Fig. 5

Myod^fh261 mutants have cranial bone defects. A. Bright field image of a live 6 dpf myod^fh261 mutant (retrospectively sequence genotyped) and a 5 dpf myod morphant showing craniofacial defects of lowered jaw and open mouth compared with sibling and control, respectively. B,C. Alcian blue and alizarin red double staining for cartilage and bone in myod^fh261 mutants and siblings. At 5 dpf (B), cartilage components in mutants have different morphology with the whole lower jaw dropping, forming a gaping mouth. Both first and second arch derivatives, such as Meckel′s (mk) and ceratohyal (ch) cartilage respectively, are bent ventrally. The ethmoid plate (eth) is only mildly affected. Little bone staining is detected in the mutant. Anterior to left, ventral (left panel) and lateral (right panel) views. At 6 dpf (C), myod^fh261 mutants show various cartilage and bone defects; the opercle (arrowheads) is missing, ceratobranchial 5 and the parasphenoid (white arrows) less ossified bone and the cleithrum is reduced. Cartilage cells in the mutant remain rounded, failing to mature into flattened columns. Anterior to left. Wholemounts in lateral view (left panel), or flatmounts of the dissected pharyngeal skeleton (ventral view, second from left) or neurocranium (dorsal view, central panel). Large boxed areas are magnified in the fourth panels, showing reduced ossification of ceratobranchial 5 and cleithrum. Small boxed areas are magnified in righthandmost panels to reveal rounded morphology of cartilage cells in the joint between Meckel′s and palatoquadrate (pq) cartilages in the myod^fh261 mutant. cl, cleithrum; nc, notochord; op, opercle; ps, parasphenoid; cb5 ceratobranchial 5. Bars = 100 μm.