Biology subjects

Motegi, F.

Publications and source records attributed to Motegi, F..

5 recordsLinked to original sources

bioRxiv2026

Spindle size scaling secures mitotic fidelity against whole-genome doubling-associated mechanical stress

Although whole-genome doubling (WGD) accompanies a drastic increase in chromosome number, post-WGD cells often continue to divide. How mitosis is sustained under increased chromosome number remains largely unknown. Here, we found that WGD cells require longer mitotic spindles than isogenic diploids to maintain spindle bipolarity. WGD increased mechanical stress on spindle poles during metaphase, associated with a higher risk of pole fragmentation. Disrupting kinetochore-microtubule attachment alleviated pole stress and fragmentation in WGD cells, suggesting that WGD-linked mechanical stress arises from spindle-chromosome interactions. Artificial spindle elongation reduced the pole stress and mitigated pole fragmentation defects in WGD cells. Our findings identify chromosome gain as a critical mechanical challenge to spindle organization and establish spindle size scaling as an adaptive mechanism that preserves mitotic fidelity after WGD.

cell biology↗

bioRxiv2024

A ZO-2 scaffolding mechanism regulates the Hippo signalling pathway.

Inhibition of proliferation upon contact is a critical cell density control mechanism governed by the Hippo signalling pathway. The biochemical signalling underlying cell density-dependent cues regulating Hippo signalling and its downstream effectors, YAP, remains poorly understood. Here, we reveal that the tight junction protein ZO-2 is required for the contact-mediated inhibition of proliferation. We additionally determined that the well-established molecular players of contact inhibition of proliferation, namely Hippo kinase LATS1 and YAP, are regulated by ZO-2, and that the scaffolding function of ZO-2 promotes the interaction with and phosphorylation of YAP by LATS1. Mechanistically, YAP is phosphorylated when ZO-2 brings LATS1 and YAP together via its SH3 and PDZ domains, respectively, subsequently leading to the cytoplasmic retention and inactivation of YAP. In conclusion, we demonstrate that ZO-2 maintains Hippo signalling pathway activation by promoting the stability of LATS1 to inactivate YAP.

cell biology↗

bioRxiv2020

Binary decision between asymmetric and symmetric cell division is defined by the balance of PAR proteins in C. elegans embryos

Coordination between cell differentiation and proliferation during development requires the balance between asymmetric and symmetric modes of cell division. However, the cellular intrinsic cue underlying the binary choice between these two division modes remains elusive. Here we show evidence in Caenorhabditis elegans that the invariable lineage of the division modes is programmed by the balance between antagonizing complexes of partitioning-defective (PAR) proteins. By uncoupling unequal inheritance of PAR proteins from that of fate determinants during zygote division, we demonstrated that changes in the balance between PAR-2 and PAR-6 are sufficient to re-program the division modes from symmetric to asymmetric and vice versa in two-cell stage embryos. The division mode adopted occurs independently of asymmetry in cytoplasmic fate determinants, cell-size asymmetry, and cell-cycle asynchrony between the sister cells. We propose that the balance between antagonizing PAR proteins represents an intrinsic self-organizing cue for binary specification of the division modes during development.

cell biology↗

bioRxiv2018

ZO-2 induces cytoplasmic retention of YAP by promoting a LATS1-ZO-2-YAP complex at tight junctions

Contact inhibition of proliferation (CIP) is a key mechanism that transduces the cell density status of tissue and organs into a unique transcriptional program by translocating YAP between the nucleus and the cytoplasm. However, the nature of the cell density-dependent cues that regulate the YAP distribution remains unclear. Here, we present evidence that tight junctions serve as a platform that controls both distribution and activity of LATS1, a kinase that phosphorylates YAP. This CIP effect is mediated by the scaffold function of junctional protein, ZO-2, by promoting LATS1 interaction with YAP in the cytoplasm, and then targeting the tripartite complex to tight junctions. There, LATS1 is activated by angiomotin and NF2, thereby stimulating YAP phosphorylation and its cytoplasmic retention. Our findings delineate novel mechanisms governing CIP, in which ZO-2 utilizes the status of cell-cell cohesion to control the phosphorylation status and therefore inactivation of YAP by LATS1 in the cytoplasm.

cell biology↗

bioRxiv2017

TPXL-1 Activates Aurora A to Clear Contractile Ring Components from the Polar Cortex During Cytokinesis

During cytokinesis, a signal from the bundled microtubules that form between the separating anaphase chromosomes promotes the accumulation of contractile ring components at the cell equator, while a signal from the centrosomal microtubule asters inhibits accumulation of contractile ring components at the cell poles. However, the molecular identity of the inhibitory signal has remained unknown. To identify molecular components of the aster-based inhibitory signal, we developed a means to monitor the removal of contractile ring proteins from the polar cortex after anaphase onset. Using this assay, we show that polar clearing is an active process that requires activation of Aurora A kinase by TPXL-1. TPXL-1 concentrates on astral microtubules coincident with polar clearing in anaphase, and its ability to recruit Aurora A and activate its kinase activity are essential for clearing. In summary, our data identify Aurora A kinase as an aster-based inhibitory signal that restricts contractile ring components to the cell equator during cytokinesis.\n\nSUMMARYDuring cytokinesis, centrosomal asters inhibit cortical contractility at the cell poles. Mangal et al. provide molecular insight into this phenomenon, showing that TPXL-1, which localizes to astral microtubules, activates Aurora A kinase to clear contractile ring proteins from the polar cortex.

cell biology↗