Shaping Cells and Organs in Drosophila by Opposing Roles of Fat Body-Secreted Collagen IV and Perlecan

Abstract

SUMMARY Basement membranes (BMs) are resilient polymer structures that surround organs in all animals. Tissues, however, undergo extensive morphological changes during development. It is not known whether the assembly of BM components plays an active morphogenetic role. To study in vivo the biogenesis and assembly of Collagen IV, the main constituent of BMs, we used a GFP-based RNAi method (iGFPi) designed to knock down any GFP-trapped protein in Drosophila. We found with this method that Collagen IV is synthesized by the fat body, secreted to the hemolymph (insect blood), and continuously incorporated into the BMs of the larva. We also show that incorporation of Collagen IV determines organ shape, first by mechanically constricting cells and second through recruitment of Perlecan, which counters constriction by Collagen IV. Our results uncover incorporation of Collagen IV and Perlecan into BMs as a major determinant of organ shape and animal form.

Procollagen export from the endoplasmic reticulum

“…TANGO1 is also required for secretion of the only collagen expressed in Drosophila (collagen IV). Interestingly, in polarized tissues of the fruitfly, TANGO1 is confined to basal ER exit sites [16,17]. These findings underscore the physiological relevance of TANGO1 in procollagen VII and procollagen IV export from the ER.…”

Companion Blood Cells Control Ovarian Stem Cell Niche Microenvironment and Homeostasis

“…Current knowledge from flies shows that ColIV originates from diverse sources during development: plasmatocytes in embryos (Bunt et al, 2010;Fessler and Fessler, 1989); fat body in the larvae (Pastor-Pareja and Xu, 2011); and follicle cells in the adult ovary (Denef et al, 2008;Lerner et al, 2013;Medioni and Noselli, 2005). But what remained unclear was the behavior of the newly synthesized ColIV from these sources and whether any specific targeting mechanism existed.…”

“…Nidogen/entactin and perlecan crosslink the laminin and ColIV networks, increasing their stability and controlling the structural integrity of the overall membrane. Drosophila ColIV consists of two a chains, a-1 (Cg25c) and a-2 (Vkg), which form heterotrimers (Blumberg et al, 1988;Lunstrum et al, 1988) that are post-translationally modified by lysyl and prolyl hydroxylases enzymes, ultimately forming a functional BM (Bunt et al, 2010;Lerner et al, 2013;Pastor-Pareja and Xu, 2011). In adult ovaries, somatic follicular cells produce (legend continued on next page) ColIV, which is basally assembled into an egg chamber BM network through a Crag/Rab10/PIs-dependent mechanism (Denef et al, 2008;Devergne et al, 2014;Lerner et al, 2013;Medioni and Noselli, 2005).…”

Invadopodia and basement membrane invasion in vivo

“…[1][2][3] The basement membrane arose at the emergence of animal multicellularity 4,5 and is a key regulator of many cellular and tissue-level functions, including cell polarity, differentiation, organ shape, and tissue compartmentalization. [6][7][8][9][10][11] Despite its dense and highly cross-linked structure, leukocytes and numerous migrating cells in development traffic through basement membranes. [12][13][14] For example, during the epithelial-tomesenchymal transitions (EMTs) that occur in gastrulation and neural crest migration, cells acquire the ability to invade through the epithelial basement membrane to initiate their migration to distant sites.…”