# Efficiency and fidelity in mitotic spindle assembly

> **NIH NIH R35** · WADSWORTH CENTER · 2020 · $451,253

## Abstract

The goal of cell division (mitosis) is to partition genetic information, in the form of chromosomes, equally into the
two daughter cells. To achieve this goal, ‘kinetochores’, specialized macromolecular complexes on
chromosomes, must attach to the poles of the ‘spindle’, a macromolecular machine assembled from dynamic
biopolymers called ‘microtubules’. Attachment defects lead to chromosome mis-segregation, which is a hallmark
of tumorigenesis. The overarching goal of our research is to reveal the mechanisms that allow the spindle to
assemble rapidly and with minimal number of errors. Our previous work demonstrates that every major step in
spindle assembly can be reached via several alternative routes. Some routes are swift but error prone, others
are accurate but not efficient. This multiplicity of alternative mechanisms prompts the hypothesis that a proper
balance in the contributions from individual mechanisms must be maintained to ensure error-free chromosome
segregation. We will test this hypothesis by quantitatively characterizing spindle assembly in normal vs.
chromosomally instable (CIN) cells that frequently mis-segregate their chromosomes. Over the next five years
we will focus our studies on the four major aspects of spindle assembly: 1) Identification of the mechanism(s) by
which direct capture of microtubules nucleated at the spindle poles suppresses the number of segregation errors.
Although only ~25% of chromosomes normally utilize direct capture, segregation errors become numerous in
the absence of this mechanism. 2) Characterization of the molecular mechanisms that govern attachment to
non-centrosomal microtubules nucleated in the immediate proximity of kinetochores, which is the main mode of
attachment employed by ~75% of chromosomes in normal cells. Specifically, we will localize microtubule-
nucleating activities to a particular domain(s) within the kinetochore and establish the role of kinesin CenpE in
the formation of microtubule bundles (K-fibers) with proper polarity of microtubules. 3) We will characterize
structural changes within the kinetochore that trigger removal of the ‘checkpoint proteins’. This process is
essential for controlling orderly progression through mitosis. 4) Finally, we will quantify how often chromosomes
in various cell types are propelled poleward by a dynein-mediated pulling force exerted at the distal end of short
K-fibers instead of the more common mechanism that involves generation of the force within the kinetochore.
Ultrastructural organization of kinetochores transported by the alternative force production mechanisms will be
compared contributions and the contributions of these mechanisms for error-free chromosome segregation will
be characterized. To achieve our goals, we employ sophisticated imaging such as laser microsurgery, precise
tracking of chromosome movements, and correlative electron-microscopy analyses conducted on the
kinetochores whose behavior was followed in live cells up to the...

## Key facts

- **NIH application ID:** 9882283
- **Project number:** 5R35GM130298-02
- **Recipient organization:** WADSWORTH CENTER
- **Principal Investigator:** Alexey L Khodjakov
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $451,253
- **Award type:** 5
- **Project period:** 2019-03-01 → 2024-02-29

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9882283

## Citation

> US National Institutes of Health, RePORTER application 9882283, Efficiency and fidelity in mitotic spindle assembly (5R35GM130298-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9882283. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*