Astral and spindle forces in PtK2 cells during anaphase B: a laser microbeam study

Area of Science:

• Cell Biology
• Mitosis Research

Background:

• PtK2 cells exhibit distinct asters and spindles during anaphase B.
• Previous studies showed spindle severing increases pole-pole separation, suggesting aster pulling forces and spindle tension.

Purpose of the Study:

• To investigate the role of asters in generating tension and regulating pole separation during anaphase B.
• To test the hypothesis that asters pull on spindle poles and the spindle limits separation rate.

Main Methods:

• Utilized a UV-laser microbeam to selectively damage asters in living PtK2 cells during early anaphase B.
• Monitored individual spindle pole movements, pole-pole separation rates, and astral microtubule dynamics post-irradiation.

Main Results:

• Irradiating a centrosome significantly reduced astral microtubules and halted the movement of the affected pole.
• The sister pole, with intact asters, accelerated its movement.
• Control irradiations showed minimal impact, validating the specific effect of aster damage.

Conclusions:

• Results support the model where asters generate pulling forces (MT-mediated) creating tension on the central spindle.
• The central spindle acts as a governor, limiting pole separation rate.
• Evidence suggests the central spindle may also exert a pushing force during anaphase B.