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.
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JOURNAL ARTICLE| 01 October 1998
Muscle-specific functions of ryanodine receptor channels in Caenorhabditis elegans
Online Issn: 1477-9137
Print Issn: 0021-9533
© 1998 by Company of Biologists
J Cell Sci (1998) 111 (19): 2885–2895.
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E.B. Maryon, B. Saari, P. Anderson; Muscle-specific functions of ryanodine receptor channels in Caenorhabditis elegans. J Cell Sci 1 October 1998; 111 (19): 2885–2895. doi: https://doi.org/10.1242/jcs.111.19.2885
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