GO:0061573 actin filament bundle retrograde transport: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0061573 (actin filament bundle retrograde transport) describes the directed movement of actin filament bundles from the cell periphery toward the interior, a process essential for cell polarity, migration, and morphogenesis.
• Nonmuscle myosin 2 motors generate the force for retrograde transport of actin bundles, and their processive filament sliding is required for bundle organization.
• Retrograde flow and bundle transport are conserved from yeast to mammals, with type II myosin and tropomyosin isoforms playing key roles in budding yeast and fission yeast.
• ADF/cofilin-mediated actin turnover directs retrograde flow during neurite formation, linking bundle transport to neuronal development.
• Dynamin2 organizes lamellipodial actin networks and orchestrates lamellar actomyosin, influencing retrograde bundle transport.
• Drosophila bristle growth depends on retrograde transport of actin bundles, providing a model for studying bundle dynamics in vivo.
Description
Actin filament bundle retrograde transport (GO:0061573) is a biological process in which actin filament bundles are distributed from the cell periphery toward the interior. This directed movement is fundamental for establishing and maintaining cell polarity, driving cell migration, and shaping cellular architecture during development. The process is powered by myosin motors and regulated by actin-binding proteins that control filament assembly and disassembly. In migrating fibroblasts, retrograde flow and myosin II activity within the leading edge deliver F-actin to the lamella, where it seeds the formation of graded polarity actomyosin II filament bundles. Similarly, in neuronal development, ADF/cofilin-mediated actin retrograde flow directs neurite formation, highlighting the importance of bundle transport in morphogenesis. In yeast, type II myosin and tropomyosin isoforms are required for retrograde actin flow, demonstrating evolutionary conservation of the mechanism. Understanding actin filament bundle retrograde transport is critical for researchers studying cell motility, cytoskeletal dynamics, and related diseases such as cancer and neurodegeneration. This article synthesizes current knowledge from authoritative sources and provides a framework for experimental investigation using CRISPR-based models.
actin filament bundle retrograde transport At A Glance
| GO ID | GO:0061573 |
|---|---|
| GO term | actin filament bundle retrograde transport |
| Ontology | biological_process |
| Synonym | actin filament cable retrograde transport |
| Major function | Directed transport of actin bundles from periphery to interior, essential for cell polarity and migration |
| Cellular context | Leading edge, lamella, and actin-rich structures in motile cells |
| Key motors | Nonmuscle myosin 2, type II myosin |
| Conservation | Observed in yeast, Drosophila, and mammalian cells |
What Is GO:0061573?
Actin filament bundle retrograde transport is the process by which actin filament bundles are moved from the cell periphery toward the cell interior, resulting in their redistribution and organization. This movement is driven by myosin motors and is coupled to actin polymerization dynamics at the leading edge.
Why Is actin filament bundle retrograde transport Important in Cell Biology?
Actin filament bundle retrograde transport is essential for fundamental cellular processes including cell migration, polarity establishment, and morphogenesis. Defects in this process contribute to cancer metastasis, neuronal development disorders, and other pathologies. Understanding its molecular mechanism provides insights into cytoskeletal regulation and offers targets for therapeutic intervention.
• Required for directed cell migration in wound healing and immune responses.
• Establishes cell polarity by delivering actin bundles to specific intracellular locations.
• Drives neurite formation and neuronal development through ADF/cofilin-mediated retrograde flow.
• Conserved from yeast to mammals, enabling genetic studies in model organisms.
• Involved in lamellipodial actin network organization and lamellar actomyosin assembly.
• Dysregulation is linked to cancer cell invasion and metastasis.
• Plays a role in Drosophila bristle morphogenesis, a model for actin bundle dynamics.
• Provides a mechanism for delivering structural components to the cell interior.
• Regulated by myosin activity and actin-binding proteins, offering multiple points for experimental manipulation.
• Critical for understanding cytoskeletal contributions to cell shape and mechanics.
What Happens During actin filament bundle retrograde transport?
Initiation at the leading edge
In simple terms: The process starts at the front of the cell where actin filaments are assembled.
Actin filament bundle retrograde transport begins at the cell periphery, where actin polymerization and myosin II activity generate forces that move actin bundles inward. In migrating fibroblasts, retrograde flow and myosin II activity within the leading cell edge deliver F-actin to the lamella, seeding the formation of graded polarity actomyosin II filament bundles. This initiation step is tightly coupled to actin assembly at the leading edge and requires nonmuscle myosin 2 filaments, which are processive in cells and can slide actin filaments over long distances.
Myosin-driven bundle translocation
In simple terms: Molecular motors called myosins pull the actin bundles toward the cell center.
Nonmuscle myosin 2 filaments generate the force for retrograde transport by sliding actin filaments relative to one another. In budding yeast, type II myosin and a tropomyosin isoform are required for retrograde actin flow, demonstrating the conserved role of myosin motors in bundle transport. Similarly, in fission yeast, myosin Vs organize actin cables, which are bundles of actin filaments, and are essential for their retrograde movement. The processive nature of myosin 2 filaments allows them to transport actin bundles over micrometer distances without dissociating.
Regulation by actin-binding proteins
In simple terms: Proteins that cut or cap actin filaments control how fast bundles move.
ADF/cofilin-mediated actin turnover is critical for retrograde flow and bundle transport. In developing neurons, ADF/cofilin regulates actin retrograde flow to direct neurite formation, showing that filament disassembly is as important as assembly for bundle movement. Dynamin2 also organizes lamellipodial actin networks and orchestrates lamellar actomyosin, influencing the retrograde transport of actin bundles. These actin-binding proteins ensure that bundles are properly remodeled as they move inward.
Delivery to the lamella and interior
In simple terms: The bundles are deposited in the middle of the cell to build structures.
As actin bundles are transported inward, they are delivered to the lamella, where they contribute to the formation of actomyosin bundles with graded polarity. This delivery is essential for maintaining the structural integrity of the lamella and for cell polarization. Competition for actin between distinct F-actin networks defines a bistable switch for cell polarization, highlighting how retrograde bundle transport contributes to cellular decision-making. In Drosophila bristles, retrograde transport of actin bundles supports growth and morphogenesis, demonstrating the importance of delivery to specific cellular domains.
Key Genes Involved in GO:0061573 actin filament bundle retrograde transport
The following genes and proteins are key players in actin filament bundle retrograde transport, based on experimental evidence from model organisms and mammalian cells.
| Gene | Major Role | Research Relevance |
|---|---|---|
| MYH9 | Nonmuscle myosin 2 heavy chain; generates force for bundle transport | Mutations cause platelet disorders and hearing loss; target for migration studies |
| MYH10 | Nonmuscle myosin 2 isoform; processive filament sliding | Essential for neuronal development and cytokinesis |
| CFL1 | Cofilin; actin depolymerization and turnover | Regulates retrograde flow in neurons and cancer cells |
| CFL2 | Cofilin isoform; actin filament disassembly | Muscle-specific roles; potential disease target |
| DNM2 | Dynamin2; organizes lamellipodial actin networks | Mutations cause centronuclear myopathy; regulates actomyosin |
| TPM1 | Tropomyosin isoform; stabilizes actin filaments | Regulates retrograde flow in yeast and mammals |
| TPM2 | Tropomyosin isoform; actin cable stability | Muscle and cytoskeletal functions |
| MYO5 | Myosin V; organizes actin cables in fission yeast | Model for myosin-driven bundle transport |
| ACTB | Beta-actin; main component of actin bundles | Mutations cause Baraitser-Winter syndrome |
| ACTG1 | Gamma-actin; cytoskeletal actin | Deafness and developmental disorders |
| PFN1 | Profilin; actin polymerization regulator | Mutations linked to ALS; affects retrograde flow |
| ARP2/3 | Actin nucleation complex | Branching and network organization |
| FMNL2 | Formin; actin elongation | Lamellipodia and cell migration |
| VASP | Actin assembly promoter | Filopodia and bundle formation |
| ZYX | Zyxin; actin bundle component | Mechanotransduction and bundle stability |
| ACTN1 | Alpha-actinin; crosslinks actin bundles | Bundle formation and stability |
| TAGLN | Transgelin; actin bundling | Smooth muscle and cancer |
| MYL9 | Myosin light chain; regulates myosin activity | Controls contractility and retrograde flow |
How Is actin filament bundle retrograde transport Regulated?
Actin filament bundle retrograde transport is regulated by myosin light chain phosphorylation, which controls myosin II activity and force generation. ADF/cofilin activity is regulated by phosphorylation and pH, modulating actin turnover and retrograde flow speed. In yeast, tropomyosin isoforms and type II myosin levels influence retrograde flow rates. Competition for actin monomers between distinct F-actin networks can create a bistable switch that determines whether cells polarize and transport bundles directionally.
actin filament bundle retrograde transport and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| MYH9 | Platelet disorders, hearing loss | Knockout in HeLa cells; point mutation in MYH9 |
| DNM2 | Centronuclear myopathy | Knock-in of patient mutations in C2C12 myoblasts |
| CFL1 | Neurodevelopmental disorders, ALS | Knockout in primary neurons; overexpression of phospho-mimetic |
| ACTB | Baraitser-Winter syndrome | Point mutation knock-in in iPSCs |
| TPM1 | Muscle disorders | Knockout in yeast; overexpression in mammalian cells |
Cancer metastasis
Actin filament bundle retrograde transport is critical for cell migration and invasion, processes that drive cancer metastasis. Dynamin2, which organizes lamellipodial actin networks, is upregulated in several cancers and promotes invasive migration. Nonmuscle myosin 2 activity, required for bundle transport, is also implicated in tumor cell motility. Targeting these pathways may reduce metastatic spread.
Neurodevelopmental disorders
ADF/cofilin-mediated actin retrograde flow directs neurite formation, and defects in this process contribute to neurodevelopmental disorders. Mutations in actin isoforms (ACTB, ACTG1) cause Baraitser-Winter syndrome and deafness, highlighting the importance of actin bundle dynamics in neuronal development. Profilin 1 (PFN1) mutations are linked to amyotrophic lateral sclerosis (ALS), further connecting retrograde transport to neurodegeneration.
Myopathies and cytoskeletal diseases
Mutations in DNM2 cause centronuclear myopathy, a disease characterized by defects in actin organization and membrane trafficking. Tropomyosin isoforms (TPM1, TPM2) regulate retrograde flow in yeast and are linked to muscle and cytoskeletal disorders. Nonmuscle myosin 2 (MYH9) mutations cause platelet disorders and hearing loss, demonstrating the broad impact of retrograde transport defects.
From actin filament bundle retrograde transport-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does MYH9 loss affect retrograde bundle transport? | MYH9 knockout in HeLa or fibroblast cells |
| How do disease mutations in DNM2 alter actin bundle dynamics? | Point mutation knock-in of DNM2 in C2C12 myoblasts |
| Can CFL1 phosphorylation regulate neurite formation? | Phospho-mutant knock-in in primary neurons |
| What is the role of TPM1 in retrograde flow? | TPM1 knockout in budding yeast |
| Does ACTB mutation affect bundle transport? | ACTB point mutation knock-in in iPSCs |
| Can overexpression of MYO5 rescue bundle transport? | Overexpression of MYO5 in fission yeast |
How to Study the actin filament bundle retrograde transport Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell imaging with Lifeact-GFP | Retrograde flow speed and bundle movement | Assessing MYH9 knockout effects |
| Kymography | Spatiotemporal dynamics of actin bundles | Quantifying retrograde transport in neurons |
| Yeast genetics | Conserved gene function in retrograde flow | Screening TPM1 and MYO5 mutants |
| Actin bundling assay | Bundle formation and crosslinking | Testing alpha-actinin and fascin |
| Proximity labeling (BioID) | Protein interactome of actin bundles | Identifying novel regulators |
| Phospho-specific antibodies | Myosin light chain and cofilin phosphorylation | Measuring regulatory changes |
| CRISPR knockout screening | Genes required for retrograde transport | High-throughput discovery |
| FRAP | Actin turnover rates in bundles | Quantifying dynamics in live cells |
Live-cell imaging of actin dynamics
Live-cell imaging using fluorescently tagged actin (e.g., Lifeact-GFP) allows real-time visualization of retrograde bundle transport. Kymography and particle tracking quantify flow speed and direction. This method is essential for assessing the effects of genetic perturbations on bundle movement.
Genetic perturbation and rescue
Knockout, knockdown, or overexpression of candidate genes (e.g., MYH9, CFL1, DNM2) followed by imaging or biochemical assays can establish causality. Rescue experiments with wild-type or mutant constructs confirm specificity. Yeast genetics provides a powerful system for rapid screening of conserved components.
Biochemical assays for actin bundling
In vitro actin bundling assays using purified proteins (e.g., alpha-actinin, fascin) and sedimentation or microscopy can measure bundle formation and stability. These assays complement cellular studies by defining direct molecular interactions.
Proteomics and interactomics
Mass spectrometry-based proteomics can identify proteins associated with actin bundles during retrograde transport. Proximity labeling (BioID) or co-immunoprecipitation can reveal dynamic interactions. These approaches uncover novel regulators and disease-relevant pathways.
How CRISPR Can Be Used to Study GO:0061573 actin filament bundle retrograde transport
Knockout
CRISPR knockout of genes such as MYH9, CFL1, or DNM2 can abolish retrograde bundle transport, revealing essential components. Knockout cell lines are valuable for rescue experiments and for testing redundancy among isoforms.
Point Mutation
Point mutation knock-in of disease-associated variants (e.g., MYH9 R702C, DNM2 R465W) allows precise modeling of human disorders affecting actin bundle transport. These models can reveal gain-of-function or dominant-negative effects.
Knock-in
Tagged knock-in of actin or myosin genes (e.g., GFP-MYH9) enables live-cell imaging of bundle transport without overexpression artifacts. Knock-in of reporter cassettes can also track transcriptional responses.
Overexpression
Overexpression of wild-type or mutant forms of MYO5, TPM1, or CFL1 can enhance or disrupt retrograde transport, providing insights into dose-dependent effects. Inducible systems allow temporal control.
How EDITGENE Supports actin filament bundle retrograde transport Research
Researchers studying actin filament bundle retrograde transport-related genes often need to determine whether a candidate gene is causally involved in the process or merely correlated. CRISPR-based models provide the gold standard for establishing causality, and EDITGENE offers a comprehensive suite of services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for actin filament bundle retrograde transport research.
Frequently Asked Questions About actin filament bundle retrograde transport
What is actin filament bundle retrograde transport?
It is the process by which actin filament bundles move from the cell periphery toward the interior, driven by myosin motors and regulated by actin-binding proteins.
What genes are involved in actin filament bundle retrograde transport?
Key genes include MYH9, MYH10, CFL1, DNM2, TPM1, and MYO5, among others.
What is the GO ID for actin filament bundle retrograde transport?
The Gene Ontology ID is GO:0061573.
How is actin filament bundle retrograde transport regulated?
It is regulated by myosin light chain phosphorylation, ADF/cofilin activity, and competition for actin monomers between networks.
Which diseases are linked to defects in actin filament bundle retrograde transport?
Cancer metastasis, neurodevelopmental disorders, myopathies, and platelet disorders have been linked to defects in this process.
What model organisms are used to study actin filament bundle retrograde transport?
Budding yeast, fission yeast, Drosophila, and mammalian cell lines are commonly used.
How can CRISPR be used to study actin filament bundle retrograde transport?
CRISPR knockout, point mutation knock-in, and tagged knock-in allow precise manipulation of genes like MYH9 and CFL1 to test their roles.
What imaging techniques visualize retrograde actin bundle transport?
Live-cell imaging with Lifeact-GFP, kymography, and FRAP are standard techniques.
Is actin filament bundle retrograde transport conserved across species?
Yes, components and mechanisms are conserved from yeast to mammals.
What is the role of myosin in actin filament bundle retrograde transport?
Nonmuscle myosin 2 and type II myosin generate the force for bundle translocation by sliding actin filaments.
Conclusion
Actin filament bundle retrograde transport (GO:0061573) is a fundamental biological process that drives cell polarity, migration, and morphogenesis. Research over the past two decades has identified key molecular players, including nonmuscle myosin 2, ADF/cofilin, and tropomyosin isoforms, and has linked defects to human diseases such as cancer and neurodevelopmental disorders. Continued investigation using CRISPR-based models and advanced imaging will further elucidate the regulatory mechanisms and therapeutic potential of targeting this pathway.
References
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- 2. Menon M et al.. 2014. Dynamin2 organizes lamellipodial actin networks to orchestrate lamellar actomyosin.. PLoS One 9(4):e94330 PMID: 24710573
- 3. Flynn KC et al.. 2012. ADF/cofilin-mediated actin retrograde flow directs neurite formation in the developing brain.. Neuron 76(6):1091-107 PMID: 23259946
- 4. Lo Presti L et al.. 2012. Myosin Vs organize actin cables in fission yeast.. Mol Biol Cell 23(23):4579-91 PMID: 23051734
- 5. Anderson TW et al.. 2008. Retrograde flow and myosin II activity within the leading cell edge deliver F-actin to the lamella to seed the formation of graded polarity actomyosin II filament bundles in migrating fibroblasts.. Mol Biol Cell 19(11):5006-18 PMID: 18799629
- 6. Huckaba TM et al.. 2006. Roles of type II myosin and a tropomyosin isoform in retrograde actin flow in budding yeast.. J Cell Biol 175(6):957-69 PMID: 17178912
- 7. Lomakin AJ et al.. 2015. Competition for actin between two distinct F-actin networks defines a bistable switch for cell polarization.. Nat Cell Biol 17(11):1435-45 PMID: 26414403
- 8. Fei X et al.. 2002. The growth of Drosophila bristles and laterals is not restricted to the tip or base.. J Cell Sci 115(Pt 19):3797-806 PMID: 12235290
