Bahadori, A. | bioRxiv Science

bioRxiv2021

Thermoplasmonic nano-rupture of cells reveals Annexin V function in plasma membrane repair

Maintaining the integrity of the cell plasma membrane (PM) is critical for the survival of cells. While an efficient PM repair machinery can aid survival of healthy cells by preventing influx of extracellular calcium, it can also constitute an obstacle in drug delivery and photothermal therapy. We show how nanoscopic holes can be applied to the cell surface thus allowing identification of molecular components with a pivotal role in PM repair. Cells are punctured by locally heating gold nanostructures at the cell surface which causes nano-ruptures in cellular PMs. Recruitment of annexin V near the hole is found to locally reshape the ruptured plasma membrane. Experiments using model membranes, containing recombinant annexin V, provide further biophysical insight into the ability of annexin V to reshape edges surrounding a membrane hole. The thermoplasmonic method provides a general strategy to monitor the response to nanoscopic injuries to the cell surface.

biophysics↗

bioRxiv2020

Cell-cell communication through FGF4 generates and maintains robust proportions of differentiated cell fates in embryonic stem cells

During embryonic development and tissue homeostasis, reproducible proportions of differentiated cell types are specified from populations of multipotent precursor cells. Molecular mechanisms that enable both robust cell type proportioning despite variable initial conditions in the precursor cells, as well as the re-establishment of these proportions upon perturbations in a developing tissue remain to be characterized. Here we report that the differentiation of robust proportions of epiblast-like and primitive endoderm-like cells in mouse embryonic stem cell cultures emerges at the population level through cell-cell communication via a short-range FGF4 signal. We characterize the molecular and dynamical properties of the communication mechanism, and show how it controls both robust cell type proportioning from a wide range of experimentally controlled initial conditions, as well as the autonomous re-establishment of these proportions following the isolation of one cell type. The generation and maintenance of reproducible proportions of discrete cell types is a new function for FGF signaling that may operate in a range of developing tissues.

developmental biology↗