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. Author manuscript; available in PMC: 2018 May 1.
Published in final edited form as: Dev Dyn. 2017 Mar 20;246(5):368–380. doi: 10.1002/dvdy.24494

Figure 7. A stage-dependent model of NRG1 signaling functions in NMJ development.

Figure 7

During early stages when motor axons first extend toward muscle targets soluble NRG1 induce AChR cluster density and in the ALD muscle also increase AChR cluster size. Once nerve muscle contact is made (middle stage), NRG1 supports the differentiation of the pre- and post-synaptic components of the NMJ leading to the proper alignment. In late stage NMJ development, NRG1 promotes the engulfment of the NMJ by perisynaptic Schwann cells. Previous studies suggest that this may be coincident with the deposition of heparan-sulfate proteoglycans (HSPGs) in the basal lamina providing a sustained source of NRG1 to the synapse (Loeb et al., 1999).