Comparison of mpx, etv2, scl, gata1, hbae3, etv2:GFP and etv2:Kaede expression. (A–L) mpx expression overlaps with scl, gata1 and hbae3, but not etv2, in the ICM of wild-type embryos at the 22-somite stage, as analyzed by two color in situ hybridization. (A–C) etv2 (arrows), and mpx (arrowheads) expression domains largely do not overlap. Maximum intensity projections of confocal images are shown. Autofluorescent yolk granules are apparent in the lower left corner in (B and C). (D–F) mpx expression partially overlaps with scl expression (selected overlapping cells, arrowheads). Single confocal slices are shown. (G–I) mpx and gata1 expression largely overlap (arrowheads, selected cells). Single confocal slices are shown. (J–L) mpx and hbae3 expression largely overlap (arrowheads, selected cells). Note that not all hbae3 cells are positive for mpx expression. Single confocal slices are shown. (M–O) Only a fraction (10.8%) of mpx-expressing cells in the ICM overlap with etv2:GFP expression at the 24 somite stage, as observed by combined ISH for mpx expression and immunohistochemistry for GFP. (P-R) etv2:Kaede and mpx:GFP expression overlaps in neutrophils (white arrowheads) in the trunk ICM region of embryos at 24 hpf. Yellow arrows denote vascular endothelial cells. (S–U) Multiple (64%) ALPM-derived mpx-expressing cells, positioned over the yolk, overlap with etv2:GFP expression at 24 hpf (white arrowheads) as observed by combined ISH for mpx expression (red) and immunohistochemistry for GFP (green). (S′–U′′) Magnified views of individual cells from S–U. Images show anterior to the left and dorsal up in all panels.