Fig. 6

Non-muscle myosin and Unc45b localize with costamere components at myoblast cell peripheries and at myosepta. Immunofluorescent staining of early zebrafish embryos (10–12 hpf) demonstrates the localization of early sarcomere components (including non-muscle myosin) to the cortices of myoblasts during somite organization (depicted in top left panel). Myocyte costamere components such as α-actinin and integrin-linked kinase (ILK) localize to the myoblast cell cortex prior to costamere formation (arrowheads). Punctae in these panels indicate nucleation of costamere components at cell attachment sites (arrows). NMM and Unc45b are similarly localized to myoblast cortices. Phalloidin staining against actin marks the myoblast cortex. Subsequently, at 12–15 hpf (lower panels), costamere components organize at the myosepta (arrowheads) as depicted schematically in bottom left panel, including α-actinin and ILK. Non-muscle myosin and Unc45b were also localized to the developing myosepta (bottom right panels).