Minus-end depolymerisation of kinetochore microtubules in C. elegans metaphase

Determine whether kinetochore microtubules in the metaphase spindle of Caenorhabditis elegans one-cell embryos depolymerize at their minus ends during mitosis, and quantify the extent of such minus-end depolymerisation relative to the proportion of open minus ends observed by electron microscopy.

Background

The study reports no global poleward flux of spindle microtubules in C. elegans metaphase but identifies a localized poleward movement near chromosomes consistent with kinetochore microtubules (kMTs) sliding along spindle microtubules. Treadmilling is considered unlikely based on genetic perturbations and the observation that many kMTs do not reach the centrosome.

Despite favoring a sliding mechanism potentially powered by KLP-18 (kinesin-12), the authors note uncertainty about whether minus-end depolymerisation of kMTs contributes to the observed dynamics, referencing evidence that a substantial fraction of kMT minus ends appear open in metaphase electron micrographs. Clarifying whether minus-end depolymerisation occurs would distinguish between sliding-only versus combined mechanisms for kMT poleward movement.

References

However, we cannot exclude that the kinetochore microtubules depolymerise from their minus-ends, consistent with 38% of the ends opened in metaphase (Redemann et al., 2017).

— Kinesin-12 KLP-18 contributes to the kinetochore-microtubule poleward flux during the metaphase of C. elegans one-cell embryo  (2507.06620 - Soler et al., 9 Jul 2025) in Discussion, Page 14