The positioning of chromosomes during cell

Adipocyte differentiation was then induced by replacing the preadipocyte medium with differentiation medium DM-2; Zen-Bio. We simulated the distribution of the normalized proximal-pair distances using Monte Carlo simulation Kozubek et al.

To test non-random distribution of the individual centromeres or pair-wise intercentromere distances in the two-dimensional space of the sperm head, we used the nonparametric Kolmogorov-Smirnov test. The boundary of the original nucleus was extended or receded in the 2D plane if the distance from the center of gravity of the nucleus P0 to the boundary R was shorter or longer than the radius of the standard nucleus.

For the delineation of the human chromosome territory CT12 and chromosome territory CT16we used whole-chromosome painting probes provided by T. Furthermore, several studies have shown that non-random radial chromosome arrangements are maintained in many different cell types, with the exception of some tumor cells Boyle et al.

We present new evidence for the existence of ordered spatial localization of individual chromosomes within nuclei. Images were collected using a digital color camera MagnaFire, Optronics Inc. Radial positions and mutual distances between CTs were evaluated using the values relative to the standardized nucleus radius.

Amira software was used only for visualization, not for data analysis. The daughter cells typically had different numbers of nucleoli. Moreover, centromeres demonstrated specific intranuclear position, and were located within a limited area of nuclear volume.

In this study, we analyzed absolute and relative intranuclear position of chromosomes in mature human sperm. Chromosome painting probes Biotin-labeled chromosome painting Probes A. Our results showed the tendencyfor non-random intranuclear location of individual chromosome territories.

We have previously shown that such a gene-density-correlated radial arrangement of chromosome territories is evolutionarily conserved in the genomes of higher primates Tanabe et al. It is tempting to speculate that activities of genes on specific chromosomes are influenced dynamically by their chromosomal and nuclear position BlobelHeslop-HarrisonCroft et al.

To obtain a smooth boundary, an Epanechnikov filter bandwidth 0. We thus did not investigate the maternal cell with regard to the daughter cells, but focused on the similarity between the two daughter cells. Summary It is known that chromosomes occupy non-random positions in the cell nucleus.

Positioning of the NOR-Bearing Chromosomes in Relation to Nucleoli in Daughter Cells after Mitosis

The aim of our study was to establish how frequently the daughter cells had equal numbers of the homologs of certain NOR-chromosomes associated with individual nucleoli.

Comparing the incidence of the nucleoli in pairs of daughter cells, we found a close correspondence with the random model Fig.

Hybridization conditions and post-hybridization washings depended on the type of DNA probes. However, it is not clear to what extent their nuclear positions, together with their neighborhoods, are conserved in daughter cells Bickmore and Chubb To address specific aspects of this problem, we used the model of the chromosomes carrying ribosomal genes.

The radial organization of chromosome territories has been well-characterized. The crucial question concerns the mechanisms underlying the institution and maintenance of chromosome order during passage through the cell cycle and between generations.

Typically, gene-poor chromosomes are located in a zone close to the nuclear perimeter, whereas gene-rich chromosomes are found at the center of the nucleus Boyle et al. We observed an alteration in the positioning of these CTs, suggesting that the translocation t 12;16which might play a key role in liposarcoma tumorigenesis, is induced by the alteration in CT location.

Second, the positions were determined assuming a uniform angular distribution Kozubek et al.

Primary monoclonal antibody against mouse fibrillarin clone 17C12kindly donated by Kenneth M. In our case, we compared data for each individual centromere position or intercentromere distance against the uniformlydistributed data set of the same sample size. In non-mammal species, limited order in chromosome organization was shown in planarians Joffe et al.

Cells were washed with PBS, fixed in 0. Geometry of the human sperm nucleus and parameters describing chromosome positioning Nuclei in human sperm cells have an ellipsoid shape with its long axis stretching from the point of the sperm tail attachment to the acrosome.

After min incubation at room temperature, cells were loaded on microscopic slide. Recent data indicate non-random radial positioning of chromosomes Sun et al. Specific chromosomal translocations have consistently been found in particular cancers and might promote tumorigenesis through the activation of specific oncogenes or the creation of fusion proteins Rabbitts, In this study, we examined the relative and radial positioning of human chromosomes 12 and 16 in both preadipocytes and adipocytes to address the question of whether or not chromosome-territory CT repositioning occurs during adipocyte differentiation.

Chromosomes, which are adjacent in mitotic rosettes, are similarly positioned in interphase nuclei Nagele et al.

Non-random positioning of chromosomes in human sperm nuclei

In the middle of G1 phase the position of chromosomes and the number of nucleoli in the nucleus are already stable and do not change significantly until the end of the interphase Walter et al. Afterrepetitions, the distributions of the proximal-pair distances were determined.

The boundary was then resegmented using the threshold determined by the procedure explained above. In the fibrillar sperm head of monotreme Watson et al.During the transition from G0 to G1 phase, the inactive X chromosomes tend to move from the envelope position to the nucleolus position in WI38 cells.

Our results imply a role of chromosome positioning in maintaining the organization of the inactive X chromosomes in different cell phases. Oscillations in Spindle Positioning during First Mitosis During cell division the miotic spindle is responsible for the segregation of chromosomes and determines the plane of cleavage.

Cell division is asymmetric, with the spindle positioned off-center towards the posterior. For example, in human fibroblasts, the positioning of chromosomes at G1 in daughter cells is closely correlated and is mainly determined by their configuration at mitosis (Sun & Yokota ). Recent data indicate non-random radial positioning of chromosomes (Sun et al.Cremer et al.Boyle et al.Tanabe et al.

). In addition, the specific positioning of chromosomes has been suggested to have functional consequences by facilitating the alignment of homologues during meiosis [29 x Meiotic chromosomes: integrating structure and function.

We have examined the relative and radial positioning of the chromosome territories of human chromosomes 12 and 16 during adipocyte differentiation, and detected a close association between the territories of chromosomes 12 and 16 in differentiated adipocytes, an association not.

Live-cell imaging of bleach-labeled chromosomes suggested that non-random relative chromosome positions are established during early anaphase [11 •]. Two nuclear halves differentially labeled by photobleaching were used to analyze chromosome positioning relative to the mitotic spindle.

The positioning of chromosomes during cell
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