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Elliptical versus circular erythrocyte marginal bands: isolation, shape conversion, and mechanical properties
W D Cohen1, Y Sorokina, I Sanchez
1Department of Biological Sciences, Hunter College, New York, New York 10021, USA.
Cell Motility and the Cytoskeleton
|July 25, 1998
Summary
The erythrocyte marginal band (MB) maintains cell shape. Newly discovered elliptical MBs challenge previous hypotheses, suggesting bound material, not external forces, generates initial ellipticity.
Area of Science:
- Cell biology
- Biophysics
- Microtubule dynamics
Background:
- Erythrocyte differentiation involves shape changes, with the marginal band (MB) of microtubules crucial for maintaining ellipsoidal shape.
- Previous hypotheses suggested external forces generate ellipticity, based on isolated MBs appearing circular.
Purpose of the Study:
- To investigate the mechanism of marginal band (MB) ellipticity generation and maintenance in erythrocytes.
- To challenge the hypothesis that external forces are solely responsible for MB shape.
Main Methods:
- Isolation of salamander erythrocyte MBs using a detergent-based method.
- Experimental manipulation of isolated MBs (incubation, enzyme treatment) to induce shape changes.
- Laser microsurgical transection to compare mechanical properties of elliptical (E-MBs) and circular (C-MBs).
Main Results:
- Most detergent-isolated MBs were initially elliptical (E-MBs) and lacked transverse material.
- E-MBs could be stabilized or converted to circular MBs (C-MBs) under specific conditions.
- Mechanical testing revealed distinct behaviors: C-MBs linearized, while E-MBs retained curvature, contradicting differential bending resistance models.
Conclusions:
- The findings challenge hypotheses based on external forces and differential bending resistance.
- A new model suggests material bound to the MB stabilizes its ellipsoidal form.
- The mechanisms for generating and maintaining MB ellipticity likely differ.