# Broken chromosome segregation during mitosis: a Drosophila model

> **NIH NIH R01** · DUKE UNIVERSITY · 2022 · $310,112

## Abstract

Chromosome double strand breaks (DSBs) that evade DNA damage checkpoints can persist into mitosis.
These DSBs are in danger of forming highly detrimental structures connected to genome shattering and tumor
progression, collectively referred to as micronuclei. To find mechanisms that prevent micronuclei, we discovered
that Drosophila papillar cells naturally inactivate DNA damage checkpoints, and as a result frequently exhibit
DNA fragments in mitosis. These fragments lack centromeres (acentric DNA), yet remarkably segregate during
papillar mitosis. This process prevents micronuclei and tissue development defects. The distinctive dependence
of papillar tissue development on acentric DNA segregation holds promise to reveal fundamental responses to
DSBs that persist into mitosis. From our combination of in vivo genetic screens, live imaging, and complementary
biochemistry approaches with collaborators, we are poised to make unique conceptual advances in this area.
 This proposal leverages our expertise, new findings, and a genetically amenable Drosophila model to
uncover regulation of broken chromosome segregation. The significance of our proposed work is evident in the
frequent contribution of micronuclei to genome instability and the evolutionary conservation of the molecules
studied, including the Alternative End Joining (Alt-EJ) repair protein DNA Polymerase Theta, conserved
monoubiquitination of the DNA repair scaffold FancD2, and the ubiquitin ligase CRL4CDT2. The innovation of our
approach derives from our model system that is evolutionarily wired to solve the challenge of frequent persistent
broken chromosomes, and the enhanced in vivo genetic screening capability of our system. These advantages
led to the preliminary data presented in this proposal. In Aim1, we will define the pathway leading to poleward
segregation of acentric DNA. In this Aim, we will identify Pol Theta domains that function in acentric DNA
segregation, pinpoint the extent to which Alt-EJ occurs in papillar cells with DSBs, and assess the role of FancD2
in regulating Pol Theta after DSBs. In Aim2, we will define the signaling pathway that promotes the transition
from lagging to segregating acentric DNA. In this Aim, we will determine if CRL4CDT2 functions together with Pol
Theta/FancD2 to promote acentric DNA segregation, uncover whether critical regulation of CRL4CDT2 activity or
in papillar cells with DSBs, and assess if inactivity of interphase checkpoints leads to a requirement for CRL4CDT2
in segregating acentric DNA in a non-papillar cell context (wing cells). In Aim 3, we will determine how regulation
of mitotic chromosome condensation contributes to segregation of acentric DNA fragments. We will build on
biochemical, genetic, and protein localization data connecting CRL4CDT2 to the mitotic complex Condensin I. We
will assess the role of CRL4CDT2 in regulating Condensin I localization during acentric DNA segregation and
determine the role of a conserved CRL4CDT2 re...

## Key facts

- **NIH application ID:** 10444196
- **Project number:** 1R01GM140138-01A1
- **Recipient organization:** DUKE UNIVERSITY
- **Principal Investigator:** Donald T. Fox
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $310,112
- **Award type:** 1
- **Project period:** 2022-09-22 → 2026-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10444196

## Citation

> US National Institutes of Health, RePORTER application 10444196, Broken chromosome segregation during mitosis: a Drosophila model (1R01GM140138-01A1). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10444196. Licensed CC0.

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