Fig. 5. Laminin B forms a repeating network in the muscle/epidermis basement membrane. Immunofluorescence micrograph of the same wild-type animal co-stained with Laminin B (green) and myosin heavy chain B (red) antibodies. (A) Laminin B is distributed in a grid-like pattern on the muscle surface. The signal appears as periodic dots (arrowheads) and as regularly spaced bands running circumferentially and longitudinally between the dots. The signal is also enhanced at muscle-muscle cell boundaries (arrow). (B) Staining showing myosin thick filament structure in the muscle cell. Thick filaments emanate from the M-line (small arrow) and interact with thin filaments that are in turn anchored to dense bodies, which are functionally analogous to vertebrate Z-lines. The arrowheads indicate the region where dense bodies are located; large arrow indicates muscle-muscle cell boundaries. (C) Superimposition of the two images above showing the relationship of the extracellular laminin network to the myofilament lattice. The longitudinal laminin band and dots corresponds to the thin-filament-containing regions of the muscle.