Rodent myoblast interactions with laminin require cell surface glycoconjugates but not laminin glycosyl groups

Application of WGA lectin staining for visualization of the connective tissue in skeletal muscle, bone, and ligament/tendon studies

During immunostaining of specific proteins in tissue sections using monoclonal and polyclonal antibodies, visualization of general tissue staining/background or major structural features is helpful to pinpoint precise localization of the protein of interest. Often in skeletal muscle research, immunostaining with antibodies against connective tissue or plasma membrane proteins (collagen 1, laminin, and caveolin 3) are used for this purpose. Although immunostaining for these proteins works well, it is time consuming, costly, limits the number of antibodies against protein of interest that can be used on a single section, and is not applicable to some staining techniques. Lectins were frequently used in earlier publications for skeletal muscle fiber boundaries and connective tissue visualization, but are not common in the current research studies. This work investigates costaining of muscle, bone, ligament, and tendon tissue sections with fluorescently tagged wheat germ agglutinin (WGA) lectin as a tool for the visualization of connective tissue. The results of this study show that fluorescent WGA lectin costaining is a cost-effective, fast, and convenient method for connective tissue visualization, especially in the studies where extensive washes reduce staining of the structures that are the primary interest of the investigation.

Nerve-independent formation of a topologically complex postsynaptic apparatus

As the mammalian neuromuscular junction matures, its acetylcholine receptor (AChR)–rich postsynaptic apparatus is transformed from an oval plaque into a pretzel-shaped array of branches that precisely mirrors the branching pattern of the motor nerve terminal. Although the nerve has been believed to direct postsynaptic maturation, we report here that myotubes cultured aneurally on matrix-coated substrates form elaborately branched AChR-rich domains remarkably similar to those seen in vivo. These domains share several characteristics with the mature postsynaptic apparatus, including colocalization of multiple postsynaptic markers, clustering of subjacent myonuclei, and dependence on the muscle-specific kinase and rapsyn for their formation. Time-lapse imaging showed that branched structures arise from plaques by formation and fusion of AChR-poor perforations through a series of steps mirroring that seen in vivo. Multiple fluorophore imaging showed that growth occurs by circumferential, asymmetric addition of AChRs. Analysis in vivo revealed similar patterns of AChR addition during normal development. These results reveal the sequence of steps by which a topologically complex domain forms on a cell and suggest an unexpected nerve-independent role for the postsynaptic cell in generating this topological complexity.