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Results for “Chromosome Breakpoints”

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PubMed1990

Sequence analysis of amplified t(14;18) chromosomal breakpoints in B-cell lymphomas.

We have explored different strategies for sequencing of major breakpoint (mbr) junctional regions in t(14;18) chromosomal translocations--the most frequent chromosomal abnormality observed in B-cell lymphomas. We demonstrate that coupling of the preparation of single-stranded DNA by asymmetric polymerase chain reaction (PCR) and direct sequencing is the method of choice for the rapid and precise determination of clone-specific bcl-2/JH fusion gene sequences. The rapidity, relative ease, and accuracy of the technique, described for the nucleotide sequence analysis of mbr t(14;18) breakpoints, permits the analysis of a relatively large number of samples and should be considered as part of the clinical evaluation of lymphoma patients. Furthermore, by providing sequence information of clone-specific DNA regions, the procedure should reduce the risk of false-positive results from PCR.

Base Sequence↗
PubMed1998

Molecular cloning of the chromosomal breakpoint in the LIS1 gene of a patient with isolated lissencephaly and balanced t(8;17).

Karyotypic analysis of a patient exhibiting a phenotype of isolated lissencephaly, and of her parents, revealed a de novo balanced translocation, t(8;17)(p11.2; p13.3). Since the lissencephaly (LIS1) gene was known to be located on 17p13.3, we investigated whether the translocation might involve this gene. We performed Southern analysis using cosmid clones that contained genomic sequences corresponding to LIS1, and found that the breakpoint was located within intron 1. As sequence analysis of the parental chromosomes in the vicinity of the breakpoint identified no additional putative transcripts, haploinsufficiency of the LIS1 gene is likely to be solely responsible for the patient's lissencephaly. Characterization of both breakpoints indicated a possible involvement of repetitive sequences in the recombigenic process that led to the translocation.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1995

Physical mapping of 3 candidate tumor suppressor genes relative to Beckwith-Wiedemann syndrome associated chromosomal breakpoints at 11p15.3.

A physical map encompassing the 3 Mb region containing the breakpoints of two Beckwith-Wiedemann Syndrome patients at chromosome band 11p15.3 is presented. The candidate tumor suppressor genes WEE1, ST5, and rhombotin, are positioned on this map relative to these Beckwith-Wiedemann syndrome translocation and inversion breakpoints.

Beckwith-Wiedemann Syndrome↗
PubMed1998

Hobo transposons causing chromosomal breakpoints.

Several laboratory surveys have shown that transposable elements (TEs) can cause chromosomal breaks and lead to inversions, as in dysgenic crosses involving P-elements. However, it is not presently clear what causes inversions in natural populations of Drosophila. The only direct molecular studies must be taken as evidence against the involvement of mobile elements. Here, in Drosophila lines transformed with the hobo transposable element, and followed for 100 generations, we show the appearance of five different inversions with hobo inserts at breakpoints. Almost all breakpoints occurred in hobo insertion sites detected in previous generations. Therefore, it can be assumed that such elements are responsible for restructuring genomes in natural populations.

Animals↗
PubMed2005

New approach for the refinement of the location of the X-chromosome breakpoint in a previously described female patient with choroideremia carrying a X;4 translocation.

Choroideremia (CHM) is an X-linked recessive ophthalmic disease characterized by a progressive degeneration of the choroid and the pigmented epithelium of the retina. We present the genetic characterization of a female patient affected with CHM who has been previously studied cytogenetically and showed a balanced translocation between chromosomes X and 4 [46,X,t(X;4)(q21;p16)]. The breakpoint in the X chromosome lies in the locus of CHM gene and for this reason, we have elucidated whether or not CHM was disrupted in the X chromosome involved in the translocation using different techniques. FISH showed that the 3'UTR and the last exons of the CHM were on the der(X) chromosome, and the 5'UTR and first exons of this gene were on the der(4) chromosome. Expression level analysis revealed that the breakpoint in the der(X) was located between exons 8 and 9 of the CHM gene because the expression level decreased from this point onwards. Based on this result the expression level analysis proved to be a valid method to pinpoint the location of breakpoints when the gene being expressed in peripheral blood is disrupted. Our results confirmed that the CHM gene was indeed disrupted in the X chromosome involved in the translocation. Besides, the nonrandom inactivation of the normal X chromosome observed using a methylation-specific polymerase chain reaction (M-PCR) technique explained the CHM in the female patient.

3' Untranslated Regions↗
PubMed1987

A chromosomal breakpoint that separates the esterase D and retinoblastoma predisposition loci in a patient with del(13)(q14q31).

A patient with severe mental retardation and other congenital abnormalities who developed retinoblastoma was shown to have a deletion on the long arm of chromosome #13 with breakpoints in regions q14 and q31. Quantitation of enzyme activity of the esterase-D gene which, together with the retinoblastoma locus, is located in region 13q14 showed levels that were equal to those of normal controls. The 13q14 breakpoint, therefore, appears to have occurred between the two loci, which places the esterase D gene in a more proximal position in this band than the retinoblastoma locus.

Carboxylesterase↗
PubMed2005

FISH approach to determine cat eye syndrome chromosome breakpoints of a patient with cat eye syndrome type II.

We report a 19-year-old man with craniofacial dysmorphic features, anorectal malformations, eye colobomas, orthopaedic anomalies, and mild neurodevelopmental delay. Cat eye syndrome (CES) was suspected, and confirmed by cytogenetic analysis which showed the presence of a supernumerary bisatellited chromosome, identified by fluorescence in situ hybridization (FISH) as invdup(22). The marker was further analyzed with six BAC clones located at the 22q11.1 and 22q11.2 regions; this analysis allowed correct assignment at low copy repeat 4 on chromosome 22 (LCR22-4) of the two breakpoints, confirming the presence of a CES chromosome type II. The patient's phenotype is considered in the light of the cytogenetic, and FISH investigations results and other patients reported in literature. Molecular definition of the breakpoints at the LCR22-4 copy confirms the role of different chromosome 22-specific LCRs in CES chromosomes generation, as well as in other chromosome 22 germ line rearrangements. Our report confirms that, unlike other conditions, i.e. the invdup(15) bisatellited dicentric marker, the CES phenotype does not appear to correlate with the size of the marker chromosome. Additional cases are necessary to be able to draw more specific genotype-phenotype correlations and to determine the outcome of patients with CES, especially when this rare condition is diagnosed in prenatal age.

Abnormalities, Multiple↗
PubMed2000

New chromosomal breakpoints in non-Hodgkin's lymphomas revealed by spectral karyotyping and G-banding.

Chromosomal rearrangements in short term cultures from nine cases of non-Hodgkin's lymphomas (NHL) were characterized by G-banding, spectral karyotyping (SKY), and fluorescence in situ hybridization (FISH). Eight of the nine cases showed complex karyotypes with chromosomal aberrations which, in most cases, could not be fully characterized by traditional G-banding analysis alone. Karyotypic abnormalities of special interest were marker chromosomes and chromosomes with added unidentified chromosomal material, as previously non-identified chromosomal translocations were hidden behind these aberrations. SKY and FISH analysis, as a complement to banding analysis, significantly improved the karyotypes in seven of the nine cases and unveiled 21 previously unidentified rearrangements with novel translocation breakpoints. Traditional G-banding alone revealed seven new rearrangements, which were all confirmed by SKY. None of these new aberrations occurred as single clonal rearrangements but as parts of complex karyotypes. Nevertheless, the chromosomal break-point regions identified should be considered as potential hot spots for genes involved in the tumorigenesis of the malignancy.

Adult↗
PubMed1993

Sublocalization of the synovial sarcoma-associated t(X;18) chromosomal breakpoint in Xp11.2 using cosmid cloning and fluorescence in situ hybridization.

In a previous study we localized the synovial sarcoma-associated t(X;18)(p11;q11) breakpoint within the ornithine aminotransferase-like 1 (OATL1) cluster on the X chromosome. This localization was delineated from both somatic cell hybrid and fluorescence in situ hybridization (FISH) analysis of patient material, using OAT-specific cDNA and YAC probes. Simultaneously, Knight et al. (1992, Mol. Hum. Genet, in press) mapped this same breakpoint in their patient material adjacent to the more proximal OATL2 region on the X chromosome. Here we report the analysis of two additional tumors and demonstrate that again in these cases the chromosomal break occurs within the OATL1 cluster. In order to further specify the breakpoint, we subcloned the OATL1 YAC (no. 2) into cosmids. At least one of these cosmids (0.38) hybridizes to sequences that bracket the translocation breakpoint, as demonstrated by both Southern blot and FISH analysis. These observations confirm and substantiate our previous findings. In addition, cosmid 0.38 should be a valuable instrument for the ultimate isolation and identification of the gene(s) involved in the development of synovial sarcoma.

Animals↗
PubMed1984

Fragile sites and chromosome breakpoints in constitutional rearrangements II. Spontaneous abortions, stillbirths and newborns.

Certain fragile sites may possibly predispose to chromosome breakage and rearrangements in meiosis. To test this hypothesis, we examined 894 breakpoints found in spontaneous abortions, stillbirths and livebirths of which 165 (18.5%) were in bands with fragile sites. Compared to an expectation of 98 (11%), there was a significant excess of breakpoints in fragile site bands (P less than 0.001). Together with data from amniocenteses, there is now evidence suggesting that certain fragile sites may be prone to fragility in meiosis.

Abortion, Spontaneous↗
PubMed1999

Rapid isolation of chromosomal breakpoints from patients with t(4;11) acute lymphoblastic leukemia: implications for basic and clinical research.

Chromosomal translocations t(4;11)(q21;q23) are associated with a group of acute lymphoblastic leukemias with very poor prognosis. From the complete sequences of the breakpoint cluster regions of the human MLL and AF-4 translocation partner genes, a novel set of 66 oligonucleotides that facilitates the rapid identification of translocation breakpoints by PCR analysis of genomic DNA was designed. For each breakpoint, a pair of optimally snited primers can be assigned, which improves the monitoring of the disease during treatment. Comparison of the breakpoints with the corresponding parental sequences also contributes to our better understanding of the illegitimate recombination events leading to these translocations.

Alu Elements↗
PubMed2000

Detailed comparative gene map of rat chromosome 1 with mouse and human genomes and physical mapping of an evolutionary chromosomal breakpoint.

We report the localization of 92 new gene-based markers assigned to rat chromosome 1 by linkage or radiation hybrid mapping. The markers were chosen to enrich gene mapping data in a region of the rat chromosome known to contain several of the principal quantitative trait loci in rodent models of human multifactorial disease. The composite map reported here provides map information on a total of 139 known genes, including 80 that have been localized in mouse and 109 that have been localized in human, and integrates the gene-based markers with anonymous microsatellites. The evolutionary breakpoints identifying 16 segments that are homologous regions in the human genome are defined. These data will facilitate genetic and comparative mapping studies and identification of novel candidate genes for the quantitative trait loci that have been localized to the region.

Animals↗
PubMed1992

Localization of 11q13 loci with respect to regional chromosomal breakpoints.

We have employed two strategies to map 13 markers located at 11q13. First, we used pulsed-field gel electrophoresis of DNA fragments obtained with methylation-sensitive restriction enzymes. The markers used in this study were scattered over 8.4 Mb and, for most of them, could not be linked one to another. A second mapping strategy employed hybridization to either DNA of somatic hybrids containing various parts of the long arm of chromosome 11 or metaphase chromosomes of a B-cell line containing the t(11;14)(q13;q32) translocation. We were able to sort out the centromeric from the telomeric probes with respect to translocation breakpoints taken as reference chromosomal landmarks by this approach. BCL1, which corresponds to the region where the t(11;14)(q13;q32) translocation breakpoints are clustered, appears as a boundary between two areas of human/mouse homology present in conserved syntenic regions on mouse chromosomes 7 and 19.

Animals↗
PubMed1992

Characterization of a 1.0 Mb YAC contig spanning two chromosome breakpoints related to Menkes disease.

Menkes disease, an X-linked recessive disorder of copper metabolism, has recently been mapped to Xq13.3 by two Menkes patients carrying chromosome rearrangements within this region. The breakpoints have been investigated by nonisotopic in situ suppression hybridization using YACs isolated from this region with the flanking markers DXS56 and PGK1. Three YACs were extending over the breakpoints at Xq13.3 and were shown to be overlapping by partial digest restriction maps, IRS-PCR fingerprinting and by the presence of common cosmid clones. These cosmids were subcloned and one of the single copy probes detected both breakpoints using rare-cutting restriction enzyme digests of the patients. All the results together localize the breakpoints to about 100 kb within the overlapping region of the YACs. Mapping of both breakpoints in a 1 Mb YAC contig implies that these YACs contain at least partially, the gene responsible for Menkes disease.

Chromosome Aberrations↗