A Genetic Approach to C. Elegans Cholinergic Signaling (original) (raw)

The identification of genes based on mutations that alter responsiveness to the paralyzing effects of the cholinergic agonist levamisole and the acetylcholinesterase inhibitor aldicarb has greatly enhanced our understanding of the mechanisms underlying neurotransmitter release and cholinergic signaling in C. elegans. However, mutations that only subtly affect drug sensitivity may still produce significant effects on synaptic function and be difficult to isolate in these kinds of screens. Alternative strategies for probing the genetic pathways that regulate neurotransmission may be valuable in identifying these classes of genes. Recent studies of cholinergic signaling in mammals have explored potential roles for nicotinic receptors in the mammalian brain by utilizing nAChR knockin mice that are hypersensitive to nicotine. We have generated strains expressing levamisole receptor subunits carrying a similar gain-of-function mutation. These strains are hypersensitive to levamisole and aldicarb, are hypercontracted, display exaggerated body bends, have kinked noses, and show reduced movement compared to wild type worms. We have used these animals to explore the downstream effects of hyper-activation and have found a dramatic effect in the localization of the nAChR acr-16. To identify new genes that may be involved in levamisole receptor signaling we have conducted a forward genetic screen for suppressors of the movement phenotype. We have isolated 15 suppressors, many of which retain levamisole sensitivity and thus would not have been isolated from traditional levamisole screens. We believe that this strategy will help us to find novel factors that play important roles in cholinergic function.