Hematopoietic phenotype of grechetto mutants. (A-D,I-J) WISH for mpx: lateral view, anterior to the left, dorsal upward. mpx expression is normal in the anterior lateral plate mesoderm of 1 dpf embryos (A-B arrows) and in the CHT of 3 dpf (I-J; CHT magnified in the inset and highlighted by arrows), but almost absent in the CHT of 5 dpf (C-D; CHT magnified in the inset and highlighted by arrows) grechetto mutants. (E-H,M-N) WISH for band3: lateral view, anterior to the left, dorsal upward. band3 expression is normal in the intermediate cell mass of 1 dpf embryos (E-F arrows), reduced in the CHT of 3 dpf (M-N; CHT magnified in the inset and highlighted by arrows), and almost absent in the CHT of 5 dpf (G-H; CHT magnified in the inset and highlighted by arrows) grechetto mutants. (K-L) WISH for lck: ventral view, anterior to the left. lck expression is lost in 5 dpf grechetto mutants (L). The bilateral zebrafish thymic region is indicated with arrows. (O-P) Quantification of the number of mpx-expressing cells (O) and band3-expressing cells (P), as counted in 15 WISH-stained embryos per condition. Cells were counted from the anterior lateral plate mesoderm (mpx) or intermediate cell mass (band3) of 1 and 2 dpf animals and from the CHT of 3, 4, and 5 dpf animals (1 and 2 dpf embryos were genotyped after counting to identify mutants). The number of cells in mutants was plotted as a ratio to the number of cells in WT siblings at the same stage normalized to 1. Error bars represent SEM. **P ≤ .005; ***P ≤ .0005 by Student t test.