Fig. 4

Developmental hypoxia induces the hif1 pathway and disrupts pathfinding via a non-cell autonomous mechanism.

Whole-mount embryos, 36 hpf, ventral views, rostral to the top, scale bar 50 μm. Images are brightfield views. (A, B) Staining for the igfbp-1 gene activated by hypoxia shows that hypoxia effectively induces the hif1 pathway. (C) DMOG activates the hif1 pathway, as shown by increased igfbp-1 expression at 36 hpf following DMOG exposure from 24–36 hpf. (D) Increasing DMOG concentration from 24–36 hpf leads to increased rates of TCPTc pathfinding errors, assayed by C/L ratios. *p<0.05; ** p<0.005. Error bars SEM. (E–H) Confocal images, 72 hpf, ventral views, rostral top. (E, F) Normal TCPT pathfinding when hif1α or activated hif1α^mut is expressed in foxP2 neurons. (G, H) Expression of hif1α^mut, but not hif1α, disrupts TCPT pathfinding when expressed in neighboring neurons. (I, J) Expression of hif1α^mut, but not hif1α, leads to activation of the hypoxia pathway as assayed by igfbp-1 expression. (K) C/L intensity ratios of experiments. *p<0.05; ** p<0.005. Error bars SEM.