The Life History of a Single Kinetochore Fiber sounds like a book a lot of us would enjoy (well, me at least). It isn’t really a book about a plucky kinetochore fiber who triumphs over a difficult childhood, but rather the focus of a fascinating recent paper. In this paper published in Molecular Biology of the Cell, LaFountain and Oldenbourg present results showing a model for kinetochore microtubule formation that occurs at kinetochores.
Kinetochore fibers link chromosomes to the mitotic spindle, which drives chromosome segregation during anaphase. The prevailing model of kinetochore fiber formation includes a “search and capture” mechanism, in which some dynamic spindle microtubules reach a kinetochore and become stabilized by the interaction. A recent paper by LaFountain and Oldenbourg shows, however, that the maturation of these kinetochore fibers depends on the addition of microtubules at the kinetochore-proximal end, with polymerization towards the spindle pole. In this study, the naturally birefringent microtubules of crane-fly spermatocytes were examined, allowing a quantitative analysis of where microtubules are added. In the images above, kinetochore-proximal addition of microtubules can be seen in the centrosome-free half-spindle (red arrows) of a crane-fly spermatocyte, from early prometaphase to metaphase (top to bottom).
LaFountain, J., & Oldenbourg, R. (2014). Kinetochore-driven outgrowth of microtubules is a central contributor to kinetochore fiber maturation in crane-fly spermatocytes Molecular Biology of the Cell, 25 (9), 1437-1445 DOI: 10.1091/mbc.E14-01-0008