Figure 7.

unc45b mutants also exhibit cell-free spaces in the somites and disruption of the myosepta like the apo2a morphants. (A–C) α-Actin–GFP transgenic wild-type (A), unc45b (B), and hsp90a (C) mutant embryos. unc45b mutant embryos exhibit cell-free spaces in the somitic musculature (B, stars) as seen in apo2a morphants. In contrast, wild-type siblings (A) and hsp90a (C) mutants do not show these gaps. (D–F) Cell-free spaces are also visible in unlabeled unc45b mutants using DIC optics (E, white stars). In contrast, wild-type siblings (D) and hsp90a mutants (F) do not exhibit these cell-free spaces in the somites. Broken lines indicate myoseptal boundaries. (G) Merge of DIC and α-actin–GFP fluorescence frames shows detachment of myofibrils (arrows) and cell-free spaces (stars) in unc45b mutants, which is seen in apo2a morphants but never seen in wild-type or morphant control embryos. (H and I) Immunohistochemistry with a β-dystroglycan (DG) antibody shows disruption of myosepta in unc45b mutants (I), whereas wild-type siblings (H) have normal chevron-shaped myosepta. (J–L) Unc45b-GFP is localized at the Z line (J, white arrow) as well as at the myosepta (blue arrow), whereas embryos expressing CapZa1-GFP show localization at the Z line exclusively (L, arrow). Immunohistochemistry with an antibody against endogenous Unc45b reveals that endogenous Unc45b is localized at the myosepta (K and K′, blue arrows) in addition to the previously shown Z line staining (K′, white arrow). Bars: (A–I and K) 40 µm; (J and L) 2 µm; (K′): 4 µm.