Lumen Morphogenesis in C. elegans Requires the Membrane-Cytoskeleton Linker erm-1

Abstract Epithelial tubes are basic building blocks of complex organs, but their architectural requirements are not well understood. Here we show that erm-1 is a unique C. elegans ortholog of the ERM family of cytoskeleton-membrane linkers, with an essential role in lumen morphogenesis. ERM-1 localizes to the luminal membranes of those tubular organ epithelia which lack stabilization by cuticle. RNA interference (RNAi), a germline deletion, and overexpression of erm-1 cause cystic luminal phenotypes in these epithelia. Confocal and ultrastructural analyses indicate that erm-1 functions directly in apical membrane morphogenesis, rather than in epithelial polarity and junction assembly as has been previously proposed for ERMs. We also show that act-5 /cytoplasmic actin and sma-1 /β-H-spectrin are required for lumen formation and functionally interact with erm-1 . Our findings suggest that there are common structural constraints on the architecture of diverse organ lumina.