Imaging individual spindle microtubule dynamics in fission yeast.

Microtubules exhibit dynamic instability, stochastically switching between infrequent phases of growth and shrinkage. In the cell, microtubule dynamic instability is further modulated by microtubule-associated proteins and motors, which are specifically tuned to cell cycle stages. For example, mitotic microtubules are more dynamic than interphase microtubules. The different parameters of microtubule dynamics can be measured from length versus time data, which are generally obtained from time-lapse acquisition using the optical microscope. The typical maximum resolution of the optical microscope is ~λ/2 or ~300 nm. This scale represents a challenge for imaging fission yeast microtubule dynamics specifically during early mitosis, where the bipolar mitotic spindle contains many short dynamic microtubules of ~1-μm scale. Here, we present a novel method to image short fission yeast mitotic microtubules. The method uses the thermosensitive reversible kinesin-5 cut7.24(ts) to create monopolar spindles, where asters of individual mitotic microtubules are presented for imaging and subsequent analysis.