cdh5 is dispensable for endothelial emergence, migration, engraftment, and differentiation of HSCs. (A) Time-lapse confocal imaging of cd41:eGFP⁺ HSCs emerging from flk1:mCherry⁺ endothelial cells in control embryos between 30 and 42 hpf (examples are demonstrated with arrows); n = 13/13. (B) cdh5 silencing in cd41:eGFP::flk1:mCherry embryos does not affect endothelial emergence of cd41:eGFP⁺ HSCs (examples are demonstrated with arrows); n = 15/15. (C) cd41:eGFP transgenic embryo fused to transparent casper embryo (wt control) using parabiotic surgery (imaged at 36 hpf), indicates that cd41:eGFP^low HSCs emerging from the control transgenic embryo migrates to casper CHT to engraft and divide (examples are demonstrated with arrows). All 10 of 10 WT parabiots survived. (D) Parabiotic surgery of cd41:eGFP transgenic embryo to transparent casper embryo shows cd41:eGFP^high platelets in circulation in transgenic and casper embryos (imaged at day 4; examples are demonstrated with arrows). (E) cdh5-MO and dextran blue–injected cd41:eGFP transgenic embryo fused to transparent casper embryo shows the emergence of cd41:eGFP^low HSCs in cdh5-silenced embryo (imaged at 36 hpf), which migrate to casper CHT via passive circulation exchange to engraft and further differentiate (examples are demonstrated with arrows). Thirty of 35 cdh5-silenced parabiots survived. (F) Four-day-old cdh5-silenced cd41:eGFP embryo fused to casper embryo, indicating that morphant cd41:eGFP^low HSCs in casper CHT differentiated into circulating cd41:eGFP^high platelets (imaged at day 4; examples with arrows). (G) Surgical fusion of cdh5-silenced and dextran blue–injected runx1+23:NLS-mCherry with casper embryo (imaged at 36 hpf) shows runx1+23:NLS-mCherry⁺ HSPCs emerging from cdh5-silenced transgenic embryo and engrafting to casper’s CHT (examples are demonstrated with arrows). Twelve of 12 parabiots survived. (H) Lateral body-to-head fusion of cdh5-silenced ruxn1+23:NLS-mCherry embryo with casper embryo, showing a lack of circulation exchange between the 2 embryos impedes migration of cdh5-silenced runx1+23:NLS-mCherry⁺ HSPCs to casper (examples are demonstrated with arrows). Five of 7 parabiots survived. (I) Flow analyses of cd41:eGFP^low HSCs at 36 hpf and cd41:eGFP^high platelets at day 4 in the control and cdh5-silenced cd41:eGFP embryos show that differentiation into platelets continues despite the lack of cdh5. Twenty embryos were used in each experiment; n = 5. *P < .05 (t test; error bars indicate s.e.m.).