Biology subjects

Barberi, L.

Publications and source records attributed to Barberi, L..

3 recordsLinked to original sources

bioRxiv2020

Transient active osmotic swelling of epithelium upon curvature induction

Generation of tissue curvature is essential to morphogenesis. However, how cells adapt to changing curvature is still unknown because tools to dynamically control curvature in vitro are lacking. Here we developed self-rolling substrates to study how flat epithelial cell monolayers adapt to a rapid, anisotropic change of curvature. We show that the primary response is an active and transient osmotic swelling of cells. This cell volume increase is not observed on inducible wrinkled substrates, where concave and convex regions alternate each other over short distances, identifying swelling as a collective response to changes of curvature with persistent sign over large distances. It is triggered by a drop in membrane tension and actin depolymerization, perceived by cells as a hypertonic shock. Osmotic swelling restores tension while actin reorganizes, probably to comply with curvature. Epithelia are thus unique materials that transiently, actively swell while adapting to large curvature induction.

biophysics↗

bioRxiv2020

Local structure of DNA toroids reveals curvature-dependent intermolecular forces

In viruses and cells, DNA is closely packed and tightly curved thanks to polyvalent cations inducing an effective attraction between its negatively charged filaments. Our understanding of this effective attraction remains very incomplete, partly because experimental data is limited to bulk measurements on large samples of mostly uncurved DNA helices. Here we use cryo electron microscopy to shed light on the interaction between highly curved helices. We find that the spacing between DNA helices in spermine-induced DNA toroidal condensates depends on their location within the torus, consistent with a mathematical model based on the competition between electrostatic interactions and the bending rigidity of DNA. We use our model to infer the characteristics of the interaction potential, and find that its equilibrium spacing strongly depends on the curvature of the filaments. In addition, the interaction is much softer than previously reported in bulk samples using different salt conditions. Beyond viruses and cells, our characterization of the interactions governing DNA-based dense structures could help develop robust designs in DNA nanotechnologies.

biophysics↗

bioRxiv2019

Anisotropic ESCRT-III architecture governs helical membrane tube formation

ESCRT-III proteins assemble into ubiquitous membrane-remodeling polymers during many cellular processes. Here we describe the structure of helical membrane tubes that are scaffolded by bundled ESCRT-III filaments. Cryo-ET reveals how the shape of the helical membrane tube arises from the assembly of distinct bundles of protein filaments that bind the membrane with different mean curvatures. Cryo-EM reveals how one of these ESCRT-III filaments engages the membrane tube through a novel interface. Mathematical modeling of the helical membrane tube suggests how its shape emerges from differences in membrane binding energy, positional rigidity, and membrane tension. Altogether, our findings support a model in which increasing the rigidity of ESCRT-III filaments through the assembly of multi-strands triggers buckling of the membrane.\n\nOne Sentence SummaryESCRT-III heteropolymers deform membranes into helical tubes.

biochemistry↗