Fig. 4

Bergapten and other psoralen compounds affect anterior–posterior patterning. (A) Chemical structures of the compounds tested. (B) Whole-mount in situ hybridization of WT AB embryos with krox-20 and myoD riboprobes. Whole-mount 10-somite stage embryos are shown from a representative experiment. The average distance between krox-20 and myoD in control embryos is 138.6 μm (±7.6 μm). The bergapten-treated embryos lose the gap between krox-20 and myoD, similar to DEAB-treated embryos. 8-MOP also affects the distance, but to a lesser degree (85.8 ± 4 μm). In contrast, PAP-1 does not affect this distance. (C) cdx4 heterozygous adults were incrossed, and the resulting embryos were treated with DMSO vehicle control, 20 μM DEAB, 33 μM 8-MOP, or 33 μM PAP-1. Whole-mount in situ hybridization was done with gata1 and cdx4 riboprobes at the 10-somite stage. 8-MOP robustly rescues gata1 expression in the cdx4-mutant embryos, whereas PAP-1 does not rescue. ss, somite stage; PAP-1, 5-(4-phenoxybutoxy)psoralen; 8-MOP, 8-methoxypsoralen. Color images available online at www.liebertonline.com/zeb.