👤 Jonathan T Pierce-Shimomura

The mechanisms by which ethanol and inhaled anesthetics influence the nervous system are poorly understood. Here we describe the positional cloning and characterization of a new mouse mutation isolated in an N-ethyl-N-nitrosourea (ENU) forward mutagenesis screen for animals with enhanced locomotor activity. This allele, Lightweight (Lwt), disrupts the homolog of the Caenorhabditis elegans (C. elegans) unc-79 gene. While Lwt/Lwt homozygotes are perinatal lethal, Lightweight heterozygotes are dramatically hypersensitive to acute ethanol exposure. Experiments in C. elegans demonstrate a conserved hypersensitivity to ethanol in unc-79 mutants and extend this observation to the related unc-80 mutant and nca-1;nca-2 double mutants. Lightweight heterozygotes also exhibit an altered response to the anesthetic isoflurane, reminiscent of unc-79 invertebrate mutant phenotypes. Consistent with our initial mapping results, Lightweight heterozygotes are mildly hyperactive when exposed to a novel environment and are smaller than wild-type animals. In addition, Lightweight heterozygotes exhibit increased food consumption yet have a leaner body composition. Interestingly, Lightweight heterozygotes voluntarily consume more ethanol than wild-type littermates. The acute hypersensitivity to and increased voluntary consumption of ethanol observed in Lightweight heterozygous mice in combination with the observed hypersensitivity to ethanol in C. elegans unc-79, unc-80, and nca-1;nca-2 double mutants suggests a novel conserved pathway that might influence alcohol-related behaviors in humans. Show less

Alternative patterns of neural activity drive different rhythmic locomotory patterns in both invertebrates and mammals. The neuro-molecular mechanisms responsible for the expression of rhythmic behavioral patterns are poorly understood. Here we show that Caenorhabditis elegans switches between distinct forms of locomotion, or crawling versus swimming, when transitioning between solid and liquid environments. These forms of locomotion are distinguished by distinct kinematics and different underlying patterns of neuromuscular activity, as determined by in vivo calcium imaging. The expression of swimming versus crawling rhythms is regulated by sensory input. In a screen for mutants that are defective in transitioning between crawl and swim behavior, we identified unc-79 and unc-80, two mutants known to be defective in NCA ion channel stabilization. Genetic and behavioral analyses suggest that the NCA channels enable the transition to rapid rhythmic behaviors in C. elegans. unc-79, unc-80, and the NCA channels represent a conserved set of genes critical for behavioral pattern generation. Show less