title: Troponin I controls ovulatory contraction of non-striated actomyosin networks in the C. elegans somatic gonad.
abstract: The myoepithelial sheath of the Caenorhabditis elegans somatic gonad has non-striated actomyosin networks that provide contractile forces during ovulation, a process in which a mature oocyte is expelled from the ovary. Troponin T and troponin C are known regulators of contraction of the myoepithelial sheath. These are two of the three components of the troponin complex that is generally considered as a striated-muscle-specific regulator of actomyosin contraction. Here, we report identification of troponin I as the third component of the troponin complex that regulates ovulatory contraction of the myoepithelial sheath. C. elegans has four genes encoding troponin-I isoforms. We found that tni-1 and unc-27 (also known as tni-2) encode two major troponin-I isoforms in the myoepithelial sheath. Combination of RNA interference and mutation of tni-1 and unc-27 resulted in loss of the troponin-I protein in the gonad and caused sterility due to defective contraction of the myoepithelial sheath. Troponin-I-depleted gonads were hypercontracted, which is consistent with the function of troponin I as an inhibitor of actomyosin contraction. Troponin I was associated with non-striated actin networks in a tropomyosin-dependent manner. Our results demonstrate that troponin I regulates contraction of non-striated actomyosin networks and is an essential cytoskeletal component of the C. elegans reproductive system.
authors.affiliation: Department of Health and Nutrition, Teikyo-Heisei University, Tokyo 170-8445, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Obinata
authors.forename: Kanako
authors.initials: K
authors.lastname: Ono
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Ono
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism*; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D005260:Female; D009119:Muscle Contraction / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D018995:Myosin Heavy Chains / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D010053:Ovary / Q000166:cytology / Q000378:metabolism*; D010060:Ovulation / Q000378:metabolism*; D010641:Phenotype; D020033:Protein Isoforms / Q000378:metabolism; D012098:Reproduction; D019209:Troponin C / Q000378:metabolism; D019210:Troponin I / Q000378:metabolism*
chemical_list: D000199:Actins; D029742:Caenorhabditis elegans Proteins; D020033:Protein Isoforms; D019209:Troponin C; D019210:Troponin I; D000205:Actomyosin; D018995:Myosin Heavy Chains
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