Biology subjects

Ferras, C.

Publications and source records attributed to Ferras, C..

4 recordsLinked to original sources

bioRxiv2022

Long-term mitotic DNA damage promotes chromokinesin-mediated missegregation of polar chromosomes in cancer cells

DNA damage response (DDR) during interphase involves active signalling and repair to ensure genomic stability. However, how mitotic cells respond to DNA damage remains poorly understood. Supported by correlative live-/fixed-cell microscopy analysis we found that mitotic cells exposed to several cancer chemotherapy compounds acquire and signal DNA damage, regardless of how they interact with DNA. In-depth analysis upon long-term DNA damage during mitosis revealed a spindle assembly checkpoint (SAC)-dependent, but DDR-independent, mitotic delay. This delay was due to the presence of misaligned chromosomes that ultimately satisfy the SAC and missegregate, leading to micronuclei formation. Mechanistically, we show that long-term mitotic DNA damage specifically stabilizes kinetochore-microtubule attachments in cancer cells, causing the missegregation of polar chromosomes due to the action of arm-ejection forces by chromokinesins. Overall, these findings unveil that long-term therapeutic DNA damage regimens contribute to genomic instability through a surprising link between the stabilization of kinetochore-microtubule attachments and chromokinesin-mediated missegregation of polar chromosomes in cancer cells.

cell biology↗

bioRxiv2022

Misaligned chromosomes that satisfy the spindle assembly checkpoint are a strong predictor of micronuclei formation in dividing cancer cells

Chromosome alignment to the spindle equator is a hallmark of mitosis that is thought to promote chromosome segregation fidelity in metazoans. Yet, chromosome alignment is only indirectly supervised by the spindle assembly checkpoint (SAC) as a byproduct of chromosome bi-orientation, and the consequences of defective chromosome alignment remain unclear. Here we investigated how human cells respond to chromosome alignment defects of distinct molecular nature by following the fate of live HeLa cells after RNAi-mediated depletion of 120 proteins previously implicated in chromosome alignment. Surprisingly, in all cases, cells frequently entered anaphase after a delay with chronically misaligned chromosomes. Using depletion of key proteins as prototypes for defective chromosome alignment, we show that chronically misaligned chromosomes often satisfy the SAC and directly missegregate. In-depth analysis of specific molecular perturbations that prevent proper kinetochore-microtubule attachments revealed that chronically misaligned chromosomes that missegregate frequently result in micronuclei. Higher-resolution live-cell imaging indicated that, contrary to most anaphase lagging chromosomes that correct and reintegrate the main nuclei, chronically misaligned chromosomes are a strong predictor of micronuclei formation in a cancer cell model of chromosomal instability, but not in normal near-diploid cells. We provide evidence supporting that intrinsic differences in kinetochore-microtubule attachment stability on misaligned chromosomes account for this distinct outcome. Thus, chronically misaligned chromosomes that satisfy the SAC may represent a previously overlooked mechanism driving chromosomal/genomic instability during cancer cell division, and we unveil genetic conditions predisposing for these events.

cell biology↗

bioRxiv2018

Coherent-hybrid STED: a tunable photo-physical pinhole for super-resolution imaging at high contrast

Resolution in microscopy is not limited by diffraction as long as a nonlinear sample response is exploited. In a paradigmatic example, stimulated-emission depletion (STED) fluorescence microscopy fundamentally breaks the diffraction limit by using a structured optical pattern to saturate depletion on a previously excited sample area. Two-dimensional (2D) STED, the canonical low-noise STED mode, structures the STED beam by using a vortex phase mask, achieving a significant lateral resolution improvement over confocal fluorescence microscopy. However, axial resolution and optical sectioning remain bound to diffraction. Here we use a tunable coherent-hybrid (CH) beam to improve optical sectioning, markedly reducing background fluorescence. CH-STED, which inherits the 2D-STED immunity to spherical aberration, diversifies the depletion strategy, allowing an optimal balance between two key metrics (lateral resolution and background suppression) to be found. CH-STED is used to perform high-contrast imaging of complex biological structures, such as the mitotic spindle and the neuron cell body.

biophysics↗

bioRxiv2018

Mitotic progression, arrest, exit or death is determined by centromere integrity and independent of de novo transcription

Recent studies have challenged the prevailing dogma that transcription is repressed during mitosis. Transcription was also proposed to sustain the spindle assembly checkpoint (SAC) for several hours in response to unattached kinetochores. Here we used live-cell imaging of human cells in culture, combined with RNA-seq and qPCR, to investigate the requirement for de novo transcription during mitosis. Under conditions of persistently unattached kinetochores, transcription inhibition with actinomycin D, or treatment with other DNA-intercalating drugs, delocalized the chromosomal passenger complex (CPC) protein Aurora B from centromeres, compromising SAC robustness and cell fate. However, we were unable to detect significant changes in transcript levels. Moreover, inhibition of transcription independently of DNA intercalation had no effect on SAC response, mitotic progression, exit or death. Mechanistically, we show that DNA intercalating agents reduce the interaction of the CPC with nucleosomes. Thus, the capacity of human cells to progress, sustain, exit or die in mitosis relies on centromere integrity, rather than de novo transcription.

cell biology↗