Temperature dependence of anaphase chromosome velocity and microtubule depolymerization

Area of Science:

• Cell Biology
• Molecular Biology
• Biophysics

Background:

• Mitosis involves precise chromosome segregation.
• Spindle birefringence reflects microtubule polymerization dynamics.

Purpose of the Study:

• To precisely determine the time course of chromosome movement and spindle birefringence decay during anaphase.
• To investigate the relationship between chromosome velocity and spindle microtubule dynamics across different temperatures.
• To explore potential common mechanisms of mitosis in plant and animal cells.

Main Methods:

• Precise determination of chromosome movement and spindle birefringence decay rates in *Tilia americana* endosperm cells and *Asterias forbesi* eggs.
• Analysis of the temperature dependence of chromosome velocity and spindle retardation decay rate constants.
• Plotting chromosome velocity against the retardation rate constant.

Main Results:

• Chromosome velocity and spindle retardation decay rate constants are exponential functions of temperature for both species.
• A positive linear relationship exists between chromosome velocity and the retardation decay rate constant across physiological temperatures.
• Chromosome velocity correlates with the rate of spindle microtubule depolymerization, not the absolute amount of microtubules.

Conclusions:

• Chromosome movement during anaphase is governed by the rate of spindle microtubule disassembly.
• A common mechanism for mitosis, involving a first-order process of spindle fiber disassembly, is suggested for plant and animal cells.
• This disassembly process irreversibly removes microtubular subunits, impacting polymerization equilibrium and chromosome movement.