Restoration of RA signaling in RA-deficient embryos rescues specification of hemogenic endothelium. (A) Phenotypic analysis of hemogenic specification in RA-treated E9.5 WT, and (B) E9.5 Raldh2^−/− littermate yolk sac. (C) Quantitative analysis of the SP compartment in RA-treated E9.5 Raldh2^−/− versus WT littermate yolk sac. All quantitative data were calculated as a percentage of the total live cell population plus or minus SEM (n ≥ 3). Statistical analysis of significance was determined by Student t test, with a confidence interval of 95% (P ≤ .05).