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PubMed2000

Polyploidy induces centromere association.

Many species exhibit polyploidy. The presence of more than one diploid set of similar chromosomes in polyploids can affect the assortment of homologous chromosomes, resulting in unbalanced gametes. Therefore, a mechanism is required to ensure the correct assortment and segregation of chromosomes for gamete formation. Ploidy has been shown to affect gene expression. We present in this study an example of a major effect on a phenotype induced by ploidy within the Triticeae. We demonstrate that centromeres associate early during anther development in polyploid species. In contrast, centromeres in diploid species only associate at the onset of meiotic prophase. We propose that this mechanism provides a potential route by which chromosomes can start to be sorted before meiosis in polyploids. This explains previous reports indicating that meiotic prophase is shorter in polyploids than in their diploid progenitors. Even artificial polyploids exhibit this phenotype, suggesting that the mechanism must be present in diploids, but only expressed in the presence of more than one diploid set of chromosomes.

Centromere↗
PubMed2000

Targeted disruption of Skp2 results in accumulation of cyclin E and p27(Kip1), polyploidy and centrosome overduplication.

The ubiquitin-proteasome pathway plays an important role in control of the abundance of cell cycle regulators. Mice lacking Skp2, an F-box protein and substrate recognition component of an Skp1-Cullin-F-box protein (SCF) ubiquitin ligase, were generated. Although Skp2(-/-) animals are viable, cells in the mutant mice contain markedly enlarged nuclei with polyploidy and multiple centrosomes, and show a reduced growth rate and increased apoptosis. Skp2(-/-) cells also exhibit increased accumulation of both cyclin E and p27(Kip1). The elimination of cyclin E during S and G(2) phases is impaired in Skp2(-/-) cells, resulting in loss of cyclin E periodicity. Biochemical studies showed that Skp2 interacts specifically with cyclin E and thereby promotes its ubiquitylation and degradation both in vivo and in vitro. These results suggest that specific degradation of cyclin E and p27(Kip1) is mediated by the SCF(Skp2) ubiquitin ligase complex, and that Skp2 may control chromosome replication and centrosome duplication by determining the abundance of cell cycle regulators.

Animals↗
PubMed2003

Rate variation among nuclear genes and the age of polyploidy in Gossypium.

Molecular evolutionary rate variation in Gossypium (cotton) was characterized using sequence data for 48 nuclear genes from both genomes of allotetraploid cotton, models of its diploid progenitors, and an outgroup. Substitution rates varied widely among the 48 genes, with silent and replacement substitution levels varying from 0.018 to 0.162 and from 0.000 to 0.073, respectively, in comparisons between orthologous Gossypium and outgroup sequences. However, about 90% of the genes had silent substitution rates spanning a more narrow threefold range. Because there was no evidence of rate heterogeneity among lineages for any gene and because rates were highly correlated in independent tests, evolutionary rate is inferred to be a property of each gene or its genetic milieu rather than the clade to which it belongs. Evidence from approximately 200,000 nucleotides (40,000 per genome) suggests that polyploidy in Gossypium led to a modest enhancement in rates of nucleotide substitution. Phylogenetic analysis for each gene yielded the topology expected from organismal history, indicating an absence of gene conversion or recombination among homoeologs subsequent to allopolyploid formation. Using the mean synonymous substitution rate calculated across the 48 genes, allopolyploid cotton is estimated to have formed circa 1.5 million years ago (MYA), after divergence of the diploid progenitors about 6.7 MYA.

Evolution, Molecular↗
PubMed2003

Evolution of clonality and polyploidy in a weevil system.

The increased interest in asexual organisms calls for in-depth studies of asexual complexes that actively give rise to new clones. We present an extensive molecular study of the Otiorhynchus scaber (Coleoptera, Curculionidae) weevil system. Three forms have traditionally been recognized: diploid sexuals, triploid, and tetraploid parthenogens. All forms coexist in a small central area, but only the polyploid parthenogens have colonized marginal areas. Analyzing the phylogenetic relationship, based on three partial mitochondrial genes, of 95 individuals from 19 populations, we find that parthenogenesis and polyploidy have originated at least three times from different diploid lineages. We observe two major mitochondrial lineages, with over 2.5% sequence divergence between the most basal groups within them, and find that current distribution and phylogenetic relationships are weakly correlated. Quite unexpectedly, we also discover diploid clones that coexist with, and are morphologically indistinguishable from, the diploid sexual females. Our results support that these diploid clones are derived directly from the diploid sexuals. We also find that it is mainly an increase in ploidy level and not the benefits of asexual reproduction that confers to polyploid parthenogens the advantage over their diploid sexual relatives.

Animals↗
PubMed1987

Post-fertilization polyploidy in human preimplantation embryos fertilized in-vitro.

The development of in-vitro fertilization (IVF) and embryo transfer (ET) as a treatment for certain forms of infertility has emphasized the need for more information on why so many preimplantation embryos fail to develop beyond the very early cleavage stages. Analysis of nuclei from embryos that had ceased to grow or that were morphologically abnormal was carried out using one of two techniques: measurement of the DNA content of their nuclei, or observation of the number of Y chromosomes per nucleus. It was found that there was a correlation between the length of time in culture and abnormal development of polyploidy in a number of the cells. On the other hand, a small proportion of polyploid cells observed in a morphologically normal expanded blastocyst probably represents the normal precursors of polyploid trophoblast cells as observed in other mammalian species.

Blastocyst↗
PubMed2006

Transient progeroid phenotype and lipodystrophy in mosaic polyploidy.

Wiedemann-Rautenstrauch syndrome is a rare disorder with a progressive course and early lethality. Severe mental and growth retardation, muscle hypotonia, a progeroid face, wrinkled skin, relative macrocephaly with late closure of the anterior fontanel, arachnodactyly and congenital heart defects are also typical. We report on a female infant with all the characteristic features of this syndrome after birth. Chromosomal studies on peripheral leukocytes showed a normal karyotype. In view of an abnormal lipid distribution and lipodystrophy, metabolic studies for congenital disorders of glycosylation have been performed with normal results. At the age of 2 years 6 months the progeroid signs were no longer present, and the patient had a striking improvement in her psychomotor development. As there are overlapping features in Wiedemann-Rautenstrauch syndrome and in mosaic polyploidy, including psychomotor retardation, reduced peripheral muscle bulk, arachnodactyly and lipodystrophy, chromosome analysis was performed in the fibroblast culture of our patient. A mosaic triploidy/tetraploidy was detected in 60% and 14% of the cells, respectively. We therefore recommend chromosome analysis of fibroblasts from patients with a neonatal presentation of progeroid features and lipodystrophy.

Abnormalities, Multiple↗
PubMed2001

Polyploidy alters advertisement call structure in gray treefrogs.

Whole-genome duplication is believed to have played a significant role in the early evolution and diversification of vertebrate animals. The establishment of newly arisen polyploid lineages of sexually reproducing animals requires assortative mating between polyploids. Here, we show that genome duplication can directly alter a phenotypic trait mediating mate choice in the absence of genotypic change. Our results suggest that the direct effect of polyploidy on behaviour is a consequence of increased cell size.

Animals↗
PubMed2005

Comparative genomics of Gossypium and Arabidopsis: unraveling the consequences of both ancient and recent polyploidy.

Both ancient and recent polyploidy, together with post-polyploidization loss of many duplicated gene copies, complicates angiosperm comparative genomics. To explore an approach by which these challenges might be mitigated, genetic maps of extant diploid and tetraploid cottons (Gossypium spp.) were used to infer the approximate order of 3016 loci along the chromosomes of their hypothetical common ancestor. The inferred Gossypium gene order corresponded more closely than the original maps did to a similarly inferred ancestral gene order predating an independent paleopolyploidization (alpha) in Arabidopsis. At least 59% of the cotton map and 53% of the Arabidopsis transcriptome showed correspondence in multilocus gene arrangements based on one or both of two software packages (CrimeStatII, FISH). Genomic regions in which chromosome structural rearrangement has been rapid (obscuring gene order correspondence) have also been subject to greater divergence of individual gene sequences. About 26%-44% of corresponding regions involved multiple Arabidopsis or cotton chromosomes, in some cases consistent with known, more ancient, duplications. The genomic distributions of multiple-locus probes provided early insight into the consequences for chromosome structure of an ancient large-scale duplication in cotton. Inferences that mitigate the consequences of ancient duplications improve leveraging of genomic information for model organisms in the study of more complex genomes.

Arabidopsis↗
PubMed1992

Polyploidy in pleomorphic adenomas with cytological atypia.

Occasionally, in fine-needle aspirates of pleomorphic salivary gland adenomas, considerable cytonuclear atypia is present, which may give rise to a false-positive diagnosis. In this study DNA cytophotometry was performed on Feulgen restained smears prepared from material obtained by needle aspirates of normal salivary glands (n = 4), pleomorphic adenomas with (n = 5) and without (n = 4) atypia and a carcinoma in a pleomorphic adenoma. The results showed a clear diploid DNA histogram in the specimens of normal salivary gland and pleomorphic adenomas without atypia. In contrast, in the pleomorphic adenomas with atypia a distinct polyploid pattern was present in three out of the five DNA histograms with DNA values in 2c, 4c and 8c ranges. In two of these cases a 16c peak was also present and in the two remaining cases tetraploidy was demonstrated. In the carcinoma a main stemline at 4c was found. This report once more emphasizes the possible atypia which may be present in FNA of pleomorphic adenomas of the salivary gland. The atypia is due to polyploidy in a histologically benign tumour.

Adenoma, Pleomorphic↗
PubMed1976

Polyploidy of the bone marrow.

In a consecutive series of 841 patients whose bone marrows were cytogenetically investigated because of verified or suspected haematological disease, 11 patients were found to have at least 10% polyploid bone marrow mitoses. The chromosome numbers varied greatly between the cells of the same patients and between the patients. In 4 cases, the number was nearly or exactly tetraploid and in 1 patient a prevalent octaploid line was seen. Structurally abnormal marker chromosomes were seen in 8 of the patients. A total of 31 bone marrow chromosome counts were performed on a young woman with acute myelomonocytic leukaemia who had had several drug-induced remissions during the 3 1/2 years of disease. The results were related to the clinical findings. On several occasions a clear-cut correlation was noted between high proportions (nearly 100%) of polyploid cells and relapse on the one hand and low proportions (as low as 0%) of polyploids and remission on the other. Of the 11 patients, 2 had chronic myeloid leukaemia, 3 acute myelomonocytic leukaemia, 3 acute myeloid leukaemia and a further 3 some other malignant haematological disorders. We conclude that polyploidy is a feature associated with rare cases of leukaemia and other malignant diseases. It is often a sign of a poor prognosis.

Adolescent↗
PubMed2000

Polyploidy in a natural population of mussel, Mytilus trossulus.

We have analyzed natural polyploidy in a population of Mytilus trossulus from Vancouver Island (British Columbia, Canada) by means of cytogenetic techniques. Results obtained are the first reporting on this type of numerical chromosome aberrations in mussels.

Animals↗
PubMed2001

Topical mitomycin C and radiation induce conjunctival DNA-polyploidy.

INTRODUCTION: Atypical cell changes often occur following treatment of premalignant or malignant conjunctival neoplasias with topical mitomycin C (MMC) and/or radiation. These reactive, non-neoplastic alterations of the conjunctival epithelium can be a differential diagnostic problem. Our aim was to investigate changes in the nuclear DNA-distribution of conjunctival epithelial cells after MMC- and radiation therapy by DNA-image-cytometry. METHODS: Conjunctival brush smears were obtained from 13 patients (13 eyes) with squamous cell carcinomas and six patients (6 eyes) with conjunctival malignant melanomas in situ before, during and after treatment. The patients were treated with MMC-drops (0.02% or 0.04%) alone (n=12), with radiation therapy (n=3) or both (n=4). At first, the obtained brush smears were evaluated by cytology. Secondly, after Feulgen restaining, the DNA content of reactively changed cells was determined using the AutoCyte-QUIC-DNA workstation. RESULTS: We observed euploid DNA-polyploidy and cytomorphological changes in all patients (19/19). We considered these alterations as reactive to treatment. Four patients showed their greatest DNA-stemline at 4c and 15 patients at 8c. This effect was observed during and following MMC-drops and/or radiation and remained stable in 94% of all patients after a mean follow-up of 22.5 months (SD 15.4). In five cases image cytometry additionally demonstrated DNA-stemline aneuploidy as an evidence of tumor recurrence. CONCLUSION: Measurements of DNA-content revealed euploid polyploidisation of morphological suspicious but benign squamous cells which is the biologic correlate of well known secondary morphologic changes following topical chemotherapy and/or radiation. DNA-image-cytometry is a useful tool in the differention of euploid polyploidization as a sign of reactive cell changes following treatment and tumor recurrences.

Adult↗
PubMed1998

Evolution by polyploidy in Amphibia: new insights.

Polyploidy is an important mechanism of evolution in lower vertebrates, resulting in gene duplication and loci duplication evolving to diploidization. In polyploid anurans DNA is increased, but RNA and protein synthesis is kept at the same levels as in their diploid counterparts. Recent cytogenetic findings in Odontophrynus americanus show: (1) amphiplasty and asynchrony of the cell division cycle in 4n and (2) intra- and interindividual alterations of chromosome 4 morphology in 4n and 2n through breaks at secondary constrictions and at/or around the centromeres, followed by the appearance of changes of centromeres position, dicentrics, bisatellited chromosomes, precocious sister-chromatid segregation, and loss or unequal segregation of the chromosomes. This genome instability suggests the presence of chromosomal aberrations with chromodomain alterations at the centromeres affecting the mechanisms ensuring normal segregation of the chromatids in anaphase of mitosis and meiosis. Cell division asynchrony and chromosome abnormalities, novel findings in polyploids, are discussed respectively in function of gene activity and putative translocations producing polymorphisms in nucleolus organizers and secondary constrictions.

Amphibians↗
PubMed1988

Megakaryocyte polyploidy and maturation in chronic granulocytic leukemia.

To understand abnormal platelet production in chronic granulocytic leukemia, polyploidization and maturation of megakaryocytes in 10 patients were studied using a technique which allows sequential immunofluorescence identification by a monoclonal platelet antibody (C17), cytophotometric determination of the relative DNA content and cytological characterization of megakaryocytes in panoptically stained smears. Compared to normal conditions the proportion of diploid promegakaryocytes was not increased, suggesting an undisturbed influx of progenitor cells into the megakaryocytic cell compartment. Small tetraploid (4c) megakaryocytes undergo maturation without further polyploidization, the so-called microkaryocytes being mature rather than immature cells. Most of the megakaryocytes show rhythmical polyploidization only up to octoploid (8c) level, indicating the inability to produce high-polyploidy cells.

Adult↗
PubMed1999

Relationship between polyploidy and pollen self-incompatibility phenotype in Petunia hybrida Vilm.

Self-incompatibility in Solanaceae is controlled by a single multiallelic locus, the S-locus. The S-allele associated ribonucleases (S-RNases) in the pistil are involved in pollen rejection. In this work, we analyzed two newly isolated lines of Petunia hybrida, termed PB and PF. They both had the same set of S-RNases (SB1- and SB2-RNases), however the PB was a self-incompatible diploid while PF was a self-compatible tetraploid. Cross pollination tests between PB and PF indicated diploid pollen from PF lost the incompatibility phenotype. In order to clarify the effects of polyploidy on pollen phenotypic change, we artificially induced tetraploid plants from a diploid SB1SB2 heterozygote (= PB) and a diploid SB1SB1 homozygote. The obtained SB1 SB1SB1SB1 homoallelic tetraploid remained self-incompatible, whereas the SB1SB1SB2SB2 heteroallelic tetraploid became self-compatible. These data suggested that the diploid heteroallelic pollen lost the incompatibility phenotype and had the characteristics of self-compatibility with SB1SB2 style.

Alleles↗
PubMedDate not supplied

Human diploid fibroblast cells in senescence; cycling through polyploidy to mitotic cells.

Previously, it was found that senescent cells can undergo a modified cell cycle with mitotic cells as the end results. The major cycling events started with polyploidization, followed by depolyploidization to multinucleated cells (MNCs). These latter cells produced mononuclear offspring cells that could express mitotic cell divisions. In this report the emphasis is on late senescent fibroblasts that exhibited the senescence-associated change in cell morphology to large flat cells. Prior to live cell photography, flat cell cultures were maintained for months in the same culture flasks and therefore judged to be in a late senescent phase. All of the cellular events outlined above were present in these old cell cultures. Time lapse pictures showed movements of mitotic daughter cells away from each other and alignment of the chromosomes on the metaphase plate was visible in other mitotic cells. These data challenge the common view that cell senescence is irreversible and, therefore, an antitumor mechanism. A new finding was that the spike in polyploid cells in the near senescent phase consisted of cells with pairs of sister chromosomes from endoreduplication of DNA (two rounds of DNA synthesis and no mitosis). The lack of cells with 92 single chromosomes (e.g., G2 tetraploid cells) suggested that these polyploid cells also went through a changed cell cycle. The question now is whether these atypical polyploid cells are a subpopulation in senescence that can undergo the cycling from polyploidy to genome-reduced mitotic cells.

Cell Culture Techniques↗
PubMed1979

Development of polyploidy in B-cells of normal and diabetic mice.

This study was designed to clarify the relationship between pancreatic B-cell polyploidization and the progress of the diabetic syndrome in genetically diabetic (C57BL/Ks-db/db) and normal control mice (C57BL/KsJ) of matched age groups. Nuclear volume was confirmed to be a proper index of the polyploid class of the B-cell by correlation with Feulgen-DNA content as measured by microdensitometry. Nuclei of B-cells, identified by aldehyde fuchsin positive cytoplasmic granules, were traced by camera lucida and their volumes determined by semiautomatic particle size analysis. Six age groups were studied: 4.5, 7, 9.5, 12, 14.5 and 17 weeks. The major conclusions are: 1) The percentage of tetraploid nuclei in normal mice is consistently between 1.0 and 2.0% from 4.5 to 14.5 weeks of age and increases to approximately 3.0% at 17 weeks of age; however, further studies are required to determined the significance of this increase; 2) in all age groups studied, percentages of polyploid nuclei are significantly greater in diabetic than in control mice; 3) the percentage of tetraploid nuclei in diabetic animals is elevated 220% over controls at 4.5 weeks of age, remains constant until 12 weeks (while other parameters such as blood glucose level and body weight continue to rise) and increases significantly between 12 and 14.5 weeks of age. Implications of both the increased polyploidy observed at the onset of disease symptoms, and the dramatic increase occurring during the later stages of the disease, are discussed.

Age Factors↗
PubMed1989

Increase in digyny explains polyploidy after in-vitro fertilization of frozen-thawed mouse oocytes.

Fewer frozen-thawed mouse oocytes cleaved to the 2-cell stage compared to fresh control oocytes fertilized in vitro (46% vs 79%). The reduced rate of 2-cell formation was only partly explained by a decreased rate of fertilization (63% vs 85%). However, subsequent development to expanded blastocysts was not different (75% vs 78%). An increased frequency of second polar body retention by fertilized frozen-thawed oocytes compared with controls (11.8% vs 1.3%) was shown to be largely responsible for the higher incidence of polyploidy (16.3% vs 3.7%). The frequency of polyspermic fertilization was not different in the two groups (3.9% vs 2.3%).

Animals↗