THE ROLE OF ACTIN-FILAMENTS IN PATTERNING THE CAENORHABDITIS-ELEGANS CUTICLE

Nematodes are covered by a cuticle with a prominent pattern of circumf erentially oriented, parallel furrows. We report here that the pattern of furrows on the first larval cuticle of Caenorhabditis elegans, whi ch is secreted during embryogenesis, is coincident with a pattern of s ubmembranous actin filament bundles in the epithelial cells that secre te the cuticle. We propose that the pattern of cortical actin filament s biases the growth of the epithelial cell membranes, creating a furro wed surface template for deposition of the first cuticle layer. This l ayer then detaches from the epithelial cell surface as additional, non patterned components of the cuticle are secreted. Furrows are present on the surfaces of each of the four larval cuticles in C. elegans and on the adult cuticle. We show that similar ordered arrays of actin fil aments appear during each of the postembryonic molts when new cuticles are synthesized. Our analysis suggests that conditions or mutations t hat affect the pattern of cuticle furrows might cause primary defects in the cytoskeletal organization of the epithelial cells that secrete the cuticle. (C) 1997 Academic Press.