Partially overlapping functions of Prrx1a/b and Jagged-Notch signaling in dorsal cartilage development.
(A-F) The expression of prrx1a and prrx1b (magenta) is largely normal in jag1b mutants (B, D) but is upregulated in ventral arch NCCs (white arrows) and reduced in dorsal NCCs upon forced Notch activation in hsp70I:Gal4; UAS:NICD embryos subjected to a 20–24 hpf heat-shock treatment. dlx2a expression (green) marks all arch NCCs. (G-I) edn1 mutants display a loss of ventral barx1 expression (green) and gain of prrx1b (magenta) (white arrowhead) (H). In jag1b; edn1 mutants, there is partial recovery of ventral barx1 expression in the second arch (white open arrowhead), which corresponds to regions where the ectopic expression of prrx1b is restored to control levels. (J, K) In 7/10 prrx1a; prrx1b mutants, jag1b expression is partially reduced in the dorsal second arch (yellow arrow). (L-O) Dissections of facial cartilage and bone derived from the first two arches show additive phenotypes in jag1b; prrx1a; prrx1b triple mutants. Similar to prrx1a; prrx1b double mutants, triple mutants display ectopic cartilage connecting Pq to the otic cartilage (black arrows). However, similar to jag1b single mutants, jag1b; prrx1a; prrx1b triple mutants also display irregularities in the main body of Pq (black arrowheads). Scale bar in K = 20 μm; scale bar in O = 100 μm.