GABAergic Motor Neuron Synapses are Defective in <i>tba-1(ju89</i>) Mutants.

<p>(A) Diagram of <i>en passant</i> neuromuscular synapses in <i>C. elegans</i>. Dots represent synapses; dorsal D neurons (DDs) form synapses onto dorsal body-wall muscles, and ventral D neurons (VDs) synapse with ventral muscles. Presynaptic termini of the inhibitory GABAergic type D motor neurons are visualized with the synaptic vesicle marker P<i>_unc-25</i>SNB-1::GFP. Each GFP puncta visible by fluorescence microscopy corresponds to the cumulative signal from all GFP-tagged vesicles at an individual synapse. (B) Morphology of the six DD motor neurons. Cell bodies are located in the ventral nerve cord. Each D neuron extends a ventral process, branches to form a commissure, and bifurcates at the dorsal nerve cord to form a dorsal process along the dorsal nerve cord. At the distal tip of each process, gap junctions are formed with adjacent DD neurons <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009655#pone.0009655-White1" target="_blank">[17]</a>. Expression pattern of SNB-1::GFP in wild-type (C) and mutant (D) dorsal nerve cord. Irregular size puncta and reduced numbers of puncta are evident in <i>ju89</i> mutants. An arrow designates the position of a DD commissure. (E) SNT-1 (synaptotagmin) expression in the dorsal nerve cord of wild-type and (F) <i>ju89</i> mutant animals. UNC-10::GFP expression along the dorsal nerve cord of (G) wild-type and (H) <i>ju89</i> worms. (I) Expression of the GABA-B receptor subunit, UNC-49::GFP, along dorsal muscles of wild-type animals and (J) <i>ju89</i> mutant worms. Gaps in UNC-49::GFP expression demonstrate the lack of post-synaptic structures in these regions. Wild-type <i>C. elegans</i> (K) have a larger body size than <i>tba-1(ju89)</i> (L). <i>C. elegans</i> move in a wavelike pattern. <i>ju89</i> mutants are uncoordinated, and the amplitude of the wave pattern is severely reduced compared to wild-type animals.