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Fig. 2 Only late chondrogenic and osteogenic marker genes display decreased expression in egr1 morphants between 24 and 48 hpf.
In situ hybridization was performed at the indicated stages for various cartilage markers, lateral views, anterior to the left. Scale bars 100 μm. (A-E) 4 ng MOcon treated control embryos, (F,G,H,I,J) 4ng splicing MOegr1 injected embryos and (K) rescue. (A,F) At 24 hpf, ap2α3 expression in cranial neural crest cells (cNCC) is not altered in morphants. (B,C,G,H) cNCC marker dlx2a is normally expressed in egr1 morphants (G,H) compared to control embryos (B,C) at 24 and 48 hpf. (D,I) Expression of the essential chondrogenic gene sox9a is not changed at 48 hpf by egr1 knock-down. (E,J,K) At 48 hpf, runx2b transcripts are absent in pharyngeal cartilage precursor cells in 4 ng MOegr1 spl embryos. Expression of runx2b is maintained in the cleithrum (cl) and ethmoid plate (ep). (K) Rescue by injection of 80 pg mRNA egr1 restores all runx2b expression domains at 48 hpf. Otic vesicle (ov), mandible (m), ceratohyal (ch), hyosymplectic (hs), ceratobranchial pairs 1 to 5 (cb1-5), cleithrum (cl), ethmoid plate (ep), stream of cNCCs (S1-S3).