title: Essential role of ADF/cofilin for assembly of contractile actin networks in the C. elegans somatic gonad.
abstract: The somatic gonad of the nematode Caenorhabditis elegans contains a myoepithelial sheath, which surrounds oocytes and provides contractile forces during ovulation. Contractile apparatuses of the myoepithelial-sheath cells are non-striated and similar to those of smooth muscle. We report the identification of a specific isoform of actin depolymerizing factor (ADF)/cofilin as an essential factor for assembly of contractile actin networks in the gonadal myoepithelial sheath. Two ADF/cofilin isoforms, UNC-60A and UNC-60B, are expressed from the unc-60 gene by alternative splicing. RNA interference of UNC-60A caused disorganization of the actin networks in the myoepithelial sheath. UNC-60B, which is known to function in the body-wall muscle, was not necessary or sufficient for actin organization in the myoepithelial sheath. However, mutant forms of UNC-60B with reduced actin-filament-severing activity rescued the UNC-60A-depletion phenotype. UNC-60A has a much weaker filament-severing activity than UNC-60B, suggesting that an ADF/cofilin with weak severing activity is optimal for assembly of actin networks in the myoepithelial sheath. By contrast, strong actin-filament-severing activity of UNC-60B was required for assembly of striated myofibrils in the body-wall muscle. Our results suggest that an optimal level of actin-filament-severing activity of ADF/cofilin is required for assembly of actin networks in the somatic gonad.
authors.affiliation: Department of Pathology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Kanako
authors.initials: K
authors.lastname: Ono
authors.forename: Sawako
authors.initials: S
authors.lastname: Yamashiro
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Ono
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000378:metabolism / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003285:Contractile Proteins / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D006066:Gonads / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008840:Microfilament Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054792:Muscle, Striated / Q000187:drug effects / Q000378:metabolism; D009135:Muscular Diseases / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D051339:Actin Depolymerizing Factors; D029742:Caenorhabditis elegans Proteins; D003285:Contractile Proteins; D008840:Microfilament Proteins; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C495209:UNC-60 protein, C elegans; D049452:Green Fluorescent Proteins