Fibronectin Extra Domains tune cellular responses and confer topographically distinct features to fibril networks

Abstract

Cellular fibronectin (FN) variants harboring one or two alternatively spliced Extra Domains (B and A) play a central bioregulatory role during development, repair processes and fibrosis. Yet, how the Extra Domains impact fibrillar assembly and function of the molecule remains unclear. Leveraging a unique biological toolset and image analysis pipeline for direct comparison of the variants, we demonstrate that the presence of one or both Extra Domains impacts FN assembly, function and physical properties of the matrix. When presented to FN-null fibroblasts, Extra Domain-containing variants differentially regulate pH homeostasis, survival, and TGF-β signaling by tuning the magnitude of cellular responses, rather than triggering independent molecular switches. Numerical analyses of fiber topologies highlight significant differences in variant-specific structural features and provide a first step for the development of a generative model of FN networks to unravel assembly mechanisms and investigate the physical and functional versatility of extracellular matrix landscapes.

A spatial statistical framework for the parametric study of fiber networks: application to fibronectin deposition by normal and activated fibroblasts

“…During tumor progression, quiescent fibroblasts become activated by environmental cues that induce their phenotypic conversion from a “normal” to a “pro-tumoral” state (Fig 1A, top). This process is characterized by actin reorganization and increased contractility of cells that result in their elongation and the deposition of a highly anisotropic ECM (9). In vitro, these changes can be mimicked by treating normal fibroblasts with Transforming Growth Factor-β (TGF-β), a potent cytokine involved in fibroblast activation in the tumor microenvironment (9) (Fig 1A, bottom).…”

“…The presence of FN Extra Domains (EDA and/or EDB) impacts FN assembly and fibrillar network organization by normal fibroblasts (9). This was demonstrated by local analysis of graph-based features (i.e.…”

“…The proposed methodology was designed for the quantification of the differences in the spatial organization of ECM networks, in normal and tumor-like architectures. In this case, we chose to analyze the matrix patterns of four alternatively spliced FN variants, which we have previously been able to discriminate with different learning approaches and relying on graph-based feature analysis (9). The current computational pipeline is now available to be tested with a MATLAB GUI.…”

“…Indeed, cFN is highly expressed during embryogenesis and in certain physiological and pathological conditions including inflammation, wound healing, and cancer. Structurally, the two forms differ by the presence in cFN of alternatively spliced sequences of about 90 amino acids, termed Extra Domain B (EDB) and Extra Domain A (EDA), that enhance FN assembly, impact matrix architecture, and tune cellular responses (9).…”

Pathogenesis of glaucoma: Extracellular matrix dysfunction in the trabecular meshwork‐A review

“…108 EDB+ fibronectin in fibrils could enhance VEGF expression and phagocytosis. [109][110][111] EDB+/EDA+ fibronectin in fibrils could potently induce TGF-β mRNA expression, 112 which in turn, would create a positive feedback loop that further drives fibronectin expression. 104 Finally, the presence of EDA+ fibronectin in fibrils could enhance exposure of the RGD sequence in fibronectin 113 and hence binding to the α5β1 integrin, which would increase stress fibre formation and alter the contractile properties of TM cells.…”