CD41-gfp transgene hematopoietic expression in live zebrafish embryos, from AGM to kidney.(A) Anatomic landmarks relevant to this study in the zebrafish embryo; although represented at 35 hpf,²⁶  it also indicates the future location of the thymus (purple) and pronephric kidney, the site of definitive hematopoiesis (yellow); the optical sectioning planes used in (B) and (C) are represented. (B-L) Live CD41-gfp embryos and larvae; (B,C,F,J,K) Confocal fluorescence images, with Bodipy TR (red) as vital histologic stain; all lateral views, rostral to the left, except (C,K,L). (B,C) Mid-trunk zone at 38 hpf; successive optical longitudinal (B) and cross (C) sections of the same embryo were obtained by laser scanning in the xy and xz mode, respectively. Yellow arrowheads, GFP^low cells in the DP joint, the zebrafish AGM; white arrowheads, DA endothelium; blue arrowheads, PCV endothelium. (D) DIC and fluorescence overlay showing the first GFP^low cells in the CHT area at 35 hpf. (E,E′) DIC (E) and fluorescence (E′) image of a CD41-GFP^low HSC-like cell in the CHT at 35 hpf. (F) GFP^low cells (arrowheads) in the trunk DP joint between DA and PCV at 48 hpf; asterisks, nonhematopoietic, pronephric duct associated GFP^low cells. (G) DIC image of a CD41-GFP^low circulating cell rolling on the PCV dorsal wall at 48 hpf. (H) Fluorescence image of GFP^low (arrowheads) and GFP^high cells in the CHT at 56 hpf; arrows point at the tethers linking GFP^high prothrombocytes to each other or to the microenvironment. (I,I′) DIC (I) and DIC+ fluorescence overlay (I′) images of the first CD41-GFP^low immigrants in the left thymus anlage at 56 hpf. (J) Left thymus at 4.5 dpf. (K,L) Pronephros area in dorsal view at 5 dpf (K) and dorso-lateral view at 8 dpf (L). da indicates dorsal aorta; pcv, posterior cardinal vein (axial vein); ca, caudal artery; cv, caudal vein; y, yolk sac; CHT, caudal hematopoietic tissue; s, somite muscle; ntc, notochord; pd, pronephric duct; phs, primary head sinus; ba, branchial arches; oe, otic epithelium; t, thymus; pf, pectoral fin; g, pronephric glomerulus; and sb, swimbladder. Bars, 20 μm in (B,C,H); 10 μm in (E,G); 50 μm in (F,J,K).