dlx gene expression during cranial bone development in zebrafish larvae in Figures 2-23. Transverse, 6-μm-thick sections of whole-mount hybridized specimens (Figs. 2, 3, 2, 8, 9, 10, 14, 15, 16, 20, 21) with their respective 2-μm-thick toluidine blue-stained reference section (5, 6, 7, 11, 12, 13, 17, 18, 19, 22, 23). Legends to all reference sections are identical to those of the hybridized sections. BC, buccal cavity; CB4, ceratobranchial cartilage 4; CB5, ceratobranchial cartilage 5; CH, ceratohyal cartilage; E, eye; HM, hyomandibular cartilage; MC, Meckel's cartilage; O, opercular bone; PQ, palatoquadrate cartilage; TC, trabecula communis; TCR, trabecula cranii. Scale bars = 20 μm.At 3 days postfertilization (dPF). Expression of dlx3b in the osteoblasts surrounding the parasphenoid bone (arrowhead).

At 3 dPF. Expression of dlx5a in the osteoblasts surrounding the parasphenoid bone (white arrowhead). Black arrowhead, expression in the condensation of mesenchmyal cells dorsal to the palatoquadrate cartilage, where the entopterygoid bone will form.

At 3 dPF. Expression of dlx5a in the mesenchymal condensations (white asterisk) surrounding Meckel's cartilage. The dentary bone will form in the condensation lateral and ventral to the cartilage.

Toluidine blue-stained reference section for Figure 2, showing the mineralized parasphenoid bone (arrowhead).

Toluidine blue-stained reference section for Figure 3. The white arrowhead indicates the mineralized parasphenoid bone, and the black arrowhead shows the mesenchymal cell condensation which will give rise to the entopterygoid bone.

Toluidine blue-stained reference section for Figure 4, showing a mesenchymal cell condensation (asterisk) lateral to Meckel's cartilage.

At 3 dPF. Expression of dlx3b in the mesenchyme lateral to Meckel's cartilage (white arrowhead) and in the ventral epidermis (black arrowhead).

At 4 dPF. Expression of dlx1a in association with the anguloarticular (white arrowhead) and retroarticular bone (black arrowhead) during synthesis and secretion of extracellular matrix.

At 4 dPF. Expression of dlx2b in the osteoblasts surrounding the mineralized maxillary bone (arrowhead).

Toluidine blue-stained reference section for Figure 8, indicating the sites corresponding to dlx3b expression (arrowheads)

Toluidine blue-stained reference section for Figure 9, showing the anguloarticular (white arrowhead) and retroarticular bone (black arrowhead), both not yet mineralized.

Toluidine blue-stained reference section for Figure 10. The arrowhead indicates the mineralized maxillary bone.

At 3 dPF. Expression of dlx5a in the mesenchmyal cell condensation where the entopterygoid bone will form (white arrowhead).

At 4 dPF. Expression of dlx1a in the mesenchymal cells (arrowhead) before the formation of the quadrate bone.

At 7 dPF. Expression of dlx4a in osteoblasts located at the ventral tip of the opercular bone (white arrowhead). dlx4a is also expressed in the mesenchyme of the gills of the fourth and fifth branchial arch (black arrowheads).

Toluidine blue-stained reference section for Figure 14. The arrowhead shows a mesenchymal cell condensation dorsal to the palatoquadrate cartilage.

Toluidine blue-stained reference section for Figure 15. The arrowhead indicates the site where the quadrate bone will form.

Toluidine blue-stained reference section for Figure 16. The white arrowhead indicates mesenchymal cells ventral to the mineralized opercular bone, and black arrowheads indicate mesenchymal cells belonging to the fourth branchial arch, which is situated more medial compared with the section in Figure 16.

At 3 dPF. Expression of dlx5a in the mesenchymal cells (black arrowhead) ventral to the hyomandibular cartilage where the perichondral hyomandibular bone will form. Lateral to the hyomandibula, dlx5a expression is strong in the osteoblasts surrounding the opercular bone (white arrowhead). Strong expression is also observed in mesenchymal cells of the fourth branchial arch. Probably this specimen is slightly advanced, given the observation that this expression connected to the hyomandibular usually only starts at 4 dPF.

At 3 dPF. Expression of dlx3b in the branchiostegal membrane. Transcripts are located in the osteoblasts surrounding branchiostegal ray 3 (black arrowhead). This gene is also expressed in mesenchymal cells of the fourth and fifth branchial arch.

Toluidine blue-stained reference section for Figure 20. The white arrowhead indicates the mineralized opercular bone, at this stage still very small. The black arrowhead indicates a group of mesenchymal cells ventral to the hyomandibular cartilage.

Toluidine blue-stained reference section for Figure 21. The black arrowhead indicates the mineralized branchiostegal ray 3, and the white arrowhead indicates the mesenchymal cell condensation later giving rise to the second branchiostegal ray.

ZFIN is incorporating published figure images and captions as part of an ongoing project. Figures from some publications have not yet been curated, or are not available for display because of copyright restrictions.

ZFIN is incorporating published figure images and captions as part of an ongoing project. Figures from some publications have not yet been curated, or are not available for display because of copyright restrictions.

ZFIN is incorporating published figure images and captions as part of an ongoing project. Figures from some publications have not yet been curated, or are not available for display because of copyright restrictions.

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