Heterochromatic Regions Of Chromosomes Research Articles

Centromeric alpha satellite DNA amplification and translocation in an unusually large chromosome 14p+ variant.

We report cytogenetic and molecular studies on a family that carries, in the father, an unusually large chromosome 14p+ variant [WSi-var(14)(p+)] and, in one of his children, a translocation [DSi-der(14)] involving the variant chromosome. Increase in the size of WSi-var(14)(p+) was estimated to be approximately 35% that of a normal chromosome 14. Presence of extra chromosomal material in this variant chromosome was demonstrated by G-banding using trypsin and staining with Leishman, G-banding using bromodeoxyuridine (BrdU) and Giemsa, and R-banding using BrdU and Giemsa. This material was positive using C-banding with BaOH and staining with Giemsa and negative in DAPI/distamycin staining, suggesting that it contained repetitive DNA but probably not of the types found in the heterochromatic regions of chromosomes 1, 9, 15, 16, and Y. Staining of the nucleolus organiser region (NOR) with AgNO3 indicated the retention of the NOR in WSi-var(14)(p+) but not in DSi-der(14). In situ hybridisation of metaphase cells with an alpha satellite DNA probe specific for human acrocentric chromosomes demonstrated a significantly increased amount of centromeric alpha sequences in WSi-var(14)(p+). Most or all of the extra alpha sequences were retained in DSi-der(14), indicating translocation near the very distal end of the enlarged region. The extra alpha satellite DNA material may have originated through amplification of some centromeric segments. The possible role of the amplified DNA in chromosomal translocations is discussed.

Heterochromatic variants and their association with neoplasias: V. Non-Hodgkin's lymphomas

A study of heterochromatic regions in chromosomes #1, #9, and #16 was performed on lymphocytes of peripheral blood from 55 normal individuals and 50 patients with non-Hodgkin's lymphoma (NHL). Heteromorphism was present in 90% of the NHL patients, compared with 44% in normal individuals (p less than 0.001). An increase of inv(1), 1qh-, and 9qh-variants was observed in malignant lymphoma patients with respect to controls.

Immunodeficiency, centromeric heterochromatin instability of chromosomes 1, 9, and 16, and facial anomalies: the ICF syndrome.

Instability of the heterochromatic centromeric regions of chromosomes 1, 9, and 16 associated with immunodeficiency was found in a four year old girl. Similar phenotypic and chromosomal abnormalities were described in a previous patient studied by us and in four other published cases. All these patients have facial anomalies in addition to combined immunodeficiency and chromosomal instability. Stretching of the heterochromatic centromeric regions of chromosomes 1, 16, and to a lesser extent, 9 and homologous and non-homologous associations of these regions were the most common cytogenetic findings in all the patients. Multi-branched configurations and whole arm deletions of chromosomes 1 or 16 or both were also found. Comparing clinical and chromosomal data we conclude that immunodeficiency, centromeric heterochromatin instability, and facial anomalies form a new syndrome, for which we propose the acronym ICF. A mutation interfering with the normal process of condensation of part of the centromeric heterochromatin is postulated as the basic chromosome defect in this syndrome.

Rye Chromatin Variation in Yugoslavian Wheats

AbstractC‐banding, which stains the heterochromatic regions of chromosomes, was utilized in order to ascertain whether or not several varieties from a Yugoslavian wheat‐breeding program contained a 1RS/1BL substitution or a 1RS/1BL translocation. Only one variety contained the 1R (1B) substitution, while in the remaining sixteen varieties, the 1RS/1BL translocation was present. The C‐banding results were confirmed utilizing an SDS‐PAGE analysis, and the results indicated that both techniques should be used together. In all of the Yugoslavian wheats containing observable rye chromatin, the C‐band corresponding to the nucleolus organizing region (NOR) was clearly reduced over that found in the wheat parents used in Yugoslavia or the other wheats from around the world containing either the substitution or the trans location. Some unknown selection pressure applied in the Yugoslavian wheat program in Novi Sad over the years has evidently caused a deletion of most of the rye NOR region.

Chromosomal alterations in cell lines derived from mouse rhabdomyosarcomas induced by crystalline nickel sulfide.

Prior studies have shown a preferential decondensation (or fragmentation) of the heterochromatic long arm of the X chromosome of Chinese hamster ovary cells when treated with carcinogenic crystalline NiS particles (crNiS). In this report, we show that the heterochromatic regions of mouse chromosomes are also more frequently involved in aberrations than euchromatic regions, although the heterochromatin in mouse cells is restricted to centromeric regions. We also present the karyotypic analyses of four cell lines derived from tumors induced by leg muscle injections of crystalline nickel sulfide which have been analyzed to determine whether heterochromatic chromosomal regions are preferentially altered in the transformed genotypes. Common to all cell lines was the presence of minichromosomes, which are acrocentric chromosomes smaller than chromosome 19, normally the smallest chromosome of the mouse karyotype. The minichromosomes were present in a majority of cells of each line although the morphology of this extra chromosome varied significantly among the cell lines. C-banding revealed the presence of centromeric DNA and thus these minichromosomes may be the result of chromosome breaks at or near the centromere. In three of the four lines a marker chromosome could be identified as a rearrangement between two chromosomes. In the fourth cell line a rearranged chromosome was present in only 15% of the cells and was not studied in detail. One of the three major marker chromosomes resulted from a centromeric fusion of chromosome 4 while another appeared to be an interchange involving the centromere of chromosome 2 and possibly the telomeric region of chromosome 17.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytogenetic instability in a family with gastric cancer recurrence

An index case with a congenital malformation syndrome enabled detection of a family that had a previous history of spontaneous abortuses and recurrence of neoplasia through three generations. Cytogenetic analysis performed on lymphocytes from 11 subjects in the second and third generation showed karyotypic alterations in both tumor bearers and apparently normal subjects. Chromosome variations consisted of: a) spontaneous chromosome fragility; b) chromosome translocations; c) polymorphisms in the heterochromatic regions in chromosomes Y, #1, #16, #22. The inheritance pattern of all chromosome rearrangements and heteromorphisms observed was established starting with the second generation, and the contribution of specific individuals was identified. Although the relationship between chromosomal instability and predisposition to gastric cancer does not appear to be coincidental, no specific chromosome alteration in normal somatic cells was shared by all members of the family who developed or are at risk of developing tumors.

Application of cloned satellite DNA sequences to molecular-cytogenetic analysis of constitutive heterochromatin heteromorphisms in man.

The cloned alpha-satellite DNA sequences were used to evaluate the specificity and possible variability of repetitive DNA in constitutive heterochromatin of human chromosomes. Five probes with high specificity to individual chromosomes (chromosomes 3, 11, 17, 18, and X) were in situ hybridized to metaphase chromosomes of different individuals. The stable position of alpha-satellite DNA sequences in heterochromatic regions of particular chromosomes was found. Therefore, the chromosome-specific alpha-satellite DNA sequences may be used as molecular markers for heterochromatic regions of certain human chromosomes. The homologous chromosomes of many individuals were characterized by cytologically visible heteromorphisms of hybridization intensity with chromosome-specific alpha-satellite DNA sequences. A special analysis of hybridization between homologues with morphological differences provided the evidence for a high resolution power of the in situ hybridization technique for evaluation of chromosome heteromorphisms. The approaches for detection of heteromorphisms in cases without morphological differences between homologues are discussed. The results obtained indicate that constitutive heterochromatin of human chromosomes has a variable amount of alpha-satellite DNA sequences. In situ hybridization of cloned satellite DNA sequences may be used as a new general approach to analysis of chromosome heteromorphisms in man.

Characterization and chromosomal localization of fast renaturing and satellite DNA sequences inPhaseolus coccineus

DNA was extracted from etiolated plantlets ofPhaseolus coccineus L. and studied by means of thermal denaturation and reassociation kinetics and CsCl analytical ultracentrifugation. A DNA fraction reassociating within an equivalent Cot of 1.15 × 10−1 (fast renaturing DNA sequences; FRS) was found to constitute 20.8% of the total DNA, 6.8% of which is composed of palindromic sequences. Analytical CsCl gradient ultracentrifugation showed a large heavier satellite banding at 1.702 g/ml (main peak 1.692g/ml); this DNA fraction was shown to consist of different components with buoyant densities of 1.696, 1.702, 1.706, and 1.714g/ml. FRS and the satellite fraction banding at 1.702 g/ml (SAT) were hybridizedin situ to the polytene chromosomes in the embryo suspensor cells after having been labeled by the nick translation method. FRS proved to be almost exclusively localized in the heterochromatic chromosome regions and several chromosome ends; SAT was found to be confined, as a rule, in the centromeric and pericentromeric heterochromatin. Different labeling patterns were detected over chromosome regions bearing 18S + 25S or 5 S ribosomal RNA cistrons and over corresponding regions of different chromosome pairs. These results are discussed for the light they may throw on certain aspects of the structure and organization at the chromosomal level of theP. coccineus genome.

Relationship between sister-chromatid exchanges and heterochromatin or DNA replication in chromosomes of Crepis capillaris

The C-band patterns, DNA late replication patterns and distribution patterns of spontaneous and γ-ray-induced SCEs in Crepis capillaris chromosomes were studied. The fluorescence plus Giemsa (FPG) technique was used for detection of SCEs and late-replicating chromosome regions after unifilar incorporation of BrdU into DNA. An asynchronous replication of both euchromatic and heterochromatic chromosome regions was established. The frequency of SCEs is increased about 2-fold by 1.5 Gy γ-rays. The localization of the sites of SCEs was analyzed with special reference to eu- and heterochromatin and early- and late-replicating regions. The data obtained showed that SCEs were distributed nonrandomly along the chromosomes. Preferential occurrence of SCEs was observed in the following chromosome regions: at the junction between eu- and heterochromatic regions, the latter being rich in late-replicating DNA; at the junction between early- and late-replicating regions, the latter not being C-band positive. Certain heterochromatic regions were more rarely involved in SCEs than expected on the basis of their length. The lowest incidence of SCEs was found in the centromeric regions. Very similar distribution patterns of spontaneous and γ-ray-induced SCEs were observed. The possible role of the differences in the time of replication of the different chromosome regions in the formation of SCEs is discussed.

Chromosomal location by in situ hybridization of the human Sau3A family of DNA repeats.

The Sau3A family is a human, clustered, highly repetitive, GC-rich DNA family. In situ hybridization studies with a plasmid carrying a Sau3A monomer as a probe have shown that Sau3A sequences are preferentially concentrated in the heterochromatic regions of human acrocentric chromosomes (D and G groups, both in pericentromeric regions and in cytological satellites) and in pericentromeric heterochromatin of chromosome 1. The same chromosomal locations were observed by using as probes two recombinant phages which carry Sau3A-positive genomic sectors. The two sectors differ for the relative proportions of monomer and multiples of Sau3A repeats, which show different extents of homology to the cloned monomer, and for the presence, in one of the two, of a small amount of an unrelated repeat (alphoid DNA). The similarity of the results obtained with the three probes suggests that heterogeneous Sau3A repeats share the same chromosomal localizations and that the two analyzed genomic sectors may not contain significant amounts of repetitive DNAs other than the Sau3A family. A comparison between the chromosomal locations of Sau3A and EcoRI families of repeats has confirmed that each family is characterized by specific chromosomal locations and that single heterochromatic regions may contain both.

Nucleolus, nucleolar chromosomes, and nucleolus-associated chromatin from early diplotene to dictyotene in the human oocyte.

The shape, relationships, relative DNA content, and nucleolar activity of the short arm of acrocentric bivalents were studied in human oocytes from early diplotene to dictyotene. At the beginning of diplotene, the short arms of the previously paired chromosomes were again separated and displayed the same morphological features as in mitotic prophase chromosomes. They were connected only with the nucleolus. In situ hybridization and silver staining showed that the nucleolar organizer regions (NORs) were located in the peripheral region of the nucleolus. Tritiated-uridine incorporation was active. At birth, the relationships of the acrocentric short arms showed increasing complexity. The chromosomes ended in nucleolus-associated chromatin blocks of irregular shape, containing large quantities of DNA as demonstrated by intense binding of 3H-actinomycin D. The number of chromosomes converging on these chromatin blocks exceeded the number of acrocentrics, suggesting that heterochromatic regions of other chromosomes were associated with the short arm of acrocentrics. In the electron microscope, the NORs were represented by fibrillar centers located on the periphery of the nucleolus and consistently connected with the blocks of dense chromatin. These relationships remained unchanged in the primordial oocyte in the adult ovary. Persistence of 3H-uridine uptake showed that the oocyte was not at a "resting" stage. The possible cytogenetic consequences of these observations are discussed.

Effect of magnesium on nickel-induced genotoxicity and cell transformation.

Raising the extracellular level of magnesium ions inhibited nickel-induced DNA strand breaks, DNA-protein crosslinks, sister chromatid exchanges, chromosomal aberrations and cell transformation. Carcinogenic nickel ions preferentially damaged centromeres and other heterochromatic regions of Chinese hamster ovary cell chromosomes. Elevation of extracellular magnesium levels prevented the effects of nickel on heterochromatin and inhibited cell transformation, but did not substantially reduce the DNA damage induced by nickel in euchromatic regions. This study suggests that heterochromatic DNA damage may be important to the nickel-induced neoplastic transformation process.

Specific decondensation of heterochromatic regions of Drosophila chromosomes-intrachromosomal and genomic control

The genomic and intrachromosomal control of condensation inhibition of heterochromatic regions of mitotic Drosophila chromosomes was studied. It is shown that decondensation is not a local property of the chromosomal regions. In particular the frequency and sometimes the pattern of decondensation is changed with translocations, inversions or loss of chromosomes. In a variety of deletions and inversions of X-chromosomal heterochromatin, which is usually decondensed, the phenomenon is absent or its pattern changed. A material effect is observed in interspecies hybrids between D. melanogaster and D. simulans: paternal chromosomes are neither more condensed or more decondensed under the influence of a maternal genome.

Distamycin A/DAPI staining of heterochromatin in male meiosis of man

The sequential staining with distamycin A/DAPI provides an ideal method for studying the behaviour of heterochromatic regions in human male meiosis. The various meiotic and postmeiotic stages were found to have different staining qualities. Although all heterochromatic regions in human pachytene cells show specific DA/DAPI fluorescence, bright and clearly stained heterochromatic blocks can be distinguished from small DA/DAPI spots. Pachytene nuclei exhibit associations between heterochromatic regions of non-homologous bivalents. The heterochromatin of bivalent 9 generally presents as a cluster of small, discrete bodies. The heterochromatic regions of chromosomes 1, 9, 15, 16 and Y are preferentially stained at diakinesis and metaphase of the second meiotic division. The specific DA/DAPI staining disappears with the progressive volume reduction of middle and late spermatid nuclei. The heterochromatin of the chromatids fuses to form a large chromocenter during spermatid differentiation.

Constitutive heterochromatin studies in patients with solid tumors.

Constitutive heterochromatin of chromosomes 1, 9, and 16 was studied in 101 patients with solid tumors and 85 controls. Lymphocyte cultures were used for performing C-banded chromosome preparations. Two homologous chromosomes were regarded as heteromorphic when there was a 25% difference between their C-band size or when they fell into different classes according to the method of Patil and Lubs (1977). A statistically significant difference between patients and controls was found in chromosome 1 heteromorphism. No statistical difference between patients and controls was found in the heteromorphism of chromosomes 9 and 16. The frequencies with which pericentric inversions of the heterochromatin in chromosomes 1 and 9 occurred in cancer patients were 9.9% and 12.9%, respectively. Patients displaying this type of polymorphism usually showed an increased rate of chromosome associations. The most frequent associations were found between heterochromatic regions of chromosomes 1 and 9 and between the chromosome 9 heterochromatin and D acrocentrics. These results support the hypothesis concerning the involvement of constitutive heterochromatin of chromosome 1 in malignant disease.

Role of chromosome aberrations in recurrent abortion: a study of 269 balanced translocations.

We have studied a sample of 5,445 couples in which the woman was ascertained to have had two or more spontaneous abortions: 396 from our Cytogenetics Unit (present series) and 5,049 from the literature (literature series). In approximately 5% of these couples one of the members was a carrier of a balanced translocation, either reciprocal (2/3 of cases) or Robertsonian (1/3). In 1% of the couples there were other chromosome anomalies, mostly gonosomal aneuploidies or mosaicisms. A pericentric inversion of the heterochromatic region of chromosome 9 was present in 3% of the couples of the present series and in 1% of the literature series. The number of female carriers exceeded significantly that of males. The probability for one member of the couple to be a carrier increased with the number of abortions at the time of ascertainment, but it does not seem modified by the concomitant presence of term pregnancies. The analysis of the cytogenetic findings in 80 cases of Robertsonian and 156 cases of reciprocal translocations suggests that some chromosomes are preferentially involved, and that in reciprocal translocations the breakpoints are not distributed at random on the chromosome arms. There is an excess of breakpoints on chromosomes 6, 7, and 22 and a dearth on chromosome 12. This distribution is significantly different from that of a sample of reciprocal translocations ascertained for a malformed child. In both samples the breakpoints seem associated with fragile sites more frequently than expected by chance. An analysis of the potential and effective chromosome imbalance suggests that in subjects with unbalanced chromosomes survival is correlated with a minimum imbalance.

Preferential localization of chemically induced breaks in heterochromatic regions of Vicia faba and Allium cepa chromosomes—II. 4-epoxyethyl-1,2-epoxy-cyclohexane interacts specifically with highly repetitive sequences of DNA in Allium cepa

The specificity of the clastogenetic effect of 4-epoxyethyl-1,2-epoxy-cyclohexane (VCH-diepoxide) on Vicia faba and Allium cepa has been investigated. Cytogenetic effect was estimated by Giemsa staining banding techniques on metaphase and anaphase analysis of chromatid and chromosome aberrations. Aberrations induced by VCH-diepoxide were preferentially located on particular Giemsa stained bands of M and S chromosomes in Vicia and in heterochromatic telomeric regions in Allium. The percentage of micronuclei and chromatin bodies (structures resembling chromocenters) into the cytoplasm was also estimated. In situ hybridization technique was used to demonstrate the presence of highly repetitive DNA sequences in the chromatin bodies extruded from Allium nuclei. The data suggest that an amplification process may be induced by the chemical compound.

Preferential localization of chemically induced breaks in heterochromatic regions of Vicia faba and Allium cepa chromosomes—I. Exogenous thymidine enhances the cytologic effects of 4-epoxyethyl-1,2-epoxy-cyclohexane

We have studied the cytogenetic effect of 4-epoxyethyl-1,2-epoxy-cyclohexane (VCH-diepoxide) on Vicia faba and Allium cepa root tip meristems. Cytogenetic effect was estimated as percentage of micronuclei formed in interphase. We have shown that specific regions of M and S chromosomes of Vicia and allium telomeric regions as well were involved in the aberrations. Moreover we have demonstrated that DNA containing cytoplasmic structures defined ‘chromatin bodies’ and resembling chromocenters were extruded into the cytoplasm of both treated species. Thymidine post treatments, after the chemical exposure, prove a synergistic effect on the clastogenetic activities of VCH-diepoxide in V. faba and A. cepa.

Cytogenetic markers in allogeneic bone marrow transplantation

Engraftment after bone marrow transplantation (BMT) can be monitored with genetic markers. Cytogenetic markers are the ones that can be studied earliest. Of 27 patients studied, 16 had a sex-mismatched donor, and in 8 cases, there were discriminative markers identified with regular Giemsa and Q-banding. In one case, there was a rather slight polymorphism of the C-bands of chromosomes #9. Thus, donors' cells were identifiable in 25 of 27 cases (93%). The markers studied easiest are the sex chromosomes in sex-mismatched BMT. Different fluorescence of the centromeric regions of chromosomes #3 and characteristic satellites of acrocentric chromosomes are rather frequent and also well suited to discriminate donors' from patients' cells. Nonprominent variabilities (fluorescence of the centromeric regions of chromosomes #4 and #6 after Q-banding), rare polymorphisms (pericentric inversions of chromosomes #1 and #9), and difficult to evaluate polymorphisms (heterochromatic regions of chromosomes #1, #9, and #16) are not very practical for the routine monitoring of engraftment after BMT.

The distribution of quinacrine on chromosomes as determined by X-ray microanalysis

The distribution of quinacrine and protein sulphur has been compared with that of DNA in euchromatic and heterochromatic regions of mouse chromosomes stained with the fluorescent dye quinacrine, using X-ray microanalysis. Heterochromatin tends to bind relatively more quinacrine than euchromatin, and contains a greater concentration of sulphur. Measurements of quinacrine fluorescence, when compared with quinacrine binding, show that the excitation of fluorescence is more efficient when the dye is bound to euchromatin than when it is bound to heterochromatin. Although this observation is consistent with the hypothesis that the dull quinacrine fluorescence of mouse centromeres is due to quenching by guanine residues, two other factors should also be considered: the lower absolute amount of dye bound to the centromeres, and a concentration-dependent quenching of fluorescence.