Definitive HSPCs in the PBI can give rise to T cells. (A) Lateral view of 3-dpf fish indicates the uncaging positions (cross 1: the trunk region; cross 2: the PBI region). (B, C) Confocal images of the flu and rag1 signals in the 5-dpf thymus. The embryos were uncaged at cross 1 in panel 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 staining. (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 staining. Arrows indicate the co-staining of flu and rag1.