GATA1 and neoplasm: To simultaneously investigate the infiltration of angiogenic sprouts into microtumors and the emergence of blood circulation in microtumors (Diameter <1 mm) in vivo, we established a xenograft tumor model in Tg(flk1:eGFP; Gata1:dsRed) double transgenic zebrafish (Fig. 1A)19, 20.