title: Specification of muscle neurotransmitter sensitivity by a Paired-like homeodomain protein in Caenorhabditis elegans.
abstract: The effects of neurotransmitters depend on the receptors expressed on the target cells. In Caenorhabditis elegans, there are two types of GABA receptors that elicit opposite effects: excitatory receptors that open cation-selective channels, and inhibitory receptors that open anion-selective channels. The four non-striated enteric muscle cells required for the expulsion step of the defecation behavior are all sensitive to GABA: the sphincter muscle expresses a classical GABA-sensitive chloride channel (UNC-49) and probably relaxes in response to GABA, while the other three cells express a cation-selective channel (EXP-1) and contract. Here we show that the expression of the exp-1 gene is under the control of dsc-1, which encodes a Paired-like homeodomain protein, a class of transcription factors previously associated with the terminal differentiation of neurons in C. elegans. dsc-1 mutants have anatomically normal enteric muscles but are expulsion defective. We show that this defect is due to the lack of expression of exp-1 in the three cells that contract in response to GABA. In addition, dsc-1, but not exp-1, affects the periodicity of the behavior, revealing an unanticipated role for the enteric muscles in regulating this ultradian rhythm.
authors.affiliation: Department of Biology, McGill University, 1205 Avenue Dr Penfield, Montréal, Québec H3A 1B1, Canada.
authors.forename: Robyn
authors.initials: R
authors.lastname: Branicky
authors.forename: Siegfried
authors.initials: S
authors.lastname: Hekimi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D003672:Defecation / Q000235:genetics / Q000502:physiology; D015801:Helminth Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism*; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D018079:Receptors, GABA / Q000096:biosynthesis / Q000235:genetics; D017384:Sequence Deletion
chemical_list: D029742:Caenorhabditis elegans Proteins; C506964:Dsc-1 protein, C elegans; C504796:EXP-1 protein, C elegans; D015801:Helminth Proteins; D018398:Homeodomain Proteins; D009124:Muscle Proteins; D018377:Neurotransmitter Agents; D018079:Receptors, GABA