title: Integrity of Narrow Epithelial Tubes in the C. elegans Excretory System Requires a Transient Luminal Matrix.
abstract: Most epithelial cells secrete a glycoprotein-rich apical extracellular matrix that can have diverse but still poorly understood roles in development and physiology. Zona Pellucida (ZP) domain glycoproteins are common constituents of these matrices, and their loss in humans is associated with a number of diseases. Understanding of the functions, organization and regulation of apical matrices has been hampered by difficulties in imaging them both in vivo and ex vivo. We identified the PAN-Apple, mucin and ZP domain glycoprotein LET-653 as an early and transient apical matrix component that shapes developing epithelia in C. elegans. LET-653 has modest effects on shaping of the vulva and epidermis, but is essential to prevent lumen fragmentation in the very narrow, unicellular excretory duct tube. We were able to image the transient LET-653 matrix by both live confocal imaging and transmission electron microscopy. Structure/function and fluorescence recovery after photobleaching studies revealed that LET-653 exists in two separate luminal matrix pools, a loose fibrillar matrix in the central core of the lumen, to which it binds dynamically via its PAN domains, and an apical-membrane-associated matrix, to which it binds stably via its ZP domain. The PAN domains are both necessary and sufficient to confer a cyclic pattern of duct lumen localization that precedes each molt, while the ZP domain is required for lumen integrity. Ectopic expression of full-length LET-653, but not the PAN domains alone, could expand lumen diameter in the developing gut tube, where LET-653 is not normally expressed. Together, these data support a model in which the PAN domains regulate the ability of the LET-653 ZP domain to interact with other factors at the apical membrane, and this ZP domain interaction promotes expansion and maintenance of lumen diameter. These data identify a transient apical matrix component present prior to cuticle secretion in C. elegans, demonstrate critical roles for this matrix component in supporting lumen integrity within narrow bore tubes such as those found in the mammalian microvasculature, and reveal functional importance of the evolutionarily conserved ZP domain in this tube protecting activity.
authors.affiliation: Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Hasreet K
authors.initials: HK
authors.lastname: Gill
authors.affiliation: Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Cohen
authors.affiliation: Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Jesus
authors.initials: J
authors.lastname: Ayala-Figueroa
authors.affiliation: Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Rachel
authors.identifier: 0000-0002-1853-9456
authors.initials: R
authors.lastname: Forman-Rubinsky
authors.affiliation: Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Corey
authors.identifier: 0000-0002-9589-6297
authors.initials: C
authors.lastname: Poggioli
authors.affiliation: Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Kevin
authors.identifier: 0000-0002-4523-7648
authors.initials: K
authors.lastname: Bickard
authors.affiliation: Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.|Department of Biology, Georgian Court University, Lakewood, New Jersey, United States of America.
authors.forename: Jean M
authors.initials: JM
authors.lastname: Parry
authors.affiliation: Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Pu
authors.initials: P
authors.lastname: Pu
authors.affiliation: Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America.
authors.forename: David H
authors.initials: DH
authors.lastname: Hall
authors.affiliation: Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Meera V
authors.identifier: 0000-0002-2940-8750
authors.initials: MV
authors.lastname: Sundaram
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D004847:Epithelial Cells / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D046529:Microscopy, Electron, Transmission; D009077:Mucins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D000072417:Protein Domains / Q000235:genetics; D013329:Structure-Activity Relationship; D015044:Zona Pellucida / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D029742:Caenorhabditis elegans Proteins; D006023:Glycoproteins; C096862:LET-653 protein, C elegans; D009077:Mucins