# Mechanisms of spindle organization for cell division

> **NIH NIH R01** · MASSACHUSETTS GENERAL HOSPITAL · 2024 · $396,760

## Abstract

During cell division, the precise positioning of the cell-cleavage plane at the center of a ~ 10-15
um long cell is essential for maintaining genome integrity. Consistently, cytokinesis failures can
lead to aneuploidy, a hallmark of tumorigenesis. This motivates a fundamental question: How
does a dividing cell find its center? It is now well established that an overlapping array of
antiparallel microtubules, known as the spindle midzone, plays a critical role. The midzone acts
as a micron scale ‘mark’ for the cell center to direct the signaling reactions that further precisely
define the site of cell-cleavage. An essential signaling protein that relocates from the
chromosomes to the midzone microtubules in anaphase is the AuroraB kinase, which is part of a
4-protein complex called Chromosome Passenger Complex (CPC). AuroraB is maximally
activated proximal to the midzone in anaphase. Its activity is important for the phosphorylation of
key cytokinesis factors that direct the formation of cell cleavage furrow. However, despite an
appreciation for its critical functions in anaphase, our knowledge of how intrinsic biophysical and
microtubule binding properties of CPC contribute to localization and activation at antiparallel
arrays is limited. Additionally, how the CPC is specifically concentrated on a specific subset of
microtubules in the spindle remains confounding. The overarching goal of the work proposed here
is to decipher how CPC is specifically localized to a narrow region of overlap formed by the plus
ends of antiparallel microtubules, and how the kinase activity of AuroraB is maximally activated
at such structures. To achieve this goal, we build on previous research where we reconstituted
antiparallel microtubule bundles, the minimal structural units of the midzone, from the collective
activity of conserved midzone motor and non-motor microtubule associated proteins. We will first
determine the intrinsic dynamics and microtubule binding properties of recombinant full-length
CPC using biophysical methods. We then take a small-scale systems biochemistry to elucidate
how the collective activity of key midzone motors and MAPs regulate the microtubule localization
of CPC. Finally, we will test key findings from our biochemical studies in cells using quantitative
analysis of CPC localization and activity in anaphase cells. In addition to fundamental mechanistic
insights on AuroraB, these studies have the potential to uncover new therapeutic strategies to
modulate its activity. The proposed in vitro reconstitutions, combined with structural and cellular
analysis, promises to provide significant new insights into the broader question of specific subsets
are microtubules are located by dense networks by signaling proteins for spatially confined activity
within the cellular cytoplasm.

## Key facts

- **NIH application ID:** 10941078
- **Project number:** 1R01GM155215-01
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** Radhika Subramanian
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $396,760
- **Award type:** 1
- **Project period:** 2024-09-01 → 2026-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10941078

## Citation

> US National Institutes of Health, RePORTER application 10941078, Mechanisms of spindle organization for cell division (1R01GM155215-01). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10941078. Licensed CC0.

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