Fig. 1

Craniofacial skeletons of mutant zebrafish larvae exhibit increased bone matrix and decreased cartilage matrix.

A–H, Alcian blue/Alizarin red-stained 6 dpf larvae, entire heads viewed laterally (A,B, eyes removed) or flat-mounted, dissected pharyngeal skeletons viewed ventrally (C–H). I–L, lateral and dorsal views of entire 8-month-old heads (I,J), and corresponding lateral view images of Alizarin red fluorescence taken by optical projection tomography (OPT; K,L). Overall gross anatomy of the head and craniofacial skeleton are similar in wild types (A) and mutants (B), although staining of cartilage and bone appeared altered in mutants. Compared to wild types (C), fam20b^b1125 (D), fam20b^b1127 (E), xylt1^b1128 (F), and xylt1^b1189 (G) mutants had increased Alizarin red staining of bone (arrows) and decreased Alcian blue staining of cartilage. There was no sided-ness to the phenotype, for defective cartilage and bone appeared symmetrically on left and right sides. Double mutant fam20b^b1127;xylt1^b1128 larvae (H) had Alizarin red staining (arrow) similar to that seen in single mutants, but more severe loss of Alcian blue staining. Relative to wild-type siblings (I), fam20b^b1127 mutant adults (J) showed foreshortened upper and lower jaws, hypoplastic midface, and bulging eyes. These overall morphological features were underlain by severe reductions to the size of the mutant craniofacial skeleton (K,L). Abbreviations: A = anterior; bsr = branchiostegal ray; ch = ceratohyal; hs = hyosymplectic; Mk = Meckel′s; op = opercle; P = posterior; pq = palatoquadrate.