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The fin blistering of nagel mutants is due to mutations in the hemicentin1 gene. (A–C) Lateral views of the posterior medial tail fin of WT larvae at 48 hpf injected with a morpholino targeting the translation site of hmcn1 mRNA (C). Blisters reminiscent of nagel mutant embryos (B) are clearly visible compared to age-matched uninjected controls (A). (D) Genetic map showing the location of the nagel locus on LG20, which did not recombine with the SSLP marker z35375. The genes within the interval, including hmcn1 (red arrow), are shown below. (E–G) Lateral views (E,F) and transverse section (G) of embryos stained by in situ hybridisation with an hmcn1 probe, showing expression in somites (F) and in the apical region of the fin fold at 16 hpf (E), 24 hpf (F), and at 48 hpf (G). (H) The zebrafish Hmcn1 protein is 5616 amino acids in length and contains a signal peptide (pink bar), a Von Willebrand factorA domain (blue box), 44 Ig-like domains (brown diamonds), six thrombospondin type-1 repeats (red ovals), a nidogen G2 domain (green triangle), five EGF-like domains (yellow bars) and a Neuralized homology repeat domain (orange bar). Mutations of the two sequenced nagel alleles and their relative locations are indicated. (I–K) Lateral views (I,J) and transverse section (K) of embryos stained by in situ hybridisation showing expression of hmcn2 in the tail region of the zebrafish embryo at 24 hpf (I) and 48 hpf (J,K). While at 24 hpf, hmcn2 is expressed in the fin fold epidermis and the somites, (I), it becomes confined to fin mesenchyme cells at 48 hpf (J,K). probe Lateral view of a 48 hpf embryo injected with fibrillin2 MO, showing strong blistering of the medial fin (M) compared to uninjected control (L). (N) Lateral view showing expression of fbn2 in the medial fin fold of the tail at 24 hpf as well as in floor plate, hypochord and notochord.
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