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Kang J, Wei S, Jia Z, Ma Y, Chen H, Sun C, Xu J, Tao J, Dong Y, Lv W, Tian H, Guo X, Bi S, Zhang C, Jiang Y, Lv H, Zhang M. Effects of genetic variation on the structure of RNA and protein. Proteomics 2024; 24:e2300235. [PMID: 38197532 DOI: 10.1002/pmic.202300235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 12/15/2023] [Accepted: 12/19/2023] [Indexed: 01/11/2024]
Abstract
Changes in the structure of RNA and protein, have an important impact on biological functions and are even important determinants of disease pathogenesis and treatment. Some genetic variations, including copy number variation, single nucleotide variation, and so on, can lead to changes in biological function and increased susceptibility to certain diseases by changing the structure of RNA or protein. With the development of structural biology and sequencing technology, a large amount of RNA and protein structure data and genetic variation data resources has emerged to be used to explain biological processes. Here, we reviewed the effects of genetic variation on the structure of RNAs and proteins, and investigated their impact on several diseases. An online resource (http://www.onethird-lab.com/gems/) to support convenient retrieval of common tools is also built. Finally, the challenges and future development of the effects of genetic variation on RNA and protein were discussed.
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Affiliation(s)
- Jingxuan Kang
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Siyu Wei
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Zhe Jia
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Yingnan Ma
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Haiyan Chen
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Chen Sun
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Jing Xu
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Junxian Tao
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Yu Dong
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Wenhua Lv
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
| | - Hongsheng Tian
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
| | - Xuying Guo
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
| | - Shuo Bi
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
| | - Chen Zhang
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
| | - Yongshuai Jiang
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Hongchao Lv
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
| | - Mingming Zhang
- College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, China
- The Epigenome-Wide Association Study Project, Harbin, China
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Madireddy A, Gerhardt J. Visualizing DNA replication by single-molecule analysis of replicated DNA. STAR Protoc 2023; 4:102721. [PMID: 38048218 PMCID: PMC10730367 DOI: 10.1016/j.xpro.2023.102721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 07/10/2023] [Accepted: 10/30/2023] [Indexed: 12/06/2023] Open
Abstract
Single-molecule analysis of replicated DNA (SMARD) is a unique technique that enables visualization of DNA replication at specific genomic regions at single-molecule resolution. Here, we present a protocol for visualizing DNA replication by SMARD. We describe steps for pulse labeling DNA, followed by isolating and stretching of genomic DNA. We then detail the detection of the replication at chromosomal regions through immunostaining and fluorescence in situ hybridization. Using SMARD, we can visualize replication initiation, progression, termination, and fork stalling. For complete details on the use and execution of this protocol, please refer to Norio et al. (2001) and Gerhardt et al. (2014).1,2.
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Affiliation(s)
- Advaitha Madireddy
- Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA; Department of Pediatrics Hematology/Oncology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, USA.
| | - Jeannine Gerhardt
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY, USA; Department of Obstetrics and Gynecology, Weill Cornell Medicine, New York, NY, USA.
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3
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Tassone F, Protic D, Allen EG, Archibald AD, Baud A, Brown TW, Budimirovic DB, Cohen J, Dufour B, Eiges R, Elvassore N, Gabis LV, Grudzien SJ, Hall DA, Hessl D, Hogan A, Hunter JE, Jin P, Jiraanont P, Klusek J, Kooy RF, Kraan CM, Laterza C, Lee A, Lipworth K, Losh M, Loesch D, Lozano R, Mailick MR, Manolopoulos A, Martinez-Cerdeno V, McLennan Y, Miller RM, Montanaro FAM, Mosconi MW, Potter SN, Raspa M, Rivera SM, Shelly K, Todd PK, Tutak K, Wang JY, Wheeler A, Winarni TI, Zafarullah M, Hagerman RJ. Insight and Recommendations for Fragile X-Premutation-Associated Conditions from the Fifth International Conference on FMR1 Premutation. Cells 2023; 12:2330. [PMID: 37759552 PMCID: PMC10529056 DOI: 10.3390/cells12182330] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 09/09/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023] Open
Abstract
The premutation of the fragile X messenger ribonucleoprotein 1 (FMR1) gene is characterized by an expansion of the CGG trinucleotide repeats (55 to 200 CGGs) in the 5' untranslated region and increased levels of FMR1 mRNA. Molecular mechanisms leading to fragile X-premutation-associated conditions (FXPAC) include cotranscriptional R-loop formations, FMR1 mRNA toxicity through both RNA gelation into nuclear foci and sequestration of various CGG-repeat-binding proteins, and the repeat-associated non-AUG (RAN)-initiated translation of potentially toxic proteins. Such molecular mechanisms contribute to subsequent consequences, including mitochondrial dysfunction and neuronal death. Clinically, premutation carriers may exhibit a wide range of symptoms and phenotypes. Any of the problems associated with the premutation can appropriately be called FXPAC. Fragile X-associated tremor/ataxia syndrome (FXTAS), fragile X-associated primary ovarian insufficiency (FXPOI), and fragile X-associated neuropsychiatric disorders (FXAND) can fall under FXPAC. Understanding the molecular and clinical aspects of the premutation of the FMR1 gene is crucial for the accurate diagnosis, genetic counseling, and appropriate management of affected individuals and families. This paper summarizes all the known problems associated with the premutation and documents the presentations and discussions that occurred at the International Premutation Conference, which took place in New Zealand in 2023.
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Affiliation(s)
- Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Sacramento, CA 95817, USA;
- MIND Institute, University of California Davis, Davis, CA 95817, USA; (B.D.); (D.H.); (V.M.-C.)
| | - Dragana Protic
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11129 Belgrade, Serbia;
- Fragile X Clinic, Special Hospital for Cerebral Palsy and Developmental Neurology, 11040 Belgrade, Serbia
| | - Emily Graves Allen
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA; (E.G.A.); (P.J.); (K.S.)
| | - Alison D. Archibald
- Victorian Clinical Genetics Services, Royal Children’s Hospital, Melbourne, VIC 3052, Australia;
- Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, VIC 3052, Australia;
- Genomics in Society Group, Murdoch Children’s Research Institute, Royal Children’s Hospital, Melbourne, VIC 3052, Australia
| | - Anna Baud
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Uniwersytetu Poznańskiego 6, 61-614 Poznan, Poland; (A.B.); (K.T.)
| | - Ted W. Brown
- Central Clinical School, University of Sydney, Sydney, NSW 2006, Australia;
- Fragile X Association of Australia, Brookvale, NSW 2100, Australia;
- NYS Institute for Basic Research in Developmental Disabilities, New York, NY 10314, USA
| | - Dejan B. Budimirovic
- Department of Psychiatry, Fragile X Clinic, Kennedy Krieger Institute, Baltimore, MD 21205, USA;
- Department of Psychiatry & Behavioral Sciences-Child Psychiatry, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Jonathan Cohen
- Fragile X Alliance Clinic, Melbourne, VIC 3161, Australia;
| | - Brett Dufour
- MIND Institute, University of California Davis, Davis, CA 95817, USA; (B.D.); (D.H.); (V.M.-C.)
- Department of Pathology and Laboratory Medicine, Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children of Northern California, School of Medicine, University of California Davis, Sacramento, CA 95817, USA;
| | - Rachel Eiges
- Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center Affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel;
| | - Nicola Elvassore
- Veneto Institute of Molecular Medicine (VIMM), 35129 Padova, Italy; (N.E.); (C.L.)
- Department of Industrial Engineering, University of Padova, 35131 Padova, Italy
| | - Lidia V. Gabis
- Keshet Autism Center Maccabi Wolfson, Holon 5822012, Israel;
- Faculty of Medicine, Tel-Aviv University, Tel Aviv 6997801, Israel
| | - Samantha J. Grudzien
- Department of Neurology, University of Michigan, 4148 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA; (S.J.G.); (P.K.T.)
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Deborah A. Hall
- Department of Neurological Sciences, Rush University, Chicago, IL 60612, USA;
| | - David Hessl
- MIND Institute, University of California Davis, Davis, CA 95817, USA; (B.D.); (D.H.); (V.M.-C.)
- Department of Psychiatry and Behavioral Sciences, School of Medicine, University of California Davis, Sacramento, CA 95817, USA
| | - Abigail Hogan
- Department of Communication Sciences and Disorders, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, USA; (A.H.); (J.K.)
| | - Jessica Ezzell Hunter
- RTI International, Research Triangle Park, NC 27709, USA; (J.E.H.); (S.N.P.); (M.R.); (A.W.)
| | - Peng Jin
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA; (E.G.A.); (P.J.); (K.S.)
| | - Poonnada Jiraanont
- Faculty of Medicine, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand;
| | - Jessica Klusek
- Department of Communication Sciences and Disorders, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, USA; (A.H.); (J.K.)
| | - R. Frank Kooy
- Department of Medical Genetics, University of Antwerp, 2000 Antwerp, Belgium;
| | - Claudine M. Kraan
- Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, VIC 3052, Australia;
- Diagnosis and Development, Murdoch Children’s Research Institute, Melbourne, VIC 3052, Australia
| | - Cecilia Laterza
- Veneto Institute of Molecular Medicine (VIMM), 35129 Padova, Italy; (N.E.); (C.L.)
- Department of Industrial Engineering, University of Padova, 35131 Padova, Italy
| | - Andrea Lee
- Fragile X New Zealand, Nelson 7040, New Zealand;
| | - Karen Lipworth
- Fragile X Association of Australia, Brookvale, NSW 2100, Australia;
| | - Molly Losh
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL 60201, USA;
| | - Danuta Loesch
- School of Psychology and Public Health, La Trobe University, Melbourne, VIC 3086, Australia;
| | - Reymundo Lozano
- Departments of Genetics and Genomic Sciences and Pediatrics, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA;
| | - Marsha R. Mailick
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA;
| | - Apostolos Manolopoulos
- Intramural Research Program, Laboratory of Clinical Investigation, National Institute on Aging, Baltimore, MD 21224, USA;
| | - Veronica Martinez-Cerdeno
- MIND Institute, University of California Davis, Davis, CA 95817, USA; (B.D.); (D.H.); (V.M.-C.)
- Department of Pathology and Laboratory Medicine, Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children of Northern California, School of Medicine, University of California Davis, Sacramento, CA 95817, USA;
| | - Yingratana McLennan
- Department of Pathology and Laboratory Medicine, Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children of Northern California, School of Medicine, University of California Davis, Sacramento, CA 95817, USA;
| | | | - Federica Alice Maria Montanaro
- Child and Adolescent Neuropsychiatry Unit, Department of Neuroscience, Bambino Gesù Children’s Hospital, IRCCS, 00165 Rome, Italy;
- Department of Education, Psychology, Communication, University of Bari Aldo Moro, 70121 Bari, Italy
| | - Matthew W. Mosconi
- Schiefelbusch Institute for Life Span Studies, University of Kansas, Lawrence, KS 66045, USA;
- Clinical Child Psychology Program, University of Kansas, Lawrence, KS 66045, USA
- Kansas Center for Autism Research and Training (K-CART), University of Kansas, Lawrence, KS 66045, USA
| | - Sarah Nelson Potter
- RTI International, Research Triangle Park, NC 27709, USA; (J.E.H.); (S.N.P.); (M.R.); (A.W.)
| | - Melissa Raspa
- RTI International, Research Triangle Park, NC 27709, USA; (J.E.H.); (S.N.P.); (M.R.); (A.W.)
| | - Susan M. Rivera
- Department of Psychology, University of Maryland, College Park, MD 20742, USA;
| | - Katharine Shelly
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA; (E.G.A.); (P.J.); (K.S.)
| | - Peter K. Todd
- Department of Neurology, University of Michigan, 4148 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA; (S.J.G.); (P.K.T.)
- Ann Arbor Veterans Administration Healthcare, Ann Arbor, MI 48105, USA
| | - Katarzyna Tutak
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Uniwersytetu Poznańskiego 6, 61-614 Poznan, Poland; (A.B.); (K.T.)
| | - Jun Yi Wang
- Center for Mind and Brain, University of California Davis, Davis, CA 95618, USA;
| | - Anne Wheeler
- RTI International, Research Triangle Park, NC 27709, USA; (J.E.H.); (S.N.P.); (M.R.); (A.W.)
| | - Tri Indah Winarni
- Center for Biomedical Research (CEBIOR), Faculty of Medicine, Universitas Diponegoro, Semarang 502754, Central Java, Indonesia;
| | - Marwa Zafarullah
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Sacramento, CA 95817, USA;
| | - Randi J. Hagerman
- MIND Institute, University of California Davis, Davis, CA 95817, USA; (B.D.); (D.H.); (V.M.-C.)
- Department of Pediatrics, School of Medicine, University of California Davis, Sacramento, CA 95817, USA
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Barreto-Galvez A, Niljikar M, Gagliardi J, Zhang R, Kumar V, Juruwala A, Pradeep A, Shaikh A, Tiwari P, Sharma K, Gerhardt J, Cao J, Kataoka K, Durbin A, Qi J, Ye BH, Madireddy A. Acetyl transferase EP300 deficiency leads to chronic replication stress mediated by defective fork protection at stalled replication forks. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.29.538781. [PMID: 37163075 PMCID: PMC10168362 DOI: 10.1101/2023.04.29.538781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Mutations in the epigenetic regulator and global transcriptional activator, E1A binding protein (EP300), is being increasingly reported in aggressive hematological malignancies including adult T-cell leukemia/lymphoma (ATLL). However, the mechanistic contribution of EP300 dysregulation to cancer initiation and progression are currently unknown. Independent inhibition of EP300 in human cells results in the differential expression of genes involved in regulating the cell cycle, DNA replication and DNA damage response. Nevertheless, specific function played by EP300 in DNA replication initiation, progression and replication fork integrity has not been studied. Here, using ATLL cells as a model to study EP300 deficiency and an p300-selective PROTAC degrader, degrader as a pharmacologic tool, we reveal that EP300-mutated cells display prolonged cell cycle kinetics, due to pronounced dysregulations in DNA replication dynamics leading to persistent genomic instability. Aberrant DNA replication in EP300-mutated cells is characterized by elevated replication origin firing due to increased replisome pausing genome-wide. We demonstrate that EP300 deficiency results in nucleolytic degradation of nascently synthesized DNA at stalled forks due to a prominent defect in fork stabilization and protection. This in turn results in the accumulation of single stranded DNA gaps at collapsed replication forks, in EP300-deficient cells. Inhibition of Mre11 nuclease rescues the ssDNA accumulation indicating a dysregulation in downstream mechanisms that restrain nuclease activity at stalled forks. Importantly, we find that the absence of EP300 results in decreased expression of BRCA2 protein expression and a dependency on POLD3-mediated error-prone replication restart mechanisms. The overall S-phase abnormalities observed lead to under-replicated DNA in G2/M that instigates mitotic DNA synthesis. This in turn is associated with mitotic segregation defects characterized by elevated micronuclei formation, accumulation of cytosolic DNA and transmission of unrepaired inherited DNA lesions in the subsequent G1-phase in EP300-deficient cells. We demonstrate that the DNA replication dynamics of EP300-mutated cells ATLL cells recapitulate features of BRCA-deficient cancers. Altogether these results suggest that mutations in EP300 cause chronic DNA replication stress and defective replication fork restart results in persistent genomic instability that underlie aggressive chemo-resistant tumorigenesis in humans.
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Deshpande M, Paniza T, Jalloul N, Nanjangud G, Twarowski J, Koren A, Zaninovic N, Zhan Q, Chadalavada K, Malkova A, Khiabanian H, Madireddy A, Rosenwaks Z, Gerhardt J. Error-prone repair of stalled replication forks drives mutagenesis and loss of heterozygosity in haploinsufficient BRCA1 cells. Mol Cell 2022; 82:3781-3793.e7. [PMID: 36099913 DOI: 10.1016/j.molcel.2022.08.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 04/21/2022] [Accepted: 08/16/2022] [Indexed: 01/05/2023]
Abstract
Germline mutations in the BRCA genes are associated with a higher risk of carcinogenesis, which is linked to an increased mutation rate and loss of the second unaffected BRCA allele (loss of heterozygosity, LOH). However, the mechanisms triggering mutagenesis are not clearly understood. The BRCA genes contain high numbers of repetitive DNA sequences. We detected replication forks stalling, DNA breaks, and deletions at these sites in haploinsufficient BRCA cells, thus identifying the BRCA genes as fragile sites. Next, we found that stalled forks are repaired by error-prone pathways, such as microhomology-mediated break-induced replication (MMBIR) in haploinsufficient BRCA1 breast epithelial cells. We detected MMBIR mutations in BRCA1 tumor cells and noticed deletions-insertions (>50 bp) at the BRCA1 genes in BRCA1 patients. Altogether, these results suggest that under stress, error-prone repair of stalled forks is upregulated and induces mutations, including complex genomic rearrangements at the BRCA genes (LOH), in haploinsufficient BRCA1 cells.
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Affiliation(s)
- Madhura Deshpande
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY 10021, USA
| | - Theodore Paniza
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY 10021, USA
| | - Nahed Jalloul
- Rutgers Cancer Institute of New Jersey and Rutgers Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ 08903, USA
| | - Gouri Nanjangud
- Molecular Cytogenetics Core Facility, Sloan Kettering Institute, New York, NY 10065, USA
| | - Jerzy Twarowski
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA
| | - Amnon Koren
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14850, USA
| | - Nikica Zaninovic
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY 10021, USA
| | - Qiansheng Zhan
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY 10021, USA
| | - Kalyani Chadalavada
- Molecular Cytogenetics Core Facility, Sloan Kettering Institute, New York, NY 10065, USA
| | - Anna Malkova
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA
| | - Hossein Khiabanian
- Rutgers Cancer Institute of New Jersey and Rutgers Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ 08903, USA
| | - Advaitha Madireddy
- Department of Pediatric Hematology/Oncology, Rutgers University, New Brunswick, NJ 08903, USA
| | - Zev Rosenwaks
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY 10021, USA
| | - Jeannine Gerhardt
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY 10021, USA; Department of Obstetrics and Gynecology, Weill Cornell Medicine, New York, NY 10021, USA.
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6
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Tabolacci E, Nobile V, Pucci C, Chiurazzi P. Mechanisms of the FMR1 Repeat Instability: How Does the CGG Sequence Expand? Int J Mol Sci 2022; 23:ijms23105425. [PMID: 35628235 PMCID: PMC9141726 DOI: 10.3390/ijms23105425] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/16/2022] Open
Abstract
A dynamic mutation in exon 1 of the FMR1 gene causes Fragile X-related Disorders (FXDs), due to the expansion of an unstable CGG repeat sequence. Based on the CGG sequence size, two types of FMR1 alleles are possible: “premutation” (PM, with 56-200 CGGs) and “full mutation” (FM, with >200 triplets). Premutated females are at risk of transmitting a FM allele that, when methylated, epigenetically silences FMR1 and causes Fragile X syndrome (FXS), a very common form of inherited intellectual disability (ID). Expansions events of the CGG sequence are predominant over contractions and are responsible for meiotic and mitotic instability. The CGG repeat usually includes one or more AGG interspersed triplets that influence allele stability and the risk of transmitting FM to children through maternal meiosis. A unique mechanism responsible for repeat instability has not been identified, but several processes are under investigations using cellular and animal models. The formation of unusual secondary DNA structures at the expanded repeats are likely to occur and contribute to the CGG expansion. This review will focus on the current knowledge about CGG repeat instability addressing the CGG sequence expands.
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Affiliation(s)
- Elisabetta Tabolacci
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
| | - Veronica Nobile
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
| | - Cecilia Pucci
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
| | - Pietro Chiurazzi
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
- UOC Genetica Medica, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
- Correspondence: ; Tel.: +39-06-3015-4606
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7
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Translesion polymerase eta both facilitates DNA replication and promotes increased human genetic variation at common fragile sites. Proc Natl Acad Sci U S A 2021; 118:2106477118. [PMID: 34815340 PMCID: PMC8640788 DOI: 10.1073/pnas.2106477118] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2021] [Indexed: 01/23/2023] Open
Abstract
Common fragile sites (CFSs) are difficult-to-replicate genomic regions that form gaps and breaks on metaphase chromosomes under replication stress. They are hotspots for chromosomal instability in cancer. Repetitive sequences located at CFS loci are inefficiently copied by replicative DNA polymerase (Pol) delta. However, translesion synthesis Pol eta has been shown to efficiently polymerize CFS-associated repetitive sequences in vitro and facilitate CFS stability by a mechanism that is not fully understood. Here, by locus-specific, single-molecule replication analysis, we identified a crucial role for Pol eta (encoded by the gene POLH) in the in vivo replication of CFSs, even without exogenous stress. We find that Pol eta deficiency induces replication pausing, increases initiation events, and alters the direction of replication-fork progression at CFS-FRA16D in both lymphoblasts and fibroblasts. Furthermore, certain replication pause sites at CFS-FRA16D were associated with the presence of non-B DNA-forming motifs, implying that non-B DNA structures could increase replication hindrance in the absence of Pol eta. Further, in Pol eta-deficient fibroblasts, there was an increase in fork pausing at fibroblast-specific CFSs. Importantly, while not all pause sites were associated with non-B DNA structures, they were embedded within regions of increased genetic variation in the healthy human population, with mutational spectra consistent with Pol eta activity. From these findings, we propose that Pol eta replicating through CFSs may result in genetic variations found in the human population at these sites.
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8
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The genetic architecture of DNA replication timing in human pluripotent stem cells. Nat Commun 2021; 12:6746. [PMID: 34799581 PMCID: PMC8604924 DOI: 10.1038/s41467-021-27115-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/29/2021] [Indexed: 12/11/2022] Open
Abstract
DNA replication follows a strict spatiotemporal program that intersects with chromatin structure but has a poorly understood genetic basis. To systematically identify genetic regulators of replication timing, we exploited inter-individual variation in human pluripotent stem cells from 349 individuals. We show that the human genome's replication program is broadly encoded in DNA and identify 1,617 cis-acting replication timing quantitative trait loci (rtQTLs) - sequence determinants of replication initiation. rtQTLs function individually, or in combinations of proximal and distal regulators, and are enriched at sites of histone H3 trimethylation of lysines 4, 9, and 36 together with histone hyperacetylation. H3 trimethylation marks are individually repressive yet synergistically associate with early replication. We identify pluripotency-related transcription factors and boundary elements as positive and negative regulators of replication timing, respectively. Taken together, human replication timing is controlled by a multi-layered mechanism with dozens of effectors working combinatorially and following principles analogous to transcription regulation.
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9
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Nakayama Y, Adachi K, Shioda N, Maeta S, Nanba E, Kugoh H. Establishment of FXS-A9 panel with a single human X chromosome from fragile X syndrome-associated individual. Exp Cell Res 2020; 398:112419. [PMID: 33296661 DOI: 10.1016/j.yexcr.2020.112419] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 11/20/2020] [Accepted: 11/26/2020] [Indexed: 11/29/2022]
Abstract
Fragile X syndrome (FXS) is the most common inheritable form of intellectual disability. FMR1, the gene responsible for FXS, is located on human chromosome Xq27.3 and contains a stretch of CGG trinucleotide repeats in its 5' untranslated region. FXS is caused by CGG repeats that expand beyond 200, resulting in FMR1 silencing via promoter hypermethylation. The molecular mechanism underlying CGG repeat expansion, a fundamental cause of FXS, remains poorly understood, partly due to a lack of experimental systems. Accumulated evidence indicates that the large chromosomal region flanking a CGG repeat is critical for repeat dynamics. In the present study, we isolated and introduced whole human X chromosomes from healthy, FXS premutation carriers, or FXS patients who carried disease condition-associated CGG repeat lengths, into mouse A9 cells via microcell-mediated chromosome transfer. The CGG repeat length-associated methylation status and human FMR1 expression in these monochromosomal hybrid cells mimicked those in humans. Thus, this set of A9 cells containing CGG repeats from three different origins (FXS-A9 panel) may provide a valuable resource for investigating a series of genetic and epigenetic CGG repeat dynamics during FXS pathogenesis.
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Affiliation(s)
- Yuji Nakayama
- Division of Radioisotope Science, Research Initiative Center, Organization for Research Initiative and Promotion, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan
| | - Kaori Adachi
- Division of Genomic Science, Research Initiative Center, Organization for Research Initiative and Promotion, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan
| | - Nofirifumi Shioda
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Shoya Maeta
- Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan
| | - Eiji Nanba
- Office for Research Strategy, Organization for Research Initiative and Promotion, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan
| | - Hiroyuki Kugoh
- Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan; Chromosome Engineering Research Center, Tottori University, 86 Nishi-cho, Yonago, Tottori, 683-8503, Japan.
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10
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Paniza T, Deshpande M, Wang N, O’Neil R, Zuccaro MV, Smith ME, Madireddy A, James D, Ecker J, Rosenwaks Z, Egli D, Gerhardt J. Pluripotent stem cells with low differentiation potential contain incompletely reprogrammed DNA replication. J Cell Biol 2020; 219:e201909163. [PMID: 32673399 PMCID: PMC7480103 DOI: 10.1083/jcb.201909163] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 02/26/2020] [Accepted: 05/13/2020] [Indexed: 12/20/2022] Open
Abstract
Reprogrammed pluripotent stem cells (PSCs) are valuable for research and potentially for cell replacement therapy. However, only a fraction of reprogrammed PSCs are developmentally competent. Genomic stability and accurate DNA synthesis are fundamental for cell development and critical for safety. We analyzed whether defects in DNA replication contribute to genomic instability and the diverse differentiation potentials of reprogrammed PSCs. Using a unique single-molecule approach, we visualized DNA replication in isogenic PSCs generated by different reprogramming approaches, either somatic cell nuclear transfer (NT-hESCs) or with defined factors (iPSCs). In PSCs with lower differentiation potential, DNA replication was incompletely reprogrammed, and genomic instability increased during replicative stress. Reprogramming of DNA replication did not correlate with DNA methylation. Instead, fewer replication origins and a higher frequency of DNA breaks in PSCs with incompletely reprogrammed DNA replication were found. Given the impact of error-free DNA synthesis on the genomic integrity and differentiation proficiency of PSCs, analyzing DNA replication may be a useful quality control tool.
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Affiliation(s)
- Theodore Paniza
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY
| | - Madhura Deshpande
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY
| | - Ning Wang
- Department of Pediatrics, Columbia University, New York, NY
| | - Ryan O’Neil
- Plant Molecular and Cellular Biology Laboratory, Salk Institute, La Jolla, CA
| | - Michael V. Zuccaro
- Department of Pediatrics, Columbia University, New York, NY
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY
| | | | - Advaitha Madireddy
- Department of Pediatric Hematology/Oncology, Rutgers University, New Brunswick, NJ
| | - Daylon James
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY
- Department of Obstetrics and Gynecology, Weill Cornell Medicine, New York, NY
| | - Joseph Ecker
- Plant Molecular and Cellular Biology Laboratory, Salk Institute, La Jolla, CA
| | - Zev Rosenwaks
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY
| | - Dieter Egli
- Department of Pediatrics, Columbia University, New York, NY
| | - Jeannine Gerhardt
- The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, NY
- Department of Obstetrics and Gynecology, Weill Cornell Medicine, New York, NY
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11
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Mystery of Expansion: DNA Metabolism and Unstable Repeats. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1241:101-124. [PMID: 32383118 DOI: 10.1007/978-3-030-41283-8_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
The mammalian genome mostly contains repeated sequences. Some of these repeats are in the regulatory elements of genes, and their instability, particularly the propensity to change the repeat unit number, is responsible for 36 well-known neurodegenerative human disorders. The mechanism of repeat expansion has been an unsolved question for more than 20 years. There are a few hypotheses describing models of mutation development. Every hypothesis is based on assumptions about unusual secondary structures that violate DNA metabolism processes in the cell. Some models are based on replication errors, and other models are based on mismatch repair or base excision repair errors. Additionally, it has been shown that epigenetic regulation of gene expression can influence the probability and frequency of expansion. In this review, we consider the molecular bases of repeat expansion disorders and discuss possible mechanisms of repeat expansion during cell metabolism.
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12
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Khristich AN, Mirkin SM. On the wrong DNA track: Molecular mechanisms of repeat-mediated genome instability. J Biol Chem 2020; 295:4134-4170. [PMID: 32060097 PMCID: PMC7105313 DOI: 10.1074/jbc.rev119.007678] [Citation(s) in RCA: 148] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Expansions of simple tandem repeats are responsible for almost 50 human diseases, the majority of which are severe, degenerative, and not currently treatable or preventable. In this review, we first describe the molecular mechanisms of repeat-induced toxicity, which is the connecting link between repeat expansions and pathology. We then survey alternative DNA structures that are formed by expandable repeats and review the evidence that formation of these structures is at the core of repeat instability. Next, we describe the consequences of the presence of long structure-forming repeats at the molecular level: somatic and intergenerational instability, fragility, and repeat-induced mutagenesis. We discuss the reasons for gender bias in intergenerational repeat instability and the tissue specificity of somatic repeat instability. We also review the known pathways in which DNA replication, transcription, DNA repair, and chromatin state interact and thereby promote repeat instability. We then discuss possible reasons for the persistence of disease-causing DNA repeats in the genome. We describe evidence suggesting that these repeats are a payoff for the advantages of having abundant simple-sequence repeats for eukaryotic genome function and evolvability. Finally, we discuss two unresolved fundamental questions: (i) why does repeat behavior differ between model systems and human pedigrees, and (ii) can we use current knowledge on repeat instability mechanisms to cure repeat expansion diseases?
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Affiliation(s)
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, Massachusetts 02155.
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13
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Poulet A, Li B, Dubos T, Rivera-Mulia JC, Gilbert DM, Qin ZS. RT States: systematic annotation of the human genome using cell type-specific replication timing programs. Bioinformatics 2019; 35:2167-2176. [PMID: 30475980 PMCID: PMC6681175 DOI: 10.1093/bioinformatics/bty957] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 11/05/2018] [Accepted: 11/21/2018] [Indexed: 12/20/2022] Open
Abstract
MOTIVATION The replication timing (RT) program has been linked to many key biological processes including cell fate commitment, 3D chromatin organization and transcription regulation. Significant technology progress now allows to characterize the RT program in the entire human genome in a high-throughput and high-resolution fashion. These experiments suggest that RT changes dynamically during development in coordination with gene activity. Since RT is such a fundamental biological process, we believe that an effective quantitative profile of the local RT program from a diverse set of cell types in various developmental stages and lineages can provide crucial biological insights for a genomic locus. RESULTS In this study, we explored recurrent and spatially coherent combinatorial profiles from 42 RT programs collected from multiple lineages at diverse differentiation states. We found that a Hidden Markov Model with 15 hidden states provide a good model to describe these genome-wide RT profiling data. Each of the hidden state represents a unique combination of RT profiles across different cell types which we refer to as 'RT states'. To understand the biological properties of these RT states, we inspected their relationship with chromatin states, gene expression, functional annotation and 3D chromosomal organization. We found that the newly defined RT states possess interesting genome-wide functional properties that add complementary information to the existing annotation of the human genome. AVAILABILITY AND IMPLEMENTATION R scripts for inferring HMM models and Perl scripts for further analysis are available https://github.com/PouletAxel/script_HMM_Replication_timing. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Axel Poulet
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - Ben Li
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | | | - Juan Carlos Rivera-Mulia
- Department of Biological Science, Center for Genomics and Personalized Medicine, Florida State University, Tallahassee, FL, USA
| | - David M Gilbert
- Department of Biological Science, Center for Genomics and Personalized Medicine, Florida State University, Tallahassee, FL, USA
| | - Zhaohui S Qin
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA
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14
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Repeat Instability in the Fragile X-Related Disorders: Lessons from a Mouse Model. Brain Sci 2019; 9:brainsci9030052. [PMID: 30832215 PMCID: PMC6468611 DOI: 10.3390/brainsci9030052] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Revised: 02/21/2019] [Accepted: 02/27/2019] [Indexed: 12/21/2022] Open
Abstract
The fragile X-related disorders (FXDs) are a group of clinical conditions that result primarily from an unusual mutation, the expansion of a CGG-repeat tract in exon 1 of the FMR1 gene. Mouse models are proving useful for understanding many aspects of disease pathology in these disorders. There is also reason to think that such models may be useful for understanding the molecular basis of the unusual mutation responsible for these disorders. This review will discuss what has been learnt to date about mechanisms of repeat instability from a knock-in FXD mouse model and what the implications of these findings may be for humans carrying expansion-prone FMR1 alleles.
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15
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Crowley JJ, Szatkiewicz J, Kähler AK, Giusti-Rodriguez P, Ancalade N, Booker JK, Carr MT JL, Crawford GE, Losh M, Stockmeier CA, Taylor AK, Piven J, Sullivan PF. Common-variant associations with fragile X syndrome. Mol Psychiatry 2019; 24:338-344. [PMID: 30531935 PMCID: PMC6457435 DOI: 10.1038/s41380-018-0290-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 10/07/2018] [Accepted: 10/09/2018] [Indexed: 12/15/2022]
Abstract
Fragile X syndrome is rare but a prominent cause of intellectual disability. It is usually caused by a de novo mutation that occurs on multiple haplotypes and thus would not be expected to be detectible using genome-wide association (GWA). We conducted GWA in 89 male FXS cases and 266 male controls, and detected multiple genome-wide significant signals near FMR1 (odds ratio = 8.10, P = 2.5 × 10-10). These findings withstood robust attempts at falsification. Fine-mapping yielded a minimum P = 1.13 × 10-14, but did not narrow the interval. Comprehensive functional genomic integration did not provide a mechanistic hypothesis. Controls carrying a risk haplotype had significantly longer FMR1 CGG repeats than controls with the protective haplotype (P = 4.75 × 10-5), which may predispose toward increases in CGG number to the premutation range over many generations. This is a salutary reminder of the complexity of even "simple" monogenetic disorders.
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Affiliation(s)
- James J Crowley
- Department of Genetics, University of North Carolina at Chapel Hill, NC, USA
| | - Jin Szatkiewicz
- Department of Genetics, University of North Carolina at Chapel Hill, NC, USA
| | - Anna K Kähler
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
| | | | - NaEshia Ancalade
- Department of Genetics, University of North Carolina at Chapel Hill, NC, USA
| | - Jessica K Booker
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, NC, USA
| | - Jennifer L Carr MT
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, NC, USA
| | | | - Molly Losh
- Department of Communication Sciences, Northwestern University, Evanston, IL, USA
| | | | | | - Joseph Piven
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. .,Carolina Institute for Developmental Disabilities, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | - Patrick F Sullivan
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. .,Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. .,Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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16
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Abu Diab M, Eiges R. The Contribution of Pluripotent Stem Cell (PSC)-Based Models to the Study of Fragile X Syndrome (FXS). Brain Sci 2019; 9:brainsci9020042. [PMID: 30769941 PMCID: PMC6406836 DOI: 10.3390/brainsci9020042] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Revised: 02/11/2019] [Accepted: 02/13/2019] [Indexed: 02/06/2023] Open
Abstract
Fragile X syndrome (FXS) is the most common heritable form of cognitive impairment. It results from a deficiency in the fragile X mental retardation protein (FMRP) due to a CGG repeat expansion in the 5′-UTR of the X-linked FMR1 gene. When CGGs expand beyond 200 copies, they lead to epigenetic gene silencing of the gene. In addition, the greater the allele size, the more likely it will become unstable and exhibit mosaicism for expansion size between and within tissues in affected individuals. The timing and mechanisms of FMR1 epigenetic gene silencing and repeat instability are far from being understood given the lack of appropriate cellular and animal models that can fully recapitulate the molecular features characteristic of the disease pathogenesis in humans. This review summarizes the data collected to date from mutant human embryonic stem cells, induced pluripotent stem cells, and hybrid fusions, and discusses their contribution to the investigation of FXS, their key limitations, and future prospects.
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Affiliation(s)
- Manar Abu Diab
- Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center, Jerusalem 91031, Israel.
- School of Medicine, Hebrew University of Jerusalem, Jerusalem 9112102, Israel.
| | - Rachel Eiges
- Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center, Jerusalem 91031, Israel.
- School of Medicine, Hebrew University of Jerusalem, Jerusalem 9112102, Israel.
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17
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The G-rich Repeats in FMR1 and C9orf72 Loci Are Hotspots for Local Unpairing of DNA. Genetics 2018; 210:1239-1252. [PMID: 30396881 DOI: 10.1534/genetics.118.301672] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Accepted: 10/15/2018] [Indexed: 12/13/2022] Open
Abstract
Pathological mutations involving noncoding microsatellite repeats are typically located near promoters in CpG islands and are coupled with extensive repeat instability when sufficiently long. What causes these regions to be prone to repeat instability is not fully understood. There is a general consensus that instability results from the induction of unusual structures in the DNA by the repeats as a consequence of mispairing between complementary strands. In addition, there is some evidence that repeat instability is mediated by RNA transcription through the formation of three-stranded nucleic structures composed of persistent DNA:RNA hybrids, concomitant with single-strand DNA displacements (R-loops). Using human embryonic stem cells with wild-type and repeat expanded alleles in the FMR1 (CGGs) and C9orf72 (GGGGCCs) genes, we show that these loci constitute preferential sites (hotspots) for DNA unpairing. When R-loops are formed, DNA unpairing is more extensive, and is coupled with the interruptions of double-strand structures by the nontranscribing (G-rich) DNA strand. These interruptions are likely to reflect unusual structures in the DNA that drive repeat instability when the G-rich repeats considerably expand. Further, we demonstrate that when the CGGs in FMR1 are hyper-methylated and transcriptionally inactive, local DNA unpairing is abolished. Our study thus takes one more step toward the identification of dynamic, unconventional DNA structures across the G-rich repeats at FMR1 and C9orf72 disease-associated loci.
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18
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Zhao XN, Usdin K. Timing of Expansion of Fragile X Premutation Alleles During Intergenerational Transmission in a Mouse Model of the Fragile X-Related Disorders. Front Genet 2018; 9:314. [PMID: 30147707 PMCID: PMC6096447 DOI: 10.3389/fgene.2018.00314] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 07/24/2018] [Indexed: 12/19/2022] Open
Abstract
Fragile X syndrome (FXS) is caused by the maternal expansion of an unstable CGG-repeat tract located in the first exon of the FMR1 gene. Further changes in repeat number occur during embryogenesis resulting in individuals sometimes being highly mosaic. Here we show in a mouse model that, in males, expansions are already present in primary spermatocytes with no additional expansions occurring in later stages of gametogenesis. We also show that, in females, expansion occurs in the post-natal oocyte. Additional expansions and a high frequency of large contractions are seen in two-cell stage embryos. Expansion in oocytes, which are non-dividing, would be consistent with a mechanism involving aberrant DNA repair or recombination rather than a problem with chromosomal replication. Given the difficulty of replicating large CGG-repeat tracts, we speculate that very large expanded alleles may be prone to contract in the mitotically proliferating spermatagonial stem cells in men. However, expanded alleles may not be under such pressure in the non-dividing oocyte. The high degree of both expansions and contractions seen in early embryos may contribute to the high frequency of somatic mosaicism that is observed in humans. Our data thus suggest an explanation for the fact that FXS is exclusively maternally transmitted and lend support to models for repeat expansion that are based on problems arising during DNA repair.
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Affiliation(s)
- Xiao-Nan Zhao
- Gene Structure and Disease Section, Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Karen Usdin
- Gene Structure and Disease Section, Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
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19
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Prenatal Diagnosis of Fragile X Syndrome in a Twin Pregnancy Complicated by a Complete Retraction. Genes (Basel) 2018; 9:genes9060287. [PMID: 29880767 PMCID: PMC6027392 DOI: 10.3390/genes9060287] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 05/31/2018] [Accepted: 06/04/2018] [Indexed: 01/09/2023] Open
Abstract
Fragile X syndrome (FXS) is usually associated with a CGG repeat expansion >200 repeats within the FMR1 gene, known as a full mutation (FM). FM alleles produce abnormal methylation of the FMR1 promoter with reduction or silencing of FMR1 gene expression. Furthermore, premutation (PM: 55–199 CGGs) and full mutation alleles usually expand in size when maternally transmitted to progeny. This study describes a PM allele carried by the mother decreasing to a normal sized allele in a male from a dichorionic diamniotic (DCDA) twin pregnancy, with the female twin inheriting FM (200–790 CGGs), PM (130 CGGs) and normal-sized (39 CGGs) alleles. Further evidence of instability of the maternal PM allele was shown by a male proband (older brother) mosaic for PM (CGG 78 and 150 CGGs) and FM (200–813 CGGs), and a high level of FMR1 promoter methylation, between 50 and 70%, in multiple tissues. The fully-retracted, normal-sized allele was identified by PCR CGG sizing in the male twin, with no evidence of a FM allele identified using Southern blot analysis in multiple tissues collected postnatally and prenatally. Consistent with this, prenatal PCR sizing (35 CGGs) showed inconsistent inheritance of the maternal normal allele (30 CGGs), with single-nucleotide polymorphism (SNP) linkage analysis confirming that the abnormal FMR1 chromosome had been inherited from the mother’s PM chromosome. Importantly, the male twin showed no significant hypermethylation of the FMR1 promoter in all pre and postnatal tissues tested, as well as normal levels of FMR1 mRNA in blood. In summary, this report demonstrates the first postnatal follow up of a prenatal case in which FMR1 mRNA levels were approaching normal, with normal levels of FMR1 promoter methylation and normal CGG size in multiple pre and postnatally collected tissues.
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20
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McGinty RJ, Mirkin SM. Cis- and Trans-Modifiers of Repeat Expansions: Blending Model Systems with Human Genetics. Trends Genet 2018; 34:448-465. [PMID: 29567336 PMCID: PMC5959756 DOI: 10.1016/j.tig.2018.02.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 02/15/2018] [Accepted: 02/19/2018] [Indexed: 12/30/2022]
Abstract
Over 30 hereditary diseases are caused by the expansion of microsatellite repeats. The length of the expandable repeat is the main hereditary determinant of these disorders. They are also affected by numerous genomic variants that are either nearby (cis) or physically separated from (trans) the repetitive locus, which we review here. These genetic variants have largely been elucidated in model systems using gene knockouts, while a few have been directly observed as single-nucleotide polymorphisms (SNPs) in patients. There is a notable disconnect between these two bodies of knowledge: knockouts poorly approximate the SNP-level variation in human populations that gives rise to medically relevant cis- and trans-modifiers, while the rarity of these diseases limits the statistical power of SNP-based analysis in humans. We propose that high-throughput SNP-based screening in model systems could become a useful approach to quickly identify and characterize modifiers of clinical relevance for patients.
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Affiliation(s)
- Ryan J McGinty
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, MA 02155, USA.
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21
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Rivera-Mulia JC, Dimond A, Vera D, Trevilla-Garcia C, Sasaki T, Zimmerman J, Dupont C, Gribnau J, Fraser P, Gilbert DM. Allele-specific control of replication timing and genome organization during development. Genome Res 2018; 28:800-811. [PMID: 29735606 PMCID: PMC5991511 DOI: 10.1101/gr.232561.117] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 04/26/2018] [Indexed: 12/14/2022]
Abstract
DNA replication occurs in a defined temporal order known as the replication-timing (RT) program. RT is regulated during development in discrete chromosomal units, coordinated with transcriptional activity and 3D genome organization. Here, we derived distinct cell types from F1 hybrid musculus × castaneus mouse crosses and exploited the high single-nucleotide polymorphism (SNP) density to characterize allelic differences in RT (Repli-seq), genome organization (Hi-C and promoter-capture Hi-C), gene expression (total nuclear RNA-seq), and chromatin accessibility (ATAC-seq). We also present HARP, a new computational tool for sorting SNPs in phased genomes to efficiently measure allele-specific genome-wide data. Analysis of six different hybrid mESC clones with different genomes (C57BL/6, 129/sv, and CAST/Ei), parental configurations, and gender revealed significant RT asynchrony between alleles across ∼12% of the autosomal genome linked to subspecies genomes but not to parental origin, growth conditions, or gender. RT asynchrony in mESCs strongly correlated with changes in Hi-C compartments between alleles but not as strongly with SNP density, gene expression, imprinting, or chromatin accessibility. We then tracked mESC RT asynchronous regions during development by analyzing differentiated cell types, including extraembryonic endoderm stem (XEN) cells, four male and female primary mouse embryonic fibroblasts (MEFs), and neural precursor cells (NPCs) differentiated in vitro from mESCs with opposite parental configurations. We found that RT asynchrony and allelic discordance in Hi-C compartments seen in mESCs were largely lost in all differentiated cell types, accompanied by novel sites of allelic asynchrony at a considerably smaller proportion of the genome, suggesting that genome organization of homologs converges to similar folding patterns during cell fate commitment.
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Affiliation(s)
- Juan Carlos Rivera-Mulia
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
| | - Andrew Dimond
- The Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, United Kingdom
| | - Daniel Vera
- Center for Genomics and Personalized Medicine, Florida State University, Tallahassee, Florida 32306, USA
| | - Claudia Trevilla-Garcia
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
| | - Takayo Sasaki
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
| | - Jared Zimmerman
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
| | - Catherine Dupont
- Department of Reproduction and Development, Erasmus MC, University Medical Center, 3015GE Rotterdam, The Netherlands
| | - Joost Gribnau
- Department of Reproduction and Development, Erasmus MC, University Medical Center, 3015GE Rotterdam, The Netherlands
| | - Peter Fraser
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
- The Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, United Kingdom
- Center for Genomics and Personalized Medicine, Florida State University, Tallahassee, Florida 32306, USA
| | - David M Gilbert
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
- Center for Genomics and Personalized Medicine, Florida State University, Tallahassee, Florida 32306, USA
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22
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Madireddy A, Kosiyatrakul ST, Boisvert RA, Herrera-Moyano E, García-Rubio ML, Gerhardt J, Vuono EA, Owen N, Yan Z, Olson S, Aguilera A, Howlett NG, Schildkraut CL. FANCD2 Facilitates Replication through Common Fragile Sites. Mol Cell 2017; 64:388-404. [PMID: 27768874 DOI: 10.1016/j.molcel.2016.09.017] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 08/08/2016] [Accepted: 09/14/2016] [Indexed: 12/27/2022]
Abstract
Common fragile sites (CFSs) are genomic regions that are unstable under conditions of replicative stress. Although the characteristics of CFSs that render them vulnerable to stress are associated mainly with replication, the cellular pathways that protect CFSs during replication remain unclear. Here, we identify and describe a role for FANCD2 as a trans-acting facilitator of CFS replication, in the absence of exogenous replicative stress. In the absence of FANCD2, replication forks stall within the AT-rich fragility core of CFS, leading to dormant origin activation. Furthermore, FANCD2 deficiency is associated with DNA:RNA hybrid formation at CFS-FRA16D, and inhibition of DNA:RNA hybrid formation suppresses replication perturbation. In addition, we also found that FANCD2 reduces the number of potential sites of replication initiation. Our data demonstrate that FANCD2 protein is required to ensure efficient CFS replication and provide mechanistic insight into how FANCD2 regulates CFS stability.
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Affiliation(s)
- Advaitha Madireddy
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | | | - Rebecca A Boisvert
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA
| | - Emilia Herrera-Moyano
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, Universidad de Sevilla, 41092 Seville, Spain
| | - María L García-Rubio
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, Universidad de Sevilla, 41092 Seville, Spain
| | - Jeannine Gerhardt
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Elizabeth A Vuono
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA
| | - Nichole Owen
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Zi Yan
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Susan Olson
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, Universidad de Sevilla, 41092 Seville, Spain
| | - Niall G Howlett
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA
| | - Carl L Schildkraut
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Aladjem MI, Redon CE. Order from clutter: selective interactions at mammalian replication origins. Nat Rev Genet 2017; 18:101-116. [PMID: 27867195 PMCID: PMC6596300 DOI: 10.1038/nrg.2016.141] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mammalian chromosome duplication progresses in a precise order and is subject to constraints that are often relaxed in developmental disorders and malignancies. Molecular information about the regulation of DNA replication at the chromatin level is lacking because protein complexes that initiate replication seem to bind chromatin indiscriminately. High-throughput sequencing and mathematical modelling have yielded detailed genome-wide replication initiation maps. Combining these maps and models with functional genetic analyses suggests that distinct DNA-protein interactions at subgroups of replication initiation sites (replication origins) modulate the ubiquitous replication machinery and supports an emerging model that delineates how indiscriminate DNA-binding patterns translate into a consistent, organized replication programme.
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Affiliation(s)
- Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, Maryland 20892, USA
| | - Christophe E Redon
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, Maryland 20892, USA
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24
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Madireddy A, Gerhardt J. Replication Through Repetitive DNA Elements and Their Role in Human Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:549-581. [PMID: 29357073 DOI: 10.1007/978-981-10-6955-0_23] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Human cells contain various repetitive DNA sequences, which can be a challenge for the DNA replication machinery to travel through and replicate correctly. Repetitive DNA sequence can adopt non-B DNA structures, which could block the DNA replication. Prolonged stalling of the replication fork at the endogenous repeats in human cells can have severe consequences such as genome instability that includes repeat expansions, contractions, and chromosome fragility. Several neurological and muscular diseases are caused by a repeat expansion. Furthermore genome instability is the major cause of cancer. This chapter describes some of the important classes of repetitive DNA sequences in the mammalian genome, their ability to form secondary DNA structures, their contribution to replication fork stalling, and models for repeat expansion as well as chromosomal fragility. Included in this chapter are also some of the strategies currently employed to detect changes in DNA replication and proteins that could prevent the repeat-mediated disruption of DNA replication in human cells. Additionally summarized are the consequences of repeat-associated perturbation of the DNA replication, which could lead to specific human diseases.
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25
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Vershkov D, Benvenisty N. Human pluripotent stem cells in modeling human disorders: the case of fragile X syndrome. Regen Med 2017; 12:53-68. [DOI: 10.2217/rme-2016-0100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Human pluripotent stem cells (PSCs) generated from affected blastocysts or from patient-derived somatic cells are an emerging platform for disease modeling and drug discovery. Fragile X syndrome (FXS), the leading cause of inherited intellectual disability, was one of the first disorders modeled in both embryonic stem cells and induced PCSs and can serve as an exemplary case for the utilization of human PSCs in the study of human diseases. Over the past decade, FXS-PSCs have been used to address the fundamental questions regarding the pathophysiology of FXS. In this review we summarize the methodologies for generation of FXS-PSCs, discuss their advantages and disadvantages compared with existing modeling systems and describe their utilization in the study of FXS pathogenesis and in the development of targeted treatment.
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Affiliation(s)
- Dan Vershkov
- The Azrieli Center for Stem Cells & Genetic Research, Department of Genetics, Silberman Institute of Life Sciences, The Hebrew University, Jerusalem 91904, Israel
| | - Nissim Benvenisty
- The Azrieli Center for Stem Cells & Genetic Research, Department of Genetics, Silberman Institute of Life Sciences, The Hebrew University, Jerusalem 91904, Israel
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26
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Macpherson JN, Murray A. Development of Genetic Testing for Fragile X Syndrome and Associated Disorders, and Estimates of the Prevalence of FMR1 Expansion Mutations. Genes (Basel) 2016; 7:genes7120110. [PMID: 27916885 PMCID: PMC5192486 DOI: 10.3390/genes7120110] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 11/10/2016] [Accepted: 11/24/2016] [Indexed: 12/15/2022] Open
Abstract
The identification of a trinucleotide (CGG) expansion as the chief mechanism of mutation in Fragile X syndrome in 1991 heralded a new chapter in molecular diagnostic genetics and generated a new perspective on mutational mechanisms in human genetic disease, which rapidly became a central paradigm (“dynamic mutation”) as more and more of the common hereditary neurodevelopmental disorders were ascribed to this novel class of mutation. The progressive expansion of a CGG repeat in the FMR1 gene from “premutation” to “full mutation” provided an explanation for the “Sherman paradox,” just as similar expansion mechanisms in other genes explained the phenomenon of “anticipation” in their pathogenesis. Later, FMR1 premutations were unexpectedly found associated with two other distinct phenotypes: primary ovarian insufficiency and tremor-ataxia syndrome. This review will provide a historical perspective on procedures for testing and reporting of Fragile X syndrome and associated disorders, and the population genetics of FMR1 expansions, including estimates of prevalence and the influence of AGG interspersions on the rate and probability of expansion.
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Affiliation(s)
- James N Macpherson
- Wessex Regional Genetics Laboratory, Salisbury NHS Foundation Trust, Salisbury District Hospital, Salisbury SP2 8BJ, UK.
| | - Anna Murray
- Medical School, University of Exeter, RILD Level 3, Royal Devon & Exeter Hospital, Barrack Road, Exeter EX2 5DW, UK.
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27
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Zhou Y, Kumari D, Sciascia N, Usdin K. CGG-repeat dynamics and FMR1 gene silencing in fragile X syndrome stem cells and stem cell-derived neurons. Mol Autism 2016; 7:42. [PMID: 27713816 PMCID: PMC5053128 DOI: 10.1186/s13229-016-0105-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 09/26/2016] [Indexed: 01/19/2023] Open
Abstract
Background Fragile X syndrome (FXS), a common cause of intellectual disability and autism, results from the expansion of a CGG-repeat tract in the 5′ untranslated region of the FMR1 gene to >200 repeats. Such expanded alleles, known as full mutation (FM) alleles, are epigenetically silenced in differentiated cells thus resulting in the loss of FMRP, a protein important for learning and memory. The timing of repeat expansion and FMR1 gene silencing is controversial. Methods We monitored the repeat size and methylation status of FMR1 alleles with expanded CGG repeats in patient-derived induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs) that were grown for extended period of time either as stem cells or differentiated into neurons. We used a PCR assay optimized for the amplification of large CGG repeats for sizing, and a quantitative methylation-specific PCR for the analysis of FMR1 promoter methylation. The FMR1 mRNA levels were analyzed by qRT-PCR. FMRP levels were determined by western blotting and immunofluorescence. Chromatin immunoprecipitation was used to study the association of repressive histone marks with the FMR1 gene in FXS ESCs. Results We show here that while FMR1 gene silencing can be seen in FXS embryonic stem cells (ESCs), some silenced alleles contract and when the repeat number drops below ~400, DNA methylation erodes, even when the repeat number remains >200. The resultant active alleles do not show the large step-wise expansions seen in stem cells from other repeat expansion diseases. Furthermore, there may be selection against large active alleles and these alleles do not expand further or become silenced on neuronal differentiation. Conclusions Our data support the hypotheses that (i) large expansions occur prezygotically or in the very early embryo, (ii) large unmethylated alleles may be deleterious in stem cells, (iii) methylation can occur on alleles with >400 repeats very early in embryogenesis, and (iv) expansion and contraction may occur by different mechanisms. Our data also suggest that the threshold for stable methylation of FM alleles may be higher than previously thought. A higher threshold might explain why some carriers of FM alleles escape methylation. It may also provide a simple explanation for why silencing has not been observed in mouse models with >200 repeats. Electronic supplementary material The online version of this article (doi:10.1186/s13229-016-0105-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yifan Zhou
- Section on Gene Structure and Disease, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD USA
| | - Daman Kumari
- Section on Gene Structure and Disease, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD USA
| | - Nicholas Sciascia
- Section on Gene Structure and Disease, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD USA ; Present Address: Laboratory of Genome Integrity, National Cancer Institute, Bethesda, MD USA
| | - Karen Usdin
- Section on Gene Structure and Disease, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD USA
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28
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Ups and Downs: Mechanisms of Repeat Instability in the Fragile X-Related Disorders. Genes (Basel) 2016; 7:genes7090070. [PMID: 27657135 PMCID: PMC5042400 DOI: 10.3390/genes7090070] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 08/30/2016] [Accepted: 09/13/2016] [Indexed: 02/06/2023] Open
Abstract
The Fragile X-related disorders (FXDs) are a group of clinical conditions resulting from the expansion of a CGG/CCG-repeat tract in exon 1 of the Fragile X mental retardation 1 (FMR1) gene. While expansions of the repeat tract predominate, contractions are also seen with the net result being that individuals can show extensive repeat length heterogeneity in different tissues. The mechanisms responsible for expansion and contraction are still not well understood. This review will discuss what is known about these processes and current evidence that supports a model in which expansion arises from the interaction of components of the base excision repair, mismatch repair and transcription coupled repair pathways.
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29
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Gerhardt J, Bhalla AD, Butler JS, Puckett JW, Dervan PB, Rosenwaks Z, Napierala M. Stalled DNA Replication Forks at the Endogenous GAA Repeats Drive Repeat Expansion in Friedreich's Ataxia Cells. Cell Rep 2016; 16:1218-1227. [PMID: 27425605 PMCID: PMC5028224 DOI: 10.1016/j.celrep.2016.06.075] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 05/31/2016] [Accepted: 06/17/2016] [Indexed: 10/21/2022] Open
Abstract
Friedreich's ataxia (FRDA) is caused by the expansion of GAA repeats located in the Frataxin (FXN) gene. The GAA repeats continue to expand in FRDA patients, aggravating symptoms and contributing to disease progression. The mechanism leading to repeat expansion and decreased FXN transcription remains unclear. Using single-molecule analysis of replicated DNA, we detected that expanded GAA repeats present a substantial obstacle for the replication machinery at the FXN locus in FRDA cells. Furthermore, aberrant origin activation and lack of a proper stress response to rescue the stalled forks in FRDA cells cause an increase in 3'-5' progressing forks, which could enhance repeat expansion and hinder FXN transcription by head-on collision with RNA polymerases. Treatment of FRDA cells with GAA-specific polyamides rescues DNA replication fork stalling and alleviates expansion of the GAA repeats, implicating DNA triplexes as a replication impediment and suggesting that fork stalling might be a therapeutic target for FRDA.
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Affiliation(s)
- Jeannine Gerhardt
- Center for Reproductive Medicine, Weill Cornell Medical College, New York, NY 10065, USA.
| | - Angela D Bhalla
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA
| | - Jill Sergesketter Butler
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA
| | - James W Puckett
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Peter B Dervan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Zev Rosenwaks
- Center for Reproductive Medicine, Weill Cornell Medical College, New York, NY 10065, USA
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA; Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61 704, Poland.
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30
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Rivera-Mulia JC, Gilbert DM. Replication timing and transcriptional control: beyond cause and effect-part III. Curr Opin Cell Biol 2016; 40:168-178. [PMID: 27115331 DOI: 10.1016/j.ceb.2016.03.022] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 03/24/2016] [Accepted: 03/29/2016] [Indexed: 11/17/2022]
Abstract
DNA replication is essential for faithful transmission of genetic information and is intimately tied to chromosome structure and function. Genome duplication occurs in a defined temporal order known as the replication-timing (RT) program, which is regulated during the cell cycle and development in discrete units referred to as replication domains (RDs). RDs correspond to topologically-associating domains (TADs) and are spatio-temporally compartmentalized in the nucleus. While improvements in experimental tools have begun to reveal glimpses of causality, they have also unveiled complex context-dependent relationships that challenge long recognized correlations of RT to chromatin organization and gene regulation. In particular, RDs/TADs that switch RT during development march to the beat of a different drummer.
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Affiliation(s)
| | - David M Gilbert
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, USA; Center for Genomics and Personalized Medicine, Florida State University, Tallahassee, FL, USA.
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31
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Hutchins JRA, Aze A, Coulombe P, Méchali M. Characteristics of Metazoan DNA Replication Origins. DNA REPLICATION, RECOMBINATION, AND REPAIR 2016. [PMCID: PMC7120227 DOI: 10.1007/978-4-431-55873-6_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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32
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Gerhardt J. Epigenetic modifications in human fragile X pluripotent stem cells; Implications in fragile X syndrome modeling. Brain Res 2015; 1656:55-62. [PMID: 26475977 DOI: 10.1016/j.brainres.2015.10.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 08/18/2015] [Accepted: 10/02/2015] [Indexed: 12/18/2022]
Abstract
Patients with fragile X syndrome (FXS) exhibit moderate to severe intellectual disabilities. In addition, one-third of FXS patients show characteristics of autism spectrum disorder. FXS is caused by a trinucleotide repeat expansion, which leads to silencing of the fragile X mental retardation (FMR1) gene. The absence of the FMR1 gene product, FMRP, is the reason for the disease symptoms. It has been suggested that repeat instability and transcription of the FMR1 gene occur during early embryonic development, while after cell differentiation repeats become stable and the FMR1 gene is silent. Epigenetic marks, such as DNA methylation, are associated with gene silencing and repeat stability at the FMR1 locus. However, the mechanisms leading to gene silencing and repeat expansion are still ambiguous, because studies at the human genomic locus were limited until now. The FXS pluripotent stem cells, recently derived from FXS adult cells and FXS blastocysts, are new useful tools to examine these mechanisms at the human endogenous FMR1 locus. This review summarizes the epigenetic features and experimental studies of FXS human embryonic and FXS induced pluripotent stem cells, generated so far. This article is part of a Special Issue entitled SI: Exploiting human neurons.
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Affiliation(s)
- Jeannine Gerhardt
- Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx 10461, USA.
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33
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Thys RG, Wang YH. DNA Replication Dynamics of the GGGGCC Repeat of the C9orf72 Gene. J Biol Chem 2015; 290:28953-62. [PMID: 26463209 PMCID: PMC4661408 DOI: 10.1074/jbc.m115.660324] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Indexed: 01/27/2023] Open
Abstract
DNA has the ability to form a variety of secondary structures in addition to the normal B-form DNA, including hairpins and quadruplexes. These structures are implicated in a number of neurological diseases and cancer. Expansion of a GGGGCC repeat located at C9orf72 is associated with familial amyotrophic lateral sclerosis and frontotemporal dementia. This repeat expands from two to 24 copies in normal individuals to several hundreds or thousands of repeats in individuals with the disease. Biochemical studies have demonstrated that as little as four repeats have the ability to form a stable DNA secondary structure known as a G-quadruplex. Quadruplex structures have the ability to disrupt normal DNA processes such as DNA replication and transcription. Here we examine the role of GGGGCC repeat length and orientation on DNA replication using an SV40 replication system in human cells. Replication through GGGGCC repeats leads to a decrease in overall replication efficiency and an increase in instability in a length-dependent manner. Both repeat expansions and contractions are observed, and replication orientation is found to influence the propensity for expansions or contractions. The presence of replication stress, such as low-dose aphidicolin, diminishes replication efficiency but has no effect on instability. Two-dimensional gel electrophoresis analysis demonstrates a replication stall with as few as 20 GGGGCC repeats. These results suggest that replication of the GGGGCC repeat at C9orf72 is perturbed by the presence of expanded repeats, which has the potential to result in further expansion, leading to disease.
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Affiliation(s)
- Ryan Griffin Thys
- From the Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia 22908
| | - Yuh-Hwa Wang
- From the Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia 22908
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Rezwan FI, Docherty LE, Poole RL, Lockett GA, Arshad SH, Holloway JW, Temple IK, Mackay DJ. A statistical method for single sample analysis of HumanMethylation450 array data: genome-wide methylation analysis of patients with imprinting disorders. Clin Epigenetics 2015; 7:48. [PMID: 25918558 PMCID: PMC4410592 DOI: 10.1186/s13148-015-0081-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 04/06/2015] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND The Illumina Infinium HumanMethylation450 BeadChip is an array-based technology for analysing DNA methylation at approximately 475,000 differentially methylated cytosines across the human genome. Hitherto, the array has been used for case-control studies, where sample numbers can be sufficient to yield statistically robust data on a genome-wide basis. We recently reported an informatic pipeline capable of yielding statistically and biologically significant results using only five cases, which expanded the use of this technology to rare disease studies. However, the clinical application of these technologies requires the ability to perform robust analysis of individual patients. RESULTS Here we report a novel informatic approach for methylation array analysis of single samples, using the Crawford-Howell t-test. We tested our approach on patients with ultra-rare imprinting disorders with aberrant DNA methylation at multiple locations across the genome, which was previously detected by targeted testing. However, array analysis outperformed targeted assays in three ways: it detected loci not normally analysed by targeted testing, detected methylation changes too subtle to detect by the targeted testing and reported broad and consistent methylation changes across genetic loci not captured by point testing. CONCLUSIONS This method has potential clinical utility for human disorders where DNA methylation change may be a biomarker of disease.
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Affiliation(s)
- Faisal I Rezwan
- Human Development and Health, Faculty of Medicine, University of Southampton, Tremona Road, Southampton, Hampshire SO16 6YD UK
| | - Louise E Docherty
- Human Development and Health, Faculty of Medicine, University of Southampton, Tremona Road, Southampton, Hampshire SO16 6YD UK ; Wessex Regional Genetics Laboratory, Salisbury NHS Foundation Trust, Salisbury District Hospital, Salisbury, Wilts SO2 8BJ UK
| | - Rebecca L Poole
- Human Development and Health, Faculty of Medicine, University of Southampton, Tremona Road, Southampton, Hampshire SO16 6YD UK ; Wessex Regional Genetics Laboratory, Salisbury NHS Foundation Trust, Salisbury District Hospital, Salisbury, Wilts SO2 8BJ UK
| | - Gabrielle A Lockett
- Human Development and Health, Faculty of Medicine, University of Southampton, Tremona Road, Southampton, Hampshire SO16 6YD UK
| | - S Hasan Arshad
- The David Hide Asthma and Allergy Research Centre, St Mary's Hospital, Newport, Isle of Wight PO30 5TG UK ; Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Tremona Road, Southampton, Hampshire SO16 6YD UK
| | - John W Holloway
- Human Development and Health, Faculty of Medicine, University of Southampton, Tremona Road, Southampton, Hampshire SO16 6YD UK
| | - I Karen Temple
- Human Development and Health, Faculty of Medicine, University of Southampton, Tremona Road, Southampton, Hampshire SO16 6YD UK ; Wessex Clinical Genetics Service, Princess Anne Hospital, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Deborah Jg Mackay
- Human Development and Health, Faculty of Medicine, University of Southampton, Tremona Road, Southampton, Hampshire SO16 6YD UK ; Wessex Regional Genetics Laboratory, Salisbury NHS Foundation Trust, Salisbury District Hospital, Salisbury, Wilts SO2 8BJ UK
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Usdin K, House NCM, Freudenreich CH. Repeat instability during DNA repair: Insights from model systems. Crit Rev Biochem Mol Biol 2015; 50:142-67. [PMID: 25608779 DOI: 10.3109/10409238.2014.999192] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The expansion of repeated sequences is the cause of over 30 inherited genetic diseases, including Huntington disease, myotonic dystrophy (types 1 and 2), fragile X syndrome, many spinocerebellar ataxias, and some cases of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Repeat expansions are dynamic, and disease inheritance and progression are influenced by the size and the rate of expansion. Thus, an understanding of the various cellular mechanisms that cooperate to control or promote repeat expansions is of interest to human health. In addition, the study of repeat expansion and contraction mechanisms has provided insight into how repair pathways operate in the context of structure-forming DNA, as well as insights into non-canonical roles for repair proteins. Here we review the mechanisms of repeat instability, with a special emphasis on the knowledge gained from the various model systems that have been developed to study this topic. We cover the repair pathways and proteins that operate to maintain genome stability, or in some cases cause instability, and the cross-talk and interactions between them.
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Affiliation(s)
- Karen Usdin
- Laboratory of Cell and Molecular Biology, NIDDK, NIH , Bethesda, MD , USA
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36
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Short B. A replication origin gets SNP’d out in fragile X syndrome. J Biophys Biochem Cytol 2014. [PMCID: PMC4151140 DOI: 10.1083/jcb.2065iti2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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