Distribution of laminin receptors at NMJs of Lama4^−/−;Lama5^M/M mice. (A and B) Dystroglycan (A) and Bcam (B) are present at higher levels in synaptic rather than extrasynaptic regions of muscle fibers in control mice. Synaptic levels of both antigens were decreased Lama4^−/−;Lama5^M/M muscle. (C and D) Integrin β1 (C) and integrin α7 (D) are concentrated at synaptic regions of both control and Lama4^−/−;Lama5^M/M muscle fibers. Longitudinal sections of sternomastoid at P60–79 muscle were stained with antibodies to laminin receptors (green) and AChRs (red). Bars, 10 μm.