Figure 3

Rgp1^-/- chondrocytes accumulate collagen II intracellularly. (A) Experimental design for immunohistochemical analysis of chondrocytes in the craniofacial head skeleton. (B) Representative images of Tg(Col2a1α:caax-eGFP) transgenic larvae in WT and rgp1^-/- cartilage (Col2, magenta; eGFP, green). Yellow arrowhead identifies intracellular collagen II. (C) Quantification of the percentage of cytosolic area occupied by collagen II signal in chondrocytes. (D) Experimental design for mosaic overexpression of zRgp1-p2A-mCherry in zebrafish chondrocytes. (E) Representative images of Tg(Col2a1α:caax-eGFP) transgenic chondrocytes in WT and rgp1^-/- cartilage (TEM images of chondrocyte membranes (PM) and adjacent mCherry, magenta; eGFP, green; Col2, white). Yellow arrowhead identifies collagen II in mCherry^- cells while empty arrowhead identifies collagen II in mCherry⁺ cells. (F) Quantification of the percentage of cytosolic area occupied by collagen II signal in chondrocytes. (G) TEM images of chondrocyte membranes and adjacent ECM proteins. (H) Quantification of TEM staining density from craniofacial chondrocyte plasma membrane to edge of cartilage tissue using ImageJ. Significance is presented by ****p<0.0001; ns, not signficant.