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Fig. 3 Regulatory element R2 of the col2a1a gene drives expression in the craniofacial cartilages. A. Fluorescent and B. merged with Nomarski images of the palatoquadrate and surrounding perichondrium of an embryo injected with DNA for both R2-E1b:EGFP and - 1.7col2a1a:mCherry-caax. C–D. Ventral view of 2 dpf embryos counterstained with wheat germ agglutinin conjugated to Alexa Fluor 647. A. Tg(1.7c2a1a:mGFP) is expressed in the ceratohyal. B. Tg(R2c2a1a:GFP) expression in the trabeculae. E. Lateral view of DAPI stained 4.1 mm SL Tg(1.7c2a1a:mGFP) embryo. F. Lateral view and G. dorsal view of head of adult Tg(R2c2a1a:GFP). H–J. Developmental time series of live larval stage Tg(R2c2a1a:GFP) fish stained with Alizarin red. H. Ventral view, I–J. Semi-lateral view. K–M. Lateral view of hyomandibular cartilages of H–J showing the process of ossification initiated ventral to facial nerve foramen. M2. Magnification of chondrocytes positive for EGFP as they begin the process of hypotrophy. Cartilages: BH, basihyal; CB, ceratobranchials; CH, ceratohyal; HM, hyomandibula; IH, interhyal joint; M, Meckel′s, PQ, palatoquadrate; SY, symplectic; TR, trabeculae. Bones: F, frontal; OP, opercula; PA, parietal. Other: e, eye; ff, facial nerve foramen; pc, perichondrium; Scale bars: A–E, K–M = 50 μm, F = 500 μm, G = 400 μm, H–J = 150 μm. Here and throughout the paper a green circle marks Tg(1.7c2a1a:mGFP) and a green disk indicates the Tg(R2c2a1a:GFP).
Reprinted from Developmental Biology, 357(2), Dale, R.M., and Topczewski, J., Identification of an evolutionarily conserved regulatory element of the zebrafish col2a1a gene, 518-31, Copyright (2011) with permission from Elsevier. Full text @ Dev. Biol.