Lmo2 is a critical regulator of PLM development. (A-H) Whole-mount embryos; posterior views; dorsal, top; numbers of embryos represented in gray. (A) Hhex expression initiated as normal, appeared reduced at 6s/7s (arrows) and was lost by 10s. (B) Runx1 was at first dependent on Scl, initiated weakly in the PLM of morphants at 8s (arrow), and increased toward the 10s stage. (C-E) Gata1, βE1, and pu.1 expression was not observed in the PLM of morphant embryos. (F-H) Scl, fli1 and gata2 expression in the PLM was unaffected in 10s morphants. (I) Data from in situ analyses are summarized schematically. Bars represent the changing expression of genes over time. *Gene expression in morphants. Purple indicates Lmo2 independence; red, Lmo2 dependence; and green, lmo2 expression.