In wild-type animals, ALM neurons have a single anteriorly directed process ( Figures 8B and 8C). In mutants with decreased Wnt signaling, ALM neurons exhibit either of two defects, with some neurons having both an anterior and a posterior process (bipolar ALMs) while others have a single posteriorly directed process (reversed ALMs) ( Figures 8B and 8C) ( Fleming et al., 2010 and Prasad and Clark, 2006). The prevalence of bipolar and reversed ALM neurons differs among Wnt mutants. These differences

in ALM defects likely result from the fact that C. elegans has five Wnt ligands, which have distinct effects on ALM polarity. For example, two prior studies showed that the effects of two Wnts (CWN-1 and EGL-20) on ALM polarity are antagonized by a third Wnt (LIN-44) ( Fleming et al., 2010 and Prasad and Clark, 2006). Thus, the precise ALM phenotype observed is determined by how Tanespimycin cell line each mutation alters signaling

by the different Wnt ligands. To further investigate PD-0332991 solubility dmso if RIG-3 plays a role in Wnt signaling, we analyzed the effect RIG-3 inactivation on ALM polarity in several genetic backgrounds. Although ALM polarity was unaltered in rig-3 single mutants, the rig-3 mutation significantly altered ALM polarity defects caused by other Wnt pathway mutations in double and triple mutants. Inactivating RIG-3 in cwn-1; egl-20 double mutants decreased the severity of ALM polarity defects: ALM reversals were significantly reduced in second cwn-1; egl-20; rig-3 triple mutants (p < 0.01, Fishers exact test), while the number of bipolar ALMs was unaffected (p = 0.21, Fishers exact test). Inactivating RIG-3 in mig-14 Wntless mutants decreased ALM reversals and increased bipolar ALMs ( Figures 8B and 8C). The different outcome in mig-14 mutants likely results from the fact that MIG-14 is required for secretion of all Wnt

ligands. By contrast, the rig-3 mutation had no effect on ALM polarity in two strains lacking CAM-1, i.e., cam-1; rig-3 double mutants and cam-1 mig-14; rig-3 triple mutants ( Figure 8C). These results lead to three conclusions. First, RIG-3 plays an important role in Wnt regulation of ALM polarity. Second, CAM-1 is absolutely required for the effects of RIG-3 on ALM polarity. Third, the effects of RIG-3 on ALM polarity and on ACR-16 levels at the NMJ can both be explained by changes in Wnt signaling. Our results lead to six primary conclusions. First, RIG-3 acts in motor neurons to prevent a form of postsynaptic plasticity that is induced by aldicarb treatment. Second, inactivating RIG-3 has no effect on baseline synaptic transmission, suggesting that the function of RIG-3 is required only during aldicarb-induced plasticity. Third, the synaptic potentiation observed in rig-3 mutants is mediated by aldicarb-induced accumulation of postsynaptic ACR-16 nAChR receptors. Fourth, RIG-3 decreases the number of mobile ACR-16 receptors available for recruitment into postsynaptic receptor fields.