A multi-layered and dynamic apical extracellular matrix shapes the vulva lumen in Caenorhabditis elegans.

Jennifer D Cohen,Alessandro P Sparacio,Alexandra C Belfi,Meera V Sundaram,Alison R Frand,Rachel Forman-Rubinsky,Hannah Maul-Newby,David H Hall

doi:10.7554/elife.57874

Abstract

Biological tubes must develop and maintain their proper diameter to transport materials efficiently. These tubes are molded and protected in part by apical extracellular matrices (aECMs) that line their lumens. Despite their importance, aECMs are difficult to image in vivo and therefore poorly understood. The Caenorhabditis elegans vulva has been a paradigm for understanding many aspects of organogenesis. Here we describe the vulva luminal matrix, which contains chondroitin proteoglycans, Zona Pellucida (ZP) domain proteins, and other glycoproteins and lipid transporters related to those in mammals. Confocal and transmission electron microscopy revealed, with unprecedented detail, a complex and dynamic aECM. Different matrix factors assemble on the apical surfaces of each vulva cell type, with clear distinctions seen between Ras-dependent (1°) and Notch-dependent (2°) cell types. Genetic perturbations suggest that chondroitin and other aECM factors together generate a structured scaffold that both expands and constricts lumen shape.

Highlights

During tubulogenesis, lumen formation and expansion generally occur in the context of fluid influx and/or apical extracellular matrix secretion (reviewed by (Luschnig & Uv, 2014; Navis & Nelson, 2016))
Ions and water are not the only molecules being secreted into nascent lumens; proteoglycans, lipids, mucins, zona pellucida (ZP) domain proteins, and/or other matrix factors are present and can contribute to lumen shaping (Devine et al, 2005; Gill et al, 2016; Hwang, Olson, Esko, & Horvitz, 2003; Jazwinska, Ribeiro, & Affolter, 2003; Lane, Koehl, Wilt, & Keller, 1993; Rosa, Metzstein, & Ghabrial, 2018; Strilić et al, 2009; Tonning et al, 2005)
Specification and generation of the seven vulva cell types occurs during the L2 and L3 larval stages, while toroid formation and other aspects of tube morphogenesis occur during the L4 stage (Figures 1 and 2)

Summary

Introduction

Lumen formation and expansion generally occur in the context of fluid influx and/or apical extracellular matrix (aECM) secretion (reviewed by (Luschnig & Uv, 2014; Navis & Nelson, 2016)). Ions and water are not the only molecules being secreted into nascent lumens; proteoglycans, lipids, mucins, zona pellucida (ZP) domain proteins, and/or other matrix factors are present and can contribute to lumen shaping (Devine et al, 2005; Gill et al, 2016; Hwang, Olson, Esko, & Horvitz, 2003; Jazwinska, Ribeiro, & Affolter, 2003; Lane, Koehl, Wilt, & Keller, 1993; Rosa, Metzstein, & Ghabrial, 2018; Strilić et al, 2009; Tonning et al, 2005) These aECM factors may act like sponges to bind and organize water molecules and generate outward pushing forces (Lane et al, 1993; Syed et al, 2012), or they may assemble into fibrils or other specialized structures to exert more localized pushing or pulling forces on tube membranes (Andrew & Ewald, 2010; Linde-Medina & Marcucio, 2018; Luschnig & Uv, 2014; Plaza, Chanut-Delalande, Fernandes, Wassarman, & Payre, 2010). The specific contents, organization, and morphogenetic roles of the luminal matrix within the developing vulva have remained, for the most part, uncharacterized

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