51
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Kato T, Kurahashi H, Emanuel BS. Chromosomal translocations and palindromic AT-rich repeats. Curr Opin Genet Dev 2012; 22:221-8. [PMID: 22402448 DOI: 10.1016/j.gde.2012.02.004] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 02/03/2012] [Accepted: 02/06/2012] [Indexed: 10/28/2022]
Abstract
Repetitive DNA sequences constitute 30% of the human genome, and are often sites of genomic rearrangement. Recently, it has been found that several constitutional translocations, especially those that involve chromosome 22, take place utilizing palindromic sequences on 22q11 and on the partner chromosome. Analysis of translocation junction fragments shows that the breakpoints of such palindrome-mediated translocations are localized at the center of palindromic AT-rich repeats (PATRRs). The presence of PATRRs at the breakpoints indicates a palindrome-mediated mechanism involved in the generation of these constitutional translocations. Identification of these PATRR-mediated translocations suggests a universal pathway for gross chromosomal rearrangement in the human genome. De novo occurrences of PATRR-mediated translocations can be detected by PCR in normal sperm samples but not somatic cells. Polymorphisms of various PATRRs influence their propensity for adopting a secondary structure, which in turn affects de novo translocation frequency. We propose that the PATRRs form an unstable secondary structure, which leads to double-strand breaks at the center of the PATRR. The double-strand breaks appear to be followed by a non-homologous end-joining repair pathway, ultimately leading to the translocations. This review considers recent findings concerning the mechanism of meiosis-specific, PATRR-mediated translocations.
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Affiliation(s)
- Takema Kato
- Division of Human Genetics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
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52
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Chiang C, Jacobsen JC, Ernst C, Hanscom C, Heilbut A, Blumenthal I, Mills RE, Kirby A, Lindgren AM, Rudiger SR, McLaughlan CJ, Bawden CS, Reid SJ, Faull RLM, Snell RG, Hall IM, Shen Y, Ohsumi TK, Borowsky ML, Daly MJ, Lee C, Morton CC, MacDonald ME, Gusella JF, Talkowski ME. Complex reorganization and predominant non-homologous repair following chromosomal breakage in karyotypically balanced germline rearrangements and transgenic integration. Nat Genet 2012; 44:390-7, S1. [PMID: 22388000 PMCID: PMC3340016 DOI: 10.1038/ng.2202] [Citation(s) in RCA: 187] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 01/17/2012] [Indexed: 12/17/2022]
Abstract
We defined the genetic landscape of balanced chromosomal rearrangements at nucleotide resolution by sequencing 141 breakpoints from cytogenetically-interpreted translocations and inversions. We confirm that the recently described phenomenon of “chromothripsis” (massive chromosomal shattering and reorganization) is not unique to cancer cells but also occurs in the germline where it can resolve to a karyotypically balanced state with frequent inversions. We detected a high incidence of complex rearrangements (19.2%) and substantially less reliance on microhomology (31%) than previously observed in benign CNVs. We compared these results to experimentally-generated DNA breakage-repair by sequencing seven transgenic animals, and revealed extensive rearrangement of the transgene and host genome with similar complexity to human germline alterations. Inversion is the most common rearrangement, suggesting that a combined mechanism involving template switching and non-homologous repair mediates the formation of balanced complex rearrangements that are viable, stably replicated and transmitted unaltered to subsequent generations.
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Affiliation(s)
- Colby Chiang
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, USA
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53
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Hermetz KE, Surti U, Cody JD, Rudd MK. A recurrent translocation is mediated by homologous recombination between HERV-H elements. Mol Cytogenet 2012; 5:6. [PMID: 22260357 PMCID: PMC3292815 DOI: 10.1186/1755-8166-5-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Accepted: 01/19/2012] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Chromosome rearrangements are caused by many mutational mechanisms; of these, recurrent rearrangements can be particularly informative for teasing apart DNA sequence-specific factors. Some recurrent translocations are mediated by homologous recombination between large blocks of segmental duplications on different chromosomes. Here we describe a recurrent unbalanced translocation casued by recombination between shorter homologous regions on chromosomes 4 and 18 in two unrelated children with intellectual disability. RESULTS Array CGH resolved the breakpoints of the 6.97-Megabase (Mb) loss of 18q and the 7.30-Mb gain of 4q. Sequencing across the translocation breakpoints revealed that both translocations occurred between 92%-identical human endogenous retrovirus (HERV) elements in the same orientation on chromosomes 4 and 18. In addition, we find sequence variation in the chromosome 4 HERV that makes one allele more like the chromosome 18 HERV. CONCLUSIONS Homologous recombination between HERVs on the same chromosome is known to cause chromosome deletions, but this is the first report of interchromosomal HERV-HERV recombination leading to a translocation. It is possible that normal sequence variation in substrates of non-allelic homologous recombination (NAHR) affects the alignment of recombining segments and influences the propensity to chromosome rearrangement.
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Affiliation(s)
- Karen E Hermetz
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA.
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54
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Characterising chromosome rearrangements: recent technical advances in molecular cytogenetics. Heredity (Edinb) 2011; 108:75-85. [PMID: 22086080 PMCID: PMC3238113 DOI: 10.1038/hdy.2011.100] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Genomic rearrangements can result in losses, amplifications, translocations and inversions of DNA fragments thereby modifying genome architecture, and potentially having clinical consequences. Many genomic disorders caused by structural variation have initially been uncovered by early cytogenetic methods. The last decade has seen significant progression in molecular cytogenetic techniques, allowing rapid and precise detection of structural rearrangements on a whole-genome scale. The high resolution attainable with these recently developed techniques has also uncovered the role of structural variants in normal genetic variation alongside single-nucleotide polymorphisms (SNPs). We describe how array-based comparative genomic hybridisation, SNP arrays, array painting and next-generation sequencing analytical methods (read depth, read pair and split read) allow the extensive characterisation of chromosome rearrangements in human genomes.
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55
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Yoshimoto M, Ludkovski O, DeGrace D, Williams JL, Evans A, Sircar K, Bismar TA, Nuin P, Squire JA. PTEN genomic deletions that characterize aggressive prostate cancer originate close to segmental duplications. Genes Chromosomes Cancer 2011; 51:149-60. [DOI: 10.1002/gcc.20939] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 09/19/2011] [Indexed: 12/30/2022] Open
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56
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Carr AM, Paek AL, Weinert T. DNA replication: failures and inverted fusions. Semin Cell Dev Biol 2011; 22:866-74. [PMID: 22020070 DOI: 10.1016/j.semcdb.2011.10.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 10/12/2011] [Indexed: 11/16/2022]
Abstract
DNA replication normally follows the rules passed down from Watson and Crick: the chromosome duplicates as dictated by its antiparallel strands, base-pairing and leading and lagging strand differences. Real-life replication is more complicated, fraught with perils posed by chromosome damage for one, and by transcription of genes and by other perils that disrupt progress of the DNA replication machinery. Understanding the replication fork, including DNA structures, associated replisome and its regulators, is key to understanding how cells overcome perils and minimize error. Replication fork error leads to genome rearrangements and, potentially, cell death. Interest in the replication fork and its errors has recently gained added interest by the results of deep sequencing studies of human genomes. Several pathologies are associated with sometimes-bizarre genome rearrangements suggestive of elaborate replication fork failures. To try and understand the links between the replication fork, its failure and genome rearrangements, we discuss here phases of fork behavior (stall, collapse, restart and fork failures leading to rearrangements) and analyze two examples of instability from our own studies; one in fission yeast and the other in budding yeast.
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Affiliation(s)
- Antony M Carr
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, Sussex, UK.
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57
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Cooper DN, Bacolla A, Férec C, Vasquez KM, Kehrer-Sawatzki H, Chen JM. On the sequence-directed nature of human gene mutation: the role of genomic architecture and the local DNA sequence environment in mediating gene mutations underlying human inherited disease. Hum Mutat 2011; 32:1075-99. [PMID: 21853507 PMCID: PMC3177966 DOI: 10.1002/humu.21557] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2011] [Accepted: 06/17/2011] [Indexed: 12/21/2022]
Abstract
Different types of human gene mutation may vary in size, from structural variants (SVs) to single base-pair substitutions, but what they all have in common is that their nature, size and location are often determined either by specific characteristics of the local DNA sequence environment or by higher order features of the genomic architecture. The human genome is now recognized to contain "pervasive architectural flaws" in that certain DNA sequences are inherently mutation prone by virtue of their base composition, sequence repetitivity and/or epigenetic modification. Here, we explore how the nature, location and frequency of different types of mutation causing inherited disease are shaped in large part, and often in remarkably predictable ways, by the local DNA sequence environment. The mutability of a given gene or genomic region may also be influenced indirectly by a variety of noncanonical (non-B) secondary structures whose formation is facilitated by the underlying DNA sequence. Since these non-B DNA structures can interfere with subsequent DNA replication and repair and may serve to increase mutation frequencies in generalized fashion (i.e., both in the context of subtle mutations and SVs), they have the potential to serve as a unifying concept in studies of mutational mechanisms underlying human inherited disease.
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Affiliation(s)
- David N Cooper
- Institute of Medical Genetics, School of Medicine, Cardiff University, Cardiff, United Kingdom.
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58
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Sobreira NLM, Gnanakkan V, Walsh M, Marosy B, Wohler E, Thomas G, Hoover-Fong JE, Hamosh A, Wheelan SJ, Valle D. Characterization of complex chromosomal rearrangements by targeted capture and next-generation sequencing. Genome Res 2011; 21:1720-7. [PMID: 21890680 DOI: 10.1101/gr.122986.111] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Translocations are a common class of chromosomal aberrations and can cause disease by physically disrupting genes or altering their regulatory environment. Some translocations, apparently balanced at the microscopic level, include deletions, duplications, insertions, or inversions at the molecular level. Traditionally, chromosomal rearrangements have been investigated with a conventional banded karyotype followed by arduous positional cloning projects. More recently, molecular cytogenetic approaches using fluorescence in situ hybridization (FISH), array comparative genomic hybridization (aCGH), or whole-genome SNP genotyping together with molecular methods such as inverse PCR and quantitative PCR have allowed more precise evaluation of the breakpoints. These methods suffer, however, from being experimentally intensive and time-consuming and of less than single base pair resolution. Here we describe targeted breakpoint capture followed by next-generation sequencing (TBCS) as a new approach to the general problem of determining the precise structural characterization of translocation breakpoints and related chromosomal aberrations. We tested this approach in three patients with complex chromosomal translocations: The first had craniofacial abnormalities and an apparently balanced t(2;3)(p15;q12) translocation; the second has cleidocranial dysplasia (OMIM 119600) associated with a t(2;6)(q22;p12.3) translocation and a breakpoint in RUNX2 on chromosome 6p; and the third has acampomelic campomelic dysplasia (OMIM 114290) associated with a t(5;17)(q23.2;q24) translocation, with a breakpoint upstream of SOX9 on chromosome 17q. Preliminary studies indicated complex rearrangements in patients 1 and 3 with a total of 10 predicted breakpoints in the three patients. By using TBCS, we quickly and precisely defined eight of the 10 breakpoints.
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Affiliation(s)
- Nara L M Sobreira
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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59
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Khan WA, Knoll JHM, Rogan PK. Context-based FISH localization of genomic rearrangements within chromosome 15q11.2q13 duplicons. Mol Cytogenet 2011; 4:15. [PMID: 21824424 PMCID: PMC3171312 DOI: 10.1186/1755-8166-4-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 08/08/2011] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Segmental duplicons (SDs) predispose to an increased frequency of chromosomal rearrangements. These rearrangements can cause a diverse range of phenotypes due to haploinsufficiency, in cis positional effects or gene interruption. Genomic microarray analysis has revealed gene dosage changes adjacent to duplicons, but the high degree of similarity between duplicon sequences has confounded unequivocal assignment of chromosome breakpoints within these intervals. In this study, we localize rearrangements within duplicon-enriched regions of Angelman/Prader-Willi (AS/PWS) syndrome chromosomal deletions with fluorescence in situ hybridization (FISH). RESULTS Breakage intervals in AS deletions were localized recursively with short, coordinate-defined, single copy (SC) and low copy (LC) genomic FISH probes. These probes were initially coincident with duplicons and regions of previously reported breakage in AS/PWS. Subsequently, probes developed from adjacent genomic intervals more precisely delineated deletion breakage intervals involving genes, pseudogenes and duplicons in 15q11.2q13. The observed variability in the deletion boundaries within previously described Class I and Class II deletion AS samples is related to the local genomic architecture in this chromosomal region. CONCLUSIONS Chromosome 15 abnormalities associated with SDs were precisely delineated at a resolution equivalent to genomic Southern analysis. This context-dependent approach can define the boundaries of chromosome rearrangements for other genomic disorders associated with SDs.
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Affiliation(s)
- Wahab A Khan
- Department of Biochemistry, University of Western Ontario, Laboratories of Genome Bioinformatics and Genomic Disorders, 1151 Richmond Street, London, ON, Canada
- Department of Pathology, University of Western Ontario, Laboratories of Genome Bioinformatics and Genomic Disorders, 1151 Richmond Street, London, ON, Canada
| | - Joan HM Knoll
- Department of Pathology, University of Western Ontario, Laboratories of Genome Bioinformatics and Genomic Disorders, 1151 Richmond Street, London, ON, Canada
| | - Peter K Rogan
- Department of Biochemistry, University of Western Ontario, Laboratories of Genome Bioinformatics and Genomic Disorders, 1151 Richmond Street, London, ON, Canada
- Department of Computer Science, University of Western Ontario, Laboratories of Genome Bioinformatics and Genomic Disorders, 1151 Richmond Street, London, ON, Canada
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60
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Luo Y, Hermetz KE, Jackson JM, Mulle JG, Dodd A, Tsuchiya KD, Ballif BC, Shaffer LG, Cody JD, Ledbetter DH, Martin CL, Rudd MK. Diverse mutational mechanisms cause pathogenic subtelomeric rearrangements. Hum Mol Genet 2011; 20:3769-78. [PMID: 21729882 DOI: 10.1093/hmg/ddr293] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Chromosome rearrangements are a significant cause of intellectual disability and birth defects. Subtelomeric rearrangements, including deletions, duplications and translocations of chromosome ends, were first discovered over 40 years ago and are now recognized as being responsible for several genetic syndromes. Unlike the deletions and duplications that cause some genomic disorders, subtelomeric rearrangements do not typically have recurrent breakpoints and involve many different chromosome ends. To capture the molecular mechanisms responsible for this heterogeneous class of chromosome abnormality, we coupled high-resolution array CGH with breakpoint junction sequencing of a diverse collection of subtelomeric rearrangements. We analyzed 102 breakpoints corresponding to 78 rearrangements involving 28 chromosome ends. Sequencing 21 breakpoint junctions revealed signatures of non-homologous end-joining, non-allelic homologous recombination between interspersed repeats and DNA replication processes. Thus, subtelomeric rearrangements arise from diverse mutational mechanisms. In addition, we find hotspots of subtelomeric breakage at the end of chromosomes 9q and 22q; these sites may correspond to genomic regions that are particularly susceptible to double-strand breaks. Finally, fine-mapping the smallest subtelomeric rearrangements has narrowed the critical regions for some chromosomal disorders.
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Affiliation(s)
- Yue Luo
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Atlanta, GA 30322, USA
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