Fig. 2. A CD41:eGFP transgene marks cells in the AGM, along the pronephric ducts and in the thymic lobes. (A) Overview of regions shown at higher magnification in fluorescent images. Purple region denotes left thymic lobe, blue region the left pronephric tubule and red region the AGM (space between axial vessels). (B-E) CD41 is expressed in the first thymic immigrants at 48 hpf. GFP⁺ cells increase in number until 78 hpf, after which GFP expression disappears. (F-I) GFP⁺ cells appear along the pronephric tubules beginning at 32 hpf, and increase in number over time. Broken lines indicate the boundaries of the duct. (J-N) GFP⁺ cells are first observed in the AGM region at 27 hpf, and increase in number over time. After 48 hpf, the AGM region greatly expands as the aorta and vein move apart. The upper broken line denotes the ventral wall of the dorsal aorta, the lower line the dorsal wall of the cardinal vein. GFP⁺ ductal cells appear ventrolateral to cells within the demarcated AGM region. Images are Nomarski/fluorescence merges. Embryos positioned anterior towards the left and dorsal side upwards.