Determining properties of spindle microtubules with femtosecond nanosurgery

In eukaryotic cells, the spindle ensures the faithful segregation of the genetic material during cell division. In this study we use femtosecond nanosurgery to quantitatively measure parameters describing the metaphase spindle. We selectively cut microtubules of metaphase spindles assembled from Xenopus egg extracts. After the cut, microtubules depolymerize rapidly. Analysis of the time-lapse imaging reveals the depolymeration dynamics and allows determining the length distribution of the microtubules. We show that the average length of microtubules in metaphase spindles increases from the pole towards the equator. We show that a spatially variable nucleation of microtubules can explain our measurements.