Alizarin red stained mineralized bone in WT and b3galt6–/– adult zebrafish. The mineralized bones in the skeleton were studied in 4 months old WT and mutant zebrafish after AR mineral staining. (A)b3galt6–/– zebrafish display malformation of the cranium, vertebral column and caudal fin. (A1-1’) The cranium shows an underdeveloped olfactory region (black line) and a smaller compacted opercular bone (asterisk). (A2-2’) The vertebral column shows extra intramembranous outgrowths located where the distal tip of the neural and haemal arches fuse to a neural and haemal spine, respectively (arrowheads). (A3-3’) In the caudal fin fusion of preural vertebrae is observed (asterisk). Associated elements show intramembranous outgrowths (arrowhead) and the presence of extra bony elements (diamond). The distal tip of the hypurals is sometimes split (transparent arrowhead). Structures indicated in the WT caudal fin: Hy1-5, hypural 1-5, Ph, parhypural. (B) Details of mineralized structures in b3galt6–/– zebrafish. (B1-1’) The fifth ceratobranchial arch and its teeth are smaller in KO zebrafish. (B2-2’) The proximal (PR) and distal radials (DR) have irregular shapes in mutant zebrafish. Proximal (asterisk) and distal radials are sometimes fused. The bracket indicates a fusion between a proximal and distal radial, and the first fin ray (FR). (B3-3’) Ribs also show extra intramembranous bone (black arrowhead). (B4-4’) More mineralization was observed at the growth zone (bracket) of the scales in mutant zebrafish (arrowhead). Scale bars = 500 μm.
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