Fig. 3

Ifng1-2 Signaling Positively Regulates HSC Emergence

(A–F) Higher frequency of ECs at the aortic floor that turn on HSC marker expression upon ifng1-2 overexpression. Still images captured at different time points during time-lapse imaging of control (lacking the hsp:ifng1-2-V5 transgene) (A–C) and tg(hsp:ifng1-2-V5) (D–F) embryos starting at 33 hpf, 8 hr after heat shock (see also Movies S1 and S2). White arrowheads point to HSCs, labeled by Tg(itga2b:EGFP) (green) and Tg(kdrl:HRAS-mCherry) (red) expression, just arisen from the aortic wall at each indicated time point.

(G–L) Ifng1-2 knockdown reduces the emergence of HSCs and consequently the development of myeloid and lymphoid cells. runx1 expression was assessed during initiation of definitive HSC development at 26 hpf in mock-injected (G) and ifng1-2 MO-injected (H) embryos. Myeloid marker mpx1 expression in 48 hpf mock-injected (I) and ifng1-2 MO-injected (J) embryos. Lymphoid marker rag1 expression in the developing thymus (black circle) of mock-injected (K) and ifng1-2 MO-injected (L) 4 dpf larvae.

(M–P) Elevated expression of runx1 upon ifng1-2 overexpression. runx1 expression in 36-38 hpf WT embryos heat-shocked (h.s.) at 10–12 hpf (M) or 20–22 hpf (O) and Tg(hsp:ifng1-2) embryos heat-shocked at 10–12 hpf (N) or 20–22 hpf (P). The number of embryos showing the representative phenotype per total number of embryos analyzed is indicated in the lower left corner. Red brackets identify the dorsal aorta (DA), and blue brackets identify the cardinal vein (CV). All images are lateral views, dorsal up and anterior to the left.