Loss of actinotrichia impairs ray patterning. (A-D) Bright-field images of wild-type (n=10 fins) (A,C) and double mutant (n=10 fins) (B,D) caudal fin rays. Joint spacing (blue arrowheads) is regular in wild-type rays (A), but irregular in double mutant rays (B). Bifurcations (red asterisks) are present in wild-type rays (A,C) but absent in double mutant rays (B,D). The wild-type rays taper (C), while, in the double mutant, rays end bluntly, with the inter-ray region receding (D). Melanocytes show a normal distribution in wild-type fins (orange arrowheads), but seem aggregated in the double mutant. Scale bars: 250 µm. (E,F) Transmitted light differential interference (TD) images of wild-type (E) (n=10 fins) and double mutant (F) (n=10 fins) caudal fin ray tips. Dotted arrows represent the direction of the actinotrichia located at the tip of each ray (E). No visible actinotrichia are found in the double mutant rays (F). The tips of double mutant rays end bluntly (F), rather than tapering distally (E). Scale bars: 50 µm. (G-J) Merged confocal and TD images of And1- (G,H) and Col2-immunostained (I,J) wild-type sibling (G,I) and double mutant (H,J) caudal fin ray tips. And1 signal is localized to actinotrichia fibers at the tips of wild-type rays (G) (n=5 fins), but is absent in double mutant rays (n=5 fins). Col2 signal also localizes to the actinotrichia in wild-type rays (I) (n=5 fins), and is found at the tips of double mutant rays (white asterisk), not forming fibers (J) (n=4 fins). Scale bars: 50 µm.
|
