Figure 4

nkx3.2 ^-/- zebrafish display defects in lower jaw-associated musculature. (A) Lateral volume rendering of the wild-type zebrafish head skeleton and relevant associated muscles. (A?) Close up of the rendered adductor mandibulae muscle bundles A1-A3. (A??) False-coloured transverse virtual thin section [position indicated by dotted line in (A)] highlighting the protractor hyoideus muscle and distinct bundles of the adductor mandibulae. (B?D) Renderings of the isolated A1, A2, and A3 bundles of the adductor mandibulae, respectively. (E, F) The left and right lateral views of a single nkx3.2 ^-/- zebrafish, with the panels in (F-F??) reversed to facilitate comparison. Arrows in (B, E?, F?) indicate the maxillary tendon of A1. Asterisk in (E?) indicates the unusual anterior attachment site of the A1 bundle to the lower jaw. Arrowheads in (E?) and (F?) indicate the abnormal organization of muscle bundles. (G, H) Dorsal view of the lower jaw skeleton and associated musculature in wild-type and nkx3.2 ^-/- fish, with the basihyal rendered transparent. In (G), the maxilla and premaxilla were also rendered as partially transparent, and the right adductor mandibulae was removed to reveal the quadrate below. In (H), arrowhead indicates protractor hyoideus muscle fibers crossing the midline. Asterisk indicates ectopic ossifications embedded in the right adductor mandibulae. Both zebrafish are 2mpf and were scanned with a voxel size of 3µm using DICE-PPC-SRµCT. aa, anguloarticular; bh, basihyal; ch, ceratohyal; d, dentary; e, eye; en, endopterygoid; hm, hyomandibula; IMA, intermandibularis anterior; m, maxilla; mc, Meckel?s cartilage; mpt, metapterygoid; PH, protractor hyoideus; pm, premaxilla; po, preopercle; q, quadrate. All scale bars, 500µm, except on virtual thin sections (A??, E??, and F??) 300µm.