf), then began to appear reduced (B, arrows). Similarly, hhex expression was reduced at 7 somites (12.5 hpf), and was lost by 10 somites (14 hpf) (C, arrows). Fli1 and lmo2 expression in the ALM at 10 somites (14 hpf) was unaffected by Scl-depletion (D, E). (F) Data from such in situ analyses are summarized schematically, as described for Figure 4.