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Biological dosimetry using human interphase peripheral blood lymphocytes.

Conventional metaphase-spread chromosome-aberration-based biodosimetry techniques for radiation dose assessment, although robust, are laborious and time consuming. The molecular cytogenetic laboratory of the Armed Forces Radiobiology Research Institute is developing simple and rapid interphase-based cytological assays that will be applicable to a broad range of radiation exposure scenarios. These assays include analysis of chromosome aberrations (premature chromosome condensation-fluorescence in situ hybridization assay) and mitochondrial DNA mutations (mtDNA4977 deletion assay) using resting human peripheral blood lymphocytes. The dose-effect relationship for radiation-induced aberrations involving chromosome 1 after 24 hours of repair at 37 degrees C in resting human peripheral blood lymphocytes was studied using fluorescence in situ hybridization after chemical induction of premature chromosome condensation as previously explained. In the present study, we examined whether gamma irradiation in the range of 0 to 7.5 Gy induces a dose-dependent increase in aberrations manifested as "excess spots." The number of excess spots per cell, reflecting aberrations involving chromosome 1, increased from 0.035 at 0.5 Gy to 0.236 at 7.5 Gy. This observed dose-effect relationship was fit with a nonlinear power model. This technique may be extended to the study of radiation-induced translocations in interphase cells for retrospective dose reconstruction. With a recently developed in situ polymerase chain reaction method to detect and quantify mtDNA deletion in interphase cells after radiation exposure in cultured human peripheral blood lymphocytes, 90% to 95% of cells are analyzable. We discuss the potential use of the mtDNA deletion assay in biological dosimetry applications. Interphase-based cytological assays may eliminate some inherent problems associated with metaphase-spread-based assays. These problems involve (1) the limited number of analyzable cells containing chromosome aberrations, which is due to various factors including radiation-induced cell death and delay in cell cycle progression into mitosis, and (2) the requirements for radiation cytogenetics expertise and tedious labor to manually score chromosome aberrations.

Chromosome Aberrations↗

[Application of interphase cytogenetics for the determination of changes in the DNA content in acute childhood lymphoid leukemia].

The authors investigated the usefulness of the interphase cytogenetic approach to reveal numerical chromosomal abnormalities. Experiments performed on normal human cells using chromosome specific (peri)centromeric probes indicated that disomy was recognized in a range of 89.1 +/- 5.4%-96.8 +/- 0.4% for the somatic chromosomes and in 98.1 +/- 0.8% for the sex chromosomes. Using positivity threshold of mean percentage of the fals monosomy and trisomy + 2 SD, chromosome loss or gain for the somatic chromosomes could be revealed beyond clonal ratio of 3.6-13.2% and 1.1-6.8%, respectively. The same value for the sex chromosomes was 3.2% and 0%, respectively. Eleven pediatric acute lymphoid leukaemia were investigated for chromosomal aneuploidy by interphase cytogenetics using chromosome specific (peri)centromeric probes for all the somatic and sex chromosomes. Results were compared with metaphase cytogenetic and flow cytometry derived gross DNA aneuploidy data. In 5 cases the leukaemic cells proved to be diploid with all three methods at both gross DNA and chromosome levels. Interphase cytogenetics revealed chromosome loss or gain in all the remaining 6 cases, however, metaphase analysis indicated numerical aberration in only 2 patients. In one of them only the increased chromosome number could have been detected without identifying the chromosomes involved and in the other one the two methods indicated trisomy for not the same chromosome. Flow cytometry data showed aneuploidy in 3 out of the 6 aneuploid leukaemia. The results imply that interphase cytogenetics might be more accurate as compared with flow cytometry and metaphase analysis to reveale aneuploidy.

Age Factors↗

Interphase fluorescence in situ hybridization detection of t(2;13)(q35;q14) in alveolar rhabdomyosarcoma--a diagnostic tool in minimally invasive biopsies.

The identification of t(2;13)(q35;q14) is a useful aid in the accurate diagnosis of rhabdomyosarcoma, distinguishing it from other small round cell tumours and supporting the distinction between alveolar and embryonal forms. Cytogenetic analysis is difficult and with the increased use of minimally invasive biopsy methods and primary chemotherapy, adequate tumour material is not always available. To overcome these difficulties, two-colour interphase fluorescence in situ hybridization (FISH) to detect t(2;13)(q35;q14) was developed and its utility in assessing minimally invasive biopsies was investigated. Two cosmid clones which mapped proximal or distal to the breakpoint region 13q14 and one yeast artificial chromosome clone that mapped distal to the 2q35 breakpoint were identified. In interphase cells containing t(2;13)(q35;q14), the configuration of cosmid and yeast artificial chromosome signals demonstrated the presence of the translocation. Five cases of rhabdomyosarcoma were analysed by interphase FISH. The t(2;13)(q35;q14) was detected in all four alveolar tumours and was confirmed by cytogenetics in two cases, but was absent in one embryonal tumour. This sensitive detection method is applicable to minimal amounts of fresh or frozen tumour.

Adolescent↗

C-terminal domain of the mitotic apparatus protein p62 targets the protein to the nucleolus during interphase.

Mitotic apparatuses from sea urchin embryos contain a protein (p62), previously shown to be required for mitotic progression. This protein localizes to the mitotic apparatus during cell division in urchin embryos and mammalian tissue culture cells. We show here by immunofluorescence that p62 is localized to the nucleus of mammalian cells during interphase and is highly concentrated in nucleoli. In addition, a fusion protein composed of full-length p62 and green fluorescent protein also localizes to nucleoli when expressed in COS-7 cells in culture. Analysis of the primary sequence of p62 reveals three distinct domains of the protein based on amino acid charge distribution: the acidic N-terminal domain, the basic C-terminal domain, and the central, M-domain, which contains alternating subdomains of clusters of acidic and basic residues. To identify the domain important for nucleolar localization during interphase, specific domains of p62 alone, or in combination with each other or with beta-galactosidase were fused to green fluorescent protein. Following confirmation of the fusion constructs by sequence analysis, the constructs were expressed in mammalian cells, expression was confirmed by immunoblotting, and the fusion proteins were localized via fluorescence microscopy. The data demonstrate that the C-terminal domain of p62 is both necessary and sufficient for the nuclear localization and nucleolar binding of p62 that is observed during interphase.

Amino Acid Sequence↗

The use of interphase FISH for prenatal diagnosis of Pallister-Killian syndrome.

Pallister-Killian syndrome (tetrasomy 12p) is a relatively rare aneuploidy syndrome characterized by the presence of mosaicism for an isochromosome 12p [i(12p)]. We report two new cases diagnosed following chorionic villus sampling and an abnormal ultrasound, respectively. Fluorescent in situ hybridization (FISH) was used to enumerate the number of interphase cells containing the isochromosome. The results of these studies illustrate the importance of the use of interphase FISH to detect the presence of the i(12p) in uncultured, non-dividing cells. A review of the literature identified 23 additional cases of Pallister-Killian syndrome diagnosed prenatally. Approximately 50 per cent of these cases were associated with the presence of a congenital diaphragmatic hernia. We suggest that a perinatal-lethal form of Pallister-Killian syndrome is underdiagnosed and recommend that all cases of prenatally detected diaphragmatic hernia be tested for Pallister-Killian syndrome using interphase FISH on uncultured amniocytes.

Abnormalities, Multiple↗

Relative efficiency of FISH on metaphase and interphase nuclei from non-mosaic trisomic or triploid fibroblast cultures.

Chromosome specific probes that are used in interphase fluorescence in situ hybridization (FISH) analysis are usually tested on disomic control samples. When used for preimplantation or prenatal diagnosis the aim is to detect aneuploidy, most frequently trisomy. In this study, skin fibroblast cultures from non-mosaic trisomic and triploid fetuses were analysed by FISH to assess probe efficiency regarding interphase detection of trisomy. Skin fibroblast cultures were used because they are considered to be stable in culture. FISH experiments were performed using centromeric probes for chromosomes X, Y, 18 and locus specific probes for chromosomes 13 and 21. In metaphase nuclei, the expected signals were found in 100% of at least 30 metaphases counted on each sample and this also confirmed non-mosaicism in agreement with conventional karyotyping of the fetuses. On interphase nuclei, however, only 80-89% of nuclei per population displayed the expected signals for autosomal probes and 90% for probes for the sex chromosomes. For each probe, a range of percentages was obtained that can be regarded as indicative of non-mosaic trisomy in uncultured specimens. In the case of prenatal samples, the expected presence of maternal cells may lead to a lowering of the threshold for a trisomic diagnosis. In the case of preimplantation diagnosis, the accuracy can be improved by the use of two probes per chromosome or by the analysis of two cells from each embryo.

Cell Nucleus↗

A component of the interphase cytoskeleton is cyclically recruited into spindle poles during mitosis.

During the transition from interphase to mitosis, proteins are recruited into forming spindle poles [Leslie, Cell Motil. Cytoskeleton 16:225-228, 1990]. Antibodies which recognize these recruited components clearly label spindle poles during mitosis but the location and character of such proteins during interphase remain a mystery. Competition assays using an antibody to a recruited spindle pole protein show that in its disperse form the spindle pole protein is a highly insoluble component of the cytoskeleton which is dispersed to such an extent during interphase that it is difficult to identify by immunolocalization. The function of recruited spindle pole proteins is unknown but the aggregation/dispersion cycle and the antigen are highly conserved, appearing in sea urchin embryos and tissue culture cells.

Animals↗

Spatial distribution patterns of interphase centromeres during retinoic acid-induced differentiation of promyelocytic leukemia cells.

BACKGROUND: The pericentromeric heterochromatin is an important element for the regulation of gene silencing. Its spatial distribution during interphase appears to be cell-type specific. This study analyzes three-dimensional (3D) centromere distribution patterns during cellular differentiation along the neutrophil pathway. METHODS: Differentiation of the promyelocytic leukemia cell line NB4 was induced by retinoic acid. Centromeres in interphase nuclei were visualized by immunofluorescence staining of centromere-associated proteins with CREST serum. 3D images of nuclei were obtained by confocal microscopy. Automated methods for the segmentation of point-like objects in 3D images were implemented to detect the position of centromeres. Features of centromere localization patterns were determined by constructing the minimal spanning tree of the centromere distribution. RESULTS: In differentiated NB4 cells, the number of centromere conglomerates (chromocenters) was decreased and the distance between chromocenters was increased as compared with untreated controls. The nuclear volume did not differ between the two groups. CONCLUSIONS: The measured rearrangement of centromeres indicates a progressive clustering of heterochromatin and a global remodeling of interphase chromosome territories during differentiation of NB4 cells. The developed methods for the analysis of 3D centromere distribution patterns provide the opportunity for a fast and objective analysis of heterochromatin remodeling.

Algorithms↗

Localization of a mouse centromeric DNA repeat in interphase nuclei.

The position of a mouse DNA repeat located near the centromere of mouse chromosomes X, 11, 13, and 17 was examined in interphase nuclei of bone marrow and fibroblast cells by in situ hybridization of 3H- or biotin-labeled DNA probe 70-38. In most laboratory mouse strains this probe recognizes a single repeat cluster (DXWas70) close to the centromere of the mouse X chromosome. In a few mouse strains, a second locus (D11Was70, D13Was70, or D17Was70, depending on the mouse strain) is located near the centromere of an autosome. In interphase nuclei from mouse strains with the X-linked locus only, two distinct sites of hybridization were found in female mice and one in male mice. These two sites remained separated during the different phases of the cell cycle (G1, early S, late S, and G2) as demonstrated by in situ hybridization of the probe to flow-sorted nuclei. In interphase nuclei from mouse strains with both the X-linked locus and an autosomal locus, four distinct sites of hybridization were found in female mice and three in male mice. Further analysis of loci DXWas70 and D17Was70 showed that these loci were often located in the outer region of nuclei from bone marrow and fibroblast cells.

Animals↗

Flow cytometric quantification of human chromosome specific repetitive DNA sequences by single and bicolor fluorescent in situ hybridization to lymphocyte interphase nuclei.

Fluorescent in situ hybridization allows for rapid and precise detection of specific nucleic acid sequences in interphase and metaphase cells. We applied fluorescent in situ hybridization to human lymphocyte interphase nuclei in suspension to determine differences in amounts of chromosome specific target sequences amongst individuals by dual beam flow cytometry. Biotinylated chromosome 1 and Y specific repetitive satellite DNA probes were used to measure chromosome 1 and Y polymorphism amongst eight healthy volunteers. The Y probe fluorescence was found to vary considerably in male volunteers (mean fluorescence 169, S.D. 35.6). It was also detectable in female volunteers (mean fluorescence 81, S.D. 10.7), because 5-10% of this repetitive sequence is located on autosomes. The Y probe fluorescence in males was correlated with the position of the Y chromosome cluster in bivariate flow karyotypes. When chromosome 1 polymorphism was studied, one person out of the group of eight appeared to be highly polymorphic, with a probe fluorescence 26% below the average. By means of fluorescent in situ hybridization on a glass slide and bivariate flow karyotyping, this 26% difference was found to be caused by a reduction of the centromere associated satellite DNA on one of the homologues of chromosome 1. The simultaneous hybridization to human lymphocyte interphase nuclei of biotinylated chromosome 1 specific repetitive DNA plus AAF-modified chromosome Y specific DNA was detected by triple beam flow cytometry. The bicolor double hybridized nuclei could be easily distinguished from the controls. When the sensitivity of this bicolor hybridization is improved, this approach could be useful for automatic detection of numerical chromosome aberrations, using one of the two probes as an internal control.

Centromere↗

Clinical impact of chromosome 1 aberrations in neuroblastoma: a metaphase and interphase cytogenetic study.

Neuroblastoma tumors are characterized by aberrations of chromosome 1. Rapid detection of these chromosomal aberrations at diagnosis could give important clues to outcome and therapy. We attempted to detect numerical and structural aberrations of chromosome 1 not only by classical metaphase cytogenetics but also by interphase cytogenetics in order to overcome difficulties of karyotyping due to diminished metaphase quality and quantity in primary neuroblastoma samples. Karyotypic changes of chromosome 1 in 53 primary neuroblastomas were evaluated. In addition, we successfully performed interphase cytogenetics using single and double in situ hybridization procedures with chromosome 1-specific repetitive DNA probes on nuclei preparations obtained from 46 and 20 tumors, respectively. Polysomies of structurally normal chromosomes 1 were predominantly seen in tumors with good prognosis, whereas deletions of 1p material were nearly exclusively confined to progressive tumors. Numerical and structural chromosome 1 aberrations as studied by metaphase and interphase cytogenetics are thus valuable prognostic markers in neuroblastoma.

Chromosome Deletion↗

Co-amplified markers alternate in megabase long chromosomal inverted repeats and cluster independently in interphase nuclei at early steps of mammalian gene amplification.

Two-colour in situ hybridization with probes for two co-amplified markers located several megabases apart on chromosome 1 has been used to analyse early stages of adenylate deaminase 2 (AMPD2) gene amplification in Chinese hamster cells. In the amplified chromosomal structures, the distribution of hybridization spots identifies megabase-long inverted repeats. Their organization is remarkably well accounted for if breakage-fusion-bridge cycles involving sister chromatids drive the amplification process at these early stages. During interphase the markers often segregate into distinct nuclear domains. Many nuclei have bulges or release micronuclei, carrying several copies of one or both markers. These observations indicate that the amplified units destabilize the nuclear organization and eventually lead to DNA breakage during interphase. We propose a model in which interphase breakage has a role in the progression of gene amplification.

AMP Deaminase↗

Sexing the human fetus and identification of polyploid nuclei by DNA-DNA in situ hybridisation in interphase nuclei.

Samples of human adult lymphocytes, fetal lymphocytes, amniotic fluid cells, and chorionic villus cells were sexed independently by cytogenetics and DNA-DNA in situ hybridisation to a tritiated Y probe. For the in situ hybridisation analysis, the presence of Y bodies (hybridisation bodies) in 100 interphase nuclei were scored after autoradiography. In all, 82/83 samples were sexed in this way (one technical failure) and 78/82 were sexed by both in situ hybridisation and cytogenetics. There was complete agreement between the two methods. There was a considerable variation (40-100%) in the percentage of interphase nuclei with a hybridisation body among the male samples, but very few nuclei from female samples showed significant hybridisation. In situ hybridisation could be used to sex the conceptus when males but not females are at risk for various X-linked genetic disorders and may also be useful for detecting 45,X/46,XY mosaicism or polyploid/diploid mosaicism. This would be particularly useful for direct preparations of chorionic villus samples, which often prove difficult to analyse cytogenetically but offer the best means of avoiding maternal contamination. Some interphase nuclei had more than one hybridisation body, and this was most commonly found among amniotic fluid cells. Comparison of sizes of nuclei with one or two hybridisation bodies strongly suggested that most of the amniotic fluid cell nuclei with two hybridisation bodies were tetraploid.

Adult↗

Interphase cytogenetics: analysis of numerical chromosome aberrations in isolated cells.

Probes which recognize pericentromeric repetitive sequences can be used to determine numerical chromosome aberrations in interphase nuclei. Under appropriate stringency conditions, these probes decorate only the chromosome from which they were derived. It has been assumed that abnormalities of signal number in interphase nuclei reflect aneuploidy rather than proliferation, but this has not been clearly demonstrated. In this paper, three alphoid probes (D3Z1, D11Z1, and DXZ1) were localized to the appropriate chromosomes and the factors governing the production of reproducible signal distributions from three aneuploid cervical carcinoma-derived epithelial cell lines were investigated. Abnormalities of signal number represent numerical chromosome aberrations rather than changes associated with proliferation. Using four simple rules of interpretation, reproducible results can be obtained with minimal technical variation and selection bias. These results demonstrate that pericentromeric repetitive probes can be used reproducibly to determine numerical chromosome aberrations independent of cell proliferation in interphase nuclei, a necessary prerequisite for the application of this approach to the analysis of human tumours.

Aneuploidy↗

Prenatal interphase FISH diagnosis of PLP1 duplication associated with Pelizaeus-Merzbacher disease.

A submicroscopic genomic duplication in Xq22.2 that contains the entire proteolipid protein 1 gene (PLP1) is responsible for the majority of Pelizaeus-Merzbacher disease (PMD) patients. We previously developed an interphase FISH assay to screen for PLP1 duplications in PMD patients using peripheral blood and lymphoblastoid cell lines. This assay has been utilized as a clinical diagnostic test in our cytogenetics laboratory. To expand usage of the interphase FISH assay to prenatal diagnosis of PLP1 duplications, we examined three PMD families with PLP1 duplications utilizing aminiotic fluid samples. In two families the FISH assay revealed fetuses with PLP1 duplications, whereas the other fetus showed a normal copy number of PLP1. Haplotype analyses, as well as an additional FISH analysis using postnatal blood samples, confirmed the results of the prenatal analyses. Our study demonstrates utility of the interphase FISH assay in the prenatal diagnosis of PLP1 duplications in PMD.

Amniotic Fluid↗

Prenatal detection of structural abnormalities of chromosome 18: associations with interphase fluorescence in situ hybridization (FISH) and maternal serum screening.

We describe two cases of prenatally ascertained isochromosome 18. Case 1 included both an isochromosome 18p and an isochromosome 18q, while Case 2 involved only an isochromosome 18q. Both of these cases were associated with a positive maternal serum triple screen trisomy 18 risk (greater than 1 in 100 risk). In addition, fluorescence in situ hybridization (FISH) was performed on uncultured amniotic fluid interphase cells in both cases looking for aneuploidy for chromosomes 13, 18, 21, X and Y. The results of the interphase analyses support the common knowledge that careful interpretation of interphase FISH analysis is necessary and that results should be followed by full cytogenetic analysis. To our knowledge these are the first reported cases of structurally abnormal chromosomes 18 being associated with a positive maternal serum triple screen for trisomy 18.

Adult↗

Cytochemical localization of actin and myosin aggregates in interphase nuclei in situ.

Biochemical and ultrastructural studies on isolated nuclear compartments have previously shown actin and myosin to be constituents of interphase nuclei. In the present work, immunocytochemistry, in conjunction with confocal microscopy and ultrastructural immunogold techniques, shows that interphase nuclei of intact dorsal root ganglion neurons and of PC12 cells contain actin and myosin. Nuclear actin was observed to be distributed throughout the nucleoplasm occurring as distinct aggregates. Frequently, prominent actin aggregates were associated with the nucleolar periphery, often near nucleolar satellites. Ultrastructurally, actin was observed to be associated with linear, electron-dense structures, putatively identified as chromatin fibers, extending from nucleoli. Use of three antibodies against subclasses of alpha-actin isoforms revealed that nuclear actin is more closely related to alpha-sarcomeric actin than to alpha-smooth muscle actin. Those aggregates associated with the nucleolus were found to be in the polymerized F-actin form, in a small fraction of neurons, as assessed by FITC-phalloidin. A myosin-like antigen was also observed to occur as intranuclear aggregates. Quantitative assays of the distribution of actin and myosin aggregates by nearest neighbour analysis indicated a distribution characterized as uniform and failed to reveal statistically significant associations between any set of aggregates. The evidence presented herein indicates that actin and myosin are constituent proteins of interphase nuclei in situ of both normal mammalian and transformed mammalian cells.

Actins↗

Ultrastructural localization of filamentous actin within neuronal interphase nuclei in situ.

Previous biochemical studies utilizing isolated nuclei and nuclear matrices have shown actin to be a constituent of the interphase nucleus. In addition, recent ultrastructural work has shown the presence of actin and myosin within nuclei of interphase cells in situ. It was unclear, however, whether this intranuclear actin is present in the unpolymerized globular actin or the filamentous (F)-actin form. The present work, using confocal microscopy and ultrastructural cytochemical techniques, demonstrates the presence of F-actin within interphase nuclei of intact, uncompromised, dorsal root ganglion neurons in vitro and in vivo. Labeling by FITC-phalloidin detected the presence of intranuclear F-actin adjacent to the nucleolar periphery in a small fraction of cells in vitro, an observation confirmed by three-dimensional reconstruction. Ultrastructural analyses of cells exposed to heavy meromyosin (HMM), showed the presence of typical "arrowhead" complexes. The observation that these complexes were associated with nucleoli confirms that the intranuclear ligand detected by FITC-phalloidin indeed represents F-actin. Postembedding labeling with HMM conjugated to 20-nm colloidal gold (HMM-Au20) resulted in labeling similar to that obtained with HMM. However, HMM-Au20 was found to label a much larger fraction of cells, both in vitro and in vivo, than did FITC-phalloidin or HMM. This finding indicates that labeling with HMM-Au20 more accurately reflects the extent of actin polymerization in nuclei. Results from double labeling with HMM-Au20 and an antibody to alpha-sarcomeric actin confirmed that only a small amount of nuclear actin is in the F-form. Together, these results represent a first ultrastructural demonstration of the presence of F-actin in nuclei of neurons. While the role of nuclear F-actin has yet to be defined, the results suggest that F-actin may represent a component of the molecular motor responsible for the dynamic positioning of specific chromatin domains into the tissue-specific, nonrandom patterns observed in many cell types.

Actins↗