Defects in hematopoiesis and vascular development in Dot1L KO embryos. (A-B) Representative pictures of WT (A) and Dot1L KO (B) embryos at E10.5, showing reduced embryo size as well as significant anemia in the Dot1L KO embryos. Note the overall pale appearance of the KO embryo. (C-D) Representative pictures of whole-mount WT (C) and Dot1L KO (D) embryos with surrounding yolk sac show that yolk sacs from Dot1L KO contain less blood and exhibit a reduction in the number of vessels compared with those from WT. (A-D) Embryos were viewed with the use of a NIKON SMZ800 stereo microscope with Plan 1× objective lenses (total 10×), and images were taken with a LEICA DFC480 camera with the use of Leica Firecam software at room temperature. (E-F) Representative enlarged pictures (20×) show that blood vessels in KO yolk sacs exhibit abnormal caliber and contain less blood compared with WT. (G-H) Representative immunofluorescence confocal images of E10.5 yolk sacs stained with anti-CD31 show a mild defect in vascular remodeling in the Dot1L KO embryos (H). Pictures are representative of 7-10 individual embryos. Pictures were viewed with an Olympus 1 × 71 microscope with 10× UPLANF1 objective lens, and images were taken by Olympus DP71 camera with the use of Olympus DP71 controller software. The fluorochrome was fluorescein isothiocyanate.