Single centrosome manipulation reveals its electric charge and associated dynamic structure

Area of Science:

• Cell Biology
• Biophysics
• Molecular Motors

Background:

• The centrosome acts as the primary microtubule-organizing center in animal cells.
• It comprises a pair of centrioles enveloped by pericentriolar material.

Purpose of the Study:

• To investigate the charge properties of individual Drosophila embryo centrosomes.
• To understand how centrosome charge influences its structure and hydrodynamic behavior.

Main Methods:

• Single-organelle electrophoresis using laser manipulation and microelectrodes.
• Measurement of centrosome size via Stokes law and thermal fluctuation spectral analysis.
• Analysis of environmental factors like pH and Ca(2+) on centrosome structure.

Main Results:

• Drosophila centrosomes exhibit a net negative charge with a low isoelectric point (3.1 +/- 0.1).
• The centrosome's effective charge is small (< 10^3 electrons), with low surface-charge density.
• Hydrodynamic size is 60% larger than electron microscopy diameter, due to electric field-induced expansion.
• This expansion is modulated by environmental pH and Ca(2+).

Conclusions:

• Centrosome charge significantly impacts its structural organization and hydrodynamic properties.
• The electric field plays a self-organizing role in centrosome structure, influenced by environmental conditions.
• The developed methodology is valuable for studying centrosome dynamics under various conditions.