Functional interaction between zebrafish gcsf and gcsfr. (A-D) Enforced gcsf expression expands the gcsfr⁺ population. Embryos were either injected with capped gcsf mRNA (+gcsf) or sham injected (−gcsf) and probed with gcsfr (A,B). The total number of gcsfr⁺ cells with or without gcsf was analyzed at 22 hpf (C) or 96 hpf (D), with mean (dashed red line), 95% confidence interval (red lines), and level of statistical significance (*P < .05; **P < .01) indicated. (E-J) Enforced gcsf expression expands myeloid populations via gcsfr. Embryos were coinjected with combinations of either scamMo or gcsfrMo1 with or without capped gcsf mRNA, as indicated, and probed with lyz (E-H). The total numbers of lyz⁺ (I) and anterior mpo⁺ cells (J) at 22 hpf were analyzed as discussed for panels C and D.