D. Co-immunofluorescence staining of Lamp1 (lysosome) and PDI (ER) in medaka fish chondrocytes with indicated genotypes treated with FGF18 (50 ng/mL for 24h). Insets showed details of colocalization of Lamp1 and PDI. Wheat germ agglutinin (WGA) was used to stain cartilage matrix. Representative images of N=3 fish/genotype/treatment. Scale bars 10 μm. Boxed area were zoomed and single and merged channels are shown. Scale bars 2 μm. 