Assessment of Chromosome Oscillations in Mammalian Cells by Live Cell Imaging.

In metaphase, chromosomes undergo a back-and-forth movement between two spindle poles called chromosome oscillation. This dynamic is necessary to maintain the robustness of chromosome segregation. This chapter describes the materials and methods required to observe chromosome oscillation in mammalian cell lines and calculate the deviation of amplitude (DAP), which is used to quantify the degree of chromosome oscillation.

Fibrous corona is reduced in cancer cell lines that attenuate microtubule nucleation from kinetochores.

Most cancer cells show increased chromosome missegregation, known as chromosomal instability (CIN), which promotes cancer progression and drug resistance. The underlying causes of CIN in cancer cells are not fully understood. Here we found that breast cancer cell lines show a reduced kinetochore localization of ROD, ZW10, and Zwilch, components of the fibrous corona, compared with non-transformed breast epithelial cell lines.

Oxidative stress induces chromosomal instability through replication stress in fibroblasts from aged mice.

Chromosomal aneuploidy has been associated with aging. However, whether and how chromosomal instability (CIN), a condition frequently seen in cancer cells in which chromosome missegregation occurs at a high rate, is associated with aging is not fully understood. Here, we found that primary fibroblasts isolated from aged mice (24 months old) exhibit an increased level of chromosome missegregation and micronucleation compared with that from young mice (2 months old), concomitant with an increased rate of aneuploid cells, suggesting the emergence of CIN.

Autocleavage of separase suppresses its premature activation by promoting binding to cyclin B1.

Accurate chromosome segregation requires timely activation of separase, a protease that cleaves cohesin during the metaphase-to-anaphase transition. However, the mechanism that maintains the inactivity of separase prior to this event remains unclear. We provide evidence that separase autocleavage plays an essential role in this process.

Deficiency of , a gene related to intellectual disability, causes impaired neuronal development and a mild behavioural phenotype.

is a gene associated with intellectual disability, which was originally identified as being involved in the maintenance of kinetochore-microtubule attachment. To explore the neuronal defects caused by deficiency, we established mice that lack . Mice that are homozygous knockout for were slightly smaller than wild-type mice and died soon after birth on pure C57BL/6J background.

High levels of chromosomal instability facilitate the tumor growth and sphere formation.

Most cancer cells show chromosomal instability (CIN), a condition in which chromosome missegregation occurs at high rates. Growing evidence suggests that CIN is not just a consequence of, but a driving force for, oncogenic transformation, although the relationship between CIN and tumorigenesis has not been fully elucidated. Here we found that conventional two-dimensional (2D) culture of HeLa cells, a cervical cancer-derived cell line, was a heterogenous population containing cells with different CIN levels.

Attenuated Chromosome Oscillation as a Cause of Chromosomal Instability in Cancer Cells.

Chromosomal instability (CIN) is commonly seen in cancer cells, and related to tumor progression and poor prognosis. Among the causes of CIN, insufficient correction of erroneous kinetochore (KT)-microtubule (MT) attachments plays pivotal roles in various situations. In this review, we focused on the previously unappreciated role of chromosome oscillation in the correction of erroneous KT-MT attachments, and its relevance to the etiology of CIN.

A mathematical model of kinetochore-microtubule attachment regulated by Aurora A activity gradient describes chromosome oscillation and correction of erroneous attachments.

Chromosome oscillation during metaphase is attenuated in cancer cell lines, concomitant with the reduction of Aurora A activity on kinetochores, which results in reduced mitotic fidelity. To verify the correlation between Aurora A activity, chromosome oscillation, and error correction efficiency, we developed a mathematical model of kinetochore-microtubule dynamics, based on stochastic attachment/detachment events regulated by Aurora A activity gradient centered at spindle poles. The model accurately reproduced the oscillatory movements of chromosomes, which were suppressed not only when Aurora A activity was inhibited, but also when it was upregulated, mimicking the situation in cancer cells.

Chromosome alignment-maintaining phosphoprotein CHAMP1 plays a role in cell survival through regulating Mcl-1 expression.

Antimitotic drugs such as vinca alkaloids and taxanes cause mitotic cell death after prolonged mitotic arrest. However, a fraction of cells escape from mitotic arrest by undergoing mitotic slippage, which is related to resistance to antimitotic drugs. Tipping the balance to mitotic cell death thus can be a way to overcome the drug resistance.

Chromosome oscillation promotes Aurora A-dependent Hec1 phosphorylation and mitotic fidelity.

Most cancer cells show chromosomal instability, a condition where chromosome missegregation occurs frequently. We found that chromosome oscillation, an iterative chromosome motion during metaphase, is attenuated in cancer cell lines. We also found that metaphase phosphorylation of Hec1 at serine 55, which is mainly dependent on Aurora A on the spindle, is reduced in cancer cell lines.

Author Correction: Lateral attachment of kinetochores to microtubules is enriched in prometaphase rosette and facilitates chromosome alignment and bi-orientation establishment.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Lateral attachment of kinetochores to microtubules is enriched in prometaphase rosette and facilitates chromosome alignment and bi-orientation establishment.

Faithful chromosome segregation is ensured by the establishment of bi-orientation; the attachment of sister kinetochores to the end of microtubules extending from opposite spindle poles. In addition, kinetochores can also attach to lateral surfaces of microtubules; called lateral attachment, which plays a role in chromosome capture and transport. However, molecular basis and biological significance of lateral attachment are not fully understood.

Phosphorylation of BACH1 switches its function from transcription factor to mitotic chromosome regulator and promotes its interaction with HMMR.

The transcription repressor BACH1 performs mutually independent dual roles in transcription regulation and chromosome alignment during mitosis by supporting polar ejection force of mitotic spindle. We now found that the mitotic spindles became oblique relative to the adhesion surface following endogenous BACH1 depletion in HeLa cells. This spindle orientation rearrangement was rescued by re-expression of BACH1 depending on its interactions with HMMR and CRM1, both of which are required for the positioning of mitotic spindle, but independently of its DNA-binding activity.

Chromokinesin Kid and kinetochore kinesin CENP-E differentially support chromosome congression without end-on attachment to microtubules.

Chromosome congression is the alignment of chromosomes at the spindle equator, and is a prerequisite for faithful chromosome segregation. Recent data suggest that before kinetochores attach to the end of microtubules (end-on attachment), chromosomes can move along microtubules towards the spindle equator through attachment of kinetochores to the lateral surface of microtubules (lateral attachment). Here we address this mechanism, focusing on the contribution of two mitotic motors, Kid and CENP-E.

CLIP-170 recruits PLK1 to kinetochores during early mitosis for chromosome alignment.

The cytoplasmic linker protein (CLIP)-170, an outer kinetochore protein, has a role in kinetochore-microtubule attachment and chromosome alignment during mitosis. However, the mechanism by which CLIP-170 is involved in chromosome alignment is not known. Here, we show that CLIP-170 colocalizes with Polo-like kinase 1 (PLK1) at kinetochores during early mitosis.

Nucleoporin Nup188 is required for chromosome alignment in mitosis.

Most cancer cells are aneuploid, which could be caused by defects in chromosome segregation machinery. Nucleoporins (Nup) are components of the nuclear pore complex, which is essential for nuclear transport during interphase, but several nucleoporins are also known to be involved in chromosome segregation. Here we report a novel function of Nup188, one of the nucleoporins regulating chromosome segregation.