2004 Midwest Worm Meeting abstract 9
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
| 1 | Biology Department, Grinnell College, Grinnell, IA 50112 |
| 2 | Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago IL 60637 |
| 3 | Current address: Virginia Commonwealth University, Richmond, VA 23284. |
During C. 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. SMA-1, an ortholog of the actin binding protein betaH-spectrin, is required for normal morphogenesis (McKeown, Praitis, & Austin, 1998). Using antisera to SMA-1, we have determined that the protein localizes to the apical membrane of epithelial cells, including the hypodermis, pharynx, gut, and excretory canal cell, during the period when these cells are rapidly elongating. We show that in the hypodermis, SMA-1 is required to maintain the association between actin and the apical membrane. Based on these results, we hypothesize that sma-1(ru18) null embryos fail to elongate because actin, which provide the driving force for cell shape change, dissociates from the apical membrane skeleton during morphogenesis. SMA-1 is a large, complex molecule with a series of distinct protein domains that include spectrin repeats, calponin homology, SH3, and pleckstrin homology domains. To elucidate the roles of these domains, we performed sequence and phenotype analysis of several classes of sma-1 mutants and SMA-1 expression constructs. This analysis indicates that 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. Our analysis also shows that SMA-1, likely acting with SPC-1 alpha-spectrin (Norman & Moerman, 2002) has additional functions required for normal elongation. SMA-1 provides structural support for the apical membrane and it is required to preserve dynamic changes in the organization of the apical membrane skeleton. Taken together, our results demonstrate the SMA-1 spectrin-based membrane skeleton plays a dynamic role in converting changes in actin organization into changes in epithelial cell shape during C. elegans embryogenesis.