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Studying the Cytoskeleton

Studying the Cytoskeleton

The cytoskeletal architecture can be studied using different microscopic and biochemical techniques. Electron microscopy was instrumental in discovering the cytoskeletal architecture around the 1960s, which allowed obtaining structural information at a high-resolution level. However, the sample preparation procedure often limits this ability in biological samples. Several protocols have been developed over the years to optimize sample preparation. In one of the protocols known as rotary...

Generation of Straight or Branched Actin Filaments

Generation of Straight or Branched Actin Filaments

The straight or branched structure formation of actin filaments is controlled by nucleating proteins such as the formins and Arp2/3 complex. Formin-mediated assembly results in straight filaments, whereas Arp2/3 protein complex-mediated assembly results in branched actin filaments.
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...

Actin Filament Depolymerization

Actin Filament Depolymerization

Actin filaments (F-actin) are composed of actin subunits. The dissociation of actin monomers can occur from either end of F-actin. The rate of dissociation is faster from the minus-end or the pointed end, where the actin subunits exist with a bound ADP, together known as ADP-actin. The depolymerization of F-actin is aided by proteins, including the actin-depolymerizing factor (ADF) and cofilin family of proteins, gelsolin, and glia maturation factor (GMF).
In F-actin, the ADF/cofilin proteins...

Formation of Higher-order Actin Filaments

Formation of Higher-order Actin Filaments

The polymerization of G-actin monomers into filamentous F-actin is a multi-step process. Once the F-actins are formed, they can bundle together in different arrangements to form higher-order networks and regulate cellular functions. Common examples include the formation of lamellipodia and filopodia at the cell's leading edge by actin reorganization in a migrating cell. The microvilli on the brush border epithelial cells are also formed through the F-actin network.
The high-order actin...

Assembly of Cytoskeletal Filaments

Assembly of Cytoskeletal Filaments

Cytoskeletal filaments are polymeric forms of smaller protein subunits. However, individual cytoskeletal filaments may easily disassemble or associate with other similar filaments to form rigid structures. Microfilaments, made of actin monomers, rely on actin-binding proteins to form bundles and create networks of individual actin filaments. Microtubules rely on microtubule-associated proteins (MAPs) to form sturdy cylindrical structures. However, the proteins involved in forming complex...

Actin Polymerization

Actin Polymerization

Actin polymerization occurs through the head-to-tail association of binding sites on monomeric actin or G-actin to form filamentous or F-actin. The polymerization can be divided into three phases ̶ nucleation, elongation, and steady-state phase.
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight...

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Related Experiment Video

Updated: Jul 2, 2025

Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles

Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles

Published on: May 5, 2022

Computational tools for quantifying actin filament numbers, lengths, and bundling.

Laura A Sherer¹, Biswaprakash Mahanta¹, Naomi Courtemanche¹

¹Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA.

|February 19, 2024

Summary

New MATLAB programs quantify actin filament dynamics. These tools enable precise measurements of actin filament length, count, and bundling, aiding the study of cytoskeletal organization and biopolymer assembly.

Keywords:

Actin Bundling Filament Fluorescence Kinetics Polymerization

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Measuring Protein Binding to F-actin by Co-sedimentation

Measuring Protein Binding to F-actin by Co-sedimentation

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Last Updated: Jul 2, 2025

Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles

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Published on: May 5, 2022

Reconstituting and Characterizing Actin-Microtubule Composites with Tunable Motor-Driven Dynamics and Mechanics

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Measuring Protein Binding to F-actin by Co-sedimentation

Measuring Protein Binding to F-actin by Co-sedimentation

Published on: May 18, 2017

Area of Science:

Cell Biology
Biophysics
Biochemistry

Background:

The actin cytoskeleton is crucial for cellular functions, with its dynamic assembly studied via fluorescent microscopy.
Analyzing actin dynamics is challenging due to interdependent and kinetic reaction processes.
Accurate quantification of actin filament behavior over time is essential for understanding cellular mechanics.

Purpose of the Study:

To develop and present two MATLAB programs for analyzing actin filament dynamics from fluorescence micrographs.
To facilitate quantitative measurements including filament counting, length determination, and bundling analysis.
To provide tools for extracting equilibrium and kinetic information from actin-based reactions.

Main Methods:

Development of custom MATLAB software for image analysis.
Application of the programs to analyze pre-assembled actin filaments under equilibrium conditions.
Utilizing the software to track actin filament crosslinking over time.

Main Results:

The developed MATLAB programs accurately quantify actin filament length, count, and bundling.
Demonstrated successful application to analyze equilibrium and time-dependent actin filament reactions.
The software provides a robust method for dissecting complex actin assembly processes.

Conclusions:

The described MATLAB programs offer valuable tools for quantitative analysis of actin cytoskeleton dynamics.
These programs can extract crucial equilibrium and kinetic data from various actin-based systems.
The methodology holds potential for broader applications in studying other biopolymer assembly processes.