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At least 19 recordsLinked to original sources
PubMed2003

An uncertainty principle in chromosome positioning.

Chromosomes are non-randomly positioned in the mammalian interphase nucleus. It is not known how patterns of chromosome positions are established or to what degree spatial arrangements of chromosomes change during the cell cycle, especially during mitosis. Two reports have applied in vivo microscopy to track chromosomes in space and time. The results highlight the inherently imperfect and probabilistic nature of chromosome positioning in the cell nucleus.

Animals↗
PubMed1991

Evolution of gene position: chromosomal arrangement and sequence comparison of the Drosophila melanogaster and Drosophila virilis sina and Rh4 genes.

The seven in absentia (sina) gene of Drosophila encodes a nuclear protein required for normal eye development. In Drosophila melanogaster, the sina gene is located within an intron of the Rh4 opsin gene. We examine here the nucleotide sequences and chromosomal arrangements of these genes in Drosophila virilis. An interspecies comparison between D. melanogaster and D. virilis reveals that the protein-coding sequences of the sina and Rh4 genes are highly conserved, but the relative chromosomal position and structural arrangement of these genes differ between the two species. In particular, the sina and Rh4 genes are widely separated in D. virilis, and there is no intron in the Rh4 gene. Our results suggest that the Rh4 gene was translocated to another chromosomal location by a retrotransposition event.

Animals↗
PubMed2003

Global chromosome positions are transmitted through mitosis in mammalian cells.

We investigated positioning of chromosomes during the cell cycle in live mammalian cells with a combined experimental and computational approach. By non-invasive labeling of chromosome subsets and tracking by 4D imaging, we could show that no global rearrangements occurred in interphase. Using the same assay, we also observed a striking order of chromosomes throughout mitosis. By contrast, our computer simulation based on stochastic movements of individual chromosomes predicted randomization of chromosome order in mitosis. In vivo, a quantitative assay for single chromosome positioning during mitosis revealed strong similarities between daughter and mother cells. These results demonstrate that global chromosome positions are heritable through the cell cycle in mammalian cells. Based on tracking of labeled chromosomes and centromeres during chromosome segregation and experimental perturbations of chromosomal order, we propose that chromosome specific timing of sister chromatid separation transmits chromosomal positions from one cell generation to the next.

Animals↗
PubMed1989

Localization of preferential sites of rearrangement within the BCR gene in Philadelphia chromosome-positive acute lymphoblastic leukemia.

The Philadelphia chromosome associated with acute lymphoblastic leukemia (ALL) has been linked to a hybrid BCR/ABL protein product that differs from that found in chronic myelogenous leukemia. This implies that the molecular structures of the two chromosomal translocations also differ. Localization of translocation breakpoints in Philadelphia chromosome-positive ALL has been impeded due to the only partial characterization of the BCR locus. We have isolated the entire 130-kilobase BCR genomic locus from a human cosmid library. A series of five single-copy genomic probes from the 70-kilobase first intron of BCR were used to localize rearrangements in 8 of 10 Philadelphia chromosome-positive ALLs. We have demonstrated that these breakpoints are all located at the 3' end of the intron around an unusual restriction fragment length polymorphism caused by deletion of a 1-kilobase fragment containing Alu family reiterated sequences. This clustering is unexpected in light of previous theories of rearrangement in Philadelphia chromosome-positive chronic myelogenous leukemia that would have predicted a random dispersion of breakpoints in the first intron in Philadelphia chromosome-positive ALL. The proximity of the translocation breakpoints to this constitutive deletion may indicate shared mechanisms of rearrangement or that such polymorphisms mark areas of the genome prone to recombination.

Base Sequence↗
PubMed1988

Heterogeneity of genomic fusion of BCR and ABL in Philadelphia chromosome-positive acute lymphoblastic leukemia.

Philadelphia chromosome-positive acute lymphoblastic leukemia occurs in two molecular forms, those with and those without rearrangement of the breakpoint cluster region on chromosome 22. The molecular abnormality in the former group is similar to that found in chronic myelogenous leukemia. To characterize the abnormality in the breakpoint cluster region-unrearranged form, we have mapped a 9;22 translocation from the Philadelphia chromosome-positive acute lymphoblastic leukemia cell line SUP-B13 by using pulsed-field gel electrophoresis and have cloned the DNA at the translocation junctions. We demonstrate a BCR-ABL fusion gene on the Philadelphia chromosome. The breakpoint on chromosome 9 is within ABL between exons Ia and II, and the breakpoint on chromosome 22 is approximately equal to 50 kilobases upstream of a breakpoint cluster region in an intron of the BCR gene. This upstream BCR breakpoint leads to inclusion of fewer BCR sequences in the fusion gene, compared with the BCR-ABL fusion gene of chronic myelogenous leukemia. Consequently, the associated mRNA and protein are smaller. The exons from ABL are the same. Analysis of leukemic cells from four other patients with breakpoint cluster region-unrearranged Philadelphia chromosome-positive acute lymphoblastic leukemia revealed a rearrangement on chromosome 22 close to the breakpoint in SUP-B13 in only one patient. These data indicate that breakpoints do not cluster tightly in this region but are scattered, possibly in a large intron. Given the large size of BCR and the heterogeneity in breakpoint location, detection of BCR rearrangement by standard Southern blot analysis is difficult. Pulsed-field gel electrophoresis should allow detection at the DNA level in every patient and thus will permit clinical correlation of the breakpoint location with prognosis.

Chromosome Mapping↗
PubMed2003

The effect of imatinib mesylate on patients with Philadelphia chromosome-positive chronic myeloid leukemia with secondary chromosomal aberrations.

PURPOSE AND EXPERIMENTAL DESIGN: The acquisition of secondary chromosomal aberrations in chronic myeloid leukemia (CML) patients with Philadelphia chromosome-positive (Ph+) karyotype signifies clonal evolution associated with disease progression to accelerated/blastic phase. Therefore, these aberrations are of clinical and biological importance. We identified 58 cases with secondary abnormalities in addition to t(9;22)(q34;q11.2) or its variants in a review of 137 CML patients treated with imatinib mesylate (STI571). Clinically 13 patients were in chronic phase, 24 in accelerated phase, and 21 in blastic phase. RESULTS: More than 50% of cases showed the major routes of CML clonal evolution [+8, i(17q), +Ph, and/or +19]. The remainder exhibited minor routes of secondary abnormalities with -17/17p-, 11p-/rearr(11p), and -7/rearr(7) as the most frequent abnormalities. Of particular interest, one case developed an inv(16)(p13q22) as a secondary anomaly during blastic transformation. The bone marrow was consistent with myelomonocytic morphology with eosinophilia. Cytogenetic responses to imatinib mesylate occurred in 15 of 58 (26%) patients; 12 achieved complete cytogenetic remission, 2 had a major response, and 1 had a minor response, with most responses noted within 3-6 months. Seven patients remain in remission >17-30 months, 2 patients relapsed between 12 and 19 months on therapy, and 1 patient was treated by bone marrow transplantation. CONCLUSIONS: Although some Ph+ CML patients with clonal evolution can have a complete cytogenetic response to imatinib mesylate, responses tend to be brief, and such patients may benefit from subsequent stem cell transplantation. Therefore, CML patients with clonal evolution may require therapy additional to imatinib mesylate for maximal eradication of the Ph+ leukemic cells.

Adult↗
PubMed2004

Dynamics of relative chromosome position during the cell cycle.

The position of chromosomal neighborhoods in living cells was followed using three different methods for marking chromosomal domains occupying arbitrary locations in the nucleus; photobleaching of GFP-labeled histone H2B, local UV-marked DNA, and photobleaching of fluorescently labeled DNA. All methods revealed that global chromosomal organization can be reestablished through one cell division from mother to daughters. By simultaneously monitoring cell cycle stage in the cells in which relative chromosomal domain positions were tracked, we observed that chromosomal neighborhood organization is apparently lost in the early G1 phase of the cell cycle. However, the daughter cells eventually regain the general chromosomal organization pattern of their mothers, suggesting an active mechanism could be at play to reestablish chromosomal neighborhoods.

Animals↗
PubMed2004

Alteration of chromosome positioning during adipocyte differentiation.

Chromosomes are highly restricted to specific chromosome territories within the interphase nucleus. The arrangement of chromosome territories is non-random, exhibiting a defined radial distribution as well as a preferential association with specific nuclear compartments, which indicates a functional role for chromosome-territory organization in the regulation of gene expression. In this report, we focus on changes in adipocyte differentiation that are related to a specific chromosomal translocation associated with liposarcoma tumorigenesis, t(12;16). We have examined the relative and radial positioning of the chromosome territories of human chromosomes 12 and 16 during adipocyte differentiation, and detected a close association between the territories of chromosomes 12 and 16 in differentiated adipocytes, an association not observed in preadipocytes. Although further studies are required to elucidate the underlying reasons for the adipocyte-specific translocation of chromosomes 12 and 16, our observations indicate that alteration of relative chromosome positioning might play a key role in the tumorigenesis of human liposarcomas. In addition, these results demonstrate the potential impact of higher order chromatin organization on the epigenetic mechanisms that control gene expression and gene silencing during cell differentiation.

Adipocytes↗
PubMed1991

BCR-ABL rearrangements in children with Philadelphia chromosome-positive chronic myelogenous leukemia.

Leukemia cells from adults with Philadelphia (Ph1)-chromosome positive chronic myelogenous leukemia (CML) have a characteristic molecular rearrangement between the BCR and ABL genes whereby major breakpoint cluster region (Mbcr) exons 2 or 3 are joined to ABL exon II. Ph1-chromosome positive CML is uncommon in children and it is unknown whether these children have similar rearrangements. We studied 17 children with Ph1-chromosome positive CML. Five were studied for Mbcr rearrangement using Southern blotting, nine for the presence of chimeric BCR-ABL mRNA using reverse transcription and polymerase chain reaction, and three for both. All eight children studied by Southern blotting had BCR rearrangement. Of 12 children in whom BCR-ABL mRNA was studied, 10 had Mbcr exon 2 joined to ABL exon II, one had Mbcr exon 3 joined to ABL II, and one had both Mbcr-ABL junctions. These data indicate a similarity to adult CML. However, mRNA processing in children may preferentially splice Mbcr exon 2 to ABL exon II. No child had BCR exon 1 joined to ABL exon II, the rearrangement typical of childhood Ph1-chromosome positive acute lymphoblastic leukemia.

Adolescent↗
PubMed1987

The effect of long-term marrow culture on the nonadherent Philadelphia chromosome-positive clone in chronic myelogenous leukemia: preliminary observations.

To evaluate the effect of long-term culture on the Philadelphia chromosome-positive nonadherent hemopoietic clone in chronic myelogenous leukemia, bone marrow aspirates from five patients were grown in culture for three to four weeks. In addition to control cultures, samples were incubated with recombinant alpha-interferon. Cytogenetic studies performed on the nonadherent hemopoietic cells demonstrated suppression of the Philadelphia chromosome-positive clones, and appearance of cells with normal diploid karyotype in two of the five patients studied; cells from the remaining three patients showed persistent Philadelphia chromosome-positive cells in 100% of the metaphases. Exposure to alpha-interferon did not enhance the suppression of the Philadelphia chromosome-positive clones. A good correlation was noted between in vitro results and in vivo cytogenetic response: the two patients whose in vitro studies showed diploid clones achieved complete hematologic remission and suppression of Philadelphia chromosome-positive metaphases with therapy. Our data suggest that long-term culture favors the growth of normal clones over Philadelphia chromosome-positive clones in the nonadherent hemopoietic cells of some patients with chronic myelogenous leukemia. The value of the procedure as an in vitro predictive test for residual normal stem cells and response to therapy and for autologous marrow in vitro purging needs further exploration.

Adult↗
PubMed2005

Non-random chromosome positioning in mammalian sperm nuclei, with migration of the sex chromosomes during late spermatogenesis.

Chromosomes are highly organized and compartmentalized in cell nuclei. The analysis of their position is a powerful way to monitor genome organization in different cell types and states. Evidence suggests that the organization of the genome could be functionally important for influencing different cellular and developmental processes, particularly at early stages of development (i.e. fertilization and the consequent entry of the sperm nucleus into the egg). The position of chromosomes in the sperm nucleus might be crucial, because their location could determine the time at which particular chromatin domains are decondensed and remodelled, allowing some epigenetic level of control or influence over subsequent paternal gene expression in the embryo. Here, we analyse genome organization by chromosome position in mammalian sperm nuclei from three breeds of pig, as a model species. We have mapped the preferential position of all chromosomes (bar one) in sperm nuclei in two dimensions and have established that the sex chromosomes are the most internally localized chromosomes in mature sperm. The distribution of two autosomes and chromosomes X and Y in sperm heads was compared in primary and secondary spermatocytes and spermatids in porcine testes. The sex chromosomes were found at the nuclear edge in primary spermatocytes, which correlates with the known position of the XY body and their position in somatic cells, whereas, in spermatids, the sex chromosomes were much more centrally located, mirroring the position of these chromosomes in ejaculated spermatozoa. This study reveals the temporal repositioning of chromosome territories in spermatogenesis.

Animals↗
PubMed2005

Treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia.

Philadelphia chromosome positive (Ph(+)) acute lymphoblastic leukemia (ALL) includes at least one-quarter of all adults with ALL. Until recently, conventional chemotherapy programs that have been effective in other precursor B-cell ALL cases have been unable to cure patients with this diagnosis. Allogeneic stem cell transplantation early in first remission has been the recommended therapy. The availability of imatinib mesylate and other tyrosine kinase inhibitors and small molecules that affect the BCR/ABL signaling pathways may be changing the treatment paradigm and the prognosis for these patients. The results from clinical trials using imatinib in the frontline setting and in relapsed patients as well as preliminary experience treating imatinib-resistant Ph(+) ALL will be described.

Adult↗
PubMed1988

Phenotypic and molecular heterogeneity in Philadelphia chromosome-positive acute leukemia.

Philadelphia chromosome-positive (Ph1) acute leukemia is a heterogeneous subset of acute leukemia with a poor prognosis. We studied five patients to determine the potential for phenotypic and molecular heterogeneity. Cellular characterization studies included light myeloperoxidase (L-MPO), terminal deoxynucleotidyl transferase (TdT), ultrastructural MPO (U-MPO), and immunophenotyping by flow cytometry using T11, T3, T4, T8, Leu 1, B1, Leu 12, HLA-DR (la), CALLA (J5), OKM1, My4, My7, My8, My9, and My10. DNA was analyzed for rearrangements of the breakpoint cluster region (bcr), immunoglobulin heavy chain, joining region (JH), immunoglobulin kappa light chain constant region (C kappa), and T cell receptor (TcR beta). RNA dot blots were hybridized by using molecular probes for MPO and TdT. We found that four of five cases were acute mixed-lineage leukemia (AMLL). One patient had acute unclassifiable leukemia. Of the four patients classified as having AMLL, three showed myeloid and lymphoid features, with one patient showing myeloid, T cell, and B cell features. The last case showed T cell and B cell features only. In one patient MPO/RNA was positive in spite of insufficient L-MPO or U-MPO to diagnose acute myelogenous leukemia (AML), thereby suggesting significant MPO gene expression before the production of sufficient MPO protein to meet the French-American-British criteria for AML. Three of the five patients showed rearrangement of bcr (cases 1, 2, and 5). Studies of these five patients support the concepts of molecular and phenotypic heterogeneity in Ph1 acute leukemia, demonstrate a high incidence of AMLL in this subset of acute leukemia, and support the use of lineage-associated molecular probes to define lineage at an earlier stage than previously possible.

Acute Disease↗
PubMedDate not supplied

Interphase FISH for follow-up of Philadelphia chromosome-positive chronic myeloid leukemia treatment.

BACKGROUND: Several attempts have been made to determine whether interphase fluorescence in situ hybridization (I-FISH) on bone marrow or peripheral blood specimens is a good alternative to conventional cytogenetics (CC) in calculating the residual proportion of Philadelphia (Ph) chromosome-positive cells during treatment follow-up of patients with chronic myeloid leukemia. MATERIALS AND METHODS: Nineteen patients were selected for I-FISH follow-up compared to CC. All samples were also classified into 4 groups according to the percentage of residual Ph chromosome-positive metaphases analyzed in CC. I-FISH was performed using the LSI bcr/abl dual ES color probe (Vysis). RESULTS: A high correlation was observed between the frequency of Ph chromosome-positive cells, assessed by CC and I-FISH (p<0.001). A high correlation was found between CC and I-FISH for 12 patients, but not for the remaining 7. Applying the same classification for I-FISH did not show a good relationship between the two techniques (p<0.001). CONCLUSION: Dual color I-FISH is a reliable method to monitor the size of the Ph chromosome-positive clone in bone marrow of treated CML patients. However, it has to be complementary to conventional cytogenetics because it cannot detect the emergence of other chromosomal abnormalities in Ph chromosome-positive or -negative cells.

Bone Marrow Cells↗
PubMed1981

9;22;15 complex translocation in Ph1 chromosome positive CML revealed by Giemsa-11 procedure in apparent lymphoid cells of blastic crisis.

A Ph1 chromosome positive chronic myeloid leukemia patient whose chronic phase lasted 7.5 years experienced a blastic transformation originating in the spleen. The spleen was infiltrated with undifferentiated blast cells that on cytogenetic analysis had a hyperdiploid karyotype and were Ph1 chromosome positive. The blast cells were negative for PAS, peroxidase. Sudan black and esterase stains. They were non-T, non-B with TdT activity. Remission was achieved in response to prednisone, vincristine, and adriamycin. Ph1 positive cells were present with cells responding to PHA stimulation throughout the course of the disease. A Giemsa-11 staining procedure male possible the ascertainment of a No. 9 translocation chromosome in blastic crisis cells that had also been present in Ph1 chromosome positive cells early in the disease. The presence of this translocation initially in myeloid cells and subsequently in apparent lymphoid cell types suggests the origin of this patient's leukemia as a pluripotential stem cell.

Azure Stains↗
PubMed1990

New type of Bcr/Abl junction in Philadelphia chromosome-positive chronic myelogenous leukemia.

A new and rare type of Bcr/Abl junction between exon C3 of the 3' portion of the Bcr gene and Abl exon 2 has been identified in the leukemic cells of two Ph1-positive chronic myelogenous leukemia patients in chronic phase. This is the fourth type of Bcr/Abl junction so far identified in Ph1-positive hematologic malignancies and is a consequence of an unusual breakpoint position on chromosome 22 that falls approximately 20 kb downstream of the major breakpoint cluster region (bcr) of the Bcr gene. The new hybrid mRNA is 540 base pairs (bp) longer than that expressed by the K562 cell line and could codify for a Bcr/Abl protein carrying 180 additional aminoacids with respect to the larger P210 protein so far identified. The hematologic phenotype expressed by the two patients carrying this unusual type of Bcr/Abl rearrangement does not significantly differ from that commonly seen in chronic myelogenous leukemia.

Amino Acid Sequence↗
PubMed1991

[T lymphoid blast crisis of Philadelphia chromosome-positive chronic myeloid leukemia: analysis of 3 cases].

BACKGROUND: To investigate the frequency of the T lymphoid phenotype in the blast crisis of chronic myelocytic leukemia (CML) with positive Philadelphia chromosome (Ph) and to evaluate the major clinical and hematologic features of the patients with this phenotype. METHODS: The presence of the TdT enzyme was assessed and specific monoclonal antibodies to the different hemopoietic lines were used to evaluate blast cells in 38 patients with blast crisis during Ph-positive CML. RESULTS: T lymphoid phenotype was found in three of the 38 patients, corresponding in all cases to immature T cells. In one patient, the blast crisis was the presenting feature of CML and in two the localization of the blast crisis was lymphadenopathic. In the two patients who could be followed up a favorable response to chemotherapy regimens including vincristine and prednisone was observed. CONCLUSIONS: Although uncommon, T lymphoid blast crisis in CML should no longer be considered exceptional. This phenotypic finding suggests that, at least in some cases, CML originates in a pluripotential stem cell common to all hemopoietic cells, including T lymphocytes.

Adult↗