Fig. 1.

The p2rx3.1 gene is expressed in cranial ectoderm at 12 hpf. Whole-mount in situ hybridization shows p2rx3.1 expression (purple) in the head at 12 hpf (a). The dotted white line shows position of eye field, the dotted black line is approximate level of transverse sections shown in panels (b–d). In b–d, the top images are of complete transverse section, with the dotted line indicating the midline and the box outlining magnified region shown below. Brown labeling is sox10 in b, foxd3 in c, and tfap2a in d. Purple labeling in all three panels is p2rx3.1, and arrow in d points to double-labeled cells