Figure 2.

Schematic model of PA patterning along the dorsal–ventral axis in zebrafish at 30–36 hpf (hours post-fertilization). Lateral view, head to the left, pharyngeal endoderm in dark yellow, pharyngeal ectoderm in dark grey. The dorsal region of PAs is established by co-operative action of jag1b and grem2 and characterized by the expression of dlx2a. The intermediate region of PAs is controlled by dlx3b/4b/5a and msxe, which are downregulated by edn1 in the pharyngeal ectoderm. The ventral region of PAs is dominated by the expression of bmp4-hand2.