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Fig. S4 scl-β MO is specific to the loss of hemogenic endothelium in scl-β morphants. (A-D) WISH of the endothelial cell-specific marker fli1 (A,B) and artery-specific marker dll4 (C,D) show comparable expression in control embryos and scl-β morphants at 24 hpf, indicating that the vascular system has developed normally in scl-β morphants. (E-H) The loss of HSCs is partially rescued in the scl-β morphant receiving scl-β PAC expression. (E) The scl-β PAC. DsRed and an SV40 polyadenylation signal cassette were inserted behind exon 1 to interrupt the transcription of scl-α, whereas the expression of scl-β is not affected. (F-H) WISH of the HSCspecific marker cmyb in the 26 hpf control embryo (F), scl-β morphant (G) and scl-β morphant injected with scl-β PAC (H). A lower magnification (8×) is shown to the left and a higher magnification (20×) of the trunk region to the right. Lateral views with anterior to the left. (I-N) Double immunostaining of Kdrl:eGFP and TUNEL in the AGM of 28 hpf scl-β morphants (I-K) and control embryos (L-N). White arrows indicate two Kdrl:eGFP+ cells undergoing apoptosis in the AGM. Scale bar: 20 μm.