title: Postsynaptic ERG potassium channels limit muscle excitability to allow distinct egg-laying behavior states in Caenorhabditis elegans.
abstract: Caenorhabditis elegans regulates egg laying by alternating between an inactive phase and a serotonin-triggered active phase. We found that the conserved ERG [ether-a-go-go (EAG) related gene] potassium channel UNC-103 enables this two-state behavior by limiting excitability of the egg-laying muscles. Using both high-speed video recording and calcium imaging of egg-laying muscles in behaving animals, we found that the muscles appear to be excited at a particular phase of each locomotor body bend. During the inactive phase, this rhythmic excitation infrequently evokes calcium transients or contraction of the egg-laying muscles. During the serotonin-triggered active phase, however, these muscles are more excitable and each body bend is accompanied by a calcium transient that drives twitching or full contraction of the egg-laying muscles. We found that ERG-null mutants lay eggs too frequently, and that ERG function is necessary and sufficient in the egg-laying muscles to limit egg laying. ERG K(+) channels localize to postsynaptic sites in the egg-laying muscle, and mutants lacking ERG have more frequent calcium transients and contractions of the egg-laying muscles even during the inactive phase. Thus ERG channels set postsynaptic excitability at a threshold so that further adjustments of excitability by serotonin generate two distinct behavioral states.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8024, USA.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Collins
authors.forename: Michael R
authors.initials: MR
authors.lastname: Koelle
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D017173:Caenorhabditis elegans / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D051638:Ether-A-Go-Go Potassium Channels / Q000502:physiology*; D005260:Female; D018613:Microscopy, Confocal; D009119:Muscle Contraction / Q000502:physiology; D009132:Muscles / Q000294:innervation* / Q000502:physiology*; D010058:Oviposition / Q000502:physiology*; D054731:PDZ Domains / Q000235:genetics; D016133:Polymerase Chain Reaction; D012701:Serotonin / Q000502:physiology; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure; D019076:Transgenes / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; D051638:Ether-A-Go-Go Potassium Channels; D012701:Serotonin; D004247:DNA