New dogs in the dogma: Lrp4 and Tid1 in neuromuscular synapse formation.

Two recent papers reported identification of a long-sought agrin coreceptor, Lrp4 (Kim et al. in Cell and Zhang et al. in Neuron). In this issue of Neuron, Linnoila et al. report the identification of a new player in the agrin-MuSK pathway, Tid1, which directly interacts with MuSK and is responsible for transducing signals from MuSK activation to AChR clustering, culminating in cross-linking to the subsynaptic cytoskeleton. These papers substantially reshape the agrin-MuSK-ACh hypothesis of neuromuscular synaptogenesis.