RT Journal Article SR Electronic T1 GABA Is Dispensable for the Formation of Junctional GABA Receptor Clusters in Caenorhabditis elegans JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 2591 OP 2599 DO 10.1523/JNEUROSCI.23-07-02591.2003 VO 23 IS 7 A1 Gally, Christelle A1 Bessereau, Jean-Louis YR 2003 UL http://www.jneurosci.org/content/23/7/2591.abstract AB At GABAergic synapses, GABA receptors form high-density clusters opposite GABA release sites. Whether GABA release per se plays a role in the formation of GABA receptor clusters remains uncertain. To address this question in vivo, we characterized GABA receptor clustering in the nematode Caenorhabditis elegans. In C. elegans, body wall muscles receive excitatory inputs from cholinergic motor neurons and inhibitory inputs from GABAergic neurons. Using immunohistochemistry and green fluorescent protein-tagged proteins, we observed that the muscle GABA receptor UNC-49 is precisely clustered opposite GABA release sites. During development, these clusters appear slightly after the detection of presynaptic vesicles. If motor axons are mislocalized as in unc-5 mutants, GABA receptors cluster opposite ectopic axons at GABA release sites. Together, these data imply that a motor neuron-derived factor is instructing GABA receptor clustering. Presynaptic localization of this clustering activity requires the neuronal kinesin UNC-104, suggesting that release of GABA from synaptic vesicles may represent the clustering signal. However,unc-25 mutants do not synthesize GABA but do cluster postsynaptic GABA receptors indistinguishably from the wild type. Therefore, at GABAergic neuromuscular junctions, GABA receptor clustering requires nerve–muscle interaction but not GABA neurotransmission.