Figure 3

Skeletal muscle necrosis initiates temporary denervation. The CFP is pseudo-colored in yellow to allow the visualization of multiple fluorophores. Necrotic IgG positive fibers are shown in green. Note we numbered the synapses in the second panel. Synapse 1: Normal synapse in a non-necrotic fiber (no IgG). Synapse 2: Expression of GAP43 in a pre-necrotic fiber (IgG is next to the fiber). Synapse 3: Onset of necrosis (green fiber without overt cellular infiltrate) leads to the activation of the Schwann cell expressing GAP43 that retracts the presynaptic nerve terminal from the postsynaptic acetylcholine receptors. Synapse 4: Infiltration of cells into the necrotic fibers led to complete retraction of the nerve and loss of the AChR clusters. Synapse 5: Re-innervation of a fragmented postsynaptic synapse in a post-necrotic fiber (note the central nuclei and absence of IgG (green)). Scale bar = 30 μm.