Candidate hypoxia-regulated gene validation. In situ hybridization images for the hypoxia-induced gene irs2 are shown under normoxia (A, B, E, F) and hypoxia (C, D, G, H) at gastrula (6 h) and segmentation (24 h) stages, dorsal view. Increased intensity and tissue distribution of irs2 expression are evident in the hypoxia-exposed group (G, H). In comparison, a control gene (ta) shows no hypoxia-dependent changes in expression (A–D). These figure panels depict additional embryo views and/or specimens analogous to Fig. 2D,E from the primary hypoxia study [1].