Comparison of mechanisms of kinetochore capture with varying number of spindle microtubules*

The mechanism by which microtubules find kinetochores during spindle formation is a key question in cell biology. Experimental studies have shown that although search-and-capture of kinetochores by dynamic microtubules is a dominant mechanism in many organisms, several other capture mechanisms are also possible. One such mechanism reported in Schizosaccharomyces pombe shows that microtubules can exhibit a prolonged pause between growth and shrinkage. During the pause, the microtubules pivoted at the spindle pole body search for the kinetochores by performing an angular diffusion. To understand the physical basis for the selection of one mechanism over another, we numerically compare the temporal efficiency of these two mechanisms by distinct models. We find that the capture timescales have non-trivial dependences on microtubule number N, and one mechanism may be preferred over the other depending on this number. While for small N (as in fission yeast), the characteristic capture times due to rotational diffusion are lesser than those for search-and-capture, the situation is reversed beyond a certain N.