Fig. 8

Jaw joint expression of trps1^J1271aGt is regulated by Edn1 signaling, and the Edn1 targets hand2 and dlx3b/4b/5a. (A-O) Confocal projections of 4 dpf anti-Collagen II and trps1^J1271aGt labeling is shown, merged in the left panel, and split in the center and right panels. Treatments are indicated in the left column. Anterior is leftwards, dorsal upwards. (A) In wild type, trps1^J1271aGt expression is faint in skeleton, and very bright in joints. (B) dlx3b;4b;5a-MO injection reduces trps1^j1271aGt in the first, (arrow) and second (arrowhead) arch joints, whereas the fused OP-BSR (tildes) bone expresses ectopic trps1^j1271aGt. (C) In hand2^S6, the jaw joint expression of trps1^J1271aGt expands dramatically, beneath broad ectopic cartilages. (D) In hand2^S6;dlx3b;4b;5a-MO, the expanded cartilages and trps1^J1271aGt expression domains in the first arch are reduced compared to uninjected hand2^S6. (E) In edn1 mutants, the first and second arch joint expression of trps1^J1271aGt is lost, and conversely the opercle-hyomandibular joint expands. Throughout these treatments, the hyomandibular-neurocranium joint (asterisk) is normal. (P) Diagram of the J1271a insertion site in trps1 ( GenBank Accession Number, GU556967) . Intronic sequence is not to scale. We identified the 5′ end ( GenBank Accession Number, GU474515) of the trps1 gene by 5′ RACE from a predicted, incomplete trps1 sequence, ENSDART0000098144. trps1 5′ RACE revealed a single 5′ noncoding exon, with the J1271a integration site in the first intron. The splice acceptor orientation in T2KSAG predicts that it should be spliced into the processed message, with translation beginning at the initiating methionine in GFP, probably making J1271a a gene trap. Scale bar: 100 μm.