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Fig. 4
Progressive deterioration of the jaw joint in zebrafish lacking prg4b.
(A) Schematics of prg4a and prg4b TALEN mutants show deleted sequences. (B) X-ray imaging shows no gross morphological bone defects of prg4a-/-; prg4b-/- mutants (DKO) at 12 mpf. (C) Alcian Blue staining shows normal facial cartilages in DKO at 6 dpf. (D) SafraninO staining shows a normal jaw joint between Meckel’s (M) and palatoquadrate (pq) cartilages in DKO at 1 mpf. (E–G) SafraninO staining at 2, 6 and 12 mpf shows increasingly abnormal joints between the jaw anguloarticular (aa) and quadrate (q) bones in DKO. Defects include acellular matrix accumulation in the cavity (asterisks, see magnified regions in E’–G’) at all stages, and synovial hyperplasia (arrowheads) and expanded deep chondrocytes (arrows) at 12 mpf. Single prg4b but not prg4a mutants showed similar jaw joint defects to DKO at 12 mpf. (H) Quantification of jaw joint defects using our modified OARSI system for zebrafish. Scale bar 50 μm, except in (B). See also Figure 4—figure supplements 1,2, and Figure 4—source data 1.