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PubMed1987

["Artificial" chromosomes].

The structural elements required for chromosome replication, segregation, and stability are replication origins, centromeres, and telomeres. DNA sequences capable of organizing these three elements have been isolated from yeast chromosomal DNA by means of recombinant DNA techniques and yeast cell transformation. It is now possible to combine these sequences into "artificial" chromosomes for yeast cells to obtain more insight into chromosome structure and function. Evidence is presented that the construction of artificial chromosomes functional in higher eukaryotes will be possible in the near future.

Base Sequence↗

PubMed2004

Microcell-mediated chromosome transfer provides evidence that polysomy promotes structural instability in tumor cell chromosomes through asynchronous replication and breakage within late-replicating regions.

It was reported earlier that normal chromosome 3 (chr3) transfer into tumor cells of different origin may suppress their ability to grow in SCID mice. Tumorigenicity may be restored by the loss of certain 3p regions. We transferred a normal cell-derived chr3 into cells of a human renal cell carcinoma line and followed the chromosomal changes during in vivo and in vitro growth. In cells cultivated for 6 weeks or more and in the tumors grown in SCID mice, supernumerary chrs3 were always rearranged, accompanied by 3p losses. Unexpectedly, we found that the rearrangements affected not only the transferred exogenous chr3, but also the endogenous chrs3. Other chromosomes that were polysomic in the recipient cells were affected as well, suggesting that polysomy may be associated with structural chromosome instability. The dominant chromosomal aberrations were unbalanced translocations with preferentially pericentromeric breakpoints. The breakpoint distribution on chr3 preferentially affected the pericentromeric 3p11 (8 breaks) and 3p12-13 (5 breaks) regions. The regions 3p14 and 3q26-27 occasionally were involved as well (one break in each case). These four regions were the latest replicating, as shown by BrdU incorporation-based replication banding. Using fluorescence in situ hybridization-based replication timing, we detected asynchronous and incomplete centromere replication in cells with 3 or 4 copies of chr3, but not in cells with 2. We concluded that in tumor cells, asynchronous and incomplete replication of polysomic chromosomal parts is associated with aberrations that have breakpoints within the late-replicating regions. This may explain the increased structural chromosome instability and preferential pericentromeric localization of breakpoints in hyperploid tumors.

Aneuploidy↗

PubMed1983

Chromosomal radiosensitivity in meiotic oocytes of Chinese hamsters.

The X-ray sensitivity of unfertilized Chinese hamster oocytes was investigated. Female Chinese hamsters were exposed to a single X-ray dose of 200R at various preovulatory phases classified into 4 stages. These stages ranged from 12 hours to 5 estrous cycles before the time of collecting the oocytes. Chromosome analysis of the irradiated oocytes in metaphase-II was performed. The frequency of oocytes with abnormal chromosomes was compared with the non-irradiated control. The frequency of the oocytes with chromosome aberrations was 42.1% in the group in which females were irradiated at metaphase-I, 9.8% in the group irradiated at 2-4 days before the time of collecting the oocytes and 10.8% in that irradiated 1 estrous cycle before the time of collecting the oocytes. In the group irradiated at the 5th estrous cycle prior to the time of collecting the oocytes, the number of oocytes with chromosome aberrations could not be distinguished from that of the control. Comparing the frequency of oocytes carrying numerical chromosome aberrations with those carrying structural chromosome aberrations, there were more obvious differences in structural aberrations than in numerical ones among the irradiated stages. It was suggested that X-ray exposures of gonads, not only at postovulatory, but also preovulatory phases, may be hazardous and should be considered more carefully in the case of humans.

Animals↗

PubMed2001

Molecular cytogenetic analysis of two primary squamous cell carcinomas of the lung using multicolor fluorescence in situ hybridization.

To fully characterize the numerous chromosomal aberrations in two human squamous cell carcinomas (SCCs) of the lung, molecular cytogenetic characterization was carried out utilizing conventional banding analysis and multicolor fluorescence in situ hybridization (mFISH), providing simultaneous color discrimination of all 24 human chromosomes. Both tumors displayed complex aneuploid karyotypes with a host of numerical and structural chromosome abnormalities. Structural aberrations common to both SCCs included rearrangements of chromosomes 1, 3p, 7q, and 8q, contributing to net loss of chromosomal sequences on 1p, 3p, and 8p, and a net gain of 8q. The recently introduced mFISH technique enabled the disclosure of cryptic translocations and the chromosomal composition of previously unrecognized marker chromosomes. Furthermore, mFISH greatly enhanced the ability to delineate chromosomal breakpoints when integrating banding information from conventional banding analysis. Eventually, the application of mFISH as a powerful approach to refine complex tumor karyotypes is expected to result in a more detailed and complete picture of cytogenetic events associated with the development and progression of solid tumors.

Aneuploidy↗

PubMed1994

Interstitial deletions of repetitive DNA blocks in dicentric human Y chromosomes.

Cytogenetic analysis of aberrant human Y chromosomes was done by fluorescence in situ hybridization (FISH) with Y specific repetitive DNA probes. It revealed an interstitial deletion of different DNA blocks in two dicentric chromosome structures. One deletion includes the total alphoid DNA structure of one centromeric region. The second deletion includes the total repetitive DYZ5 DNA structure in the pericentromeric region of one short Y arm. Both dicentric Y chromosomes were iso(Yp) chromosomes with break and fusion point located in Yq11, the euchromatic part of the long Y arm. Their phenotypic appearance was "abnormal", resembling small monocentric Yq-chromosomes in metaphase plates. Mosaic cell lines, usually included in karyotypes with dicentric Y chromosomes, were not observed. It is assumed that both deletion events suppress the kinetochore activity in one Y centromeric region and thus stabilize its dicentric structure. Local interstitial deletion events had not been described in dicentric human Y chromosomes, but are common in dicentric yeast chromosomes. This raises the question of whether deletion events in dicentric human chromosomes are rare or restricted to the Y chromosome or also represent a general possibility for stabilization of a dicentric chromosome structure in human.

Centromere↗

PubMed1995

Structure and partitioning of bacterial DNA: determined by a balance of compaction and expansion forces?

The mechanisms that determine chromosome structure and chromosome partitioning in bacteria are largely unknown. Here we discuss two hypotheses: (i) the structure of the Escherichia coli nucleoid is determined by DNA binding proteins and DNA supercoiling, representing a compaction force on the one hand, and by the coupled transcription/translation/translocation of plasma membrane and cell wall proteins, representing an expansion force on the other hand; (ii) the two forces are important for the partitioning process of chromosomes.

Chromosomes, Bacterial↗

PubMed1976

Relationship of chromosome changes to neoplastic cell transformation.

Chromosomal abnormalities are a frequent concomitant of neoplasia, and although it is tempting to relate these mutations and alterations in chromatin (DNA) function to cancer, their relationship to the initiation or progression of carcinogenesis is unknown. Mammalian cells in culture, after interacting with chemical carcinogens, often exhibit chromosome damage consisting of breaks and exchanges of chromatid material. The pattern of damage of banded metaphases indicates that negative bands are especially vulnerable to the action of chemical carcinogens, probably because of differential chromatin condensation. Damage to individual chromosomes may be random or nonrandom, depending on the species. Cell death can be correlated with chromatid alterations that occur shortly after treatment with chemical carcinogens. There is also a correlation between mutagenic and carcinogenic activity of some chemical carcinogens and the frequency of sister chromatid exchanges. The question of whether specific chromosome changes are absolutely required for neoplastic transformation cannot be answered because of conflicting data and diverse results from studies even with known carcinogens. Cell transformation may occur without any visible chromosome changes. A universal specific numerical or visible structural chromosomal alteration is not necessarily associated with chemical or viral transformation. Chromosome changes are independent of the etiologic agents: different carcinogens may produce transformation associated with the same abnormal chromosomes, but not all transformed lines invariably exhibit the same abnormality, even with the same chemical. In some species, chromosome having nucleolar organizer regions may be more frequently involved in numerical or structural deviations. Progressively growing tumors also may occur as a result of the proliferation of transformed cells without detectable chromosome changes, indicating that tumorigenicity need not be related to an imbalance of chromosome number or structure. Our studies indicate that chromosome changes are not essential for establishment of neoplasms but that karyotypic instability may result in response to selective growth pressures.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1978

Recombinant chromosome as a result of pericentric inversion of X chromosome.

A structural X chromosome abnormality was found in the karyotype of a tall patient with gonadal dysgenesis and with no extragenital anomalies. Based on her mother's karyotype, which showed a pericentric inversion of the X chromosome: 46,X,inv(X)(p22q24), as well as from G and R banding, we concluded that the abnormal X chromosome of our patient was a recombinant chromosome that had originated as a result of one crossing over in the inversion loop during gametogenesis in her mother. The recombinant X chromosome had a partial delection of Xq and a partial duplication of Xp: 46,X,rec(S),dup p,inv(X)(p22q24). After BUDR incorporation, the abnormal X chromosome of the patient and that of her mother showed a late replication. The karyotype-phenotype correlation and the nonrandom inactivation of the inverted X chromosome in the mother are discussed.

Adult↗

PubMed2003

Partial duplication of the APBA2 gene in chromosome 15q13 corresponds to duplicon structures.

BACKGROUND: Chromosomal abnormalities affecting human chromosome 15q11-q13 underlie multiple genomic disorders caused by deletion, duplication and triplication of intervals in this region. These events are mediated by highly homologous segments of DNA, or duplicons, that facilitate mispairing and unequal cross-over in meiosis. The gene encoding an amyloid precursor protein-binding protein (APBA2) was previously mapped to the distal portion of the interval commonly deleted in Prader-Willi and Angelman syndromes and duplicated in cases of autism. RESULTS: We show that this gene actually maps to a more telomeric location and is partially duplicated within the broader region. Two highly homologous copies of an interval containing a large 5' exon and downstream sequence are located approximately 5 Mb distal to the intact locus. The duplicated copies, containing the first coding exon of APBA2, can be distinguished by single nucleotide sequence differences and are transcriptionally inactive. Adjacent to APBA2 maps a gene termed KIAA0574. The protein encoded by this gene is weakly homologous to a protein termed X123 that in turn maps adjacent to APBA1 on 9q21.12; APBA1 is highly homologous to APBA2 in the C-terminal region and is distinguished from APBA2 by the N-terminal region encoded by this duplicated exon. CONCLUSION: The duplication of APBA2 sequences in this region adds to a complex picture of different low copy repeats present across this region and elsewhere on the chromosome.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Evidence that both genetic instability and selection contribute to the accumulation of chromosome alterations in cancer.

Cancer cells contain many genetic alterations, and genetic instability may be important in tumourigenesis. We evaluated 58 breast and ovarian cancer cell lines for microsatellite instability (MSI) and chromosomal instability (CIN). MSI was identified in 3/33 breast and 5/25 ovarian cell lines, and 7/8 MSI lines showed an inactivation of mismatch repair. Average ploidy by centromeric fluorescence in situ hybridization (FISH) of MSI (n = 8, average ploidy = 2.65) and microsatellite stable (MSS; n = 7, average ploidy = 3.01) cell lines was not different, due to the presence of three aneuploid MSI lines, and two near-diploid MSS lines. However, the variability of the centromeric FISH data was different between MSI and MSS (P = 0.049). The complexity of structural chromosomal rearrangements was not different between MSI and MSS. Thus, MSI and numerical CIN are not mutually exclusive, and structural CIN occurs independently of MSI or numerical CIN. Dynamic genetic instability was evaluated in three cell lines-MSI diploid (MT-3), MSS diploid (SUM159) and MSS aneuploid (MT-1). Ten clones of each of these cell lines were analysed by centromeric FISH and six-colour chromosome painting. The variation in chromosome number was different among all three cell lines (P < 0.001). MT-3 appeared numerically constant (94% of centromeric FISH signals matched the mode). SUM159 was 88% constant; however, 7% of cells had duplicated chromosomes. MT-1 was 82% constant; most changes were chromosomal losses. The six-colour FISH data showed that SUM159 had more stable structural chromosomal alterations (e.g. chromosomal translocations) compared with MT-3 and MT-1, but had no increase in unstable changes (e.g. chromatid breaks) when compared with MT-3. MT-1 had fewer unstable changes than both MT-3 and SUM159. These data suggest that numerical CIN may contribute to aneuploidy, but that selection plays an important role, particularly for the accumulation of structural chromosomal changes.

Breast Neoplasms↗

PubMed1996

Cytogenetic abnormalities are frequent in uncultured prostate cancer cells.

Despite attempts by several laboratories to identify consistent chromosome abnormalities in cancer of the prostate, relatively few clonal changes have been found. We compared analysis of metaphases from uncultured specimens of primary prostate cancer (direct preparations) with those obtained from short-term culture using various media. While the number of metaphases in uncultured specimens was low, and chromosome morphology fair to poor, structural chromosome changes could be identified as clonal in 5 of 14 specimens (36%). In contrast, while clonal abnormalities were found in 20 of 61 (33%) specimens analyzed after short-term culture, these abnormalities were predominantly numerical and simple structural changes. Two tumors metastatic to lymph nodes were studied using direct preparations; both were near tetraploid, with multiple structural abnormalities, including isochromosome 8q in both and del(8)(p21) in one. Cytogenetic analyses of metastatic prostate tumors have been very limited, and these data suggest that formation of an i(8q) may be the mechanism by which loss of heterozygosity of 8p, reported frequently in molecular analyses, occurs. Our findings indicate that prostate cancers, like most solid tumors, do have clonal chromosome abnormalities that are frequently complex, but the method that reproducibly yields representative karyotypes from this particular tumor remains to be identified.

Aged↗

PubMed2003

Analysis of insect holocentric chromosomes by atomic force microscopy.

In order to go in depth into the analysis of holocentric chromosome structure, atomic force microscopy (AFM) was applied to metaphase plates of the aphid Megoura viciae. AFM showed that aphid chromatids adhere to one another without any prominent structure detectable between them and without any evidence of chromosomal constrictions. AFM thus provided new and reliable evidences at a nanomolecular level concerning the holocentric structure of aphid chromosomes, without any of the artefacts due to sample staining or coating that are usually associated with electron microscopy.

Animals↗

PubMed1981

Frequency and types of induced and spontaneous chromosome aberrations in relation to cell kinetics.

Induced and spontaneous structural chromosome aberrations (SCA) were studied in a child accidentally radiated with a high dose of 192Ir, and in three sibs with Fanconi's anemia, analyzing by separate first division metaphases (FDM) and second division metaphases (SDM). The results showed that the number of SCA, number of cells with aberrations, and SCA per cell were markedly higher in FDM in all patients. Furthermore, for some type of structural changes like dicentric chromosomes and chromatid interchanges, the differences were particularly striking. The importance of ascertaining FDM identified with proper techniques, for the study of the clastogenic effect of environmental agents and some aspects related to the differences in cytogenetic features found in diverse tissues in Fanconi's anemia are discussed.

Anemia, Aplastic↗

PubMed2006

Assessing genetic diversity of Brazilian reef fishes by chromosomal and DNA markers.

Little is known on genetics of Brazilian coral reef fish and most of this information is limited to chromosome characterization of major representative species. The diploid chromosome number in marine fish varies from 2n= 22-26 to 2n = 240-260. Despite of this apparent diversity, most studied marine species have a diploid complement with 48 acrocentric chromosomes. This latter trend is mostly observed among Perciformes, an important major taxon of coral reef fishes. Studies in the families Pomacentridae, Pomacanthidae and Chaetodontidae, for example, have shown a common karyotype pattern entirely formed by 48 uniarmed chromosomes. However, rare numerical and structural chromosome polymorphisms and cryptic chromosome rearrangements involving heterochromatin segments and/or nucleolar organizing sites have been reported among such fishes. Although new chromosome forms can contribute to the establishment of genetically isolated populations, their role in reef fish speciation at marine realm still is an open question. More recently, genomic DNA analyses using RAPD and microsatellites, and sequencing and RFLP of mitochondrial DNA have increasingly been used in Atlantic reef fish species. Genetic homogeneity over wide geographical ranges has been reported for different fish groups, in contrast to several cases of population substructuring related to environmental constraints or evolutionary history. Amazonas outflow and upwelling on the Southeastern coast of Brazil are believed to be strong barriers to dispersal of some reef species. Moreover, it is suggested that the pattern of speciation and population structure at South Atlantic is quite distinctive from Pacific Ocean, even when comparing closely related taxa. Further genetic studies are strongly encouraged in Brazilian reef fishes in order to provide a reliable scenario of the genetic structure in this important and diverse fish group.

Animals↗

PubMed2002

Structural analysis of aberrant chromosomes that occur spontaneously in diploid Saccharomyces cerevisiae: retrotransposon Ty1 plays a crucial role in chromosomal rearrangements.

The structural analysis of aberrant chromosomes is important for our understanding of the molecular mechanisms underlying chromosomal rearrangements. We have identified a number of diploid Saccharomyces cerevisiae clones that have undergone loss of heterozygosity (LOH) leading to functional inactivation of the hemizygous URA3 marker placed on the right arm of chromosome III. Aberrant-sized chromosomes derived from chromosome III were detected in approximately 8% of LOH clones. Here, we have analyzed the structure of the aberrant chromosomes in 45 LOH clones with a PCR-based method that determines the ploidy of a series of loci on chromosome III. The alterations included various deletions and amplifications. Sequencing of the junctions revealed that all the breakpoints had been made within repeat sequences in the yeast genome, namely, MAT-HMR, which resulted in intrachromosomal deletion, and retrotransposon Ty1 elements, which were involved in various translocations. Although the translocations involved different breakpoints on different chromosomes, all breakpoints were exclusively within Ty1 elements. Some of the resulting Ty1 elements left at the breakpoints had a complex construction that indicated the involvement of other Ty1 elements not present at the parental breakpoints. These indicate that Ty1 elements are crucially involved in the generation of chromosomal rearrangements in diploid yeast cells.

Chromosome Aberrations↗

PubMed1982

A total population study of diagnosed chromosome abnormalities in Queensland, Australia.

Aneuploidy and structural chromosome rearrangements comprise a significant group of abnormalities in the general population. The true incidence of such abnormalities can be obtained by large research studies of consecutive newborns. In practice, the observed incidence of such chromosome abnormalities is obtained by karyotyping subjects who present for clinical reasons. The difference between the observed clinically indicated rates and the assumed rate (by comparison with data from consecutive newborn studies) would allow the estimation of the unrecognised chromosome abnormality load in the general population. The difference between these two rates would provide valuable data concerning the appropriateness of selection techniques for routine chromosome analysis. This paper reports such a study, from Queensland, Australia. A total population 5-year survey (1976-1980) of the diagnosed chromosome abnormalities in this unselected primary population of 2.2 million people is reported. Five hundred and eighty-nine chromosome abnormalities were detected in a consecutive series of 6092 karyotypes performed (9.7%). This figure is significantly lower than that found in most other reported series where case selection for karyotyping is determined by clinical criteria. In this current study the annual diagnostic rate for chromosome abnormalities was 5.41 per 100,000 of the general population. Cumulative frequency histograms for all types of chromosome abnormality, by age, are presented. In current practice, 32% of chromosome abnormalities are not diagnosed until adult life. Fifty percent of cases of chromosome abnormality (of all types) remain undiagnosed by the age of 1 year, in spite of a relatively liberal acceptance rate on the part of laboratories offering routine karyotyping services. It is concluded that a positive diagnostic rate greater than 10%, in routine chromosome laboratories, probably indicates that more than half the true cases of chromosome abnormality in a population are being missed.

Adolescent↗

PubMed2004

Cytogenetic and molecular cytogenetic analyses in diffuse astrocytomas.

Diffuse astrocytomas are highly variable tumors and show complex biologic behavior that is based on multi-step oncogenesis. We report cytogenetic and molecular cytogenetic investigations in 23 cases of diffuse astrocytomas. The results of conventional karyotyping, interphase fluorescence in situ hybridization (FISH), comparative genomic hybridization, multicolor FISH, and spectral karyotyping are reported. Various numerical and structural chromosomal aberrations were identified. Clustering of structural alterations in the short arm of chromosome 2 (2p) and the long arm of chromosome 7 (7q) were detected. Using spectral karyotyping, additional chromosome rearrangements not detectable by conventional methods were found. Some of these anomalies have not been previously described in diffuse astrocytomas. An independent validation of these discrepant findings is required.

Aneuploidy↗

PubMed2001

Localization of cold shock proteins to cytosolic spaces surrounding nucleoids in Bacillus subtilis depends on active transcription.

Using immunofluorescence microscopy and a fusion of a cold shock protein (CSP), CspB, to green fluorescent protein (GFP), we showed that in growing cells Bacillus subtilis CSPs specifically localize to cytosolic regions surrounding the nucleoid. The subcellular localization of CSPs is influenced by the structure of the nucleoid. Decondensed chromosomes in smc mutant cells reduced the sizes of the regions in which CSPs localized, while cold shock-induced chromosome compaction was accompanied by an expansion of the space in which CSPs were present. As a control, histone-like protein HBsu localized to the nucleoids, while beta-galactosidase and GFP were detectable throughout the cell. After inhibition of translation, CspB-GFP was still present around the nucleoids in a manner similar to that in cold-shocked cells. However, in stationary-phase cells and after inhibition of transcription, CspB was distributed throughout the cell, indicating that specific localization of CspB depends on active transcription and is not due to simple exclusion from the nucleoid. Furthermore, we observed that nucleoids are more condensed and frequently abnormal in cspB cspC and cspB cspD double-mutant cells. This suggests that the function of CSPs affects chromosome structure, probably through coupling of transcription to translation, which is thought to decondense nucleoids. In addition, we found that cspB cspD and cspB cspC double mutants are defective in sporulation, with a block at or before stage 0. Interestingly, CspB and CspC are depleted from the forespore compartment but not from the mother cell. In toto, our findings suggest that CSPs localize to zones of newly synthesized RNA, coupling transcription with initiation of translation.

Bacillus subtilis↗