Figure 4
From: A conserved juxtacrine signal regulates synaptic partner recognition in Caenorhabditis elegans
Expression of UNC-6 in AVA or UNC-40 in PHB is sufficient for SPR. (A) Expression of p AVA::unc-6 in unc-6 mutants and p PHB::unc-40 in unc-40 mutants restores NLG-1 GRASP fluorescence, labeling PHB-AVA synapses. NLG-1 GRASP fluorescence is also significantly rescued in unc-6 mutants by expressing a membrane-tethered unc-6 in AVA ( p AVA::MTunc-6). ***P < 0.001, **P < 0.01, u-test. (B) Neurite contact between PHB and AVA is significantly rescued by expression of p AVA::unc-6 or p AVA::MTunc-6 in unc-6 mutants and p PHB::unc-40 in unc-40 mutants. ***P < 0.001, **P < 0.01, t-test. (A,B) Two lines were examined for each transgene; in all cases, both lines gave similar results. Wild-type n = 254, unc-6 n = 87, unc-6; p AVA::unc-6 n = 70, unc-6; p AVA::MTunc-6 n = 84, unc-40 n = 85, and unc-40; p PHB::unc-40 n = 79 animals. (C) PHB axon guidance to the preanal ganglion is restored by expression of p PHB::unc-40 in unc-40 mutants but not by expression of p AVA::unc-6 in unc-6 mutants. Wild-type n = 94, unc-6 n = 180, unc-40 n = 147, unc-6; p AVA::unc-6 n = 144, and unc-40; p PHB::unc-40 n = 108 animals. **P < 0.01, NS, not significant, χ2 goodness-of-fit test. (D) Overexpression of p AVA::unc-6 and p AVA::MTunc-6 in wild-type animals increases NLG-1 GRASP fluorescence intensity, indicating an increase in PHB-AVA synapses, while overexpressing p PHB::unc-40 does not, indicating that the UNC-6 signal is limiting. Two lines were examined for each transgene with the exception of p PHB::unc-40 overexpression, where three lines were examined; in all cases, all lines gave similar results. Wild-type n = 165, p AVA::unc-6OE n = 82, p AVA::MTunc-6OE n = 79, and p PHB::unc-40OE n = 119 animals. ***P < 0.001, **P < 0.01, NS, not significant, u-test. (A-D) P-values were adjusted for multiple comparisons using the Hochberg method. (E) Schematic and (F) micrograph of UNC-40 subcellular localization. UNC-40::GFP is localized to the region of contact with AVA within the PHB axon, but is excluded from the commissure and dendrite. Yellow scale bar: 5 μm.