Fig. 1. Cell types responding to hedgehog signaling in ES embryoid bodies and yolk sacs. (A) Day 13 R1 ES Ptch-lacZ embryoid body expressing ß-gal in the mesothelial layer surrounding blood islands (arrows) and beneath the visceral endoderm between blood islands. (B) Ptch-lacZ (ß-gal) and PECAM are expressed in distinct patterns in adjacent sections in day 13 embryoid bodies. (C) Double staining demonstrates overlapping expression for ß-gal and -SMA around blood islands (arrows) and between them in day 12 embryoid bodies. (D) 10.5 dpc Ptch-lacZ yolk sacs express ß-gal around blood vessels and in the mesothelial layer. (E) -SMA is also expressed around and between vessels in 10.5 dpc yolk sacs. Scale bars: 100 µm.