Biology subjects

Gemble, S.

Publications and source records attributed to Gemble, S..

6 recordsLinked to original sources

bioRxiv2026

Profilin 1 maintains cell cycle fidelity to prevent unscheduled genome doubling and polyploidy in cancer

Whole-genome doubling (WGD) represents a major route to genome instability and therapeutic resistance in cancer; yet, the mechanisms enabling genome duplication in p53-proficient cells remain poorly understood. Here, we identify Profilin 1 (PFN1) loss as a driver of WGD through impaired mitotic entry. Using FUCCI live-cell imaging and single-cell genomic profiling, we show that PFN1-deficient cells bypass mitosis and undergo endoreplication, generating tetraploid cells. Rather than undergoing stable arrest after mitotic bypass, these genome-doubled cells retain proliferative capacity and proceed through aberrant mitotic divisions, thereby amplifying genomic instability. Proteomic analyses reveal coordinated attenuation of late cell-cycle programs, including downregulation of key mitotic regulators such as CDK1, PLK1 and CKS2, consistent with impaired G2/M transition. Despite accumulating polyploidy, PFN1-knockout cells fail to activate an effective p53 tetraploidy checkpoint and display increased nuclear MDM2, promoting cell-cycle arrest evasion and chemotherapeutic resistance. We supported clinical relevance by an orthotopic osteosarcoma xenograft model, in which PFN1-deficient SaOS2 cells showed enhanced metastatic dissemination, and by pan-cancer TCGA analyses confirming a recurrent association between PFN1 loss and WGD. Together, these findings identify Profilin 1 as a safeguard of cell-cycle fidelity whose loss enables genome doubling, cellular plasticity and therapy tolerance.

cancer biology↗

bioRxiv2025

A novel mechanism for centrosome expulsion ensures metabolic activity in polyploid cells

Programmed polyploidy is often linked to increase cell size to support enhanced metabolism, barrier function or regeneration. In certain polyploid cells, the cytoskeleton is drastically remodeled-most notably by eliminating centrosomes. However, the purpose and mechanisms underlying centrosome elimination have remained unclear. We investigated this question in Drosophila acentrosomal salivary glands (SGs), a physiological polyploid model where cells reach high chromosome content through endoreplication. Using genetic tools, live imaging approaches, super-resolution microscopy combined with tissue clearing and electron microscopy, our study uncovers a novel centrosome elimination pathway in vivo. This process requires non-muscle myosin II (MyoII) activity and the macroautophagic machinery to drive centrosome release into the lumen of the salivary glands via autolysosomal exocytosis. Failure to eliminate centrosomes disrupts the mitochondria network, impairing respiration and ATP production. Our findings reveal a previously unknown mechanism that removes centrosomes through the secretory autophagy pathway to protect mitochondrial function and support the high metabolic demands of polyploid cells.

cell biology↗

bioRxiv2025

Mitotic slippage causes nuclear instability in polyploid cells

Whole-genome duplication (WGD), leading to polyploidy can arise in physiological and pathological contexts1-5. WGD can occur via non-canonical cell cycles such as mitotic slippage, cytokinesis failure or endoreplication1,3. Whether the routes to WGD influence the behaviour of the resulting polyploid cells remains unclear. Here, we compared these routes under both physiological and non-physiological conditions. Remarkably, only mitotic slippage led to widespread nuclear abnormalities defined by highly variable nuclear deformations that we termed nuclear instability. Mechanistically, we found that these nuclei were softer - due to high levels of histone 3 phosphorylation in G1 altering chromatin compaction - and thus more vulnerable to microtubule-driven deformations. The resulting nuclear instability leads to local nuclear reorganisation and changes in 3D genome organisation impacting ultimately gene expression. Importantly, we observed similar nuclear instability in megakaryocytes, which are physiological polyploid cells that we show here to be generated by mitotic slippage, providing a molecular mechanism for their atypical nuclear architecture6,7. In striking contrast, nuclear shape was stable in different physiological polyploid cells generated by cytokinesis failure and endoreplication. Overall, our findings highlight that the route towards WGD matters and that mitotic slippage uniquely destabilizes nuclear architecture, with implications for both physiology and disease.

cell biology↗

bioRxiv2023

Centrosome amplification primes for apoptosis and favors the response to chemotherapy in ovarian cancer beyond multipolar divisions

Centrosome amplification is a feature of cancer cells associated with chromosome instability and invasiveness. Enhancing chromosome instability and subsequent cancer cell death via centrosome unclustering and multipolar divisions is an aimed-for therapeutic approach. Here we show that centrosome amplification favors responses to conventional chemotherapy independently of multipolar divisions and chromosome instability. We perform single-cell live imaging of chemotherapy responses in epithelial ovarian cancer cell lines and observe increased cell death when centrosome amplification is induced. By correlating cell fate with mitotic behaviors, we show that enhanced cell death occurs independently of chromosome instability. We identify that cells with centrosome amplification are primed for apoptosis. We show they are dependent on the apoptotic inhibitor BCL-XL, and that this is not a consequence of mitotic stresses associated with centrosome amplification. Given the multiple mechanisms that promote chemotherapy responses in cells with centrosome amplification, we assess such a relationship in an epithelial ovarian cancer patient cohort. We show that high centrosome numbers associate with improved chemotherapy responses and longer overall survival. Our work identifies apoptotic priming as a clinically relevant consequence of centrosome amplification, expanding our understanding of this pleiotropic cancer cell feature.

cell biology↗

bioRxiv2021

Mechanisms of genetic instability in a single S-phase following whole genome doubling

Diploid and stable karyotypes are associated with health and fitness in animals. In contrast, whole genome duplications (WGDs) - doubling full chromosome content - are linked to genetic instability (GIN) and frequently found in human cancers 1-3. It has been established that WGDs fuel chromosome instability through abnormal mitosis 4-8, however, the immediate consequences of tetraploidy in the first interphase are not known. This is an essential question because single WGD events such as cytokinesis failure can promote tumorigenesis 9. Here, we found that newly born tetraploid human cells undergo high rates of DNA damage during DNA replication in the first S-phase. Using DNA combing and single cell sequencing, we show that DNA replication dynamics is perturbed, generating under- and over-replicated regions. Mechanistically, we found that these defects result from the lack of protein mass scaling up at the G1/S transition, which impairs the fidelity of DNA replication. This work shows that within a single interphase, unscheduled tetraploid cells can acquire highly abnormal karyotypes. These findings provide an explanation for the GIN landscape that favors tumorigenesis after tetraploidization.

cell biology↗

bioRxiv2019

Topoisomerase IIα Prevents, But Does Not Resolve, Ultrafine Anaphase Bridges By Two Mechanisms

Topoisomerase II (Topo II), a well-conserved double-stranded DNA (dsDNA)-specific decatenase, processes dsDNA catenanes resulting from DNA replication during mitosis. Topo II defects lead to an accumulation of ultrafine anaphase bridges (UFBs), a type of chromosome non-disjunction. Topo II has been reported to resolve DNA anaphase threads, possibly accounting for the increase in UFB frequency upon Topo II inhibition. We hypothesized that the excess UFBs might also result, at least in part, from an impairment of the prevention of UFB formation by Topo II. We found that Topo II inhibition promotes UFB formation without affecting UFB resolution during anaphase. Moreover, we showed that Topo II inhibition promotes the formation of two types of UFBs depending on cell-cycle phase. Topo II inhibition during S-phase compromises complete DNA replication, leading to the formation of UFB-containing unreplicated DNA, whereas Topo II inhibition during mitosis impedes DNA decatenation at metaphase-anaphase transition, leading to the formation of UFB-containing DNA catenanes. Thus, Topo II activity is essential to prevent UFB formation in a cell-cycle dependent manner, but dispensable for UFB resolution during anaphase.

cell biology↗