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[The formation of an endoplasmic microfilament layer during fibroblast spreading]
Abstract:
Spread fibroblasts contain a dense microfilament sheath under the dorsal cell surface in the endoplasmic region. The formation of the sheath during spreading of mouse embryo fibroblasts was studied using electron microscopy of platinum replicas. At the first stages of spreading the actin meshwork comprising the pseudopodial cytoskeleton arises at the cell edges. The actin of unattached pseudopodia moves centripetally and forms a circular microfilament bundle at the endoplasm periphery. Simultaneously, the microfilament cortex in the endoplasm appears to disassemble. Due to a continuous supply of polymerized actin from the periphery to the circular bundle the latter becomes wider to cover gradually the endoplasm and to form the microfilament sheath. Anchoring of centripetally moving microfilaments at the sites of cellular contacts with the substratum leads to the formation of radial actin bundles.
Insights
Mouse embryo fibroblast spreading involves actin remodeling. Initially at cell edges, actin moves inward to form a sheath, creating radial bundles and disassembling the endoplasm cortex.
Area of Science:
- Cell Biology
- Cytoskeleton Dynamics
- Electron Microscopy
Context:
- Fibroblast spreading is a fundamental cellular process.
- The dynamic remodeling of the actin cytoskeleton is crucial for cell shape and movement.
- Understanding these dynamics requires advanced imaging techniques.
Purpose:
- To investigate the dynamic formation of the microfilament sheath during fibroblast spreading.
- To elucidate the role of actin polymerization and depolymerization in this process.
- To visualize cytoskeletal rearrangements using high-resolution electron microscopy.
Summary:
- During mouse embryo fibroblast spreading, actin initially forms a meshwork at cell edges.
- This actin undergoes centripetal movement, disassembling the endoplasm cortex and forming a peripheral circular bundle.
- This bundle expands to create a dorsal microfilament sheath, with anchoring to the substratum forming radial actin bundles.
Impact:
- Provides detailed insights into the spatiotemporal organization of the actin cytoskeleton during cell spreading.
- Highlights the dynamic interplay between peripheral actin assembly and central actin disassembly.
- Offers a model for understanding cytoskeletal remodeling in cell migration and tissue development.