Fig. 4

Whole mount in situ hybridization (WISH) for type I collagen genes in zebrafish embryos.

(a) WISH for col1a1a, col1a1b and col1a2 at different time points (24, 48, 72 and 96 hpf) of zebrafish development. Expression patterns are similar for all three type I collagen genes. However, expression of col1a1a, but not of col1a1b nor col1a2, was clearly noted in the fin fold (indicated by the arrowhead) and in the pectoral fins at 96 hpf. (b) Expression of col1a1a, col1a1b and col1a2 at 96 hpf in the pectoral fin (black arrowheads). Only for col1a1a a clear signal could be detected. Note that basal epidermal cells are similarly labeled for all three collagen type I genes (open arrowheads). (c) Cross (CI-CIII) and sagittal (CIV-CV) sections of 96 hpf WISH specimens, showing details of expression of col1a1a in various cell or tissue types: meninges (CI, arrowheads), osteoblasts surrounding the parasphenoid bone (Ps, CII, CIV) and the cleithrum (Cl, CV), fibroblasts of the mandibulo-hyoid ligament (Mhl, CII, CV) and of the tendon of the sternohyoideus muscle (Tsh, CII) and distal epidermal/subepidermal layers of the pectoral fins (CIII). Mesenchymal cells around ceratobranchials 1-4 display a weak, and around ceratobranchial 5 a somewhat stronger signal (Cb 1-5, CIV). CVI shows the expression of col1a1a in the basal cells of the epidermis. Further abbreviations: B, brain; Ch, ceratohyal; E, eye; Nc, notochord; Pf, pectoral fin; Y, yolk. Cavity marked by * on CII is an artefact.