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Thakur J, Packiaraj J, Henikoff S. Sequence, Chromatin and Evolution of Satellite DNA. Int J Mol Sci 2021; 22:ijms22094309. [PMID: 33919233 PMCID: PMC8122249 DOI: 10.3390/ijms22094309] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/16/2021] [Accepted: 04/17/2021] [Indexed: 12/15/2022] Open
Abstract
Satellite DNA consists of abundant tandem repeats that play important roles in cellular processes, including chromosome segregation, genome organization and chromosome end protection. Most satellite DNA repeat units are either of nucleosomal length or 5–10 bp long and occupy centromeric, pericentromeric or telomeric regions. Due to high repetitiveness, satellite DNA sequences have largely been absent from genome assemblies. Although few conserved satellite-specific sequence motifs have been identified, DNA curvature, dyad symmetries and inverted repeats are features of various satellite DNAs in several organisms. Satellite DNA sequences are either embedded in highly compact gene-poor heterochromatin or specialized chromatin that is distinct from euchromatin. Nevertheless, some satellite DNAs are transcribed into non-coding RNAs that may play important roles in satellite DNA function. Intriguingly, satellite DNAs are among the most rapidly evolving genomic elements, such that a large fraction is species-specific in most organisms. Here we describe the different classes of satellite DNA sequences, their satellite-specific chromatin features, and how these features may contribute to satellite DNA biology and evolution. We also discuss how the evolution of functional satellite DNA classes may contribute to speciation in plants and animals.
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Affiliation(s)
- Jitendra Thakur
- Department of Biology, Emory University, Atlanta, GA 30322, USA;
- Correspondence:
| | - Jenika Packiaraj
- Department of Biology, Emory University, Atlanta, GA 30322, USA;
| | - Steven Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA;
- Fred Hutchinson Cancer Research Center, Howard Hughes Medical Institute, Seattle, WA 98109, USA
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2
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Kwapisz M, Morillon A. Subtelomeric Transcription and its Regulation. J Mol Biol 2020; 432:4199-4219. [PMID: 32035903 PMCID: PMC7374410 DOI: 10.1016/j.jmb.2020.01.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 01/14/2020] [Accepted: 01/14/2020] [Indexed: 12/13/2022]
Abstract
The subtelomeres, highly heterogeneous repeated sequences neighboring telomeres, are transcribed into coding and noncoding RNAs in a variety of organisms. Telomereproximal subtelomeric regions produce non-coding transcripts i.e., ARRET, αARRET, subTERRA, and TERRA, which function in telomere maintenance. The role and molecular mechanisms of the majority of subtelomeric transcripts remain unknown. This review depicts the current knowledge and puts into perspective the results obtained in different models from yeasts to humans.
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Affiliation(s)
- Marta Kwapisz
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, France
| | - Antonin Morillon
- ncRNA, Epigenetic and Genome Fluidity, CNRS UMR 3244, Sorbonne Université, PSL University, Institut Curie, Centre de Recherche, 26 rue d'Ulm, 75248, Paris, France.
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Li Z, Shang X, Luo S, Zhu F, Wei X, Zhou W, Ye Y, Yan T, Cai R, Xu X. Characterization of two novel Alu element-mediated α-globin gene cluster deletions causing α 0-thalassemia by targeted next-generation sequencing. Mol Genet Genomics 2020; 295:505-514. [PMID: 31897801 DOI: 10.1007/s00438-019-01637-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 12/06/2019] [Indexed: 10/25/2022]
Abstract
α-thalassemia is an inherited blood disorder commonly caused by deletions or point mutations involving one or both α-globin genes. Recent studies shed new light on the critical role of upstream enhancers multi-species conserved sequences (MCSs) in the ordered regulation of α-globin gene expression. Herein, we reported two unrelated probands with deletions in α-globin genes and MCSs, respectively. The proband from Family A is a compound heterozygote carrying a known α+ mutation (-α3.7) and a novel 60.2 kb deletion causing the absence of both α-globin genes. The proband from Family B, on the other hand, is a compound heterozygote with a known α0 mutation (--SEA) and a novel deletion involving only upstream regulatory elements MCS-R1, R2 and R3, while the α-globin genes remain intact. Notably, both these two patients suffered varied extent of anemia, indicating that the loss of enhancer elements could equally lead to reduced synthesis of α-globin. Upon these observations, we then confirmed the exact breakpoints of these two novel deletions using a targeted next-generation sequencing (NGS) previously established by our group, which may enable further elucidation of the rearrangement mechanisms on these deletions and functional dissection of MCSs. Taken together, our study reports a reliable NGS-based molecular screening approach for accurate identification of copy number variations (CNVs) in the α-globin cluster and the genetic diagnosis of these two probands may help to extend the spectrum of α-thalassemia mutations in Chinese population.
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Affiliation(s)
- Zhiming Li
- Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Xuan Shang
- Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, Guangdong, China.,Guangdong Genetics Testing Engineering Research Center, Guangzhou, 510515, Guangdong, China
| | - Shiqiang Luo
- Department of Medical Genetics, Liuzhou Municipal Maternity and Child Healthcare Hospital, Liuzhou, 545001, Guangxi, China
| | - Fei Zhu
- Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Xiaofeng Wei
- Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, Guangdong, China.,Guangdong Genetics Testing Engineering Research Center, Guangzhou, 510515, Guangdong, China
| | - Wanjun Zhou
- Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, Guangdong, China.,Guangdong Genetics Testing Engineering Research Center, Guangzhou, 510515, Guangdong, China
| | - Yuhua Ye
- Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, Guangdong, China.,Guangdong Genetics Testing Engineering Research Center, Guangzhou, 510515, Guangdong, China
| | - Tizhen Yan
- Department of Medical Genetics, Liuzhou Municipal Maternity and Child Healthcare Hospital, Liuzhou, 545001, Guangxi, China
| | - Ren Cai
- Department of Medical Genetics, Liuzhou Municipal Maternity and Child Healthcare Hospital, Liuzhou, 545001, Guangxi, China
| | - Xiangmin Xu
- Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, Guangdong, China. .,Guangdong Genetics Testing Engineering Research Center, Guangzhou, 510515, Guangdong, China.
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Van Wyk S, Wingfield BD, De Vos L, Santana QC, Van der Merwe NA, Steenkamp ET. Multiple independent origins for a subtelomeric locus associated with growth rate in Fusarium circinatum. IMA Fungus 2018; 9:27-36. [PMID: 30018870 PMCID: PMC6048564 DOI: 10.5598/imafungus.2018.09.01.03] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 02/19/2018] [Indexed: 12/28/2022] Open
Abstract
Fusarium is a diverse assemblage that includes a large number of species of considerable medical and agricultural importance. Not surprisingly, whole genome sequences for many Fusarium species have been published or are in the process of being determined, the availability of which is invaluable for deciphering the genetic basis of key phenotypic traits. Here we investigated the distribution, genic composition, and evolutionary history of a locus potentially determining growth rate in the pitch canker pathogen F. circinatum. We found that the genomic region underlying this locus is highly conserved amongst F. circinatum and its close relatives, except for the presence of a 12 000 base pair insertion in all of the examined isolates of F. circinatum. This insertion encodes for five genes and our phylogenetic analyses revealed that each was most likely acquired through horizontal gene transfer from polyphyletic origins. Our data further showed that this region is located in a region low in G+C content and enriched for repetitive sequences and transposable elements, which is situated near the telomere of Chromosome 3 of F. circinatum. As have been shown for other fungi, these findings thus suggest that the emergence of the unique 12 000 bp region in F. circinatum is linked to the dynamic evolutionary processes associated with subtelomeres that, in turn, have been implicated in the ecological adaptation of fungal pathogens.
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Affiliation(s)
- Stephanie Van Wyk
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa
| | - Brenda D Wingfield
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa
| | - Lieschen De Vos
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa
| | - Quentin C Santana
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa
| | - Nicolaas A Van der Merwe
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa
| | - Emma T Steenkamp
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa
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Guilherme RS, Hermetz KE, Varela PT, Perez ABA, Meloni VA, Rudd MK, Kulikowski LD, Melaragno MI. Terminal 18q deletions are stabilized by neotelomeres. Mol Cytogenet 2015; 8:32. [PMID: 25969696 PMCID: PMC4427916 DOI: 10.1186/s13039-015-0135-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 04/14/2015] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND All human chromosomes are capped by tandem repeat (TTAGGG)n sequences that protect them against end-to-end fusion and are essential to chromosomal replication and integrity. Therefore, after a chromosomal breakage, the deleted chromosomes must be stabilized by retaining the telomere or acquiring a new cap, by telomere healing or telomere capture. There are few reports with molecular approaches on the mechanisms involved in stabilization of 18q terminal deletions. RESULTS In this study we analyzed nine patients with 18q terminal deletion identified by G-banding and genomic array. FISH using PNA probe revealed telomeric signals in all deleted chromosomes tested. We fine-mapped breakpoints with customized arrays and sequenced six terminal deletion junctions. In all six deleted chromosomes sequenced, telomeric sequences were found directly attached to the breakpoints. Little or no microhomology was found at the breakpoints and none of the breaks sequenced were located in low copy repeat (LCR) regions, though repetitive elements were found around the breakpoints in five patients. One patient presented a more complex rearrangement with two deleted segments and an addition of 17 base pairs (bp). CONCLUSIONS We found that all six deleted chromosomes sequenced were probably stabilized by the healing mechanism leading to a neotelomere formation.
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Affiliation(s)
- Roberta Santos Guilherme
- Department of Morphology and Genetics, Universidade Federal de São Paulo, Rua Botucatu 740, CEP 04023-900, São Paulo, Brazil
| | - Karen E Hermetz
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street Northeast, GA 30322, Atlanta, USA
| | - Patrícia Teixeira Varela
- Department of Biophysics, Universidade Federal de São Paulo, Rua Três de Maio 100, CEP 04023-900, São Paulo, Brazil
| | - Ana Beatriz Alvarez Perez
- Department of Morphology and Genetics, Universidade Federal de São Paulo, Rua Botucatu 740, CEP 04023-900, São Paulo, Brazil
| | - Vera Ayres Meloni
- Department of Morphology and Genetics, Universidade Federal de São Paulo, Rua Botucatu 740, CEP 04023-900, São Paulo, Brazil
| | - M Katharine Rudd
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street Northeast, GA 30322, Atlanta, USA
| | - Leslie Domenici Kulikowski
- Department of Pathology, Laboratório de Citogenômica, Universidade de São Paulo, Avenida Dr. Enéas Carvalho de Aguiar 255, CEP 05403-000, São Paulo, Brazil
| | - Maria Isabel Melaragno
- Department of Morphology and Genetics, Universidade Federal de São Paulo, Rua Botucatu 740, CEP 04023-900, São Paulo, Brazil
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Mehdipour P, Javan F, Savad S, Karbassian H, Atri M. Personalized evolutionary hypothesis in genomics and auxiliary lymph node through diverse subtelomeric signal profile. Cell Biol Int 2015; 43:1353-1364. [PMID: 25644206 DOI: 10.1002/cbin.10448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Accepted: 01/20/2015] [Indexed: 02/05/2023]
Abstract
Few available data on the genomic-somatic evolution in breast cancer create limitation to provide the appropriate clinical managements. As an example, human subtelomeres (ST) are diverse-prone and variable targets. STs, as hot spots, have positive and negative impacts on the status of health and malady. We showed higher subtelomere signal copy number (SCN) of specific chromosomes in genomics than in auxiliary lymph node (ALN). Dissimilarity of signal intensity (SI) is found for all chromosomes. Significantly higher SI in genomics than in ALN cells were specified as chromosomes 5, 6, 9-12, 16-19 for weak; 1, 5-9, 19, X for medium; and 2, 5, 9, 10, 16, 18 for strong SI. For lacking, and presence of one and two SCNs; p/q ratio reflected differences for all chromosomes; but, 2, 3, 5, 7, 8, 10, 16, 18, 20, and X chromosomes were involved for three SCN. Chromosomes 1, 4, 9, 12, 17-19 lacked three SCN in ALN and lymphocytes. Weak SI ratio was higher in p- than in q-arm in majority of chromosomes. Manner of evolution and diversity in p- and q-arms is expressive of a novel definition as two diverse domains with a personalized insight. These data have been accompanied by periodic charts as ST array profiles which provide specific and individualized pattern in breast neoplasm. Such profiling at genomics level could be considered as a prediction through the patients' life. Moreover, subtelomere territory by interacting with protein expression of Ki67, cyclin D1, and cyclin E; and molecular targets including telomere length at genomics and somatic level provides package of information to bridge cancer cell biology to the cancer clinic as "puzzling paradigm."
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Affiliation(s)
- Parvin Mehdipour
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
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Martin CL, Ledbetter DH. Molecular cytogenetic analysis of telomere rearrangements. CURRENT PROTOCOLS IN HUMAN GENETICS 2015; 84:8.11.1-8.11.15. [PMID: 25599669 PMCID: PMC4410364 DOI: 10.1002/0471142905.hg0811s84] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Genomic imbalances involving the telomeric regions of human chromosomes, which contain the highest gene concentration in the genome, are proposed to have severe phenotypic consequences. For this reason, it is important to identify telomere rearrangements and assess their contribution to human pathology. This unit describes the structure and function of human telomeres and outlines several methodologies that can be employed to study these unique regions of human chromosomes. It is a revision of the original version of the unit published in 2000, now including an introductory section describing advances in the discipline that have taken place since the original publication.
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Affiliation(s)
- Christa Lese Martin
- Autism and Developmental Medicine Institute, Geisinger Health System, Danville, Pennsylvania
| | - David H Ledbetter
- Autism and Developmental Medicine Institute, Geisinger Health System, Danville, Pennsylvania
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Hosseini M, Goodstadt L, Hughes JR, Kowalczyk MS, de Gobbi M, Otto GW, Copley RR, Mott R, Higgs DR, Flint J. Causes and consequences of chromatin variation between inbred mice. PLoS Genet 2013; 9:e1003570. [PMID: 23785304 PMCID: PMC3681629 DOI: 10.1371/journal.pgen.1003570] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 05/02/2013] [Indexed: 12/28/2022] Open
Abstract
Variation at regulatory elements, identified through hypersensitivity to digestion by DNase I, is believed to contribute to variation in complex traits, but the extent and consequences of this variation are poorly characterized. Analysis of terminally differentiated erythroblasts in eight inbred strains of mice identified reproducible variation at approximately 6% of DNase I hypersensitive sites (DHS). Only 30% of such variable DHS contain a sequence variant predictive of site variation. Nevertheless, sequence variants within variable DHS are more likely to be associated with complex traits than those in non-variant DHS, and variants associated with complex traits preferentially occur in variable DHS. Changes at a small proportion (less than 10%) of variable DHS are associated with changes in nearby transcriptional activity. Our results show that whilst DNA sequence variation is not the major determinant of variation in open chromatin, where such variants exist they are likely to be causal for complex traits. Regulatory sites of the genome affect gene expression and complex traits, including disease susceptibility. Variable regulatory sites are potentially interesting because they are a likely cause of phenotypic variation, providing a bridge between sequence and transcriptional variation. In this paper we identify regions of the genome where DNA is not wrapped up in chromatin (hence potentially regulatory) in eight inbred strains of mice. We compare sites that vary among strains and compare them to non-variable sites. We show that more than half of variable sites cannot be attributed to local sequence variation. Functional consequences (in terms of readily detectable changes in gene expression) are associated with less than 10% of variable DNase I hypersensitive sites. We show that variable sites are enriched for sequence variants contributing to complex traits in mice.
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Affiliation(s)
- Mona Hosseini
- Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
| | - Leo Goodstadt
- Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
| | - Jim R. Hughes
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Monika S. Kowalczyk
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Marco de Gobbi
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Georg W. Otto
- Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
| | | | - Richard Mott
- Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
| | - Douglas R. Higgs
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Jonathan Flint
- Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
- * E-mail:
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9
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Research proceedings on primate comparative genomics. Zool Res 2013; 33:108-18. [DOI: 10.3724/sp.j.1141.2012.01108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Abstract
The globin gene disorders including the thalassemias are among the most common human genetic diseases with more than 300,000 severely affected individuals born throughout the world every year. Because of the easy accessibility of purified, highly specialized, mature erythroid cells from peripheral blood, the hemoglobinopathies were among the first tractable human molecular diseases. From the 1970s onward, the analysis of the large repertoire of mutations underlying these conditions has elucidated many of the principles by which mutations occur and cause human genetic diseases. This work will summarize our current knowledge of the α-thalassemias, illustrating how detailed analysis of this group of diseases has contributed to our understanding of the general molecular mechanisms underlying many orphan and common diseases.
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Affiliation(s)
- Douglas R Higgs
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK.
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11
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Guenzl PM, Barlow DP. Macro lncRNAs: a new layer of cis-regulatory information in the mammalian genome. RNA Biol 2012; 9:731-41. [PMID: 22617879 DOI: 10.4161/rna.19985] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In the past ten years, long non-protein-coding RNAs (lncRNAs) have been shown to comprise a major part of the mammalian transcriptome and are predicted from their highly specific expression patterns, to play a role in regulating protein-coding gene expression in development and disease. Many lncRNAs particularly those lying in imprinted clusters, are predominantly unspliced "macro" transcripts that can also show a low level of splicing, and both the unspliced and spliced transcript have the potential to be functional. Three known imprinted macro lncRNAs have been shown to silence from three to ten genes in cis in imprinted gene clusters. We review here the potential for functional macro lncRNAs, defined here as "inefficiently-spliced lncRNAs" to play a wider cis-regulatory role in the mammalian genome. This potential has been underestimated by the inability of current RNA-seq technology to annotate unspliced macro lncRNAs.
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Affiliation(s)
- Philipp M Guenzl
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, AKH-BT25.3, Vienna 1090, Austria
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Reynolds GE, Gao Q, Miller D, Snow BE, Harrington LA, Murnane JP. PIF1 disruption or NBS1 hypomorphism does not affect chromosome healing or fusion resulting from double-strand breaks near telomeres in murine embryonic stem cells. DNA Repair (Amst) 2011; 10:1164-73. [PMID: 21945094 DOI: 10.1016/j.dnarep.2011.09.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Revised: 08/29/2011] [Accepted: 09/02/2011] [Indexed: 11/26/2022]
Abstract
Telomerase serves to maintain telomeric repeat sequences at the ends of chromosomes. However, telomerase can also add telomeric repeat sequences at DNA double-strand breaks (DSBs), a process called chromosome healing. Here, we employed a method of inducing DSBs near telomeres to query the role of two proteins, PIF1 and NBS1, in chromosome healing in mammalian cells. PIF1 was investigated because the PIF1 homolog in Saccharomyces cerevisiae inhibits chromosome healing, as shown by a 1000-fold increase in chromosome in PIF1-deficient cells. NBS1 was investigated because the functional homolog of NBS1 in S. cerevisiae, Xrs2, is part of the Mre11/Rad50/Xrs2 complex that is required for chromosome healing due to its role in the processing of DSBs and recruitment of telomerase. We found that disruption of mPif1 had no detectable effect on the frequency of chromosome healing at DSBs near telomeres in murine embryonic stem cells. Moreover, the Nbs1(ΔB) hypomorph, which is defective in the processing of DSBs, also had no detectable effect on the frequency of chromosome healing, DNA degradation, or gross chromosome rearrangements (GCRs) that result from telomeric DSBs. Although we cannot rule out small changes in chromosome healing using this system, it is clear from our results that knockout of PIF1 or the Nbs1(ΔB) hypomorph does not result in large differences in chromosome healing in murine cells. These results represent the first genetic assessment of the role of these proteins in chromosome healing in mammals, and suggest that murine cells have evolved mechanisms to ensure the functional redundancy of Pif1 or Nbs1 in the regulation of chromosome healing.
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Affiliation(s)
- Gloria E Reynolds
- Department of Radiation Oncology, University of California San Francisco, 2340 Sutter Street, San Francisco, CA 94143-1331, United States
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Higgs DR, Gibbons RJ. The molecular basis of α-thalassemia: a model for understanding human molecular genetics. Hematol Oncol Clin North Am 2010; 24:1033-54. [PMID: 21075279 DOI: 10.1016/j.hoc.2010.08.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Down-regulation of α-globin synthesis causes α-thalassemia with underproduction of fetal (HbF, α(2)γ(2)) and adult (HbA, α(2)β(2)) hemoglobin. This article focuses on the human α-globin cluster, which has been characterized in great depth over the past 30 years. In particular the authors describe how the α genes are normally switched on during erythropoiesis and switched off as hematopoietic stem cells commit to nonerythroid lineages. In addition, the principles by which α-globin expression may be perturbed by natural mutations that cause α-thalassemia are reviewed.
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Affiliation(s)
- Douglas R Higgs
- John Radcliffe Hospital, MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headington, Oxford, UK.
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14
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Chromosome looping at the human alpha-globin locus is mediated via the major upstream regulatory element (HS -40). Blood 2009; 114:4253-60. [PMID: 19696202 DOI: 10.1182/blood-2009-03-213439] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Previous studies in the mouse have shown that high levels of alpha-globin gene expression in late erythropoiesis depend on long-range, physical interactions between remote upstream regulatory elements and the globin promoters. Using quantitative chromosome conformation capture (q3C), we have now analyzed all interactions between 4 such elements lying 10 to 50 kb upstream of the human alpha cluster and their interactions with the alpha-globin promoter. All of these elements interact with the alpha-globin gene in an erythroid-specific manner. These results were confirmed in a mouse model of human alpha globin expression in which the human cluster replaces the mouse cluster in situ (humanized mouse). We have also shown that expression and all of the long-range interactions depend largely on just one of these elements; removal of the previously characterized major regulatory element (called HS -40) results in loss of all the interactions and alpha-globin expression. Reinsertion of this element at an ectopic location restores both expression and the intralocus interactions. In contrast to other more complex systems involving multiple upstream elements and promoters, analysis of the human alpha-globin cluster during erythropoiesis provides a simple and tractable model to understand the mechanisms underlying long-range gene regulation.
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15
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Costa V, Casamassimi A, Roberto R, Gianfrancesco F, Matarazzo MR, D'Urso M, D'Esposito M, Rocchi M, Ciccodicola A. DDX11L: a novel transcript family emerging from human subtelomeric regions. BMC Genomics 2009; 10:250. [PMID: 19476624 PMCID: PMC2705379 DOI: 10.1186/1471-2164-10-250] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 05/28/2009] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND The subtelomeric regions of human chromosomes exhibit an extraordinary plasticity. To date, due to the high GC content and to the presence of telomeric repeats, the subtelomeric sequences are underrepresented in the genomic libraries and consequently their sequences are incomplete in the finished human genome sequence, and still much remains to be learned about subtelomere organization, evolution and function. Indeed, only in recent years, several studies have disclosed, within human subtelomeres, novel gene family members. RESULTS During a project aimed to analyze genes located in the telomeric region of the long arm of the human X chromosome, we have identified a novel transcript family, DDX11L, members of which map to 1pter, 2q13/14.1, 2qter, 3qter, 6pter, 9pter/9qter, 11pter, 12pter, 15qter, 16pter, 17pter, 19pter, 20pter/20qter, Xpter/Xqter and Yqter. Furthermore, we partially sequenced the underrepresented subtelomeres of human chromosomes showing a common evolutionary origin. CONCLUSION Our data indicate that an ancestral gene, originated as a rearranged portion of the primate DDX11 gene, and propagated along many subtelomeric locations, is emerging within subtelomeres of human chromosomes, defining a novel gene family. These findings support the possibility that the high plasticity of these regions, sites of DNA exchange among different chromosomes, could trigger the emergence of new genes.
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Affiliation(s)
- Valerio Costa
- Institute of Genetics and Biophysics A, Buzzati-Traverso , CNR, 80131 Naples, Italy.
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16
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The role of the polycomb complex in silencing alpha-globin gene expression in nonerythroid cells. Blood 2008; 112:3889-99. [PMID: 18689541 DOI: 10.1182/blood-2008-06-161901] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although much is known about globin gene activation in erythroid cells, relatively little is known about how these genes are silenced in nonerythroid tissues. Here we show that the human alpha- and beta-globin genes are silenced by fundamentally different mechanisms. The alpha-genes, which are surrounded by widely expressed genes in a gene dense region of the genome, are silenced very early in development via recruitment of the Polycomb (PcG) complex. By contrast, the beta-globin genes, which lie in a relatively gene-poor chromosomal region, are not bound by this complex in nonerythroid cells. The PcG complex seems to be recruited to the alpha-cluster by sequences within the CpG islands associated with their promoters; the beta-globin promoters do not lie within such islands. Chromatin associated with the alpha-globin cluster is modified by histone methylation (H3K27me3), and silencing in vivo is mediated by the localized activity of histone deacetylases (HDACs). The repressive (PcG/HDAC) machinery is removed as hematopoietic progenitors differentiate to form erythroid cells. The alpha- and beta-globin genes thus illustrate important, contrasting mechanisms by which cell-specific hematopoietic genes (and tissue-specific genes in general) may be silenced.
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17
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Gao Q, Reynolds GE, Wilcox A, Miller D, Cheung P, Artandi SE, Murnane JP. Telomerase-dependent and -independent chromosome healing in mouse embryonic stem cells. DNA Repair (Amst) 2008; 7:1233-49. [PMID: 18502190 DOI: 10.1016/j.dnarep.2008.04.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2007] [Revised: 04/01/2008] [Accepted: 04/03/2008] [Indexed: 01/04/2023]
Abstract
Telomeres play an important role in protecting the ends of chromosomes and preventing chromosome fusion. We have previously demonstrated that double-strand breaks near telomeres in mammalian cells result in either the addition of a new telomere at the site of the break, termed chromosome healing, or sister chromatid fusion that initiates chromosome instability. In the present study, we have investigated the role of telomerase in chromosome healing and the importance of chromosome healing in preventing chromosome instability. In embryonic stem cell lines that are wild type for the catalytic subunit of telomerase (TERT), chromosome healing at I-SceI-induced double-strand breaks near telomeres accounted for 22 of 35 rearrangements, with the new telomeres added directly at the site of the break in all but one instance. In contrast, in two TERT-knockout embryonic stem cell lines, chromosome healing accounted for only 1 of 62 rearrangements, with a 23 bp insertion at the site of the sole chromosome-healing event. However, in a third TERT-knockout embryonic stem cell line, 10PTKO-A, chromosome healing was a common event that accounted for 20 of 34 rearrangements. Although this chromosome healing also occurred at the I-SceI site, differences in the microhomology at the site of telomere addition demonstrated that the mechanism was distinct from that in wild-type embryonic stem cell lines. In addition, the newly added telomeres in 10PTKO-A shortened with time in culture, eventually resulting in either telomere elongation through a telomerase-independent mechanism or loss of the subtelomeric plasmid sequences entirely. The combined results demonstrate that chromosome healing can occur through both telomerase-dependent and -independent mechanisms, and that although both mechanisms can prevent degradation and sister chromatid fusion, neither mechanism is efficient enough to prevent sister chromatid fusion from occurring in many cells experiencing double-strand breaks near telomeres.
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Affiliation(s)
- Qing Gao
- Department of Radiation Oncology, University of California, San Francisco, CA 94103, USA
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18
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Higgs DR, Wood WG. Long-range regulation of ?? globin gene expression during erythropoiesis. Curr Opin Hematol 2008; 15:176-83. [DOI: 10.1097/moh.0b013e3282f734c4] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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19
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Lese CM, Ledbetter DH. Molecular cytogenetic analysis of telomere rearrangements. ACTA ACUST UNITED AC 2008; Chapter 8:Unit 8.11. [PMID: 18428312 DOI: 10.1002/0471142905.hg0811s24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Genomic imbalances involving the telomeric regions of human chromosomes, which contain the highest gene concentration in the genome, are proposed to have severe phenotypic consequences. For this reason, it is important to identify telomere rearrangements and assess their contribution to human pathology. This unit describes the structure and function of human telomeres and outlines several FISH-based methodologies that can be employed to study these unique regions of human chromosomes.
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Affiliation(s)
- C M Lese
- The University of Chicago, Chicago, Illinois, USA
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20
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Gibson WT, Harvard C, Qiao Y, Somerville MJ, Lewis MES, Rajcan-Separovic E. Phenotype-genotype characterization of alpha-thalassemia mental retardation syndrome due to isolated monosomy of 16p13.3. Am J Med Genet A 2008; 146A:225-32. [PMID: 18076105 DOI: 10.1002/ajmg.a.32056] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
An 8-year-old Caucasian girl presented with mild dysmorphic features and intellectual disability (ID) affecting multiple spheres. Dysmorphisms included a high forehead with up-slanting palpebral fissures, prominent nasal root and bridge, flattened maxilla, high-arched palate, and anterior frenulum. Structural brain anomalies included reduced periventricular white matter volume and thin corpus callosum. The presence of HbH bodies and her clinical presentation raised suspicion for autosomal alpha-thalassemia mental retardation syndrome (ATR-16). Whole-genome array analysis at 1 Mb resolution was performed, which revealed a sub-microscopic loss of 16p involving clones RP11-344L6 at 0.1 Mb, RP1-121I4 at 0.2 Mb and RP11-334D3 at 1 Mb. FISH confirmed deletion (del) of the terminal clone (RP1-121I4) on 16pter, which was de novo in origin. The more proximal clone RP11-334D3 (at 1 Mb) showed diminished FISH signal intensity on one of the homologues, suggesting that one breakpoint occurred within this clone. Quantitative PCR (qPCR) confirmed a de novo deletion encompassing SOX8 (at 0.97 Mb). ATR-16 is characterized by ID with mild, nonspecific dysmorphic features, and is associated with terminal del16p (MIM No. 141750). Cases of isolated monosomy for 16p are rarely described; such descriptions help to delineate the syndrome in the absence of confounding karyotypic anomalies. We describe detailed molecular cytogenetic and clinical findings relating to a subject with ATR-16.
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Affiliation(s)
- William T Gibson
- Department of Medical Genetics, Child and Family Research Institute, UBC, Vancouver, BC, Canada.
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21
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Abstract
Over the past 20 years, there has been an increasing awareness that gene expression can be regulated by multiple cis-acting sequences located at considerable distances (10-1000 kb) from the genes they control. Detailed investigation of a few specialized mammalian genes, including the genes controlling the synthesis of hemoglobin, provide important models to understand how such long-range regulatory elements act. In general, these elements contain a high density of evolutionarily conserved, transcription factor-binding sites and in many ways resemble the upstream regulatory elements found adjacent to the promoters of genes in simpler organisms, differing only in the distance over which they act. We have investigated in detail how the remote regulatory elements of the alpha-globin cluster become activated as hematopoietic stem cells (HSCs) undergo commitment, lineage specification, and differentiation to form red blood cells. In turn, we have addressed how, during this process, the upstream elements control the correct spatial and temporal expression from the alpha-gene promoter which lies approximately 60 kb downstream of these elements. At present too few loci have been studied to determine whether there are general principles underlying long-range regulation but some common themes are emerging.
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22
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Fathallah H, Portnoy G, Atweh GF. Epigenetic analysis of the human alpha- and beta-globin gene clusters. Blood Cells Mol Dis 2007; 40:166-73. [PMID: 18029204 DOI: 10.1016/j.bcmd.2007.08.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2007] [Revised: 05/31/2007] [Accepted: 08/02/2007] [Indexed: 12/01/2022]
Abstract
K562 erythroleukemia cells have been widely used as a model for the study of globin gene regulation. A number of agents have been shown to activate or suppress globin gene expression in these cells. However, the molecular effects of these agents on the epigenetic configuration of the alpha- and gamma-globin genes that encode HbF are not known. In this report, we investigated the relationship between globin expression and histone acetylation of the human alpha- and beta-globin clusters in the fetal erythroid environment of K562 cells. Our studies suggest that acetylation of histone H3 may be important in regulating developmental stage-specific expression of the different beta-like globin genes while acetylation of both histones H3 and H4 may be important for the regulation of tissue-specific expression of these genes. In contrast, acetylation of both histones H3 and H4 at the alpha-like globin promoters appears to be important for both developmental stage- and tissue-specific expression. Interestingly, butyrate-induced activation of alpha-globin gene expression in K562 cells is associated with significant increase in histone acetylation levels while TPA-induced inhibition is associated with decreased histone acetylation at its promoters. In contrast, changes in histone acetylation and DNA methylation do not appear to be important in the regulation of gamma-globin gene expression by the same agents. These data suggest that the butyrate-mediated induction of the fetal gamma-globin genes in K562 cells is not a direct result of its histone deacetylase inhibitor activity of butyrate on the chromatin of the gamma-globin promoters, while the induction of the alpha-globin genes could be a result of a direct effect of butyrate on chromatin at its promoters. This is another example of the important differences in the molecular mechanisms of regulation of the genes of the alpha- and beta-like globin clusters.
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Affiliation(s)
- Hassana Fathallah
- Mount Sinai School of Medicine, Division of Hematology/Medical Oncology, Box 1079, One, Gustave L. Levy Place, New York, NY 10029, USA.
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23
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Kehrer-Sawatzki H, Cooper DN. Understanding the recent evolution of the human genome: insights from human-chimpanzee genome comparisons. Hum Mutat 2007; 28:99-130. [PMID: 17024666 DOI: 10.1002/humu.20420] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The sequencing of the chimpanzee genome and the comparison with its human counterpart have begun to reveal the spectrum of genetic changes that has accompanied human evolution. In addition to gross karyotypic rearrangements such as the fusion that formed human chromosome 2 and the human-specific pericentric inversions of chromosomes 1 and 18, there is considerable submicroscopic structural variation involving deletions, duplications, and inversions. Lineage-specific segmental duplications, detected by array comparative genomic hybridization and direct sequence comparison, have made a very significant contribution to this structural divergence, which is at least three-fold greater than that due to nucleotide substitutions. Since structural genomic changes may have given rise to irreversible functional differences between the diverging species, their detailed analysis could help to identify the biological processes that have accompanied speciation. To this end, interspecies comparisons have revealed numerous human-specific gains and losses of genes as well as changes in gene expression. The very considerable structural diversity (polymorphism) evident within both lineages has, however, hampered the analysis of the structural divergence between the human and chimpanzee genomes. The concomitant evaluation of genetic divergence and diversity at the nucleotide level has nevertheless served to identify many genes that have evolved under positive selection and may thus have been involved in the development of human lineage-specific traits. Genes that display signs of weak negative selection have also been identified and could represent candidate loci for complex genomic disorders. Here, we review recent progress in comparing the human and chimpanzee genomes and discuss how the differences detected have improved our understanding of the evolution of the human genome.
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24
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Wallace HAC, Marques-Kranc F, Richardson M, Luna-Crespo F, Sharpe JA, Hughes J, Wood WG, Higgs DR, Smith AJH. Manipulating the Mouse Genome to Engineer Precise Functional Syntenic Replacements with Human Sequence. Cell 2007; 128:197-209. [PMID: 17218265 DOI: 10.1016/j.cell.2006.11.044] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2006] [Revised: 09/29/2006] [Accepted: 11/15/2006] [Indexed: 11/19/2022]
Abstract
We have devised a strategy (called recombinase-mediated genomic replacement, RMGR) to allow the replacement of large segments (>100 kb) of the mouse genome with the equivalent human syntenic region. The technique involves modifying a mouse ES cell chromosome and a human BAC by inserting heterotypic lox sites to flank the proposed exchange interval and then using Cre recombinase to achieve segmental exchange. We have demonstrated the feasibility of this approach by replacing the mouse alpha globin regulatory domain with the human syntenic region and generating homozygous mice that produce only human alpha globin chains. Furthermore, modified ES cells can be used iteratively for functional studies, and here, as an example, we have used RMGR to produce an accurate mouse model of human alpha thalassemia. RMGR has general applicability and will overcome limitations inherent in current transgenic technology when studying the expression of human genes and modeling human genetic diseases.
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Affiliation(s)
- Helen A C Wallace
- Institute for Stem Cell Research, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JQ, United Kingdom
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25
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Abstract
Genomic instability has been proposed to play an important role in cancer by accelerating the accumulation of genetic changes responsible for cancer cell evolution. One mechanism for chromosome instability is through the loss of telomeres, which are DNA-protein complexes that protect the ends of chromosomes and prevent chromosome fusion. Telomere loss can occur as a result of exogenous DNA damage, or spontaneously in cancer cells that commonly have a high rate of telomere loss. Mouse embryonic stem cells and human tumor cell lines that contain a selectable marker gene located immediately adjacent to a telomere have been used to investigate the consequences of telomere loss. In both cell types, telomere loss is followed by either the addition of a new telomere on to the end of the broken chromosome, or sister chromatid fusion and prolonged breakage/fusion/bridge (B/F/B) cycles that result in DNA amplification and large terminal deletions. The regions amplified by B/F/B cycles can then be transferred to other chromosomes, either through the formation of double-minute chromosomes that reintegrate at other sites, or through end-to-end fusions between chromosomes. B/F/B cycles eventually end when a chromosome acquires a new telomere by one of several mechanisms, the most common of which is translocation, which can involve either nonreciprocal transfer or duplication of all or part of an arm of another chromosome. Telomere acquisition involving nonreciprocal translocations results in the loss of a telomere on the donor chromosome, which subsequently becomes unstable. In contrast, translocations involving duplications do not destabilize the donor chromosome, although they result in allelic imbalances. Thus, the loss of a single telomere can generate a wide variety of chromosome alterations commonly associated with human cancer, not only on the chromosome that originally lost its telomere, but other chromosomes as well. Factors promoting spontaneous telomere loss and the resulting B/F/B cycles are therefore likely to be important in generating the karyotypic changes associated with human cancer.
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Affiliation(s)
- John P Murnane
- Department of Radiation Oncology, University of California, San Francisco, 1855 Folsom Street, MCB 200, San Francisco, CA 94103, USA.
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26
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Oates NA, van Vliet J, Duffy DL, Kroes HY, Martin NG, Boomsma DI, Campbell M, Coulthard MG, Whitelaw E, Chong S. Increased DNA methylation at the AXIN1 gene in a monozygotic twin from a pair discordant for a caudal duplication anomaly. Am J Hum Genet 2006; 79:155-62. [PMID: 16773576 PMCID: PMC1474116 DOI: 10.1086/505031] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Accepted: 04/05/2006] [Indexed: 11/03/2022] Open
Abstract
The AXIN1 gene has been implicated in caudal duplication anomalies. Its coding region was sequenced in both members of a monozygotic (MZ) twin pair discordant for a caudal duplication anomaly, but no mutation was found. Using bisulfite sequencing, we examined methylation at the promoter region of the AXIN1 gene in these twins and in twin and age-matched singleton controls. Methylation of the promoter region in peripheral blood mononucleated cells was variable among individuals, including MZ pairs. In the MZ pair discordant for the caudal duplication, this region of the affected twin was significantly more methylated than that of the unaffected twin (P < .0001), which was significantly more methylated than those of the controls (P = .02). We have confirmed that this CpG island does function as a promoter in vitro and that its activity is inversely proportional to the extent of methylation. This finding raises the possibility that hypermethylation of the AXIN1 promoter, by mechanisms as yet undetermined, is associated with the malformation. This case may be paradigmatic for some cases of MZ discordance.
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Affiliation(s)
- N A Oates
- School of Molecular and Microbial Biosciences, University of Sydney, Australia
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27
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De Gobbi M, Viprakasit V, Hughes JR, Fisher C, Buckle VJ, Ayyub H, Gibbons RJ, Vernimmen D, Yoshinaga Y, de Jong P, Cheng JF, Rubin EM, Wood WG, Bowden D, Higgs DR. A regulatory SNP causes a human genetic disease by creating a new transcriptional promoter. Science 2006; 312:1215-7. [PMID: 16728641 DOI: 10.1126/science.1126431] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We describe a pathogenetic mechanism underlying a variant form of the inherited blood disorder alpha thalassemia. Association studies of affected individuals from Melanesia localized the disease trait to the telomeric region of human chromosome 16, which includes the alpha-globin gene cluster, but no molecular defects were detected by conventional approaches. After resequencing and using a combination of chromatin immunoprecipitation and expression analysis on a tiled oligonucleotide array, we identified a gain-of-function regulatory single-nucleotide polymorphism (rSNP) in a nongenic region between the alpha-globin genes and their upstream regulatory elements. The rSNP creates a new promoterlike element that interferes with normal activation of all downstream alpha-like globin genes. Thus, our work illustrates a strategy for distinguishing between neutral and functionally important rSNPs, and it also identifies a pathogenetic mechanism that could potentially underlie other genetic diseases.
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Affiliation(s)
- Marco De Gobbi
- Medical Research Council Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, OX3 9DS, UK
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28
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Andrew T, Aviv A, Falchi M, Surdulescu GL, Gardner JP, Lu X, Kimura M, Kato BS, Valdes AM, Spector TD. Mapping genetic loci that determine leukocyte telomere length in a large sample of unselected female sibling pairs. Am J Hum Genet 2006; 78:480-6. [PMID: 16400618 PMCID: PMC1380290 DOI: 10.1086/500052] [Citation(s) in RCA: 207] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Accepted: 11/21/2005] [Indexed: 12/31/2022] Open
Abstract
Telomeres play a central role in cellular senescence and cancer pathobiology and are associated with age-related diseases such as atherosclerosis and dementia. Telomere length varies between individuals of the same age, is influenced by DNA-damaging factors such as oxidative stress, and is heritable. We performed a quantitative-trait linkage analysis using an approximate 10-cM genomewide map for mean leukocyte terminal-restriction fragment (TRF) lengths measured by Southern blotting, in 2,050 unselected women aged 18-80 years, comprising 1,025 complete dizygotic twin pairs. Heritability of mean batch-adjusted TRF was 36% (95% confidence interval [CI] 18%-48%), with a large common environmental effect of 49% (95% CI 40%-58%). Significant linkage was observed on chromosome 14 (LOD 3.9) at 14q23.2, and suggestive linkage at 10q26.13 (LOD 2.4) and 3p26.1 (LOD 2.7). This is the first report of loci, mapped in a sample of healthy individuals, that influence mean telomere variation in humans.
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Affiliation(s)
- Toby Andrew
- Twin Research and Genetic Epidemiology Unit, St. Thomas' Hospital, London SE1 7EH, United Kingdom.
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29
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Bolzán AD, Bianchi MS. Telomeres, interstitial telomeric repeat sequences, and chromosomal aberrations. Mutat Res 2006; 612:189-214. [PMID: 16490380 DOI: 10.1016/j.mrrev.2005.12.003] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2005] [Revised: 12/29/2005] [Accepted: 12/30/2005] [Indexed: 11/18/2022]
Abstract
Telomeres are specialized nucleoproteic complexes localized at the physical ends of linear eukaryotic chromosomes that maintain their stability and integrity. The DNA component of telomeres is characterized by being a G-rich double stranded DNA composed by short fragments tandemly repeated with different sequences depending on the species considered. At the chromosome level, telomeres or, more properly, telomeric repeats--the DNA component of telomeres--can be detected either by using the fluorescence in situ hybridization (FISH) technique with a DNA or a peptide nucleic acid (PNA) (pan)telomeric probe, i.e., which identifies simultaneously all of the telomeres in a metaphase cell, or by the primed in situ labeling (PRINS) reaction using an oligonucleotide primer complementary to the telomeric DNA repeated sequence. Using these techniques, incomplete chromosome elements, acentric fragments, amplification and translocation of telomeric repeat sequences, telomeric associations and telomeric fusions can be identified. In addition, chromosome orientation (CO)-FISH allows to discriminate between the different types of telomeric fusions, namely telomere-telomere and telomere-DNA double strand break fusions and to detect recombination events at the telomere, i.e., telomeric sister-chromatid exchanges (T-SCE). In this review, we summarize our current knowledge of chromosomal aberrations involving telomeres and interstitial telomeric repeat sequences and their induction by physical and chemical mutagens. Since all of the studies on the induction of these types of aberrations were conducted in mammalian cells, the review will be focused on the chromosomal aberrations involving the TTAGGG sequence, i.e., the telomeric repeat sequence that "caps" the chromosomes of all vertebrate species.
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Affiliation(s)
- Alejandro D Bolzán
- Laboratorio de Citogenética y Mutagénesis, Instituto Multidisciplinario de Biología Celular (IMBICE), C.C. 403, 1900 La Plata, Argentina.
| | - Martha S Bianchi
- Laboratorio de Citogenética y Mutagénesis, Instituto Multidisciplinario de Biología Celular (IMBICE), C.C. 403, 1900 La Plata, Argentina
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30
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Chakalova L, Debrand E, Mitchell JA, Osborne CS, Fraser P. Replication and transcription: shaping the landscape of the genome. Nat Rev Genet 2006; 6:669-77. [PMID: 16094312 DOI: 10.1038/nrg1673] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
As the relationship between nuclear structure and function begins to unfold, a picture is emerging of a dynamic landscape that is centred on the two main processes that execute the regulated use and propagation of the genome. Rather than being subservient enzymatic activities, the replication and transcriptional machineries provide potent forces that organize the genome in three-dimensional nuclear space. Their activities provide opportunities for epigenetic changes that are required for differentiation and development. In addition, they impose physical constraints on the genome that might help to shape its evolution.
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Affiliation(s)
- Lyubomira Chakalova
- Laboratory of Chromatin and Gene Expression, The Babraham Institute, Babraham Research Campus, Cambridge CB2 4AT, United Kingdom
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31
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Higgs DR, Garrick D, Anguita E, De Gobbi M, Hughes J, Muers M, Vernimmen D, Lower K, Law M, Argentaro A, Deville MA, Gibbons R. Understanding α-Globin Gene Regulation: Aiming to Improve the Management of Thalassemia. Ann N Y Acad Sci 2005; 1054:92-102. [PMID: 16339655 DOI: 10.1196/annals.1345.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Over the past 50 years, many advances in our understanding of the general principles controlling gene expression during hematopoiesis have come from studying the synthesis of hemoglobin. Discovering how the alpha- and beta-globin genes are normally regulated and documenting the effects of inherited mutations that cause thalassemia have played a major role in establishing our current understanding of how genes are switched on or off in hematopoietic cells. Previously, nearly all mutations causing thalassemia have been found in or around the globin loci, but rare inherited and acquired trans-acting mutations are being found more often. Such mutations have demonstrated new mechanisms underlying human genetic disease. Furthermore, they are revealing new pathways in the regulation of globin gene expression that, in turn, may open up new avenues for improving the management of patients with common types of thalassemia.
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Affiliation(s)
- D R Higgs
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DS, United Kingdom.
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32
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Hughes JR, Cheng JF, Ventress N, Prabhakar S, Clark K, Anguita E, De Gobbi M, de Jong P, Rubin E, Higgs DR. Annotation of cis-regulatory elements by identification, subclassification, and functional assessment of multispecies conserved sequences. Proc Natl Acad Sci U S A 2005; 102:9830-5. [PMID: 15998734 PMCID: PMC1174996 DOI: 10.1073/pnas.0503401102] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
An important step toward improving the annotation of the human genome is to identify cis-acting regulatory elements from primary DNA sequence. One approach is to compare sequences from multiple, divergent species. This approach distinguishes multispecies conserved sequences (MCS) in noncoding regions from more rapidly evolving neutral DNA. Here, we have analyzed a region of approximately 238kb containing the human alpha globin cluster that was sequenced and/or annotated across the syntenic region in 22 species spanning 500 million years of evolution. Using a variety of bioinformatic approaches and correlating the results with many aspects of chromosome structure and function in this region, we were able to identify and evaluate the importance of 24 individual MCSs. This approach sensitively and accurately identified previously characterized regulatory elements but also discovered unidentified promoters, exons, splicing, and transcriptional regulatory elements. Together, these studies demonstrate an integrated approach by which to identify, subclassify, and predict the potential importance of MCSs.
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Affiliation(s)
- Jim R Hughes
- Medical Research Council Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DS, United Kingdom
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33
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Manton KJ, Douglas ML, Netzel-Arnett S, Fitzpatrick DR, Nicol DL, Boyd AW, Clements JA, Antalis TM. Hypermethylation of the 5' CpG island of the gene encoding the serine protease Testisin promotes its loss in testicular tumorigenesis. Br J Cancer 2005; 92:760-9. [PMID: 15685234 PMCID: PMC2361880 DOI: 10.1038/sj.bjc.6602373] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The Testisin gene (PRSS21) encodes a glycosylphosphatidylinositol (GPI)-linked serine protease that exhibits testis tissue-specific expression. Loss of Testisin has been implicated in testicular tumorigenesis, but its role in testis biology and tumorigenesis is not known. Here we have investigated the role of CpG methylation in Testisin gene inactivation and tested the hypothesis that Testisin may act as a tumour suppressor for testicular tumorigenesis. Using sequence analysis of bisulphite-treated genomic DNA, we find a strong relationship between hypermethylation of a 385 bp 5′ CpG rich island of the Testisin gene, and silencing of the Testisin gene in a range of human tumour cell lines and in 100% (eight/eight) of testicular germ cell tumours. We show that treatment of Testisin-negative cell lines with demethylating agents and/or a histone deacetylase inhibitor results in reactivation of Testisin gene expression, implicating hypermethylation in Testisin gene silencing. Stable expression of Testisin in the Testisin-negative Tera-2 testicular cancer line suppressed tumorigenicity as revealed by inhibition of both anchorage-dependent cell growth and tumour formation in an SCID mouse model of testicular tumorigenesis. Together, these data show that loss of Testisin is caused, at least in part, by DNA hypermethylation and histone deacetylation, and suggest a tumour suppressor role for Testisin in testicular tumorigenesis.
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Affiliation(s)
- K J Manton
- Leukaemia Foundation and Cellular Oncology Laboratories, Queensland Institute of Medical Research, Queensland, Australia
- School of Life Science, Queensland University of Technology, Queensland, Australia
| | - M L Douglas
- School of Medicine, Southern Clinical Division, University of Queensland, Princess Alexandra Hospital, Queensland, Australia
| | - S Netzel-Arnett
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | | | - D L Nicol
- School of Medicine, Southern Clinical Division, University of Queensland, Princess Alexandra Hospital, Queensland, Australia
| | - A W Boyd
- Leukaemia Foundation and Cellular Oncology Laboratories, Queensland Institute of Medical Research, Queensland, Australia
| | - J A Clements
- School of Life Science, Queensland University of Technology, Queensland, Australia
| | - T M Antalis
- Leukaemia Foundation and Cellular Oncology Laboratories, Queensland Institute of Medical Research, Queensland, Australia
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Physiology, University of Maryland School of Medicine, 15601 Crabbs Branch Way, Rockville, MD 20855, USA. E-mail:
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34
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Martin J, Han C, Gordon LA, Terry A, Prabhakar S, She X, Xie G, Hellsten U, Chan YM, Altherr M, Couronne O, Aerts A, Bajorek E, Black S, Blumer H, Branscomb E, Brown NC, Bruno WJ, Buckingham JM, Callen DF, Campbell CS, Campbell ML, Campbell EW, Caoile C, Challacombe JF, Chasteen LA, Chertkov O, Chi HC, Christensen M, Clark LM, Cohn JD, Denys M, Detter JC, Dickson M, Dimitrijevic-Bussod M, Escobar J, Fawcett JJ, Flowers D, Fotopulos D, Glavina T, Gomez M, Gonzales E, Goodstein D, Goodwin LA, Grady DL, Grigoriev I, Groza M, Hammon N, Hawkins T, Haydu L, Hildebrand CE, Huang W, Israni S, Jett J, Jewett PB, Kadner K, Kimball H, Kobayashi A, Krawczyk MC, Leyba T, Longmire JL, Lopez F, Lou Y, Lowry S, Ludeman T, Manohar CF, Mark GA, McMurray KL, Meincke LJ, Morgan J, Moyzis RK, Mundt MO, Munk AC, Nandkeshwar RD, Pitluck S, Pollard M, Predki P, Parson-Quintana B, Ramirez L, Rash S, Retterer J, Ricke DO, Robinson DL, Rodriguez A, Salamov A, Saunders EH, Scott D, Shough T, Stallings RL, Stalvey M, Sutherland RD, Tapia R, Tesmer JG, Thayer N, Thompson LS, Tice H, Torney DC, Tran-Gyamfi M, Tsai M, Ulanovsky LE, Ustaszewska A, Vo N, White PS, Williams AL, Wills PL, Wu JR, Wu K, Yang J, Dejong P, Bruce D, Doggett NA, Deaven L, Schmutz J, Grimwood J, Richardson P, Rokhsar DS, Eichler EE, Gilna P, Lucas SM, Myers RM, Rubin EM, Pennacchio LA. The sequence and analysis of duplication-rich human chromosome 16. Nature 2004; 432:988-94. [PMID: 15616553 DOI: 10.1038/nature03187] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2004] [Accepted: 11/15/2004] [Indexed: 01/30/2023]
Abstract
Human chromosome 16 features one of the highest levels of segmentally duplicated sequence among the human autosomes. We report here the 78,884,754 base pairs of finished chromosome 16 sequence, representing over 99.9% of its euchromatin. Manual annotation revealed 880 protein-coding genes confirmed by 1,670 aligned transcripts, 19 transfer RNA genes, 341 pseudogenes and three RNA pseudogenes. These genes include metallothionein, cadherin and iroquois gene families, as well as the disease genes for polycystic kidney disease and acute myelomonocytic leukaemia. Several large-scale structural polymorphisms spanning hundreds of kilobase pairs were identified and result in gene content differences among humans. Whereas the segmental duplications of chromosome 16 are enriched in the relatively gene-poor pericentromere of the p arm, some are involved in recent gene duplication and conversion events that are likely to have had an impact on the evolution of primates and human disease susceptibility.
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Affiliation(s)
- Joel Martin
- DOE Joint Genome Institute, 2800 Mitchell Avenue, Walnut Creek, California 94598, USA
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35
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Riethman H, Ambrosini A, Castaneda C, Finklestein JM, Hu XL, Paul S, Wei J. Human subtelomeric DNA. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2004; 68:39-47. [PMID: 15338601 DOI: 10.1101/sqb.2003.68.39] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- H Riethman
- The Wistar Institute, Philadelphia, Pennsylvania 19104, USA
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36
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Tusell L, Latre L, Ponsa I, Miró R, Egozcue J, Genescà A. Capping of radiation-induced DNA breaks in mouse early embryos. JOURNAL OF RADIATION RESEARCH 2004; 45:415-422. [PMID: 15613787 DOI: 10.1269/jrr.45.415] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The aim of the study was to investigate the spectrum and frequencies of chromosome aberrations induced by the exposure of different mouse spermatogenic germ cell stages to ionizing radiation. Male mice were exposed in vivo to X-rays. Chromosome aberrations were analyzed in first- and second-embryonic cleavages obtained from mating irradiated males with nonirradiated females at different periods after radiation exposure. A combination of telomeric and centromeric labeling as well as whole Y chromosome painting was used to characterize the rejoining pattern and the telomere status of the radiation-induced DNA breaks. The frequency of chromosome aberrations observed in eggs fertilized with sperm irradiated at the early spermatid stage was markedly higher than the frequency in eggs fertilized with sperm irradiated at the other spermatogenic stages when reference was made to the chromosome aberrations recovered in early embryos. At the first division postirradiation, distal rejoining of broken chromosome ends (in regard to the position of the centromere) was more frequent than proximal rejoining; thus compound acentric fragments were more frequently observed than dicentric chromosomes. The presence of additional telomere signals at the broken chromosome ends in mouse germ cells and early embryos, compatible with de novo formation of telomeres, was not frequent.
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Affiliation(s)
- Laura Tusell
- Unitat de Biologia Cellular, Departament de Biologia Cellular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona, Bellaterra, Spain.
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37
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Stewart DR, Huang A, Faravelli F, Anderlid BM, Medne L, Ciprero K, Kaur M, Rossi E, Tenconi R, Nordenskjöld M, Gripp KW, Nicholson L, Meschino WS, Capua E, Quarrell OWJ, Flint J, Irons M, Giampietro PF, Schowalter DB, Zaleski CA, Malacarne M, Zackai EH, Spinner NB, Krantz ID. Subtelomeric deletions of chromosome 9q: A novel microdeletion syndrome. Am J Med Genet A 2004; 128A:340-51. [PMID: 15264279 DOI: 10.1002/ajmg.a.30136] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Fluorescent in situ hybridization (FISH) screening of subtelomeric rearrangements has resulted in the identification of previously unrecognized chromosomal causes of mental retardation with and without dysmorphic features. This article reports the phenotypic and molecular breakpoint characterization in a cohort of 12 patients with subtelomeric deletions of chromosome 9q34. The phenotypic findings are consistent amongst these individuals and consist of mental retardation, distinct facial features and congenital heart defects (primarily conotruncal defects). Detailed breakpoint mapping by FISH, microsatellite and single nucleotide polymorphism (SNP) genotyping analysis has narrowed the commonly deleted region to an approximately 1.2 Mb interval containing 14 known transcripts. The majority of the proximal deletion breakpoints fall within a 400 kb interval between SNP markers C12020842 proximally and C80658 distally suggesting a common breakpoint in this interval.
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Affiliation(s)
- Douglas R Stewart
- Division of Human Genetics and Molecular Biology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
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38
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Yalcin B, Fullerton J, Miller S, Keays DA, Brady S, Bhomra A, Jefferson A, Volpi E, Copley RR, Flint J, Mott R. Unexpected complexity in the haplotypes of commonly used inbred strains of laboratory mice. Proc Natl Acad Sci U S A 2004; 101:9734-9. [PMID: 15210992 PMCID: PMC470780 DOI: 10.1073/pnas.0401189101] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2004] [Indexed: 01/21/2023] Open
Abstract
Investigation of sequence variation in common inbred mouse strains has revealed a segmented pattern in which regions of high and low variant density are intermixed. Furthermore, it has been suggested that allelic strain distribution patterns also occur in well defined blocks and consequently could be used to map quantitative trait loci (QTL) in comparisons between inbred strains. We report a detailed analysis of polymorphism distribution in multiple inbred mouse strains over a 4.8-megabase region containing a QTL influencing anxiety. Our analysis indicates that it is only partly true that the genomes of inbred strains exist as a patchwork of segments of sequence identity and difference. We show that the definition of haplotype blocks is not robust and that methods for QTL mapping may fail if they assume a simple block-like structure.
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Affiliation(s)
- B Yalcin
- Wellcome Trust Centre for Human Genetics, Oxford University, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
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39
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Tufarelli C, Hardison R, Miller W, Hughes J, Clark K, Ventress N, Frischauf AM, Higgs DR. Comparative analysis of the alpha-like globin clusters in mouse, rat, and human chromosomes indicates a mechanism underlying breaks in conserved synteny. Genome Res 2004; 14:623-30. [PMID: 15060003 PMCID: PMC383306 DOI: 10.1101/gr.2143604] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We have sequenced and fully annotated a 65,871-bp region of mouse Chromosome 17 including the Hba-ps4 alpha-globin pseudogene. Comparative sequence analysis with the functional alpha-globin loci at human Chromosome 16p13.3 and mouse Chromosome 11 shows that this segment of mouse Chromosome 17 contains a group of three alpha-like pseudogenes (Hba-psm-Hba-ps4-Hba-q3), similar to the duplicated sets found at the functional mouse cluster on Chromosome 11. In addition, exons 7 to 12 of the mLuc7L gene are present just downstream from the pseudogene cluster, indicating that this clone contains the region in which human 16p13.3 switches in synteny between mouse Chromosomes 11 and 17. Comparison of the sequences around the alpha-like clusters on the two mouse chromosomes reveals the presence of conserved tandem repeats. We propose that these repetitive elements have played a role in the fragmentation of the mouse alpha cluster during evolution.
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Affiliation(s)
- Cristina Tufarelli
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK
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40
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Riethman H, Ambrosini A, Castaneda C, Finklestein J, Hu XL, Mudunuri U, Paul S, Wei J. Mapping and initial analysis of human subtelomeric sequence assemblies. Genome Res 2004; 14:18-28. [PMID: 14707167 PMCID: PMC314271 DOI: 10.1101/gr.1245004] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Physical mapping data were combined with public draft and finished sequences to derive subtelomeric sequence assemblies for each of the 41 genetically distinct human telomere regions. Sequence gaps that remain on the reference telomeres are generally small,well-defined,and for the most part,restricted to regions directly adjacent to the terminal (TTAGGG)n tract. Of the 20.66 Mb of subtelomeric DNA analyzed, 3.01 Mb are subtelomeric repeat sequences (Srpt),and an additional 2.11 Mb are segmental duplications. The subtelomeric sequence assemblies are enriched >25-fold in short,internal (TTAGGG)n-like sequences relative to the rest of the genome; a total of 114 (TTAGGG)n-like islands were found,55 within Srpt regions,35 within one-copy regions,11 at one-copy/Srpt or Srpt/segmental duplication boundaries,and 13 at the telomeric ends of assemblies. Transcripts were annotated in each assembly,noting their mapping coordinates relative to their respective telomere and whether they originate in duplicated DNA or single-copy DNA. A total of 697 transcripts were found in 15.53 Mb of one-copy DNA,76 transcripts in 2.11 Mb of segmentally duplicated DNA,and 168 transcripts in 3.01 Mb of Srpt sequence. This overall transcript density is similar (within approximately 10%) to that found genome-wide. Zinc finger-containing genes and olfactory receptor genes are duplicated within and between multiple telomere regions.
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Affiliation(s)
- Harold Riethman
- The Wistar Institute, Philadelphia, Pennsylvania 19104, USA.
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41
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Abstract
Abstract
Over the past fifty years, many advances in our understanding of the general principles controlling gene expression during hematopoiesis have come from studying the synthesis of hemoglobin. Discovering how the α and β globin genes are normally regulated and documenting the effects of inherited mutations which cause thalassemia have played a major role in establishing our current understanding of how genes are switched on or off in hematopoietic cells. Previously, nearly all mutations causing thalassemia have been found in or around the globin loci, but rare inherited and acquired trans-acting mutations are being found with increasing frequency. Such mutations have demonstrated new mechanisms underlying human genetic disease. Furthermore, they are revealing new pathways in the regulation of globin gene expression which, in turn, may eventually open up new avenues for improving the management of patients with common types of thalassemia.
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Affiliation(s)
- Douglas R Higgs
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, UK
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42
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Murnane JP, Sabatier L. Chromosome rearrangements resulting from telomere dysfunction and their role in cancer. Bioessays 2004; 26:1164-74. [PMID: 15499579 DOI: 10.1002/bies.20125] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Telomeres play a vital role in protecting the ends of chromosomes and preventing chromosome fusion. The failure of cancer cells to properly maintain telomeres can be an important source of the chromosome instability involved in cancer cell progression. Telomere loss results in sister chromatid fusion and prolonged breakage/fusion/bridge (B/F/B) cycles, leading to extensive DNA amplification and large deletions. These B/F/B cycles end primarily when the unstable chromosome acquires a new telomere by translocation of the ends of other chromosomes. Many of these translocations are nonreciprocal, resulting in the loss of the telomere from the donor chromosome, providing a mechanism for transfer of instability from one chromosome to another until a chromosome acquires a telomere by a mechanism other than nonreciprocal translocation. B/F/B cycles can also result in other forms of chromosome rearrangements, including double-minute chromosomes and large duplications. Thus, the loss of a single telomere can result in instability in multiple chromosomes, and generate many of the types of rearrangements commonly associated with human cancer.
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Affiliation(s)
- John P Murnane
- Radiation Oncology Research Laboratory, University of California, San Francisco, CA 94103, USA.
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43
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Tufarelli C, Stanley JAS, Garrick D, Sharpe JA, Ayyub H, Wood WG, Higgs DR. Transcription of antisense RNA leading to gene silencing and methylation as a novel cause of human genetic disease. Nat Genet 2003; 34:157-65. [PMID: 12730694 DOI: 10.1038/ng1157] [Citation(s) in RCA: 386] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2003] [Accepted: 04/04/2003] [Indexed: 11/09/2022]
Abstract
Nearly all human genetic disorders result from a limited repertoire of mutations in an associated gene or its regulatory elements. We recently described an individual with an inherited form of anemia (alpha-thalassemia) who has a deletion that results in a truncated, widely expressed gene (LUC7L) becoming juxtaposed to a structurally normal alpha-globin gene (HBA2). Although it retains all of its local and remote cis-regulatory elements, expression of HBA2 is silenced and its CpG island becomes completely methylated early during development. Here we show that in the affected individual, in a transgenic model and in differentiating embryonic stem cells, transcription of antisense RNA mediates silencing and methylation of the associated CpG island. These findings identify a new mechanism underlying human genetic disease.
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Affiliation(s)
- Cristina Tufarelli
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK
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44
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Keller K, Williams C, Wharton P, Paulk M, Bent-Williams A, Gray B, Ward A, Stalker H, Wallace M, Carter R, Zori R. Routine cytogenetic and FISH studies for 17p11/15q11 duplications and subtelomeric rearrangement studies in children with autism spectrum disorders. Am J Med Genet A 2003; 117A:105-11. [PMID: 12567405 DOI: 10.1002/ajmg.a.10042] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
To assess the frequency of cytogenetic abnormalities in children with autism spectrum disorders (ASDs), routine G-banded cytogenetic analyses and FISH studies to rule out 15q11.2 and 17p11.2 duplications were performed on 49 children with ASDs. Blood samples were further studied using a complete set of subtelomeric FISH probes. Routine chromosome study showed that one child had a small duplication of chromosome 5: 46,XY,dup(5)(p?14.2p?15.1). Another child had an interstitial duplication of the Prader-Willi and Angelman syndrome critical region of chromosome 15, detected by FISH analysis. The detection of these two cases underscores the importance of obtaining routine chromosome and 15q11-q13 FISH analyses in children with ASDs. No instance of 17p11.2 duplication was observed. Subtelomeric analysis did not reveal abnormalities in any of the subjects.
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Affiliation(s)
- Kory Keller
- Raymond C Philips Unit, Division of Genetics, Department of Pediatrics, University of Florida, Gainesville, Florida 32610-0296, USA
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45
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Viprakasit V, Kidd AMJ, Ayyub H, Horsley S, Hughes J, Higgs DR. De novo deletion within the telomeric region flanking the human alpha globin locus as a cause of alpha thalassaemia. Br J Haematol 2003; 120:867-75. [PMID: 12614224 DOI: 10.1046/j.1365-2141.2003.04197.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have identified and characterized a Scottish individual with alpha thalassaemia, resulting from a de novo 48 kilobase (kb) deletion from the telomeric flanking region of the alpha globin cluster which occurred as a result of recombination between two misaligned repetitive elements that normally lie approximately 83 kb and 131 kb from the 16p telomere. The deletion removes two previously described putative regulatory elements (HS-40 and HS-33) but leaves two other elements (HS-10 and HS-8) intact. Analysis of this deletion, together with eight other published deletions of the telomeric region, showed that they all severely downregulated alpha globin expression. Together they defined a 20.4-kb region of the human alpha cluster, which contains all of the positive cis-acting elements required to regulate alpha globin expression. Comparative analysis of this region with the corresponding segment of the mouse alpha globin cluster demonstrated conserved non-coding sequences corresponding to the putative regulatory elements HS-40 and HS-33. Although the role of HS-40 as an enhancer of alpha globin expression is fully established, these observations suggest that the role of HS-33 and other sequences in this region should be more fully investigated in the context of the natural human and mouse alpha globin loci.
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Affiliation(s)
- Vip Viprakasit
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, UK
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46
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Guy J, Hearn T, Crosier M, Mudge J, Viggiano L, Koczan D, Thiesen HJ, Bailey JA, Horvath JE, Eichler EE, Earthrowl ME, Deloukas P, French L, Rogers J, Bentley D, Jackson MS. Genomic sequence and transcriptional profile of the boundary between pericentromeric satellites and genes on human chromosome arm 10p. Genome Res 2003; 13:159-72. [PMID: 12566394 PMCID: PMC420363 DOI: 10.1101/gr.644503] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2002] [Accepted: 11/04/2002] [Indexed: 11/24/2022]
Abstract
Contiguous finished sequence from highly duplicated pericentromeric regions of human chromosomes is needed if we are to understand the role of pericentromeric instability in disease, and in gene and karyotype evolution. Here, we have constructed a BAC contig spanning the transition from pericentromeric satellites to genes on the short arm of human chromosome 10, and used this to generate 1.4 Mb of finished genomic sequence. Combining RT-PCR, in silico gene prediction, and paralogy analysis, we can identify two domains within the sequence. The proximal 600 kb consists of satellite-rich pericentromerically duplicated DNA which is transcript poor, containing only three unspliced transcripts. In contrast, the distal 850 kb contains four known genes (ZNF248, ZNF25, ZNF33A, and ZNF37A) and up to 32 additional transcripts of unknown function. This distal region also contains seven out of the eight intrachromosomal duplications within the sequence, including the p arm copy of the approximately 250-kb duplication which gave rise to ZNF33A and ZNF33B. By sequencing orthologs of the duplicated ZNF33 genes we have established that ZNF33A has diverged significantly at residues critical for DNA binding but ZNF33B has not, indicating that ZNF33B has remained constrained by selection for ancestral gene function. These results provide further evidence of gene formation within intrachromosomal duplications, but indicate that recent interchromosomal duplications at this centromere have involved transcriptionally inert, satellite rich DNA, which is likely to be heterochromatic. This suggests that any novel gene structures formed by these interchromosomal events would require relocation to a more open chromatin environment to be expressed.
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Affiliation(s)
- Jane Guy
- The Institute of Human Genetics, The International Centre for Life, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 3BZ, UK
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47
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Mahy NL, Perry PE, Bickmore WA. Gene density and transcription influence the localization of chromatin outside of chromosome territories detectable by FISH. J Cell Biol 2002; 159:753-63. [PMID: 12473685 PMCID: PMC2173389 DOI: 10.1083/jcb.200207115] [Citation(s) in RCA: 219] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Genes can be transcribed from within chromosome territories; however, the major histocompatibilty complex locus has been reported extending away from chromosome territories, and the incidence of this correlates with transcription from the region. A similar result has been seen for the epidermal differentiation complex region of chromosome 1. These data suggested that chromatin decondensation away from the surface of chromosome territories may result from, and/or may facilitate, transcription of densely packed genes subject to coordinate regulation.To investigate whether localization outside of the visible confines of chromosome territories can also occur for regions that are not coordinately regulated, we have examined the spatial organization of human 11p15.5 and the syntenic region on mouse chromosome 7. This region is gene rich but its genes are not coordinately expressed, rather overall high levels of transcription occur in several cell types. We found that chromatin from 11p15.5 frequently extends away from the chromosome 11 territory. Localization outside of territories was also detected for other regions of high gene density and high levels of transcription. This is shown to be partly dependent on ongoing transcription. We suggest that local gene density and transcription, rather than the activity of individual genes, influences the organization of chromosomes in the nucleus.
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MESH Headings
- Animals
- Cell Nucleus/drug effects
- Cell Nucleus/genetics
- Cells, Cultured
- Chromatin/chemistry
- Chromatin/genetics
- Chromatin/metabolism
- Chromosome Painting
- Chromosomes, Artificial, P1 Bacteriophage/genetics
- Chromosomes, Human, Pair 11/genetics
- Chromosomes, Human, Pair 11/metabolism
- Chromosomes, Mammalian/genetics
- Chromosomes, Mammalian/metabolism
- Cosmids/genetics
- DNA/genetics
- DNA/metabolism
- Dactinomycin/pharmacology
- Dichlororibofuranosylbenzimidazole/pharmacology
- Fibroblasts/cytology
- Fibroblasts/drug effects
- Fibroblasts/metabolism
- Genes
- Genetic Markers
- Genome, Human
- Humans
- In Situ Hybridization, Fluorescence/methods
- Lymphocyte Activation
- Lymphocytes/cytology
- Lymphocytes/drug effects
- Lymphocytes/metabolism
- Mice
- Nucleic Acid Synthesis Inhibitors/pharmacology
- Physical Chromosome Mapping
- Synteny
- Telomere/chemistry
- Transcription, Genetic
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48
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Abstract
The alpha-globin gene cluster is located at the very tip of the short arm of chromosome 16. It produces the alpha-like globins, which is combined with the beta-like globins to form hemoglobin, and its mutants cause alpha-thalassemia, which is one of the most common genetic diseases. Its expression shows a tissue and developmental stage specificity that is balanced with that of the beta-globin gene cluster. In this article, we summarize the research on the control of expression of the alpha-globin gene cluster, mainly with respect to the alpha-major regulatory element (alpha-MRE): HS-40, the tissue-specific and developmental control of its expression, and its chromosomal environment. In summary, the alpha-globin gene cluster is expressed in an open chromosomal environment; HS-40, the 5'-flanking sequence, the transcribed region, and the 3'-flanking sequence interact to fully regulate its expression.
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Affiliation(s)
- Hua-bing Zhang
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, P. R. China
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49
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Anguita E, Sharpe JA, Sloane-Stanley JA, Tufarelli C, Higgs DR, Wood WG. Deletion of the mouse alpha-globin regulatory element (HS -26) has an unexpectedly mild phenotype. Blood 2002; 100:3450-6. [PMID: 12393394 DOI: 10.1182/blood-2002-05-1409] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Natural deletions of the region upstream of the human alpha-globin gene cluster, together with expression studies in cell lines and transgenic mice, identified a single element (HS -40) as necessary and perhaps sufficient for high-level expression of the alpha-globin genes. A similar element occupies the corresponding position upstream of the mouse (m) alpha-globin genes (mHS -26) and was thought to have similar functional properties. We knocked out mHS -26 by homologous recombination and observed the surprising result that instead of the expected severe alpha-thalassemia phenotype, the mice had a mild disease. Transcription levels of the mouse genes were reduced by about 50%, but homozygotes were healthy, with normal hemoglobin levels and only mild decreases in mean corpuscular volume and mean corpuscular hemoglobin. These results may indicate differences in the regulation of the alpha-globin clusters in mice and humans or that additional cis-acting elements remain to be characterized in one or both clusters.
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Affiliation(s)
- Eduardo Anguita
- Medical Research Council Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom
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Lo AWI, Sabatier L, Fouladi B, Pottier G, Ricoul M, Murnane JP. DNA amplification by breakage/fusion/bridge cycles initiated by spontaneous telomere loss in a human cancer cell line. Neoplasia 2002; 4:531-8. [PMID: 12407447 PMCID: PMC1503667 DOI: 10.1038/sj.neo.7900267] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2002] [Accepted: 07/24/2002] [Indexed: 11/09/2022]
Abstract
The development of genomic instability is an important step in generating the multiple genetic changes required for cancer. One consequence of genomic instability is the overexpression of oncogenes due to gene amplification. One mechanism for gene amplification is the breakage/fusion/bridge (B/F/B) cycle that involves the repeated fusion and breakage of chromosomes following the loss of a telomere. B/F/B cycles have been associated with low-copy gene amplification in human cancer cells, and have been proposed to be an initiating event in high-copy gene amplification. We have found that spontaneous telomere loss on a marker chromosome 16 in a human tumor cell line results in sister chromatid fusion and prolonged periods of chromosome instability. The high rate of anaphase bridges involving chromosome 16 demonstrates that this instability results from B/F/B cycles. The amplification of subtelomeric DNA on the marker chromosome provides conclusive evidence that B/F/B cycles initiated by spontaneous telomere loss are a mechanism for gene amplification in human cancer cells.
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Affiliation(s)
- Anthony W I Lo
- Radiation Oncology Research Laboratory, University of California, 1855 Folsom Street, MCB 200, San Francisco, CA 94103, USA
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