SMA-1 spectrin has essential roles in epithelial cell sheet morphogenesis in C. elegans |
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Authors: | Praitis Vida Ciccone Emily Austin Judith |
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Institution: | Biology Department, Grinnell College, Grinnell, IA 50112, USA. praitis@grinnell.edu |
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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. |
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Keywords: | CH calponin homology PH pleckstrin homology SH3 Sarc homology 3 SBMS spectrin-based membrane skeleton SR spectrin repeat GFP green fluorescent protein CFs circumferential actin fibers AJ adhesion junctions |
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