Reduced expression of RUNX1, FLK-1, and CD41 in Zfat−/− blood islands. Expressions of RUNX1 at E8.0 (Top), FLK-1 at E8.0 (Middle), and CD41 at E8.25 (Bottom) in the blood islands. Expressions were detected by immunohistochemical staining using each antibody. The region surrounded by the dotted line represents hematopoietic progenitor cells. (Scale bars, 50 μm.)