A genetic screen in zebrafish defines 9 essential genes for HSC emergence. (A) Screening strategy. Heterozygous adults from each insertional (ins.) mutant line were crossed, embryos raised until 36 to 40 hpf of development, fixed in paraformaldehye, and processed by in situ hybridization for c-myb expression in the AGM. (B) Table listing the hi alleles uncovered in the screen, the gene disrupted in each line, and previously isolated alleles. (C) Whole-mount in situ hybridization for c-myb, runx1, and rag1 transcripts in wild-type, hdac, plcg1, and tbx16 mutant animals. (Columns 1 and 2) Lateral views, anterior left; 36 to 40 hpf; low magnification (original magnification ×10) and higher magnification (original magnification ×40) of the trunk region. HSC gene expression in the AGM is indicated by ➤ in subpanels i and ii. (Column 3) Dorsal view, anterior up; 4 dpf; bilateral rag1 expression in thymi is indicated by ➤ in subpanel iii.