cGAL, a temperature-robust GAL4–UAS system for Caenorhabditis elegans

The GAL4–UAS system is a powerful tool for manipulating gene expression, but its application in Caenorhabditis elegans has not been described. Here we systematically optimize the system's three main components to develop a temperature-optimized GAL4–UAS system (cGAL) that robustly controls gene expression in C. elegans from 15 to 25 °C. We demonstrate this system's utility in transcriptional reporter analysis, site-of-action experiments and exogenous transgene expression; and we provide a basic driver and effector toolkit

A stochastic neuronal model predicts random search behaviors at multiple spatial scales in C. elegans

Random search is a behavioral strategy used by organisms from bacteria to humans to locate food that is randomly distributed and undetectable at a distance. We investigated this behavior in the nematode Caenorhabditis elegans, an organism with a small, well-described nervous system. Here we formulate a mathematical model of random search abstracted from the C. elegans connectome and fit to a large-scale kinematic analysis of C. elegans behavior at submicron resolution. The model predicts behavioral effects of neuronal ablations and genetic perturbations, as well as unexpected aspects of wild type behavior. The predictive success of the model indicates that random search in C. elegans can be understood in terms of a neuronal flip-flop circuit involving reciprocal inhibition between two populations of stochastic neurons. Our findings establish a unified theoretical framework for understanding C. elegans locomotion and a testable neuronal model of random search that can be applied to other organisms

cGAL, a temperature-robust GAL4–UAS system for Caenorhabditis elegans

The GAL4–UAS system is a powerful tool for manipulating gene expression, but its application in Caenorhabditis elegans has not been described. Here we systematically optimize the system's three main components to develop a temperature-optimized GAL4–UAS system (cGAL) that robustly controls gene expression in C. elegans from 15 to 25 °C. We demonstrate this system's utility in transcriptional reporter analysis, site-of-action experiments and exogenous transgene expression; and we provide a basic driver and effector toolkit

LETTERS A hub-and-spoke circuit drives pheromone attraction and social behaviour in C. elegans

Innate social behaviours emerge from neuronal circuits that interpret sensory information on the basis of an individual's own genotype, sex and experience. The regulated aggregation behaviour of the nematode Caenorhabditis elegans, a simple animal with only 302 neurons, is an attractive system to analyse these circuits. Wild social strains of C. elegans aggregate in the presence of specific sensory cues, but solitary strains do not Many naturally isolated social strains of C. elegans aggregate into feeding groups with dozens of animals, although other strains, including the laboratory strain N2, are solitary How NPR-1 acts to regulate behaviour is not well understood. A previous report using a genomic npr-1 fragment identified the oxygensensing URX neuron as a site of npr-1 action, but behavioural rescue was incomplete, with rescue of aggregation, partial rescue of bordering, and no rescue of rapid movement We next addressed whether RMG expression of npr-1 is sufficient to suppress aggregation. No RMG-specific promoter is known, so an intersectional strategy was developed to drive npr-1 expression only in cells that express both flp-21 and ncs-1, using Cre-mediated recombination between loxP sites that flanked transcriptional stop sequences. When ncs-1::nCre and flp-21::LoxStopLox::GFP strains were crossed together, the intersection between ncs-1 and flp-21 allowed strong and consistent GFP expression only in RMG and M2 pharyngeal neurons Mammalian neuropeptide Y receptors generally inhibit neurotransmitter release Inspection of the C. elegans wiring diagram 13 revealed that RMG is the hub of a gap-junction network connecting seven classes of neurons, including the oxygen-sensitive URX neurons and the nociceptive ASH and ADL neurons previously implicated in aggregation behaviou

LETTERS A hub-and-spoke circuit drives pheromone attraction and social behaviour in C. elegans

Innate social behaviours emerge from neuronal circuits that interpret sensory information on the basis of an individual's own genotype, sex and experience. The regulated aggregation behaviour of the nematode Caenorhabditis elegans, a simple animal with only 302 neurons, is an attractive system to analyse these circuits. Wild social strains of C. elegans aggregate in the presence of specific sensory cues, but solitary strains do not Many naturally isolated social strains of C. elegans aggregate into feeding groups with dozens of animals, although other strains, including the laboratory strain N2, are solitary How NPR-1 acts to regulate behaviour is not well understood. A previous report using a genomic npr-1 fragment identified the oxygensensing URX neuron as a site of npr-1 action, but behavioural rescue was incomplete, with rescue of aggregation, partial rescue of bordering, and no rescue of rapid movement We next addressed whether RMG expression of npr-1 is sufficient to suppress aggregation. No RMG-specific promoter is known, so an intersectional strategy was developed to drive npr-1 expression only in cells that express both flp-21 and ncs-1, using Cre-mediated recombination between loxP sites that flanked transcriptional stop sequences. When ncs-1::nCre and flp-21::LoxStopLox::GFP strains were crossed together, the intersection between ncs-1 and flp-21 allowed strong and consistent GFP expression only in RMG and M2 pharyngeal neurons Mammalian neuropeptide Y receptors generally inhibit neurotransmitter release Inspection of the C. elegans wiring diagram 13 revealed that RMG is the hub of a gap-junction network connecting seven classes of neurons, including the oxygen-sensitive URX neurons and the nociceptive ASH and ADL neurons previously implicated in aggregation behaviou

Specific expression of channelrhodopsin-2 in single neurons of Caenorhabditis elegans.

Optogenetic approaches using light-activated proteins like Channelrhodopsin-2 (ChR2) enable investigating the function of populations of neurons in live Caenorhabditis elegans (and other) animals, as ChR2 expression can be targeted to these cells using specific promoters. Sub-populations of these neurons, or even single cells, can be further addressed by restricting the illumination to the cell of interest. However, this is technically demanding, particularly in free moving animals. Thus, it would be helpful if expression of ChR2 could be restricted to single neurons or neuron pairs, as even wide-field illumination would photostimulate only this particular cell. To this end we adopted the use of Cre or FLP recombinases and conditional ChR2 expression at the intersection of two promoter expression domains, i.e. in the cell of interest only. Success of this method depends on precise knowledge of the individual promoters' expression patterns and on relative expression levels of recombinase and ChR2. A bicistronic expression cassette with GFP helps to identify the correct expression pattern. Here we show specific expression in the AVA reverse command neurons and the aversive polymodal sensory ASH neurons. This approach shall enable to generate strains for optogenetic manipulation of each of the 302 C. elegans neurons. This may eventually allow to model the C. elegans nervous system in its entirety, based on functional data for each neuron