Related Experiment Video
Updated: Jun 27, 2026
05:50
Measuring Cell-Edge Protrusion Dynamics during Spreading using Live-Cell Microscopy
Published on: November 1, 2021
Spontaneous membrane protrusion and cell morphogenesis via self-propelled actin filaments
Kio Yagami1, Takunori Minegishi1,2, Kentarou Baba1
1Laboratory of Systems Neurobiology and Medicine, Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Japan.
EMBO Reports
|June 25, 2026
Summary
Cells form protrusions using Self-propelled Treadmilling Actin filaments (SpTAs). These actin assemblies move directionally, driving membrane protrusion and cellular polarization for migration.
Area of Science:
- Cell Biology
- Biophysics
- Cytoskeleton Dynamics
Background:
- Cell morphogenesis and protrusion formation are crucial but incompletely understood processes.
- Actin filaments are key regulators of cell shape, typically influenced by biochemical signals.
- Intrinsic mechanisms for cell protrusion formation exist, independent of external cues.
Purpose of the Study:
- To investigate intrinsic mechanisms driving cell morphogenesis and protrusion formation.
- To characterize the movement and behavior of actin filament assemblies within cells.
- To elucidate the role of actin dynamics in cellular polarization and migration.
Main Methods:
- Observation and characterization of actin filament assembly dynamics.
- Analysis of directional polymerization and disassembly of actin filaments.
- Investigation of actin particle motion and accumulation at the cell periphery.
Main Results:
- Actin filament assemblies exhibit directional movement, termed Self-propelled Treadmilling Actin filaments (SpTAs).
- SpTAs move as discrete, self-propelled particles, driving membrane protrusion by outward-oriented polymerization.
- SpTAs accumulate at cell protrusions, guided by membrane curvature, enhancing protrusion growth and cellular polarization.
Conclusions:
- Actin filament assemblies function as a novel class of biological active particles.
- SpTA dynamics provide a new intrinsic mechanism for cell morphogenesis and protrusion formation.
- This molecular-scale motion orchestrates higher-order cellular organization, including migration and polarization.
Related Concept Videos
01:13Actin Polymerization and Cell Motility
Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
01:28Types of Membrane Protrusions
The protrusion of the cell surface is an initial step for several cellular processes, including cell migration, phagocytosis, and neurite outgrowth. These membrane protrusions are a result of cytoskeletal rearrangement. The most widely observed cell protrusions include lamellipodia, pseudopodia, filopodia, microvilli, invadopodia, and podosomes. These protrusions can be of two types — static or dynamic.
The microvilli, an example of stable protrusions, are finger-like projections with a...
The microvilli, an example of stable protrusions, are finger-like projections with a...
01:09Cell Migration
Cell migration, the process by which cells move from one location to another, is essential for the proper development and viability of organisms throughout their life. When cells are not able to migrate properly to their ordained locations, various disorders may occur. For example, disruption in cell migration causes chronic inflammatory diseases such as arthritis.
01:19Cell Migration
Cell migration is a process by which the cells move from one location to another, playing an essential role in embryological development, repair and regeneration, immune response, and metastasis. Cells migrate in response to chemical or mechanical signals generated by specific organs or tissues. The overall mechanism includes three steps - polarization, protrusion, and release. Polarization involves the formation of a distinct cell front and rear, which determines the direction of movement.
01:39Mechanism of Filopodia Formation
Filopodia are thin, actin-rich cellular protrusions that play an important role in many fundamental cellular functions. They vary in their occurrence, length, and positioning in different cell types, suggesting their diverse roles.
Their main function is to guide migrating cells during normal tissue morphogenesis or cancer metastasis by recognizing and making initial contacts with the extracellular matrix. However, they can also act as stationary cell anchors or help to establish communication...
Their main function is to guide migrating cells during normal tissue morphogenesis or cancer metastasis by recognizing and making initial contacts with the extracellular matrix. However, they can also act as stationary cell anchors or help to establish communication...
01:31Mechanism of Lamellipodia Formation
Cells migrating in response to external stimuli form lamellipodia, which are thin membrane protrusions supported by a mesh of linked, branched, or unbranched actin filaments. These actin filaments interact with myosin motor proteins, creating the dynamic actomyosin complex within the cytoskeleton. Contractility, or the ability to generate contractile stress, is inherent to the actomyosin complex. It helps cells detect the stiffness of the surrounding ECM and exert contractile force for...