Serna-Morales, E. | 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

EphB2 and ERK signaling are required for heterotypic contact inhibition of locomotion to drive cell sorting

Interactions between different cell-types can induce distinct contact inhibition of locomotion (CIL) responses that are hypothesized to control population-wide behaviors during embryogenesis [1, 2]. However, our understanding of the signals that lead to cell-type specific repulsion, and the precise capacity of heterotypic CIL responses to drive emergent behaviors is lacking. Using a new in vitro model of heterotypic CIL between epithelial and mesenchymal cells, we show that fibrosarcoma cells (HT1080), but not fibroblasts (NIH3T3), are actively repelled by epithelial cells in culture. We show that knocking down EphB2 in fibrosarcoma cells specifically leads to disruption of the repulsion phase of CIL in response to interactions with epithelial cells. Furthermore, this heterotypic interaction requires ERK activation, downstream of EphB2 signaling. We also examine the population-wide effects when these various cell combinations, and their specific heterotypic CIL responses, are allowed to interact in culture. Mixtures of fibrosarcoma and epithelial cells - unlike fibroblasts and epithelial cells - lead to complete sorting and segregation of the two populations, and inhibiting their distinct CIL response by knocking down EphB2 or ERK in fibrosarcoma cells disrupts this emergent sorting behavior. Our understanding of the mechanisms underlying developmental behaviors such as cell sorting is lacking as predominant sorting hypotheses, such as differential adhesion, have recently been found inadequate in predicting the sorting of mesenchymal cells [3, 4]. These data suggest that heterotypic CIL responses, in conjunction with processes such as differential adhesion, may aid the sorting of cell populations during embryogenesis.

cell biology↗