The positioning of chromosomes during cell

We present new evidence for the existence of ordered spatial localization of individual chromosomes within nuclei.

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

Recent studies demonstrated specific and non-random chromosome architecture in sperm nuclei. Recent studies have reported that the close juxtaposition of interphase chromosomes plays an important role in such basic cellular processes as gene expression.

Moreover, centromeres demonstrated specific intranuclear position, and were located within a limited area of nuclear volume.

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, The reasons underlying the occurrence of this specific translocation in liposarcomas, however, have remained elusive.

Measurements of distances in digitized images were performed in Sigma Scan Pro 5. Tilgen and co-authors studied the arrangement of five chromosome pairs in human spermatozoa and each pair was found to have a non-random spatial distribution.

Non-random positioning of chromosomes in human sperm nuclei

Third, the CTCT16 pair with the minimum distance of the two possible combinations was selected and the proximal distance was determined. Amira software was used only for visualization, not for data analysis.

Recent data indicate non-random radial positioning of chromosomes Sun et al. In this study, we analyzed absolute and relative intranuclear position of chromosomes in mature human sperm.

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.

The differentiated adipocyte cells were maintained in adipocyte medium AM-1; Zen Bio. We simulated the distribution of the normalized proximal-pair distances using Monte Carlo simulation Kozubek et al. Additionally, the relative positions of centromeres were non-random; some were found in close proximity, while other pairs showed significantly greater intercentromere distances.

Our results showed the tendencyfor non-random intranuclear location of individual chromosome territories. The observed chromosome order is discussed in relation to sperm nuclei decondensation, and reactivation during fertilization.

The resultant fusion protein is crucial to the transforming activity of the translocation, through its promotion of the unscheduled expression of the adipocyte differentiation gene DOL54 Kuroda et al.

In this model the appearance of the pairs of daughter cells with i and j nucleoli was calculated as product of the experimentally found frequencies of the cells with i and j nucleoli.

Fluorescent in situ hybridization Methods of FISH in application to sperm cells have been described in detail earlier Zalensky et al.

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. After min incubation at room temperature, cells were loaded on microscopic slide.

After deposition on a microscope slide, nuclei flatten Zalensky et al. Although a significant passive diffusion of chromosomes does occur within the interphase nuclei as a whole, chromosomes are largely constrained within a limited subregion of the nucleus Marshall et al.

Permeabilization was performed as previously described Solovei et al. To obtain a smooth boundary, an Epanechnikov filter bandwidth 0.

The statistical analysis software R version 1. Materials and methods Sperm cells were collected from semen obtained from donors with proven fertility. However, because technical limitations render the spatial analysis of chromosome position difficult, it remains unclear whether radial positioning is conserved in all normal cell types.

Thus, although the total number of chromosomes associated with nucleoli is variable, our data indicate that the position of the NOR-bearing chromosomes in relation to nucleoli is partly conserved through mitosis.

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.

Three-dimensional fluorescence in-situ hybridization 3D-FISH and the detection of labeled probes were performed according to protocols described elsewhere Cremer et al. Abstract In human spermatozoa, the arrangement of chromosomes is non-random.

We thus did not investigate the maternal cell with regard to the daughter cells, but focused on the similarity between the two daughter cells. In non-mammal species, limited order in chromosome organization was shown in planarians Joffe et al.

Thus, the existence of a defined chromosome positioning in human sperm nuclei seems possible, although our knowledge is still very limited. Mean values, standard errors, and frequency distributions were determined using the Microsoft Excel or Prism GraphPad Inc. We compared the association of chosen NOR-bearing chromosomes NOR-chromosomes with nucleoli, as well as the numbers of nucleoli, in the pairs of daughter cells, and established how frequently the daughter cells had equal numbers of the homologs of certain NOR-chromosomes associated with individual nucleoli.

The preparations of the couples of postmitotic cells were obtained by shaking and seeding mitotic cells on the glass coverslips.

We additionally compared our data with a random model. In vivo time-lapse observations encompassing a period from mitosis to mid G1 showed that the cells of different pairs did not mix during this period data not shown. More recently, data using fluorescent in situ hybridization FISH started to emerge indicating specific chromosome location in human sperm nuclei Luetjens 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.

Furthermore, the observation of chromosome positioning in some rare diploid spermatozoa (~%) showed that this order was the same between the two sets of chromosomes in a given nucleus and. Key words: chromosome positioning, nucleoli, NORs, daughter cells Introduction Chromosomes are not randomly arranged in the vertebrate cell nucleus (Cremer and Cremer.

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.

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. ). The Rabl configuration is established during anaphase and is maintained during interphase. (b) Radial positioning of chromosomes results in the preferential localization of chromosome territories towards either the periphery or the interior of the nucleus depending on their size or gene density.

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The positioning of chromosomes during cell
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