The fli1EGFP-positive hematopoietic cells in the ICM labeled before circulation initiation can contribute to T cells. (A) Live image of the 21-hpf Tg(fli1:eGFP) transgenic embryo indicates the uncaging positions in the anterior (cross 1) or posterior (cross 2) part of the ICM. (B, C) Confocal images of the flu and rag1 signals in the 5-dpf thymus. The embryos were uncaged at cross 1 in A, fixed at 5 dpf, and co-stained with flu and rag1 RNA. (B/C) Merged image of panels B and C. (B'/C') Superimposed view of panels B/C and DAPI signal (blue). (D, E) Confocal images of the flu and rag1 signals in the 5-dpf thymus. The embryos were uncaged at cross 2 in panel A, fixed at 5 dpf, and co-stained with flu and rag1 RNA. (D/E) Merged image of panels D and E. (D'/E') Superimposed view of panels D/E and DAPI signal (blue). Arrows indicate the overlapping of flu and rag1 staining.