title: Muscle-specific functions of ryanodine receptor channels in Caenorhabditis elegans.
abstract: Ryanodine receptor channels regulate contraction of striated muscle by gating the release of calcium ions from the sarcoplasmic reticulum. Ryanodine receptors are expressed in excitable and non-excitable cells of numerous species, including the nematode C. elegans. Unlike vertebrates, which have at least three ryanodine receptor genes, C. elegans has a single gene encoded by the unc-68 locus. We show that unc-68 is expressed in most muscle cells, and that the phenotypic defects exhibited by unc-68 null mutants result from the loss of unc-68 function in pharyngeal and body-wall muscle cells. The loss of unc-68 function in the isthmus and terminal bulb muscles of the pharynx causes a reduction in growth rate and brood size. unc-68 null mutants exhibit defective pharyngeal pumping (feeding) and have abnormal vacuoles in the terminal bulb of the pharynx. unc-68 is required in body-wall muscle cells for normal motility. We show that UNC-68 is localized in body-wall muscle cells to flattened vesicular sacs positioned between the apical plasma membrane and the myofilament lattice. In unc-68 mutants, the vesicles are enlarged and densely stained. The flattened vesicles in body-wall muscle cells thus represent the C. elegans sarcoplasmic reticulum. Morphological and behavioral phenotypes of unc-68 mutants suggest that intracellular calcium release is not essential for excitation-contraction coupling in C. elegans.
authors.affiliation: Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706, USA. ebmaryon@facstaff.wisc.edu.
authors.forename: E B
authors.initials: EB
authors.lastname: Maryon
authors.forename: B
authors.initials: B
authors.lastname: Saari
authors.forename: P
authors.initials: P
authors.lastname: Anderson
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D020013:Calcium Signaling; D005260:Female; D015870:Gene Expression; D017238:Genes, Helminth; D008297:Male; D008854:Microscopy, Electron; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D009154:Mutation; D010614:Pharynx / Q000002:abnormalities; D010641:Phenotype; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000502:physiology*; D014018:Tissue Distribution
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel