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SNP array of AML and MDS specimens with dic(20;22)

ABSTRACT: This study describes a recurrent dicentric chromosome formed by telomere fusion between chromosome 20 and chromosome 22 in myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML). This is the first description of a recurrent telomere fusion event in myeloid malignancy. The derivative chromosome is further characterised by the presence of nucleolus organiser region material from the chromosome 22 short arm, loss of the putative tumour suppressor gene at 20q12 and secondary rearrangements including gain or amplification of 20q material adjacent to the deletion encompassing 20q12. The presence of residual telomere sequence at the site of translocation in three of the four cases is compelling support for telomere fusion, and supports previous evidence that over half of dicentric chromosomes involving 20q are produced by telomere fusion events. We propose that the sequence of events producing this chromosome abnormality is initial formation of an unstable dicentric chromosome by 20q and 22p telomere fusion, followed by breakage-fusion-bridge cycles causing 20q12 deletion and 20q11.2 gain which provide a growth advantage to the cell. Selection of these clones contributes to leukaemogenesis. Finding recurrent patterns in the complex genome reorganisation events which characterise poor prognosis, complex karyotype AML and MDS will help us understand the mechanisms and oncogenic driver mutations in these poorly understood malignancies.

ORGANISM(S): Homo sapiens

PROVIDER: GSE64050 | GEO | 2016/06/30

SECONDARY ACCESSION(S): PRJNA269963

REPOSITORIES: GEO

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SNP array of AML and MDS specimens with dic(20;22)

Project description:This study describes a recurrent dicentric chromosome formed by telomere fusion between chromosome 20 and chromosome 22 in myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML). This is the first description of a recurrent telomere fusion event in myeloid malignancy. The derivative chromosome is further characterised by the presence of nucleolus organiser region material from the chromosome 22 short arm, loss of the putative tumour suppressor gene at 20q12 and secondary rearrangements including gain or amplification of 20q material adjacent to the deletion encompassing 20q12. The presence of residual telomere sequence at the site of translocation in three of the four cases is compelling support for telomere fusion, and supports previous evidence that over half of dicentric chromosomes involving 20q are produced by telomere fusion events. We propose that the sequence of events producing this chromosome abnormality is initial formation of an unstable dicentric chromosome by 20q and 22p telomere fusion, followed by breakage-fusion-bridge cycles causing 20q12 deletion and 20q11.2 gain which provide a growth advantage to the cell. Selection of these clones contributes to leukaemogenesis. Finding recurrent patterns in the complex genome reorganisation events which characterise poor prognosis, complex karyotype AML and MDS will help us understand the mechanisms and oncogenic driver mutations in these poorly understood malignancies. The sample consists of leukaemia specimens from three different cases of AML and MDS. The consistent feature was the presence of a dicentric chromosome formed from chromosomes 20 and 22.

2016-06-30 | E-GEOD-64050 | biostudies-arrayexpress

Multiplex Enhanced Reduced Representation Bisulfite Sequencing (mERRBS) Analysis of dic(1;7)(q10;p10) in Myelodysplastic Syndromes (MDS) compared to control cohort and therapy-related Myeloid Neoplasms (t-MN)

Project description:The unbalanced translocation t(1;7)(q10;p10), generating 1q trisomy and 7q monosomy, is due to centromere-centromere juxtaposition. This dicentric chromosome is a recurrent change in myelodysplastic syndromes (MDS), with half the cases arising after chemo/radio-therapy. To date, given the absence of genes within the centromeric regions, no specific molecular events have been identified in this cytogenetic subgroup. We first identified a comprehensive genetic and epigenetic landscape of MDS with dic(1;7)(q10;p10) and compared it to normal controls and other therapy-related Myeloid Neoplasms (t-MNs). RNA-seq showed a unique downregulated signature in dic(1;7) cases, affecting more than 80% of differentially expressed genes. As revealed by pathway and gene ontology analyses, downregulation of ATP-binding cassette (ABC) transporters and of genes related to lipid metabolism, and upregulation of p53 signaling were the most relevant biological features of dicentric-positive MDS. Despite 1q trisomy, more than 50% of 1q deregulated genes were downregulated. This partial gene dosage effect was clarified by epigenetic analysis, which highlighted the presence of a specific hypermethylated pattern on 1q. Furthermore, in a supervised analysis, hypermethylation in all dicentrics clustered at intronic enhancers and was enriched for Krüppel-like transcription factors binding sites. Low expression levels of enhancer putative target genes accounted for more than 30% of the downregulated signature. Our findings demonstrate that alteration of centromeric DNA in dic(1;7) cases imposes a specific transcriptional program, driven by a unique epigenomic signature.

2019-09-01 | GSE118475 | GEO

Affymetrix SNP array data for dic(1;7)(q10;p10) in Myelodysplastic Syndromes (MDS)

2019-09-01 | GSE118477 | GEO

Expression Analysis of dic(1;7)(q10;p10) in Myelodysplastic Syndromes (MDS) compared to control cohort and therapy-related Myeloid Neoplasms (t-MN)

2019-09-01 | GSE118476 | GEO

Functional centromere lost centromeric specific sequences but gain new sequences from nearby chromosomal arm.

Project description:We identified a newly formed dicentric chromosome (sDic-15) in maize from intrachromosomal recombination and BFB cycles, in which only one centromere is active. The centromeres lost CentC sequences and dramatic reduced the CRM sequences, but when the molecular features of functional centromeres such as CENH3 was examined, they were present. Immunolocalization analysis of phosphorylation of H3T3, H3ser-10 and H2A levels on this new centromere shows a pattern typical of a functional centromere. Meiotic analysis revealed that this dicentric chromosome is table and transmit very well. To examine the new sequences associated with CENH3 in this centromere, chromatin immunoprecipitation (ChIP) was carried out with anti-CENH3 antibodies and material from young seedlings with or without dicentric chromosome. We mapped the ChIP-Seq reads to the reference genome and found a 723kb region from the short arm of maize chromosome 9 involve the new centromere formation. This region is gene-poor and full of TEs, but genes in this region are transcribed. The original 723kb region shows a high DNA methylation level as native centromeres but had no significant change when it involved into new centromere formation. The reactivation of this newly formed centromere indicated that centromere reactivation may not dependent on the relatively intact DNA sequences or topology of original inactive centromere. ChIP-seq was carried out with anti-CENH3 antibodies using material from young seedlings with and without sDic-15 chromosome. For sDic-15, some ChIPed DNA was treated with sodium bisulfite and prepared for Illumina sequencing to test its methylation level.

2013-06-25 | E-GEOD-43140 | biostudies-arrayexpress

The Architecture and Evolution of Cancer Neochromosomes

Project description:We isolated and analyzed, at single-nucleotide resolution, cancer-associated neochromosomes from well- and/or dedifferentiated liposarcomas. Neochromosomes, which can exceed 600 Mb in size, initially arise as circular structures following chromothripsis involving chromosome 12. The core of the neochromosome is amplified, rearranged, and corroded through hundreds of breakage-fusion-bridge cycles. Under selective pressure, amplified oncogenes are overexpressed, while coamplified passenger genes may be silenced epigenetically. New material may be captured during punctuated chromothriptic events. Centromeric corro- sion leads to crisis, which is resolved through neocentromere formation or native centromere capture. Finally, amplification terminates, and the neochromosome core is stabilized in linear form by telomere capture. This study investigates the dynamic mutational processes underlying the life history of a special form of cancer mutation.

2015-01-13 | E-MTAB-3235 | biostudies-arrayexpress

Telomere dysfunction and fusion during the progression of chronic lymphocytic leukaemia: evidence for a telomere crisis

Project description:We performed single-molecule telomere length and telomere fusion analysis in patients at different stages of chronic lymphocytic leukaemia (CLL). Our work identified the shortest telomeres ever recorded in primary human tissue reinforcing the concept that there is significant cell division in CLL. Furthermore, we provide direct evidence that critical telomere shortening, dysfunction and fusion contribute to disease progression. The frequency of short telomeres and fusion events increased with advanced disease, but importantly these were also found in a subset of early-stage patient samples indicating that these events can precede disease progression. Sequence analysis of fusion events isolated from individuals with the shortest telomeres revealed limited numbers of repeats at the breakpoint, sub-telomeric deletion and microhomology. Array-CGH analysis of individuals displaying evidence of telomere dysfunction revealed large-scale genomic rearrangements that were concentrated in the telomeric regions; this was not observed in samples with longer telomeres. Array CGH was undertaken on six individuals (five CLL stage C and one stage A) that displayed evidence of telomere dysfunction, and four (three CLL stage A and one stage B) that displayed longer and apparently stable telomeres.

2010-05-28 | E-GEOD-22016 | biostudies-arrayexpress

Functional centromere lost centromeric specific sequences but gain new sequences from nearby chromosomal arm.

2013-06-25 | GSE43140 | GEO

Telomeric Abnormalities in Colorectal Diseases by Fluorescent in Situ Hybridization Technique

Project description:Colorectal carcinoma is a heterogeneous disease that is caused by the interaction of genetic and environmental factors. colorectal carcinoma encompasses a complex disease with different molecular pathways and biological characteristics arising from a multi-step process that implicates several genetic and epigenetic events . The multi-step genetic model involves the loss of function of tumor suppressor genes, such as adenomatous polyposis coli (APC), Telomeres could be a promising marker due to the fact that their lengths change in the colorectal polyp-carcinoma sequence . Moreover, telomere length (TL) is altered in blood cells in patients with colorectal carcinoma * These findings could suggest that changes in TL may take place before the development of the tumor . The two main forms of inflammatory bowel disease (IBD), ulcerative colitis (UC) and Crohn’s disease (CD) are characterized by chronic intestinal inflammation and risk of progression to colon cancer. One proposed cause of the latter characteristic is chromosome instability, since the rearrangement of genetic material can lead to activation of oncogenes, loss of tumor suppressor genes and other changes that lead to uncontrolled cell growth. Chromosome instability is particularly associated with UC and has been observed in colon epithelial cells and peripheral blood mononuclear cell. Since genomic instability in peripheral blood mononuclear cells (PBMCs) has been used as a biomarker for global cancer risk in a number of diseases, the latter observation suggests the possibility of a chromosome instability syndrome in UC that could affect all tissues. One possible cause of chromosome instability is telomere dysfunction .

| 2248650 | ecrin-mdr-crc

Large inverted duplications form via a hairpin mechanism

Project description:Inverted duplications are a common type of copy number variation (CNV) in germline and somatic genomes. Large duplications that include many genes can lead to both neurodevelopmental phenotypes in children and gene amplifications in tumors. There are several models for inverted duplication formation, most of which include a dicentric chromosome intermediate followed by breakage-fusion-bridge (BFB) cycles, but the mechanisms that give rise to the inverted dicentric chromosome in most inverted duplications remain unknown. Here we have combined high-resolution array CGH, custom sequence capture, next-generation sequencing, and long-range PCR to analyze the breakpoints of 50 nonrecurrent inverted duplications in patients with intellectual disability, autism, and congenital anomalies. Sequence analysis of breakpoint junctions reveals a normal-copy disomic spacer between inverted and non-inverted copies of the duplication. Further, short inverted repeats are present at the boundary of the disomic spacer and the inverted duplication. These data support a mechanism of inverted duplication formation whereby a chromosome with a double-strand break intrastrand pairs with itself to form a “hairpin” intermediate that, after DNA replication, produces a dicentric inverted chromosome with a disomic spacer corresponding to the site of the hairpin. We also find evidence of short insertions and inversions at inverted duplication junctions, consistent with a DNA replication-based CNV mechanism. This process can give rise to inverted duplications adjacent to terminal deletions, inverted duplications juxtaposed to translocations, and inverted duplication ring chromosomes High resolution array CGH; two-color experiment, clinical patient vs. normal control gDNA; sex mis-matched

2013-04-03 | E-GEOD-45395 | biostudies-arrayexpress

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