Extent and rate of chromosome segregation in two intraspecific mouse cell hybrids: A9 × diploid foetal erythrocyte and A9 × B82

1979 ◽  
Vol 36 (1) ◽  
pp. 215-221
Author(s):  
M.H. Russell ◽  
B.J. McGee ◽  
E. Engel
Keyword(s):  
Chromosome Segregation ◽  
Wild Type Mouse ◽  
Mouse Cell ◽  
Chromosome Loss ◽  
Wild Type ◽  
Banding Patterns ◽  
Chromosomal Segregation ◽  
Cell Hybrids ◽  
Telocentric Chromosomes ◽  
Hybrid Lines

Patterns of chromosome segregation were studied in 2 different intraspecific mouse cell hybrids: (1) A9 × B82, formed by fusing 2 cell lines of heteroploid fibroblasts, and (2) UWE, originating from the fusion of A9 cells with euploid foetal erythrocytes. Detailed analyses of Giemsa (G)-banded chromosomes and chromosome arms of both parental and hybrid cells were made for each hybrid type, in order to determine the specificity of the losses and to assess the influence of ploidy and cell differentiation. Unlike the A9 × B82 hybrids, which revealed a significant chromosome loss under selective tissue culture pressures only after 9 months, the UWE hybrids showed a sharp reduction in the total chromosome number during the initial 2 months under similar pressures. However, with no additional cloning, UWE remained karyotypically stable after that time. This rapid chromosomal segregation in UWE hybrids may be caused by properties of the parental foetal erythrocytes. In UWE cells, the majority of the chromosome arms were retained or duplicated. Less than a quarter of the total number of chromosome arms were segregated or lost, and these were all chromosome arms with abnormal mouse G-banding patterns, present only in the heteroploid A9 parental cells. In two of the four A9 × B82 hybrid lines, there was marked segregation of chromosome arms whose banding patterns were identical to those of wild type mouse telocentric chromosomes. For both types of intraspecific cell hybrids, two thirds or more of the chromosome arms had banding patterns which were the same as those of the wild type genome.

scholarly journals Reduced Mad2 expression keeps relaxed kinetochores from arresting budding yeast in mitosis

2011 ◽  
Vol 22 (14) ◽  
pp. 2448-2457 ◽  
Author(s):  
Erin L. Barnhart ◽  
Russell K. Dorer ◽  
Andrew W. Murray ◽  
Scott C. Schuyler
Keyword(s):  
Chromosome Segregation ◽  
Budding Yeast ◽  
Spindle Checkpoint ◽  
Chromosome Loss ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Diploid Cells ◽  
Antimicrotubule Drugs

Chromosome segregation depends on the spindle checkpoint, which delays anaphase until all chromosomes have bound microtubules and have been placed under tension. The Mad1–Mad2 complex is an essential component of the checkpoint. We studied the consequences of removing one copy of MAD2 in diploid cells of the budding yeast, Saccharomyces cerevisiae. Compared to MAD2/MAD2 cells, MAD2/mad2Δ heterozygotes show increased chromosome loss and have different responses to two insults that activate the spindle checkpoint: MAD2/mad2Δ cells respond normally to antimicrotubule drugs but cannot respond to chromosomes that lack tension between sister chromatids. In MAD2/mad2Δ cells with normal sister chromatid cohesion, removing one copy of MAD1 restores the checkpoint and returns chromosome loss to wild-type levels. We conclude that cells need the normal Mad2:Mad1 ratio to respond to chromosomes that are not under tension.

Chromosome segregation from cell hybrids. IV. Movement and position of segregant set chromosomes in early-phase interspecific cell hybrids

1988 ◽  
Vol 89 (1) ◽  
pp. 49-56
Author(s):  
P.A. Zelesco ◽  
J.A. Graves
Keyword(s):  
Chromosome Segregation ◽  
Early Phase ◽  
Metaphase Plate ◽  
Central Position ◽  
Chromosome Loss ◽  
Human Chromosomes ◽  
Hybrid Cells ◽  
Multipolar Mitosis ◽  
Cell Hybrids ◽  
G 11

We searched for evidence of aberrant movement or position of segregant set chromosomes in C-banded and G-11-banded early-phase hamster-mouse and hamster-human cell hybrids that had been prepared with minimal disruption. No evidence was obtained for an increased frequency of multipolar mitosis, delayed or precocious metaphase congression or anaphase segregation, or for exclusion of chromosomes from the daughter nuclei. However, in hamster-human hybrids, segregant set (human) chromosomes were observed to assume a central position within a ring of hamster chromosomes on the metaphase plate. Such non-random positioning may imply that the centromeres of segregant chromosomes make aberrant, or simply less efficient, attachments to the spindle in hybrid cells. This aberrant position may perhaps result indirectly in chromosome loss by interfering with the normal processes of replication, repair or transcription.

Chromosome segregation from cell hybrids.II. Do differences in parental cell growth rates and phase times determine direction of loss?

1986 ◽  
Vol 28 (5) ◽  
pp. 735-743 ◽  
Author(s):  
Jennifer A. Marshall Graves ◽  
Jaclyn M. Wrigley
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Chinese Hamster ◽  
Parental Cell ◽  
S Phase ◽  
Chromosome Loss ◽  
Parent Cell ◽  
Cycle Times ◽  
Cell Hybrids ◽  
The One

The hypothesis that the direction of chromosome segregation in cell hybrids is determined by the interaction of parent cell cycles, or S-phase times, predicts that the segregant parent will always be the one with the longer cycle, or the longer S phase, and that late replicating chromosomes will be more frequently lost. We have tested this hypothesis by studying cell cycle parameters of mouse, Chinese hamster, and platypus parent cells and by observing chromosome loss and replication patterns in hybrids between them. Two types of hybrids have been studied: mouse–hamster hybrids showed gradual segregation, in one or other direction, of 10–60% chromosomes, while rodent–platypus hybrids (which could be selected under conditions optimal for either parent cell) showed rapid and extreme segregation of platypus chromosomes. We found no correlation between the direction of segregation and the relative lengths of parental cycle times, or phase times, nor between sequence of replication and frequency with which segregant chromosomes are lost. We therefore conclude that the direction and extent of segregation is not directly determined by the interaction of parental cycle or phase times.Key words: cell hybrids, chromosome loss, cell cycle, S phase.

Chromosome segregation from cell hybrids. I. The effect of parent cell ploidy on segregation from mouse – Chinese hamster hybrids

1984 ◽  
Vol 26 (5) ◽  
pp. 557-563 ◽  
Author(s):  
Jennifer A. Marshall Graves
Keyword(s):  
Chromosome Number ◽  
Chromosome Segregation ◽  
Chinese Hamster ◽  
Chromosome Loss ◽  
Parent Cell ◽  
Cell Hybrids ◽  
Parental Factor ◽  
Species Combination ◽  
Mouse Cells ◽  
Input Ratio

To determine whether the dosage of some parental factor influences the direction and extent of chromosome segregation, I have constructed hybrids between polyploid series of mouse and Chinese hamster lines. The input ratio of mouse: hamster chromosomes varied from 3.3 (in hybrids between diploid hamster and polyploid mouse cells) and 0.9 (in hybrids between polyploid hamster and near-diploid mouse cells). Mouse chromosomes were retained and hamster chromosomes were lost from all hybrids with input ratios ≥ 1.3; the extent of hamster chromosome loss increased from 25 to 60% as the proportion of mouse chromosomes was increased. Reverse segregation was observed in hybrids in which the ratio was 0.9; hybrids between polyploid hamster and diploid mouse cells retained most hamster chromosomes and lost 52% of mouse chromosomes. I conclude that the direction and extent of chromosome segregation from these hybrids depends on the dosage of some factor contained in the parent cells; because the volumes of polyploid cells are proportional to chromosome number, this factor could be chromosomal, nuclear, or cytoplasmic. Dosage differences should therefore be considered when comparing chromosome segregation from hybrids with cells of the same species combination, but which might differ in chromosome number (e.g., diploid lines and established lines), or cell volume (e.g., cells from different tissues).Key words: cell hybrids, mouse – hamster, segregation, chromosome loss, ploidy.

Karyotypic analyses of parental and hybrid intraspecific mouse cells, A9/B82, by giemsa- and centromeric-banding

1977 ◽  
Vol 25 (1) ◽  
pp. 59-71
Author(s):  
M.H. Russell ◽  
E. Engel ◽  
W.K. Vaughn ◽  
B.J. McGee
Keyword(s):  
Chromosome Numbers ◽  
Clonal Selection ◽  
Hybrid Cell ◽  
Continuous Cultivation ◽  
Banding Patterns ◽  
Telocentric Chromosomes ◽  
Mouse Cells ◽  
Parental Lines ◽  
Hybrid Lines ◽  
Hybrid Cell Lines

Hybrids between A9 (HGPRT-) and B82 (TK-), mouse heteroploid fibroblast lines, were obtained through continuous cultivation and clonal selection; such hybrids showed marked segregation and by conventional stains displayed chromosome numbers and distribution similar to that of either parental type. Detailed analyses by Giemsa (G)- and centromeric-banding of these parental lines, and of 4 of the reduced hybrids, maintained in culture for up to 5 years, revealed the following points: (1) The distribution of the majority of individual chromosomal classes was similar for 3 of the hybrid cell lines. (2) Over two-thirds of the chromosomal arms in both the parental lines and hybrid lines were identical to normal mouse telocentric chromosomes. (3) For 2 of the hybrid lines, segregation was particularly marked with respect to those chromosomal arms whose G-banding patterns were identical to the wild-type genome; this indicated that segregation had occurred at the expense of redundant chromosomal material introduced by cell fusion. These banded studies demonstrated that segregation chiefly accounted for the sharp reduction in chromosome numbers while recombination accounted for the chromosome heterogeneity of the hybrid cells as compared to the parental genomes.

Chromosome segregation from cell hybrids. VII. Reverse segregation from karyoplast hybrids suggests control by cytoplasmic factors

Genome ◽  
1992 ◽  
Vol 35 (3) ◽  
pp. 537-540 ◽  
Author(s):  
Jennifer A. Marshall Graves ◽  
Iole Barbieri
Keyword(s):  
Chromosome Segregation ◽  
Human Cell ◽  
Chinese Hamster ◽  
Segregation Pattern ◽  
Chromosome Loss ◽  
Human Chromosomes ◽  
Cell Hybrids ◽  
Cytoplasmic Factors

Using human and Chinese hamster established lines as cell parents, we constructed hamster–human cell hybrids and human cell – hamster karyoplast hybrids. The cell hybrids retained one or two sets of hamster chromosomes and lost most of the human chromosomes. The karyoplast hybrids, however, retained a full set of human chromosomes and lost most of the Chinese hamster chromosomes. This reverse segregation pattern implies that cytoplasmic factors are major determinants of the direction of chromosome segregation.Key words: cell hybrids, chromosome loss, cytoplasmic factors, reverse segregation.

scholarly journals The Role of Cdh1p in Maintaining Genomic Stability in Budding Yeast

Genetics ◽  
2003 ◽  
Vol 165 (2) ◽  
pp. 489-503 ◽  
Author(s):  
Karen E Ross ◽  
Orna Cohen-Fix
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Chromosome Loss ◽  
Cyclin Dependent Kinase ◽  
Anaphase Promoting Complex ◽  
Growth Defects ◽  
Genes Encoding ◽  
Specificity Factor

Abstract Cdh1p, a substrate specificity factor for the cell cycle-regulated ubiquitin ligase, the anaphase-promoting complex/cyclosome (APC/C), promotes exit from mitosis by directing the degradation of a number of proteins, including the mitotic cyclins. Here we present evidence that Cdh1p activity at the M/G1 transition is important not only for mitotic exit but also for high-fidelity chromosome segregation in the subsequent cell cycle. CDH1 showed genetic interactions with MAD2 and PDS1, genes encoding components of the mitotic spindle assembly checkpoint that acts at metaphase to prevent premature chromosome segregation. Unlike cdh1Δ and mad2Δ single mutants, the mad2Δ cdh1Δ double mutant grew slowly and exhibited high rates of chromosome and plasmid loss. Simultaneous deletion of PDS1 and CDH1 caused extensive chromosome missegregation and cell death. Our data suggest that at least part of the chromosome loss can be attributed to kinetochore/spindle problems. Our data further suggest that Cdh1p and Sic1p, a Cdc28p/Clb inhibitor, have overlapping as well as nonoverlapping roles in ensuring proper chromosome segregation. The severe growth defects of both mad2Δ cdh1Δ and pds1Δ cdh1Δ strains were rescued by overexpressing Swe1p, a G2/M inhibitor of the cyclin-dependent kinase, Cdc28p/Clb. We propose that the failure to degrade cyclins at the end of mitosis leaves cdh1Δ mutant strains with abnormal Cdc28p/Clb activity that interferes with proper chromosome segregation.

scholarly journals Mechanism of Aurora-B Degradation and Its Dependency on Intact KEN and A-Boxes: Identification of an Aneuploidy-Promoting Property

2005 ◽  
Vol 25 (12) ◽  
pp. 4977-4992 ◽  
Author(s):  
Hao G. Nguyen ◽  
Dharmaraj Chinnappan ◽  
Takeshi Urano ◽  
Katya Ravid
Keyword(s):  
Chromosome Segregation ◽  
Fluorescent Protein ◽  
Point Mutations ◽  
Degradation Pathway ◽  
Aurora B ◽  
Stable Form ◽  
Wild Type ◽  
Green Fluorescent ◽  
Critical Regions

ABSTRACT The kinase Aurora-B, a regulator of chromosome segregation and cytokinesis, is highly expressed in a variety of tumors. During the cell cycle, the level of this protein is tightly controlled, and its deregulated abundance is suspected to contribute to aneuploidy. Here, we provide evidence that Aurora-B is a short-lived protein degraded by the proteasome via the anaphase-promoting cyclosome complex (APC/c) pathway. Aurora-B interacts with the APC/c through the Cdc27 subunit, Aurora-B is ubiquitinated, and its level is increased upon treatment with inhibitors of the proteasome. Aurora-B binds in vivo to the degradation-targeting proteins Cdh1 and Cdc20, the overexpression of which accelerates Aurora-B degradation. Using deletions or point mutations of the five putative degradation signals in Aurora-B, we show that degradation of this protein does not depend on its D-boxes (RXXL), but it does require intact KEN boxes and A-boxes (QRVL) located within the first 65 amino acids. Cells transfected with wild-type or A-box-mutated or KEN box-mutated Aurora-B fused to green fluorescent protein display the protein localized to the chromosomes and then to the midzone during mitosis, but the mutated forms are detected at greater intensities. Hence, we identified the degradation pathway for Aurora-B as well as critical regions for its clearance. Intriguingly, overexpression of a stable form of Aurora-B alone induces aneuploidy and anchorage-independent growth.

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