Biology subjects

Landino, J.

Publications and source records attributed to Landino, J..

5 recordsLinked to original sources

bioRxiv2025

Membrane composition-dependent patterning of Rho and F-actin in an artificial cell cortex

Cortical excitability, a phenomenon in which the cell cortex is dynamically patterned with waves of F-actin assembly, has been described in a variety of animal model systems, including embryos of mammals, flies, frogs and echinoderms, as well as a variety of cultured cells. While the cortical F-actin network is closely linked with the plasma membrane, it is not known if membrane composition or fluidity regulates dynamic cytokinetic patterning. Phospholipids partition within the plasma membrane during cytokinesis, and phosphoinositides play a key regulatory role in other excitable systems, suggesting a role for membrane-dependent regulation of cytokinetic patterning. Here we use an artificial reconstituted cell cortex comprised of Xenopus egg extract and supported lipid bilayers (SLBs) to show that membrane composition regulates self-organized cortical patterning. We find that manipulating levels of candidate lipids, including phosphatidylinositol 4,5-bisphosphate, phosphatidylethanolamine, sphingomyelin and cholesterol, results in both quantitative and qualitative changes in the dynamics of traveling waves and standing oscillatory patterns of active Rho and F-actin, as well as the kinetics of Rho activation and F-actin assembly on supported lipid bilayers. Our findings demonstrate that membrane composition directly regulates the assembly of cortical F-actin, as well as emergent active Rho and F-actin patterning. SIGNIFICANCE STATEMENTO_LIThe cell cortex self-organizes dynamic patterns of active Rho and F-actin during cytokinesis, but it remains unknown whether and how the membrane composition impacts these dynamics. C_LIO_LIThis study uses in vitro reconstitution of the cell cortex to directly manipulate membrane composition and finds that introducing different lipids induces changes in cortical dynamics of active Rho and F-actin. C_LIO_LIThese findings reveal that membrane compositions regulates self-organized cortical dynamics, independently of changes to membrane fluidity. This work furthers our understanding of the mechanistic relationship between membrane composition, GTPase signaling, and cortical F-actin assembly. C_LI

biochemistry↗

bioRxiv2023

Neighbor cells restrain furrowing during epithelial cytokinesis

Cytokinesis challenges epithelial tissue homeostasis by generating forces that pull on neighboring cells via cell-cell junctions. Previous work has shown that junction reinforcement at the furrow in Xenopus laevis epithelia regulates the speed of furrowing1. This suggests the cytokinetic array that drives cell division is subject to resistive forces from epithelial neighbor cells. We show here that contractility factors accumulate in neighboring cells near the furrow during cytokinesis. Additionally, increasing neighbor cell stiffness, via [a]-actinin overexpression, or contractility, through optogenetic Rho activation in one neighbor cell, slows or asymmetrically pauses furrowing, respectively. Notably, optogenetic stimulation of neighbor cell contractility on both sides of the furrow induces cytokinetic failure and binucleation. We conclude that forces from the cytokinetic array in the dividing cell are carefully balanced with restraining forces generated by neighbor cells, and neighbor cell mechanics regulate the speed and success of cytokinesis. HighlightsO_LINeighboring cells assemble actomyosin arrays adjacent to the cytokinetic furrow C_LIO_LIOverexpression of an F-actin cross-linker in neighbor cells slows furrowing C_LIO_LIOptogenetic activation of contractility in one neighbor pauses furrow ingression C_LIO_LIHyper-contractility in both neighbors restrains furrowing & cells fail cytokinesis C_LI

cell biology↗

bioRxiv2022

A versatile pattern-forming cortical circuit based on Rho, F-actin, Ect2 and RGA-3/4

Many cells can generate complementary traveling waves of actin filaments (F-actin) and cytoskeletal regulators. This phenomenon, termed cortical excitability, results from coupled positive and negative feedback loops of cytoskeletal regulators. The nature of these feedback loops, however, remains poorly understood. We assessed the role of the Rho GAP RGA-3/4 in the cortical excitability that accompanies cytokinesis in both frog and starfish. RGA-3/4 localizes to the cytokinetic apparatus, "chases" Rho waves in an F-actin-dependent manner and, when co-expressed with the Rho GEF Ect2, is sufficient to convert the normally quiescent, immature Xenopus oocyte cortex into a dramatically excited state. Experiments and modeling show that changing the ratio of RGA-3/4 to Ect2 produces a range of cortical behaviors from pulses to complex waves of Rho activity. We conclude that RGA-3/4, Ect2, Rho and F-actin form the core of a circuit that drives a diverse range of cortical behaviors, and demonstrate that the immature oocyte is a powerful model for characterizing these dynamics. SummaryMichaud et al. identify Ect2 and RGA-3/4 as core components of the cortical excitability circuit associated with cytokinesis. Additionally, they demonstrate that the immature Xenopus oocyte is a powerful model for characterizing excitable dynamics.

cell biology↗

bioRxiv2022

Cell cycle and developmental control of cortical excitability in Xenopus laevis

Interest in cortical excitability - the ability of the cell cortex to generate traveling waves of protein activity - has grown considerably over the past twenty years. Attributing biological functions to cortical excitability requires an understanding of the natural behavior of excitable waves and the ability to accurately quantify wave properties. Here we have investigated and quantified the onset of cortical excitability in X. laevis eggs and embryos, and the changes in cortical excitability throughout early development. We found that cortical excitability begins to manifest shortly after egg activation. Further, we identified a close relationship between wave properties - such as wave frequency and amplitude - and cell cycle progression as well as cell size. Finally, we identified quantitative differences between cortical excitability in the cleavage furrow relative to non-furrow cortical excitability and showed that these wave regimes are mutually exclusive.

cell biology↗

bioRxiv2021

Rho and F-actin self-organize within an artificial cell cortex

The cell cortex, comprised of the plasma membrane and underlying cytoskeleton, undergoes dynamic reorganizations during a variety of essential biological processes including cell adhesion, cell migration, and cell division1,2. During cell division and cell locomotion, for example, waves of filamentous-actin (F-actin) assembly and disassembly develop in the cell cortex in a process termed "cortical excitability"3-7. In developing frog and starfish embryos, cortical excitability is generated through coupled positive and negative feedback, with rapid activation of Rho-mediated F-actin assembly followed in space and time by F-actin-dependent inhibition of Rho8,9. These feedback loops are proposed to serve as a mechanism for amplification of active Rho signaling at the cell equator to support furrowing during cytokinesis, while also maintaining flexibility for rapid error correction in response to movement of the mitotic spindle during chromosome segregation10. In this paper, we develop an artificial cortex based on Xenopus egg extract and supported lipid bilayers (SLBs), to investigate cortical Rho and F-actin dynamics11. This reconstituted system spontaneously develops two distinct dynamic patterns: singular excitable Rho and F-actin waves and non-traveling oscillatory Rho and F-actin patches. Both types of dynamic patterns have properties and dependencies similar to the cortical excitability previously characterized in vivo9. These findings directly support the longstanding speculation that the cell cortex is a self-organizing structure and present a novel approach for investigating mechanisms of Rho-GTPase-mediated cortical dynamics. HighlightsO_LIAn artificial cell cortex comprising Xenopus egg extract on a supported lipid bilayer self-organizes into complex, dynamic patterns of active Rho and F-actin C_LIO_LIWe identified two types of reconstituted cortical dynamics - excitable waves and coherent oscillations C_LIO_LIReconstituted waves and oscillations require Rho activity and F-actin polymerization C_LI

cell biology↗