FOG-1 is necessary for erythroid/thrombocytic development in zebrafish. Uninjected control embryos (A,D,G), FOG-1 MO-injected embryos (B,E,H), and FOG-1 MO coinjected with FOG-1 cRNA (C,F,I). Lateral views of 24-hpf embryos processed by WISH to reveal band3 expression (A-C). Lateral (D-Di,E-Ei,F-Fi) and ventral (Dii,Eii,Fii) views of 48 hpf embryos processed by o-dianisidine staining (D-F) to reveal hemoglobinized cells. Lateral view at the trunk level of 4-dpf transgenic zebrafish [Tg(cd41:eGFP)] embryos to reveal eGFP⁺ thrombocytes (G-I). FOG-1 morphant embryos display reduction or complete absence of band3 expression in the ICM (A-B black brackets, inset magnification). The morphant embryos show severe anemia when stained with o-dianisidine (D-E black arrows). Injection of FOG-1 MO in the transgenic zebrafish [Tg(cd41:eGFP)] produces complete absence of eGFP⁺ thrombocytes at 4 dpf (G-H white brackets). The anemic phenotype is fully rescued by coinjection of FOG-1 cRNA in the morphant embryos (C,F). In contrast, the thrombocytic phenotype is only partially rescued (I, white arrow). The bars represent quantification of the normalized phenotypes (mean ± SD) with the numbers of embryos analyzed in each category indicated above the bar (J-L). White, black, and gray bars represent embryos with normal, reduced, and absence of erythroid/thrombocytic markers, respectively. Data were derived from 3 independent experiments. The statistical significance, marked by lines for each paired condition, was analyzed using analysis of variance; *P < .001; **P < .02.