Mink, M. | Search bioRxiv

bioRxiv2022

Extracellular matrix assembly stress drives Drosophila central nervous system morphogenesis

The forces controlling tissue morphogenesis are attributed to cellular-driven activities and any role for extracellular matrix (ECM) is assumed to be passive. However, all polymer networks, including ECM, can theoretically develop autonomous stresses during their assembly. Here we examine the morphogenetic function of an ECM prior to reaching homeostatic equilibrium by analyzing de novo ECM assembly during Drosophila ventral nerve cord (VNC) condensation. Asymmetric VNC shortening and a rapid decrease in surface area correlate with exponential assembly of Collagen-IV (Col4) surrounding the tissue. Concomitantly, a transient developmentally-induced Col4 gradient leads to coherent long-range flow of ECM, which equilibrates the Col4 network. Finite element analysis and perturbation of Col4 network formation through the generation of dominant Col4-truncations that affect assembly, reveals that VNC morphodynamics is driven by a sudden increase in ECM-driven surface tension. These data highlight that ECM assembly stress and associated network instabilities can actively participate in tissue morphogenesis.

developmental biology↗

bioRxiv2018

Type IV collagen is essential for proper function of integrin-mediated adhesion in Drosophila muscle fibers

Congenital muscular dystrophy (CMD), a subgroup of myopathies and a genetically and clinically heterogeneous group of inherited muscle disorders is characterized by progressive muscle weakness, fiber size variability, fibrosis, clustered necrotic fibers, and central myonuclei present in regenerating muscle. Type IV collagen (COL4A1) mutations have recently been identified in patients with intracerebral, vascular, renal, ophthalmologic pathologies and congenital muscular dystrophy, consistent with diagnoses of Walker-Warburg Syndrome or Muscle-Eye-Brain disease. Morphological characteristics of muscular dystrophy have also been demonstrated Col4a1 mutant mice. Yet, several aspects of the pathomechanism of COL4A1-associated muscle defects remained largely uncharacterized. Based on the results of genetic, histological, molecular, and biochemical analyses in an allelic series of Drosophila col4a1 mutants, we provide evidence that col4a1 mutations associate with severely compromised muscle fibers within the single-layer striated muscle of the common oviduct, characterized by loss of sarcomere structure, disintegration and streaming of Z-discs, and aberrant integrin expression within the M-discs, indicating an essential role for the COL4A1 protein. Features of altered cytoskeletal phenotype include actin bundles traversing over sarcomere units, amorphous actin aggregates, atrophy and aberrant fiber size. The mutant COL4A1-associated defects appear to recapitulate integrin-mediated adhesion phenotypes observed in Drosophila by RNA-inhibition. Our results provide insight into the mechanistic details of COL4A1-associated muscle disorders and suggest a role for integrin-collagen interaction in the maintenance of sarcomeres.

genetics↗