Wdr1 is necessary for the maintenance of neutrophils in developing zebrafish. (A) Sudan black–stained 3-dpf carmin embryos and siblings reveal a large reduction in neutrophils in carmin mutants. Scale bar, 100 µm. (B) 50 live Tg(lyz:GFP) carmin and sibling embryos were imaged by confocal fluorescence microscopy (left), and the total number of neutrophils was counted in a subset at several stages between 1.5 dpf/36 hpf and 3 dpf/72 hpf (right). Statistical significance of the difference between mutant and sibling embryos was determined by one-way ANOVA, with Sidak’s multiple comparisons test; not significant (ns), P > 0.05; **, P ≤ 0.01; ***, P ≤ 0.001. Data shown as mean ± SD. Scale bar, 200 µm. (C) Mutation mapping (left) and subsequent sequence analysis (right) revealed a W-to-R substitution at position 540, close to the C terminus of Wdr1. (D) Number of neutrophils at 56 hpf in the caudal half (from midtrunk to tail tip) of WT embryos injected with either of two splice-blocking morpholinos against Wdr1 (n = 16 for each category), all from the same experiment (no pooling); this experiment was repeated at least four times. Data are mean ± SEM. ****, P < 0.0001 with two-tailed unpaired t test .