Fig. 2. Hematopoietic potential of Alk3 CKO and Smad4 CKO embryos. E9.5 Alk3 CKO yolk sacs (A), E10.5 fetal liver (D), Smad4 CKO yolk sacs (E; upper, E8.5; lower, E9.5) were dissociated and plated into methylcellulose cultures with hematopoietic cytokines. Four to seven days later, colonies were counted and plotted. Bar indicates the average number of colonies; error bars indicate standard deviations; n, number of embryos. One representative result is shown. Similar results were obtained from three independent experiments. Ery, erythrocytes; Mac, macrophage, CFU-E, colony forming unit-erythrocyte; BFU-E, burst forming unit-erythrocyte. (B) Genomic PCR of sorted FLK1⁺ or TER119⁺ cells in E9.5 yolk sacs. Lane 1, molecular marker; lane 2, sorted cells from Flk1^+/CreAlk3^{floxed/floxed}; lane 3, sorted cells from Alk3^{floxed/floxed}; lane 4; whole yolk sac cells from Alk3^{floxed/floxed}; lane 5, whole yolk sac cells from Flk1^+/CreAlk3^+/floxed. (C) Genomic PCR on hematopoietic colonies grown from E9.5 Alk3 CKO yolk sac replating. Lane 1, Alk3^{floxed/floxed}; lane 2, Flk1^+/CreAlk3^+/floxed; lane 3, Flk1^+/CreAlk3^{floxed/floxed}; lane 4, Alk3^+/floxed; lane 5, positive control; lane 6, Negative control (H₂O).