Characterization ofDrosophila Nidogen/entactinreveals roles in basement membrane stability, barrier function and nervous system patterning

Abstract

Basement membranes (BMs) are specialized layers of extracellular matrix (ECM) mainly composed of Laminin, type IV Collagen, Perlecan and Nidogen/entactin (NDG). Recent in vivo studies challenged the initially proposed role of NDG as a major ECM linker molecule by revealing dispensability for viability and BM formation. Here, we report the characterization of the single Ndg gene in Drosophila. Embryonic Ndg expression was primarily observed in mesodermal tissues and the chordotonal organs, whereas NDG protein localized to all BMs. Although loss of Laminin strongly affected BM localization of NDG, Ndg-null mutants exhibited no overt changes in the distribution of BM components. Although Drosophila Ndg mutants were viable, loss of NDG led to ultrastructural BM defects that compromised barrier function and stability in vivo. Moreover, loss of NDG impaired larval crawling behavior and reduced responses to vibrational stimuli. Further morphological analysis revealed accompanying defects in the larval peripheral nervous system, especially in the chordotonal organs and the neuromuscular junction (NMJ). Taken together, our analysis suggests that NDG is not essential for BM assembly but mediates BM stability and ECMdependent neural plasticity during Drosophila development.

Atypical basement membranes and basement membrane diversity – what is normal anyway?

“…A striking example of tissue-specific effects is presented by Drosophila Nidogen (Ndg). Ndg mutant flies are viable, presenting mild fertility and behavioral defects (Dai et al, 2018;Wolfstetter et al, 2019). When BMs of Ndg mutant animals were examined, dramatic loss of BM integrity was observed only in the fat body and some adult muscles (Fig.…”

“…Two different laminin heterotrimers can form with alternative α chains encoded by genes Laminin A (LanA) and wing blister (wb), whereas unique β and γ chains are encoded by the Laminin B1 (LanB1) and Laminin B2 (LanB2) genes (Fessler et al, 1987;Kusche-Gullberg et al, 1992;Martin et al, 1999;Goodman, 1988, 1989). One perlecan protein encoded by terribly reduced optic lobes (trol) (Park et al, 2003;Voigt et al, 2002) and the product of Nidogen (Ndg) (Dai et al, 2018;Wolfstetter et al, 2019;Wolfstetter et al, 2009) complete the Drosophila LNCP set. For all four, transgenically expressed tagged versions, mutants and tissue-specific RNAi tools are available and have been used in multiple studies.…”

DSS-induced damage to basement membranes is repaired by matrix replacement and crosslinking

“…Despite their power, these systems may not be suitable for analyzing repair because in vitro analysis removes cells from the architectural and mechanical environment of the tissue, both of which are likely important for matrix repair. More recently, biochemical studies on matrix assembly (Fox et al, 1991;Ries et al, 2001;Takagi et al, 2003;Hopf et al, 1999) have been complemented by genetic analysis of animals with mutant basement membrane proteins, and these analyses were critical in identifying an order of assembly: laminin first, as collagen IV and nidogen each require laminin, and perlecan requires collagen IV (Pöschl et al, 2004;Urbano et al, 2009;Pastor-Pareja and Xu, 2011;Wolfstetter et al, 2019). Whole-animal mutants for basement membrane proteins are embryonic lethal, however, and the analysis of repair requires conditional mutants that can be induced temporally, after assembly has been completed.…”

Molecular Events Controlling Cessation of Trunk Neural Crest Migration and Onset of Differentiation

“…CRMPs have been known to regulate actin dynamics as well as Semaphorin/Neuropilin signaling which affects both axonal pathfinding and NCC migration. A true novel finding was the presence of osteonidogen, this gene encodes a cell-ECM adhesion as part of the BM complex, a member of the Nidogen family of basement membrane proteins that binds collagen and are important for proper neuronal stability ( Figure 2F; Wolfstetter et al, 2019).…”