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Results for “polyploidy”

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PubMed1996

Effect of long-term treatment with propionyl-L-carnitine on smooth muscle cell polyploidy in spontaneously hypertensive rats.

Experimental studies suggest that DNA content is increased in the smooth muscle cells of the arteries of hypertensive animals. It is unclear whether an increase in DNA content occurring in the smooth muscle cells of hypertensive rats represents a pressure-dependent effect. To evaluate the antihypertensive effect of long-term treatment with propionyl-L-carnitine and the possible morphological changes in thoracic smooth muscle cells correlated with this effect, we studied 4-month-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) randomly divided into five groups. One group of SHR was treated with propionyl-L-carnitine for 12 months; the other four groups of SHR and WKY received no treatment and were controls. We used static and flow cytometry to evaluate the polyploid cell content in thoracic aorta smooth muscle cells. Systolic pressure in untreated SHR progressively increased during the experiment. Treatment did not significantly influence pressure values in SHR. In WKY, blood pressure was significantly lower than that in treated and untreated age-matched SHR (2P < .02). The number of polyploid smooth muscle cells was significantly lower in the propionyl-L-carnitine-treated SHR than in the untreated rats (2P < .04) and similar to values for WKY. The reduction of polyploid cells in treated SHR was paralleled by a significant decrease of the aortic total DNA content, whereas no modifications occurred in smooth muscle cell mass. Long-term treatment with propionyl-L-carnitine may interfere with cellular mechanisms regulating the secondary responses involved in DNA synthesis.

Animals↗
PubMed2005

Loss of Drosophila borealin causes polyploidy, delayed apoptosis and abnormal tissue development.

The chromosomal passenger complex (CPC) is a key regulator of mitosis in many organisms, including yeast and mammals. Its components co-localise at the equator of the mitotic spindle and function interdependently to control multiple mitotic events such as assembly and stability of bipolar spindles, and faithful chromosome segregation into daughter cells. Here, we report the first detailed characterisation of a CPC mutation in Drosophila, using a loss-of-function allele of borealin (borr). Like its mammalian counterpart, Borr colocalises with the CPC components Aurora B kinase and Incenp in mitotic Drosophila cells, and is required for their localisation to the mitotic spindle. borr mutant cells show multiple mitotic defects that are consistent with loss of CPC function. These include a drastic reduction of histone H3 phosphorylation at serine 10 (a target of Aurora B kinase), a pronounced attenuation at prometaphase and multipolar spindles. Our evidence suggests that borr mutant cells undergo multiple consecutive abnormal mitoses, producing large cells with giant nuclei and high ploidy that eventually apoptose. The delayed apoptosis of borr mutant cells in the developing wing disc appears to cause non-autonomous repair responses in the neighbouring wild-type epithelium that involve Wingless signalling, which ultimately perturb the tissue architecture of adult flies. Unexpectedly, during late larval development, cells survive loss of borr and develop giant bristles that may reflect their high degree of ploidy.

Animals↗
PubMed1993

Association of ultrarapid freezing of mouse oocytes with increased polyploidy at the pronucleate stage, reduced cell numbers in blastocysts and impaired fetal development.

Mature mouse oocytes were frozen ultrarapidly with a cryoprotectant solution consisting of 3.5 mol dimethylsulfoxide l-1 and 0.5 mol sucrose l-1 or exposed to the freezing solution and recovered. Freshly collected oocytes were used as controls. After ultrarapid freezing and thawing, a high mean percentage of oocytes (78%) survived. The incidence of parthenogenetic activation in frozen-thawed oocytes was not increased. After insemination in vitro, the rate of two-cell formation was decreased (59% versus 69%). Examination of the chromosome complement of first-cleavage embryos revealed that the incidence of polyploid embryos was four times that of the control group (23% versus 6%). Fewer fertilized eggs progressed to the blastocyst stage (49% versus 81%) and the mean number of cells per blastocyst was decreased. Furthermore, the capacity of transferred blastocysts to develop in vivo was reduced. Autopsy at day 17 of gestation revealed that the proportion of embryos implanting was lower in the embryos derived from ultrarapidly frozen-thawed oocytes. Furthermore, some of the living fetuses were abnormal, but our sample size is too small for the effect to be significant. In the solution control group, no differences were found compared with the control group. Although the study needs further results to draw definite conclusions, our findings question whether the applied protocol is suitable for mouse oocytes.

Animals↗
PubMed2006

A novel approach for characterizing expression levels of genes duplicated by polyploidy.

Studying gene expression in polyploids is complicated by genomewide gene duplication and the problem of distinguishing transcript pools derived from each of the two homeologous genomes such as the A- and D-genomes of allotetraploid Gossypium. Short oligonucleotide probes designed to specifically target several hundred homeologous gene pairs of Gossypium were printed on custom NimbleGen microarrays. These results demonstrate that relative expression levels of homeologous genes may be measured by microarrays and that deviation from equal expression levels of homeologous loci may be common in the allotetraploid nucleus of Gossypium.

Base Sequence↗
PubMed2005

Two ancient rounds of polyploidy in rice genome.

An ancient genome duplication (PPP1) that predates divergence of the cereals has recently been recognized. We report here another potentially older large-scale duplication (PPP2) event that predates monocot-dicot divergence in the genome of rice (Oryza sativa L.), as inferred from the age distribution of pairs of duplicate genes based on recent genome data for rice. Our results suggest that paleopolyploidy was widespread and played an important role in the evolution of rice.

Biological Evolution↗
PubMed2005

The absence of p53 aggravates polyploidy and centrosome number abnormality induced by Aurora-C overexpression.

Aurora-C is the third member of the aurora serine/threonine kinase family and was found only in mammals. Because Aurora-C is overexpressed in many different types of cancer cells we decided to analyze the consequences of Aurora-C overexpression in human cells. We first investigated the subcellular localization of overexpressed GFP-Aurora-C in mitosis and interphase in HeLa cells. As expected, during mitosis, we found that Aurora-C mimics Aurora-B. Surprisingly, in few interphase cells, we found that Aurora-C localized to the centrosome, like Aurora-A. We then examined the phenotype generated by Aurora-C overexpression. Basically it looked similar to the phenotypes observed after overexpression of the other Aurora kinases. We observed an augmentation of polyploid cells containing more than two centrosomes. More interestingly this phenotype was aggravated in the absence of a functional p53. Although the physiological function of Aurora-C in somatic cells remains to be clarified, our results, just like for the two other Aurora kinases, raised the question of a role of Aurora-C in the development and progression of cancer especially in the presence of mutated p53.

Aurora Kinase B↗
PubMed2006

Molecular cloning and characterization of a novel calcium-dependent protein kinase gene IiCPK2 Responsive to polyploidy from tetraploid Isatis indigotica.

A novel calcium-dependent protein kinase gene (designated as IiCPK2) was cloned from tetraploid Isatis indigotica. The full-length cDNA of IiCPK2 was 2585 bp long with an open reading frame (ORF) of 1878 bp encoding a polypeptide of 625 amino acid residues. The predicted IiCPK2 polypeptide included three domains: a kinase domain, a junction domain (or autoinhibitory region), and a C-terminal calmodulin-like domain (or calcium-binding domain), which presented a typical structure of plant CDPKs. Further analysis of IiCPK2 genomic DNA revealed that it contained 7 exons, 6 introns and the length of most exons was highly conserved. Semi-quantitative RTPCR revealed that the expression of IiCPK2 in root, stem and leaf were much higher in tetraploid sample than that in diploid progenitor. Further expression analysis revealed that gibberellin (GA3), NaCl and cold treatments could upregulate the IiCPK2 transcription. All our findings suggest that IiCPK2 might participate in the cold, high salinity and GA3 responsive pathways.

Amino Acid Sequence↗
PubMed1976

[Spontaneous polyploidy in laboratory mice. Embryological and cytogenetic analysis].

The developmental patterns of mice with spontaneous genomic aberrations at the pre- and post-implantation embryonic stages have been studied. The frequency of spontaneous triploidy varies in different strains from 1.7 to 5.8%. Digeny is the principal cytogenetical mechanism for triploidy. The triploid embryos of all the strains under study are characterized by the total delay of development already at the blastocyst stage. The most of triploids die at the stages of neurula and beginning of active organogenesis. A few triploids are resorbed during placentation. In the CBA mice, the triploidization results in the characteristic syndrome: disproportionally reduced amniotic vesicle, hypertrophied allantoic rudiment, reduction of neural plate, absence of head folds, notochord and mesenchyme. The spontaneous tetraploidy in mice occurs very rarely and is accompanied by severe developmental defects already at the preimplantation stages.

Animals↗
PubMed2001

[Somatic polyploidy in neurons of the gastropod molluscs. II. Dynamics of DNA synthesis in the process of postnatal growth of CNS neurons in Succineid snail].

A study was made of the age dynamics of polyploidization and dynamics of DNA synthesis in neuron cell nuclei during the postnatal growth of the gastropod pulmonate snail Succinea lauta. According to cytophotometrical results, the degree of polyploidization in neuron nuclei increases from young to adult individuals, varying from 2c to 16,384c. In the visceral complex, the maximum and medium ploidy values of the neuron nuclei are higher by almost 4-8 times than those in cerebral and pedal ganglia. The medium level of ploidy in adult snails increases by 5.7 times in the visceral complex of ganglia and by 4.1-4.2 times in the pedal and cerebral ganglia. According to 3H-thymidine autoradiography, DNA synthesis in neuron nuclei occurs during the whole life of the snail. In young individuals the neurons have the highest activity of DNA synthesis--the index of labeled nuclei of neurons making in total 50.2%. In older age, a steady decrease in the index of labeled nuclei is observed--in total to 35.8% and 7.0% in small and large adult snails, respectively. The state of summer hibernation completely stops DNA syntheses in neurons, but emergency from hibernation is accompanied by restoration of DNA syntheses.

Animals↗
PubMed2002

[Somatic polyploidy in neurons of the gastropod mollusca. III. Mitosis and endomitosis in the postnatal development of neurons in the Succinea snail central nervous system].

General morphology of chromatin, the number of chromosomes and chromocenters in normal condition and at the increase of bivalent cation (Ca2+, Mg2+) concentration were studied with the purpose to reveal mechanisms of polyploidization of neuron nuclei in the snail Succinea lauta (Gastropoda, Pulmonata). The morphology of nuclei was studied on squashed preparations. Normal diploid mitoses are described in the cerebral ganglia. A possibility is supposed that part of neurons or neuroblasts in the central nervous system (CNS) of succineid snail may divide mitotically. It has been shown that the basic mechanism of neuron postnatal growth is endomitotic polyploidization of nuclei. The transition from ordinary mitosis to polyploid cycles occurs via restitutional (polyploidizing) mitosis (4c2n-->4c4n). The next endocycles are carried out by means of classic endomitosis up to reaching the highest ploidy levels--4096n--16,384n. The study of general morphology of chromatin and chromocenters at normal condition and at artificial compactization enabled us to exclude any probability of polyteny in the CNS of lauta.

Animals↗