Dynamics of cell release from AGM to CHT: CD41-gfp expression marks competency to leave the AGM. (A-E) Live follow-up of AGM cells labeled by laser-mediated uncaging of caged fluorescein at 26 hpf; left lateral views, rostral to the left. (A,B) DIC (A) and fluorescence (B) image of the trunk just after uncaging fluorescein all along the DP joint; vertical lines separate the parts captured at a slightly different focus. (C-E) Depending on the embryo, the first photolabeled cell is detected in the CHT at 32 hpf (C), 33 hpf (D), or 34 hpf (E), all with hematopoietic progenitor morphology, and in the CV lumen. (F-K) Follow-up of AGM cells labeled by laser-mediated uncaging of caged rhodamine in CD41-gfp transgenic embryos. (F) Uncaging of cells along the DA-PCV joint at 37 hpf. (G) Two hours later, some of these labeled cells, still in the trunk, have rounded up (white arrow) and/or entered the PCV (black arrow). (H,I) At the same time, the very first red labeled cells are detected in the CHT; these cells are all GFP⁺, and with similar early progenitor morphology, including sharply defined dot-like nucleoli. (J,K) Seventeen hours post uncaging, most red labeled cells in the CHT are still GFP⁺, with more diverse morphologies. Scale bars, 100 μm (B), 20 μm (C-E,F), 10 μm (G-K).