AbstractDuring cytokinesis, animal cells rapidly remodel the equatorial cortex to build an aligned array of actin filaments called the contractile ring. Local reorientation of filaments by equatorial contraction is thought to underlie the emergence of filament alignment during ring assembly. Here, combining single molecule analysis and modeling in one-cell C. elegans embryos, we show that filaments turnover is far too fast for reorientation of single filaments by equatorial contraction/cortex compression to explain the observed alignment, even if favorably oriented filaments are selectively stabilized. Instead, by tracking single Formin/CYK-1::GFP speckles to monitor local filament assembly, we identify a mechanism that we call filament-guided filament assembly (FGFA), in which existing filaments serve as templates to guide/orient the growth of new filaments. We show that FGFA sharply increases the effective lifetime of filament orientation, providing structural memory that allows slow equatorial contraction to build and maintain highly aligned filament arrays, despite rapid turnover of individual filaments.

The specific conductivity of aqueous cetyltrimethylammonium bromide solutions has been investigated below and above the critical micelle concentration, in order to elucidate slow structural changes. Around the Krafft temperature (?25?C) the monomer solubility reaches the critical micelle concentration, and a significant increase in charge transport is recorded. When a temperature decreases, the micellar surfactant solution passes through the Krafft temperature, and a hysteresis phenomenon is observed with the appearance of crystals in a solution. We have scrutinized the conditions leading to this hysteresis and quantified some of the relevant parameters. We also outline a simple procedure that allows the ?erasure? of such structural memory effects, which are potentially detrimental to the formation of adsorbed self-assembled monolayers from solution.

The cytoskeleton provides structural integrity to cells and serves as a key component in mechanotransduction. Tensins are thought to provide a force-bearing linkage between integrins and the actin cytoskeleton; yet, direct evidence of tensin’s role in mechanotransduction is lacking. We here report that local force application to epithelial cells using a micrometer-sized needle leads to rapid accumulation of cten (tensin 4), but not tensin 1, along a fibrous intracellular network. Surprisingly, cten-positive fibers are not actin fibers; instead, these fibers are keratin intermediate filaments. The dissociation of cten from tension-free keratin fibers depends on the duration of cell stretch, demonstrating that the external force favors maturation of cten−keratin network interactions over time and that keratin fibers retain remarkable structural memory of a cell’s force-bearing state. These results establish the keratin network as an integral part of force-sensing elements recruiting distinct proteins like cten and suggest the existence of a mechanotransduction pathway via keratin network.

Thin CuOx-based nanosheets with structural memory were prepared by ions exchange of layered double oxides for efficient phenol removal.