Figure 1
Figure 1. A Flk-1+ origin for embryonic blood cells of Flk1+/Cre;Rosa26R-LacZ embryos. (A-E′) E8.5 embryos. (F,F′) E9.5 embryo. (A) Whole-mount image of 3 representative Flk1+/Cre;Rosa26R-LacZ E8.5 embryos. *Plane of major blood islands in yolk sacs. (A′) Whole-mount high-power magnification of an embryo showing stained dorsal aorta (◀, ▶). (B) Control E8.5 embryos display no LacZ+ cells in their yolk sacs or embryo proper. *Plane of major blood islands in yolk sacs. (C,D) Five-micrometer sections through Flk1+/Cre;Rosa26R-LacZ E8.5 embryos. (C′,D′) High-power views of blood islands from embryos in panels C and D, respectively. (E,E′) Sections of a control embryo showing an absence of LacZ+ cells in the embryo, yolk sac, or blood islands. (F,G) Representative FACS plots of E9.5 R26R-EYFP and E9.5 Flk1+/Cre;Rosa26R-EYFP yolk sacs staining for the erythroid cell marker Ter119 and macrophage marker Mac1, respectively (y-axis) and EYFP (x-axis) to assess the origin of these lineage cells within the E9.5 yolk sac. On the right panel, summary data of multiple experiments (n = 8) analyzing the yolk sacs of Flk1+Cre;Rosa26R-EYFP mice. Numbers indicate the percentage of Ter119+ and Mac1+ cells that are either EYFP− or EYFP+, respectively. The bars represent SD of the mean percentage of total Ter119+ and Mac1+ cells, respectively. (H) Transverse section through an E9.5 embryo. LPC indicates left pericardial-peritoneal cavity; LVV, left vitelline vein; NT, neural tube; RPC right pericardial-peritoneal cavity; and RVV, right viteline vein. (H′) Magnification of region containing paired dorsal aorta demonstrating uniformity of LacZ+ blood cells in the embryonic circulation. (A-H') For whole mount embryo images, embryos were bathed in 1× PBS and photographed with an Olympus (Center Valley, PA) DP25 camera attached to an Olpmpus BH-2 dissecting microscope at either 25× or 63× magnification. The same camera was used with an Olympus BX-51 upright microscope to document sectioned embryos with either 40× or 90× oil immersion lenses. Images were captured with Olympus DP2-BSW software and processed with Adobe Photoshop CS 10.0.1.

A Flk-1+ origin for embryonic blood cells of Flk1+/Cre;Rosa26R-LacZ embryos. (A-E′) E8.5 embryos. (F,F′) E9.5 embryo. (A) Whole-mount image of 3 representative Flk1+/Cre;Rosa26R-LacZ E8.5 embryos. *Plane of major blood islands in yolk sacs. (A′) Whole-mount high-power magnification of an embryo showing stained dorsal aorta (◀, ▶). (B) Control E8.5 embryos display no LacZ+ cells in their yolk sacs or embryo proper. *Plane of major blood islands in yolk sacs. (C,D) Five-micrometer sections through Flk1+/Cre;Rosa26R-LacZ E8.5 embryos. (C′,D′) High-power views of blood islands from embryos in panels C and D, respectively. (E,E′) Sections of a control embryo showing an absence of LacZ+ cells in the embryo, yolk sac, or blood islands. (F,G) Representative FACS plots of E9.5 R26R-EYFP and E9.5 Flk1+/Cre;Rosa26R-EYFP yolk sacs staining for the erythroid cell marker Ter119 and macrophage marker Mac1, respectively (y-axis) and EYFP (x-axis) to assess the origin of these lineage cells within the E9.5 yolk sac. On the right panel, summary data of multiple experiments (n = 8) analyzing the yolk sacs of Flk1+Cre;Rosa26R-EYFP mice. Numbers indicate the percentage of Ter119+ and Mac1+ cells that are either EYFP− or EYFP+, respectively. The bars represent SD of the mean percentage of total Ter119+ and Mac1+ cells, respectively. (H) Transverse section through an E9.5 embryo. LPC indicates left pericardial-peritoneal cavity; LVV, left vitelline vein; NT, neural tube; RPC right pericardial-peritoneal cavity; and RVV, right viteline vein. (H′) Magnification of region containing paired dorsal aorta demonstrating uniformity of LacZ+ blood cells in the embryonic circulation. (A-H') For whole mount embryo images, embryos were bathed in 1× PBS and photographed with an Olympus (Center Valley, PA) DP25 camera attached to an Olpmpus BH-2 dissecting microscope at either 25× or 63× magnification. The same camera was used with an Olympus BX-51 upright microscope to document sectioned embryos with either 40× or 90× oil immersion lenses. Images were captured with Olympus DP2-BSW software and processed with Adobe Photoshop CS 10.0.1.

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