We have designed a real-time computer vision system, the Multi-Worm Tracker (MWT), that can simultaneously quantify the behavior of dozens of Caenorhabditis elegans on a traditional petri plate at video rates. Three traditional behavioral paradigms are examined using this system: spontaneous movement on food, where the behavior changes over tens of minutes; chemotaxis, where turning events must be detected accurately to determine strategy; and habituation of response to tap, where the response is stochastic and changes over time. In each case, manual analysis or automated single-worm tracking would be tedious and time-consuming, but the MWT system allows rapid quantification of behavior with minimal human effort. Thus, this system will enablelarge scale forward and reverse genetic screens for complex behaviors.

Dopamine has been implicated in the modulation of diverse forms of behavioral plasticity, including appetitive learning and addiction. An important challenge is to understand how dopamine's effects at the cellular level alter the properties of neural circuits to modify behavior. In the nematode C. elegans, dopamine modulates habituation of an escape reflex triggered by body touch. In the absence of food, animals habituate more rapidly than in the presence of food; this contextual information about food availability is provided by dopaminergic mechanosensory neurons that sense the presence of bacteria. We find that dopamine alters habituation kinetics by selectively modulating the touch responses of the anterior-body mechanoreceptors; this modulation involves a D1-like dopamine receptor, a Gq/PLC-beta signaling pathway, and calcium release within the touch neurons. Interestingly, the body touch mechanoreceptors can themselves excite the dopamine neurons, forming a positive feedback loop capable of integrating context and experience to modulate mechanosensory attention.

Inhibitory GABAergic transmission is required for proper circuit function in the nervous system. However, our understanding of molecular mechanisms that preferentially influence GABAergic transmission, particularly presynaptic mechanisms, remains limited. We previously reported that the ubiquitin ligase EEL-1 preferentially regulates GABAergic presynaptic transmission. To further explore how EEL-1 functions, here we performed affinity purification proteomics using Caenorhabditis elegans and identified the O-GlcNAc transferase OGT-1 as an EEL-1 binding protein. This observation was intriguing, as we know little about how OGT-1 affects neuron function. Using C. elegans biochemistry, we confirmed that the OGT-1/EEL-1 complex forms in neurons in vivo and showed that the human orthologs, OGT and HUWE1, also bind in cell culture. We observed that, like EEL-1, OGT-1 is expressed in GABAergic motor neurons, localizes to GABAergic presynaptic terminals, and functions cell-autonomously to regulate GABA neuron function. Results with catalytically inactive point mutants indicated that OGT-1 glycosyltransferase activity is dispensable for GABA neuron function. Consistent with OGT-1 and EEL-1 forming a complex, genetic results using automated, behavioral pharmacology assays showed that ogt-1 and eel-1 act in parallel to regulate GABA neuron function. These findings demonstrate that OGT-1 and EEL-1 form a conserved signaling complex and function together to affect GABA neuron function. GABA neurons are a critical component of nervous systems across the animal kingdom from mammals (1, 2) to simple invertebrates, such as Caenorhabditis elegans (3, 4). They provide essential inhibitory activity within neural circuits. In humans, various dysfunctions in GABA neurons and the imbalance between excitatory and inhibitory neurotransmission contribute to neurodevelopmental disorders (5, 6). Thus, understanding how GABA neuron function is regulated is critical for our understanding of nervous system function and disease. Much remains unknown about molecular mechanisms that preferentially affect GABAergic transmission. Core presynaptic machinery, such as synaptotagmin, the SNARE complex, and active zone proteins, influence both glutamatergic and GABAergic transmission (7, 8). A few post-synaptic regulators that preferentially or specifically affect GABAergic transmission are known, including Gephyrin, Neuroligin2, Slitrk3, and GARHLs (9-13). In mammals, less is known about presynaptic GABA-specific regulators, but some proteins, such as synapsins, can differentially impact inhibitory transmission compared with excitatory transmission (14, 15). In C. elegans, core presynaptic components play conserved roles in neurotransmission in the motor circuit, a model circuit with balanced excitatory cholinergic and inhibitory GABAergic neuron function (4, 16). Like mammals, relatively few proteins are known that preferentially regulate presynaptic GABA function in C. elegans. Nonetheless, the worm motor circuit has proven valuable for identifying mol...

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