High Pu.1 level supports the production of embryonic macrophages, whereas low Pu.1 level supports embryonic neutrophil production. (A-B) WISH of cebp1 expression in 23 hpf siblings (sib; panel A arrows) and pu.1^G242D mutants (panel B arrows). (C-D) WISH of apoeb expression in 3 dpf sib (panel C arrows) and pu.1^G242D mutants (D). (A-D) Embryos are viewed dorsally with the anterior to the left. (E-F) WISH of lyz expression in 30 hpf sib (panel E arrows) and pu.1^G242D mutants (panel F arrows). (G-H) WISH of csf1ra expression in 22 hpf sib (G) and pu.1^G242D mutants (H). White arrows indicate csf1ra expression in macrophage; and black arrowheads, its expression by neural crest cells. (I-J) WISH of cebp1 expression in 23 hpf control (panel I arrows) and pu.1 morphants (panel J, n = 35 of 38). (K-L) WISH of apoeb expression in 3 dpf control (panel K arrows) and pu.1 morphants (panel L, n = 29 of 29). (I-L) Embryos are viewed dorsally with the anterior to the left. (M-N) SB staining of 36 hpf control (panel M arrows) and pu.1 morphants (N, n = 45 of 48).