title: SMA-1 spectrin has essential roles in epithelial cell sheet morphogenesis in C. elegans.
abstract: During Caenorhabditis elegans development, the embryo acquires its vermiform shape due to changes in the shape of epithelial cells, a process that requires an apically localized actin cytoskeleton. We show that SMA-1, an ortholog of beta(H)-spectrin required for normal morphogenesis, localizes to the apical membrane of epithelial cells when these cells are rapidly elongating. In spc-1 alpha-spectrin mutants, SMA-1 localizes to the apical membrane but its organization is altered, consistent with the hypothesis these proteins act together to form an apically localized spectrin-based membrane skeleton (SBMS). SMA-1 is required to maintain the association between actin and the apical membrane; sma-1 mutant embryos fail to elongate because actin, which provides the driving force for cell shape change, dissociates from the apical membrane skeleton during morphogenesis. Analysis of sma-1 expression constructs and mutant strains indicates SMA-1 maintains the association between actin and the apical membrane via interactions at its N-terminus and this activity is independent of alpha-spectrin. SMA-1 also preserves dynamic changes in the organization of the apical membrane skeleton. Taken together, our results show the SMA-1 SBMS plays a dynamic role in converting changes in actin organization into changes in epithelial cell shape during C. elegans embryogenesis.
authors.affiliation: Biology Department, Grinnell College, Grinnell, IA 50112, USA. praitis@grinnell.edu
authors.forename: Vida
authors.initials: V
authors.lastname: Praitis
authors.forename: Emily
authors.initials: E
authors.lastname: Ciccone
authors.forename: Judith
authors.initials: J
authors.lastname: Austin
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics*; D018388:Codon, Terminator; D004625:Embryo, Nonmammalian / Q000502:physiology*; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D008565:Membrane Proteins / Q000235:genetics*; D009024:Morphogenesis; D009154:Mutation; D009928:Organ Specificity; D010614:Pharynx / Q000196:embryology; D017384:Sequence Deletion; D040521:Subcutaneous Tissue / Q000196:embryology
chemical_list: D029742:Caenorhabditis elegans Proteins; D018388:Codon, Terminator; D008565:Membrane Proteins; C503419:SMA-1 protein, C elegans