Expression of the spi1:EGFP transgene. (A-B) Transient expression in injected embryos. Two images taken 2 seconds apart, showing movement of fluorescent cells in circulation. The relative movement of 2 individual cells moving in contrary directions is indicated by white and red arrows. (C-I). Stable myeloid-specific expression. Panel C shows a vertical Z-series of images captured by confocal microscopy and projected to form a single image demonstrating EGFP-expressing cells over the yolk in green in an F₂ embryo. Panels D-F show whole-mount in situ hybridization of embryos with an spi1 probe revealing expression in the rostral lateral plate mesoderm at around 14 hpf (D-F; blue arrowheads), and in cells over the yolk sac from around 18 hpf (E-F; arrowheads). Panels G-I show EGFP expression in pronouncedly fluorescent (flu⁺⁺) F₃ embryos (G-I; green arrowheads) recapitulating the in situ hybridization patterns shown. Original magnification, × 40.