Rescue of embryonic mast cells completely in notch1b morphants and partially in pu.1 morphants by injecting gata2 mRNA. Zebrafish notch1b or pu.1 morpholino and gata2 mRNA were injected in 1 to 4 cell stage wild-type embryos followed by WISH for cpa5 expression at 28 hpf. (A) notch1b morphants demonstrate decreased cpa5 expression (n = 33) and gata2 expression (n = 8) compared with wild-type embryos (n = 34 and 16, respectively) that is completely rescued by injecting gata2 mRNA (n = 25). (B) pu.1 morphants demonstrate a dramatic decrease in cpa5-positive mast cells (n = 24) compared with wild-type embryos (n = 34) that is partially rescued by injecting gata2 mRNA (n = 29; Leica MZ6 microscope, 5× objective). Bar graphs represent the percent of embryos categorized by WISH expression levels.