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PubMedDate not supplied

Tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate enhances sister chromatid exchanges and numerical and structural chromosome aberrations in primary mouse epidermal cell cultures.

The tumor 12-O-tetradecanoyl-phorbol-13-acetate (TPA) moderately stimulated sister chromatid exchanges in primary epidermal cultures (PEC) from C3H mice, and strongly enhanced structural chromosome aberrations. In G-banded metaphases for TPA (10-(8) and 10-(6) M for 54 h) treated PEC aneuploidy (hypo- and hyperdiploidy) increased and structural aberrations were enhanced 8- to 10-fold. Breaks, fragments and metacentric chromosomes had raised 7- to 11-fold. Chromatid interchanges (tri- and quadri-radials) and centromeric splitting, virtually absent in controls, appeared in 4--8% of metaphases. The non-promoting 4-O-methyl-TPA did not induce chromosomal alterations. These substantial effects on the genetic material of target cells represent a new aspect of the mechanism of action of tumor-promoting phorbol esters.

Animals↗
PubMed2004

Integrating genetic linkage maps with pachytene chromosome structure in maize.

Genetic linkage maps reveal the order of markers based on the frequency of recombination between markers during meiosis. Because the rate of recombination varies along chromosomes, it has been difficult to relate linkage maps to chromosome structure. Here we use cytological maps of crossing over based on recombination nodules (RNs) to predict the physical position of genetic markers on each of the 10 chromosomes of maize. This is possible because (1). all 10 maize chromosomes can be individually identified from spreads of synaptonemal complexes, (2). each RN corresponds to one crossover, and (3). the frequency of RNs on defined chromosomal segments can be converted to centimorgan values. We tested our predictions for chromosome 9 using seven genetically mapped, single-copy markers that were independently mapped on pachytene chromosomes using in situ hybridization. The correlation between predicted and observed locations was very strong (r(2) = 0.996), indicating a virtual 1:1 correspondence. Thus, this new, high-resolution, cytogenetic map enables one to predict the chromosomal location of any genetically mapped marker in maize with a high degree of accuracy. This novel approach can be applied to other organisms as well.

Chromosome Mapping↗
PubMed2002

Prenatal and postnatal characterization of Y chromosome structural anomalies by molecular cytogenetic analysis.

We describe three cases in which we used fluorescence in situ hybridization (FISH), polymerase chain reaction (PCR) and comparative genomic hybridization (CGH) to characterize Y chromosome structural anomalies, unidentifiable by conventional G-banding. Case 1 was a 46,X,+mar karyotype; FISH analysis revealed an entire marker chromosome highlighted after hybridization with the Y chromosome painting probe. The PCR study showed the presence of Y chromosome markers AMG and SY620 and the absence of SY143, SY254 and SY147. CGH results confirmed the loss of Yq11.2-qter. These results indicated the presence of a deletion: del(Y)(q11.2). Case 2 was a 45,X [14]/46,XY[86] karyotype with a very small Y chromosome. The PCR study showed the presence of Y chromosome markers SY620 and AMG, and the absence of SY143, SY254 and SY147. CGH results showed gain of Yq11.2-pter and loss of Yq11.2-q12. These results show the presence of a Yp isodicentric: idic(Y)(q11.2). Case 3 was a 45,X,inv(9)(p11q12)[30]/46,X,idic(Y)(p11.3?),inv(9)(p11q12)[70] karyotype. The FISH signal covered all the abnormal Y chromosome using a Y chromosome paint. The PCR study showed the presence of Y chromosome markers AMG, SY620, SY143, SY254 and SY147. CGH only showed gain of Yq11.2-qter. These results support the presence of an unbalanced (Y;Y) translocation. Our results show that the combined use of molecular and classical cytogenetic methods in clinical diagnosis may allow a better delineation of the chromosome regions implicated in specific clinical disorders.

Adolescent↗
PubMed2002

Single cell CGH analysis reveals a high degree of mosaicism in human embryos from patients with balanced structural chromosome aberrations.

We have performed comparative genomic hybridization (CGH) analysis of single blastomeres from human preimplantation embryos of patients undergoing preimplantation genetic diagnosis (PGD) for inherited structural chromosome aberrations and from embryos of IVF couples without known chromosomal aberrations. The aim was to verify the PGD results for the specific translocation, reveal the overall genetic balance in each cell and visualize the degree of mosaicism regarding all the chromosomes within the embryo. We successfully analysed 94 blastomeres from 28 human embryos generated from 13 couples. The single cell CGH could verify most of the unbalanced translocations detected by PGD. Some of the embryos exhibited a mosaic pattern regarding the chromosomes involved in the translocation, and different segregation could be seen within an embryo. In addition to the translocations, we found a high degree of numerical aberrations including monosomies, trisomies and duplications or deletions of parts of chromosomes. All of the embryos (100%) were mosaic, containing more than one chromosomally uniform cell line, or even chaotic with a different chromosomal content in each blastomere.

Blastocyst↗
PubMed1980

[Prenatal diagnosis in parents with a balanced structural chromosome aberration (author's transl)].

By means of 10 case reports, the significance of prenatal diagnosis and the risk for the progeny of parents with a balanced structural chromosomal aberration are demonstrated. The aberrations were ascertained through: a previous malformed child, previous miscarriages or stillbirths or through fetal cell analysis during prenatal diagnosis performed for independent reasons. Theoretical considerations concerning the estimates of risk figures in these families are presented and the currently available risk values which are the basis of the indication for prenatal diagnosis, given.

Adult↗
PubMed1989

Effects of in vivo heat treatment on lampbrush chromosome structure in amphibian oocytes.

When Pleurodeles (Amphibian, Urodele) females were subjected to high temperatures (32-35 degrees C) for varying periods of time (45 min to 7 days), lampbrush chromosome structure underwent striking modifications. These changes included a numerical reduction in normal loops and progressive disorganization of RNP matrices of various loops. The degree of such disorganization was a function of the intensity and duration of the stress. These modifications were completely reversible when females or oocytes were returned to a normal breeding temperature (20 degrees C). Results are discussed in comparison with previous studies on morphological changes induced by heat shock in lampbrush chromosomes carried out in vitro.

Animals↗
PubMed1995

Altered metaphase chromosome structure in xrs-5 cells is not related to its radiation sensitivity or defective DNA break rejoining.

The chinese hamster ovary (CHO) cell line xrs-5 is a radiation-sensitive derivative of CHO-K1 cells. The xrs-5 cells have a defect in DNA double-strand break rejoining and show alterations in chromosome structure and nuclear morphology. The relationship between radiation sensitivity and metaphase chromosome morphology was examined in 12 'revertant' xrs-5 clones isolated following treatment with 5-azacytidine. nine of the clones were radioresistant while the other three retained xrs-5-like radiation sensitivity. Chromosome morphology reverted to CHO-K1-like characteristics in three of the radioresistant clones and one of the radiosensitive clones suggesting that the over-condensed metaphase chromosome morphology of xrs-5 cells does not underlie its radiation sensitivity. Radiation sensitivity did correlate with DNA double-strand break rejoining ability. The radioresistant clones showing the over-condensed xrs-5-like chromosome morphology were also slightly more sensitive to the topoisomerase II inhibitor etoposide (VP-16) than CHO-K1, suggesting that the over-condensed morphology might be due to alterations in the phosphorylation of chromatin proteins.

Animals↗
PubMedDate not supplied

[Structural chromosomal aberrations in parents with spontaneous abortions].

In the Laboratory for Human Cytogenetics of the University Hospital Department of Gynecology and Obstetrics in Beograd a cytogenetic analysis of 30 families with spontaneous abortion was performed. In two families structural chromosome aberrations--Y chromosome deletion and 13/14 translocation--were detected. Phenotypic normal male members of one family revealed the same type of deletion of the larger part of the distal region of the long Y chromosome arm (46, X, del (Y) (q12)). In the other family, in a phenotypically normal parent, a balanced translocation (45, XY, t (13/14)) was observed. The authors discuss the correlation between structural aberrations. Yq delation and 13/14 translocation on the one hand and spontaneous abortion on the other.

Abortion, Spontaneous↗
PubMed1987

X-ray- and neutron-induced chromosome damage detected by flow cytometry compared to cell lethality and chromosome structural changes.

V79 Chinese hamster cells were irradiated in G0 phase with 200 kV X rays or 14 MeV neutrons, and dose-response curves were determined for three end points: chromosome damage detected by flow cytometric analysis of chromosomes isolated from metaphase cells in irradiated cultures; loss of clonogenic capacity; and induction of dicentric, tricentric, and ring chromosomes. The changes observed in the flow karyotypes from irradiated cultures were quantitatively evaluated by computer analysis. Estimates of the frequencies of chromosome lesions were derived from an analysis of the flow cytometric measurements by means of a comparison with model calculations simulating the effect of chromosome changes on flow karyotypes. The results indicate that lesions assayed by flow cytometry occur three times more frequently than lethal lesions, while the chromosomal structural changes detected by microscopic analysis were about 10 times less frequent than the lesions detected by flow cytometry. Dose-response curves for X rays and neutrons show that cell reproductive death and changes in flow karyotypes result from damage, induced with a similar relative biological effectiveness. Dose-effect relations derived from changes in flow karyotypes, which can be obtained within 24 h after irradiation, might be of value as a predictive test for the sensitivity of cells for loss of clonogenic capacity.

Animals↗
PubMed1987

New structural chromosomal rearrangements in congenital leukemia.

The karyotypic abnormalities and clinical data on three patients in whom acute leukemia was diagnosed within the first 6 months of life are presented. The four structural chromosomal rearrangements detected in the bone marrow from these patients, i.e., t(7;12)(q36;p13) and t(1;19)(q11;q11) in case 1, t(2;10;11;12)(q21q31;p13;q13;q24) in case 2, and t(11;19)(q23;p13) in case 3, have not previously been associated with congenital leukemia. Acquired chromosomal changes have until now been reported in only 31 leukemic infants in this age group. Of the total material, 18 patients had acute lymphoblastic leukemia and 16 had acute nonlymphocytic leukemia. The by far most frequently recorded cytogenetic aberration has been t(4q;11q), seen in 14 cases of lymphoblastic leukemia. Although t(4q;11q) has not been found in a single patient with acute nonlymphocytic leukemia, these leukemias have often had other rearrangements involving the same region of 11q. Hence, genetic material around 4q21 may be active in lymphocytic differentiation, whereas gene(s) in 11q23 may be important in the neoplastic process in a less cell-type specific manner and perhaps particularly vulnerable to neoplastic rearrangement in fetal life. The finding of four cases out of 34 with translocations between 11q23 and chromosome 19 indicates that this rearrangement might characterize a specific cytogenetic subgroup of leukemia in the very young.

Acute Disease↗
PubMed1988

The RAD6 gene of yeast: a link between DNA repair, chromosome structure and protein degradation?

Among the DNA repair mutants of the yeast Saccharomyces cerevisiae, the rad6 mutants are characterized by a highly pleiotropic phenotype. Most remarkably, these mutants are sensitive towards a variety of DNA-damaging agents and deficient in mutation induction. The RAD6 gene has been cloned and most recently, ubiquitin-conjugating activity of the Rad6 protein has been demonstrated. In this brief review, the properties of rad6 mutants are discussed in the light of these new findings. The available data hint at a connection between DNA repair, mutagenesis, chromosome structure and protein degradation.

Chromosomes↗
PubMed2006

Chromosome structural changes in diploid and tetraploid A genomes of Gossypium.

The genus Gossypium, which comprises a divergent group of diploid species and several recently formed allotetraploids, offers an excellent opportunity to study polyploid genome evolution. In this study, chromosome structural variation among the A, At, and D genomes of Gossypium was evaluated by comparative genetic linkage mapping. We constructed a fully resolved RFLP linkage map for the diploid A genome consisting of 275 loci using an F2 interspecific Gossypium arboreum x Gossypium herbaceum family. The 13 chromosomes of the A genome are represented by 12 large linkage groups in our map, reflecting an expected interchromosomal translocation between G. arboreum and G. herbaceum. The A-genome chromosomes are largely collinear with the D genomes, save for a few small inversions. Although the 2 diploid mapping parents represent the closest living relatives of the allotetraploid At-genome progenitor, 2 translocations and 7 inversions were observed between the A and At genomes. The recombination rates are similar between the 2 diploid genomes; however, the At genome shows a 93% increase in recombination relative to its diploid progenitors. Elevated recombination in the Dt genome was reported previously. These data on the At genome thus indicate that elevated recombination was a general property of allotetraploidy in cotton.

Chromosome Inversion↗