Biology subjects

Godek, K.

Publications and source records attributed to Godek, K..

4 recordsLinked to original sources

bioRxiv2024

Cell Competition Eliminates Aneuploid Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) maintain diploid populations for generations despite a persistently high rate of mitotic errors that cause aneuploidy, or chromosome imbalances. Consequently, to maintain genome stability, aneuploidy must inhibit hPSC proliferation, but the mechanisms are unknown. Here, we surprisingly find that homogeneous aneuploid populations of hPSCs proliferate unlike aneuploid non-transformed somatic cells. Instead, in mosaic populations, cell non-autonomous competition between neighboring diploid and aneuploid hPSCs eliminates less fit aneuploid cells. Aneuploid hPSCs with lower Myc or higher p53 levels relative to diploid neighbors are outcompeted but conversely gain a selective advantage when Myc and p53 relative abundance switches. Thus, although hPSCs frequently missegregate chromosomes and inherently tolerate aneuploidy, Myc- and p53-driven cell competition preserves their genome integrity. These findings have important implications for the use of hPSCs in regenerative medicine and for how diploid human embryos are established despite the prevalence of aneuploidy during early development.

cell biology↗

bioRxiv2023

Cyclin A/Cdk1 promotes chromosome alignment and timely mitotic progression

To ensure genomic fidelity a series of spatially and temporally coordinated events are executed during prometaphase of mitosis, including bipolar spindle formation, chromosome attachment to spindle microtubules at kinetochores, the correction of erroneous kinetochore-microtubule (k-MT) attachments, and chromosome congression to the spindle equator. Cyclin A/Cdk1 kinase plays a key role in destabilizing k-MT attachments during prometaphase to promote correction of erroneous k-MT attachments. However, it is unknown if Cyclin A/Cdk1 kinase regulates other events during prometaphase. Here, we investigate additional roles of Cyclin A/Cdk1 in prometaphase by using an siRNA knockdown strategy to deplete endogenous Cyclin A from human cells. We find that depleting Cyclin A significantly extends mitotic duration, specifically prometaphase, because chromosome alignment is delayed. Unaligned chromosomes display erroneous monotelic, syntelic, or lateral k-MT attachments suggesting that bioriented k-MT attachment formation is delayed in the absence of Cyclin A. Mechanistically, chromosome alignment is likely impaired because the localization of the kinetochore proteins BUB1 kinase, KNL1, and MPS1 kinase are reduced in Cyclin A-depleted cells. Moreover, we find that Cyclin A promotes BUB1 kinetochore localization independently of its role in destabilizing k-MT attachments. Thus, Cyclin A/Cdk1 facilitates chromosome alignment during prometaphase to support timely mitotic progression.

cell biology↗

bioRxiv2022

A Pluripotent Developmental State Confers a Low Fidelity of Chromosome Segregation

Human pluripotent stem cells (hPSCs) frequently become aneuploid with abnormal chromosome numbers due to mitotic chromosome segregation errors during propagation in culture. Yet, we do not understand why hPSCs exhibit a low mitotic fidelity. Here we investigate the mechanisms responsible for mitotic errors in hPSCs and show that the primary cause is lagging chromosomes with improper merotelic chromosome microtubule attachments in anaphase. Accordingly, we can improve merotelic error correction and reduce lagging chromosome rates in hPSCs using small molecules that prolong mitotic duration or destabilize chromosome microtubule attachments providing chemical strategies to preserve genome stability. Strikingly, we also demonstrate that mitotic error rates correlate with developmental potential decreasing upon differentiation and loss of pluripotency and conversely increasing after reprogramming to a pluripotent state. Thus, chromosome segregation fidelity is inherently low in hPSCs and depends on developmental state in normal human cells.

cell biology↗

bioRxiv2021

Chromosome segregation fidelity is controlled by small changes in kinetochore phospho-occupancy

Kinetochore protein phosphorylation promotes the correction of erroneous microtubule attachments to ensure faithful chromosome segregation during cell division. Determining how phosphorylation executes error correction requires an understanding of whether kinetochore substrates are completely (i.e. all-or-none) or only fractionally phosphorylated. Using quantitative mass spectrometry (MS), we measured phospho-occupancy on the conserved kinetochore protein Hec1 (NDC80) that directly binds microtubules. None of the positions measured exceeded [~]50% phospho-occupancy, and the cumulative phospho-occupancy changed by only [~]20% in response to changes in microtubule attachment status. The narrow dynamic range of phospho-occupancy is maintained by ongoing phosphatase activity. Further, both Cdk1-Cyclin B1 and Aurora kinases phosphorylate Hec1 to enhance error correction in response to different types of microtubule attachment errors. Thus, networks of kinases and phosphatases maintain low inherent phospho-occupancy to promote microtubule attachment to kinetochores while providing for high sensitivity of kinetochore-microtubule attachments to very small changes in phospho-occupancy to ensure high mitotic fidelity.

cell biology↗