Gata2 knockdown causes a decrease in blood circulation in gata1^T301K/T301K embryos during primitive hematopoiesis. (A) gata2 expression in gata1 mutant embryos analyzed by whole-mount RNA in situ hybridization. Lateral views of the embryo tails show gata2 expression in the posterior ICM. Embryos were harvested at 24 hpf. Individual embryos were imaged and genotyped (wild-type, n = 4/4; gata1^T301K/vlt, n = 5/7; gata1^vlt/vlt, n = 3/3). Original magnification ×50. (B) Bar graphs showing the percentage of wild-type, gata1^+/T301K, and gata1^T301K/T301K embryos with reduced blood circulation 72 hours after gata2 morpholino injection. There was a significant reduction of gata1^T301K/T301K embryos with normal circulation after injection (*). UI indicates uninjected embryos; INJ, gata2 MO injected embryos. (C) By χ² analysis, the number of injected embryos maintaining normal blood circulation was significantly lower for the gata1^T301K/T301K embryos but not for the gata1^+/T301K embryos. The numbers shown in parentheses are the numbers of embryos expected for each phenotype based on wild-type data.