Rescue of hematopoiesis in gata1^T301K/vlt embryos. (A) Recovery of blood circulation in gata1^T301K/vlt embryos between 7 and 13 dpf. gata1^vlt/vlt embryos were bloodless and never recovered blood circulation. Twenty embryos of each genotype were monitored daily. (B) Survival curves of gata1^T301K/vlt and gata1^T301K/T301K (blue) and gata1^vlt/vlt (red) embryos from fertilization to 30 dpf. Twenty embryos of each genotype were monitored daily. (C) Lateral views of the tails of 48 hpf embryos after RNA in situ hybridization with erythroid markers α-globin embryonic forms 1 (αe1) and 2 (αe2), showing the absence of globin expression in the CHT region of gata1^vlt/vlt embryos (n = 14/14) and relatively normal globin expression in gata1^T301K/vlt (n = 7/9), gata1^T301K/T301K (n = 4/4), and wild-type (n = 8/8) embryos. (D) Noncirculating cd41-GFP^low cells in the CHT (white arrows, right inset) of 4 dpf embryos. No significant difference was detected in this cell population in gata1^vlt/vlt (n = 15/15) and gata1^T301K/vlt (n = 25/25) embryos compared with the wild-type embryos (n = 30/30). Original magnifications ×80 (C) and ×50 (D).