Figure 5

Comp distribution in zebrafish tissues at different stages of development. Immunostainings were performed using an affinity-purified rabbit antiserum directed against zebrafish Comp. (A–D), whole mount staining of 11hpf (A), 19hpf (B), 24 hpf (C) and 72 hpf (D) zebrafish. At 11-24 hpf Comp is expressed in the somites (A–C, brown peroxidase staining) and at 72 hpf in the myosepta (D, green fluorescence). E-L, immunostaining was carried out on paraffin-embedded tissue sections from 100 hpf (E, F), 2-month-old (G–J) and adult (K, L) zebrafish by alkaline phosphatase-conjugated streptavidin and Fast Red staining. In the head, at 100 hpf Comp is expressed in tendinous tissues (arrows), but not in cartilage (c) (E, F). Comp is also found in the pectoral fin (arrowheads). A transverse section through a vertebral body displays Comp in the notochord (framed) most strongly in the notochord sheath (arrows), but not in vertebral cartilage (c) of 2-month-old zebrafish (G, H, J). Consecutive transverse sections (H-J) show a variable expression around vacuolated notochord cells, most prominent at positions with a narrow notochord (J). Comp was also found in tendinous structures that attach muscles to the vertebra (G, H, J) (arrowheads). In adult zebrafish (K, L) Comp is still expressed in myosepta (m, arrows) and around ribs (r, arrowheads) where the skeletal muscles are attached. (Asterisks in E, F) Unspecific staining of kidney tubules by the secondary antibody, see also Supplementary Figure 2. Bars: 50 µm in (G–J), 100 µm in (E, F, K, L) and 200 µm in (D).