The protein agrin is a principal component of a signaling pathway that underlies the formation of the neuromuscular junction (NMJ), which is the synaptic connections between motor neurons and muscle fibers.
Agrin is released by the pre-synaptic terminal and binds to Lrp4 receptors on the muscle fiber. Signal transduction from Lrp4 receptors involves activation and tyrosine phosphorylation of the receptor tyrosine kinase MuSK that directly associates with Lrp4.
Next, MuSK phosphorylates and recruits the adaptor protein Dok-7. Activation of Dok-7 ultimately results in the phosphorylation and clustering of acetylcholine receptors (AChR) on the post-synaptic membrane.
From the statements below, select only those that confirm the role of the Agrin-MuSK signaling pathway in synaptic differentiation as described above.
Select ALL that apply.