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Xie L, Li H, Xiao M, Chen N, Zang X, Liu Y, Ye H, Tang C. Epigenetic insights into Fragile X Syndrome. Front Cell Dev Biol 2024; 12:1432444. [PMID: 39220684 PMCID: PMC11362040 DOI: 10.3389/fcell.2024.1432444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2024] [Accepted: 08/05/2024] [Indexed: 09/04/2024] Open
Abstract
Fragile X Syndrome (FXS) is a genetic neurodevelopmental disorder closely associated with intellectual disability and autism spectrum disorders. The core of the disease lies in the abnormal expansion of the CGG trinucleotide repeat sequence at the 5'end of the FMR1 gene. When the repetition exceeds 200 times, it causes the silencing of the FMR1 gene, leading to the absence of the encoded Fragile X mental retardation protein 1 (FMRP). Although the detailed mechanism by which the CGG repeat expansion triggers gene silencing is yet to be fully elucidated, it is known that this process does not alter the promoter region or the coding sequence of the FMR1 gene. This discovery provides a scientific basis for the potential reversal of FMR1 gene silencing through interventional approaches, thereby improving the symptoms of FXS. Epigenetics, a mechanism of genetic regulation that does not depend on changes in the DNA sequence, has become a new focus in FXS research by modulating gene expression in a reversible manner. The latest progress in molecular genetics has revealed that epigenetics plays a key role in the pathogenesis and pathophysiological processes of FXS. This article compiles the existing research findings on the role of epigenetics in Fragile X Syndrome (FXS) with the aim of deepening the understanding of the pathogenesis of FXS to identify potential targets for new therapeutic strategies.
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Affiliation(s)
- Liangqun Xie
- The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, China
- Department of Obstetrics and Gynecology, The First College of Clinical Medical Science, Yichang Central People’s Hospital, Three Gorges University, Yichang, Hubei, China
| | - Huiying Li
- Department of Obstetrics and Gynecology, The First College of Clinical Medical Science, Yichang Central People’s Hospital, Three Gorges University, Yichang, Hubei, China
| | - MengLiang Xiao
- Department of Obstetrics and Gynecology, The First College of Clinical Medical Science, Yichang Central People’s Hospital, Three Gorges University, Yichang, Hubei, China
| | - Ningjing Chen
- Department of Obstetrics and Gynecology, The First College of Clinical Medical Science, Yichang Central People’s Hospital, Three Gorges University, Yichang, Hubei, China
| | - Xiaoxiao Zang
- The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, China
| | - Yingying Liu
- Department of Obstetrics and Gynecology, The First College of Clinical Medical Science, Yichang Central People’s Hospital, Three Gorges University, Yichang, Hubei, China
| | - Hong Ye
- Department of Obstetrics and Gynecology, The First College of Clinical Medical Science, Yichang Central People’s Hospital, Three Gorges University, Yichang, Hubei, China
| | - Chaogang Tang
- The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, China
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Rodrigues B, Sousa V, Yrigollen CM, Tassone F, Villate O, Allen EG, Glicksman A, Tortora N, Nolin SL, Nogueira AJA, Jorge P. FMR1 allelic complexity in premutation carriers provides no evidence for a correlation with age at amenorrhea. Reprod Biol Endocrinol 2024; 22:71. [PMID: 38907244 PMCID: PMC11191145 DOI: 10.1186/s12958-024-01227-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 05/09/2024] [Indexed: 06/23/2024] Open
Abstract
BACKGROUND Premutations in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene, defined as between 55 and 200 CGGs, have been implicated in fragile X-associated primary ovarian insufficiency (FXPOI). Only 20% of female premutation carriers develop early ovulatory dysfunction, the reason for this incomplete penetrance is unknown. This study validated the mathematical model in premutation alleles, after assigning each allele a score representing allelic complexity. Subsequently, allelic scores were used to investigate the impact of allele complexity on age at amenorrhea for 58 premutation cases (116 alleles) previously published. METHODS The allelic score was determined using a formula previously described by our group. The impact of each allelic score on age at amenorrhea was analyzed using Pearson's test and a contour plot generated to visualize the effect. RESULTS Correlation of allelic score revealed two distinct complexity behaviors in premutation alleles. No significant correlation was observed between the allelic score of premutation alleles and age at amenorrhea. The same lack of significant correlation was observed regarding normal-sized alleles, despite a nearly significant trend. CONCLUSIONS Our results suggest that the use of allelic scores combination have the potential to explain female infertility, namely the development of FXPOI, or ovarian dysfunction, despite the lack of correlation with age at amenorrhea. Such a finding is of great clinical significance for early identification of females at risk of ovulatory dysfunction, enhancement of fertility preservation techniques, and increasing the probability for a successful pregnancy in females with premutations. Additional investigation is necessary to validate this hypothesis.
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Affiliation(s)
- Bárbara Rodrigues
- Molecular Genetics Laboratory, Laboratory Genetics Service, Genetics and Pathology Clinic, Unidade Local de Saúde de Santo António (ULSSA), Porto, Portugal
- UMIB - Unit for Multidisciplinary Research in Biomedicine, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal
- ITR - Laboratory for Integrative and Translational Research in Population Health, Porto, Portugal
| | - Vanessa Sousa
- Molecular Genetics Laboratory, Laboratory Genetics Service, Genetics and Pathology Clinic, Unidade Local de Saúde de Santo António (ULSSA), Porto, Portugal
- UMIB - Unit for Multidisciplinary Research in Biomedicine, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal
- ITR - Laboratory for Integrative and Translational Research in Population Health, Porto, Portugal
- Cytogenetics Laboratory, Department of Microscopy, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal
| | - Carolyn M Yrigollen
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA, USA
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Stockton Blvd, USA
- MIND Institute, School of Medicine, University of California, Davis, CA, USA
| | - Olatz Villate
- Pediatric Oncology Group, Biocruces Bizkaia Health Research Institute, Barakaldo, Biscay, Basque Country, Spain
| | - Emily G Allen
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
| | - Anne Glicksman
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY, USA
| | - Nicole Tortora
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY, USA
| | - Sarah L Nolin
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY, USA
| | - António J A Nogueira
- CESAM - Center for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro, Portugal
| | - Paula Jorge
- Molecular Genetics Laboratory, Laboratory Genetics Service, Genetics and Pathology Clinic, Unidade Local de Saúde de Santo António (ULSSA), Porto, Portugal.
- UMIB - Unit for Multidisciplinary Research in Biomedicine, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal.
- ITR - Laboratory for Integrative and Translational Research in Population Health, Porto, Portugal.
- Cytogenetics Laboratory, Department of Microscopy, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal.
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Zhang Y, Liu X, Li Z, Li H, Miao Z, Wan B, Xu X. Advances on the Mechanisms and Therapeutic Strategies in Non-coding CGG Repeat Expansion Diseases. Mol Neurobiol 2024:10.1007/s12035-024-04239-9. [PMID: 38780719 DOI: 10.1007/s12035-024-04239-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 05/02/2024] [Indexed: 05/25/2024]
Abstract
Non-coding CGG repeat expansions within the 5' untranslated region are implicated in a range of neurological disorders, including fragile X-associated tremor/ataxia syndrome, oculopharyngeal myopathy with leukodystrophy, and oculopharyngodistal myopathy. This review outlined the general characteristics of diseases associated with non-coding CGG repeat expansions, detailing their clinical manifestations and neuroimaging patterns, which often overlap and indicate shared pathophysiological traits. We summarized the underlying molecular mechanisms of these disorders, providing new insights into the roles that DNA, RNA, and toxic proteins play. Understanding these mechanisms is crucial for the development of targeted therapeutic strategies. These strategies include a range of approaches, such as antisense oligonucleotides, RNA interference, genomic DNA editing, small molecule interventions, and other treatments aimed at correcting the dysregulated processes inherent in these disorders. A deeper understanding of the shared mechanisms among non-coding CGG repeat expansion disorders may hold the potential to catalyze the development of innovative therapies, ultimately offering relief to individuals grappling with these debilitating neurological conditions.
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Affiliation(s)
- Yutong Zhang
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China
| | - Xuan Liu
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China
| | - Zeheng Li
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China
| | - Hao Li
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China
- Department of Neurology, The Fourth Affiliated Hospital of Soochow University, Suzhou, 215124, China
| | - Zhigang Miao
- The Institute of Neuroscience, Soochow University, Suzhou City, China
| | - Bo Wan
- The Institute of Neuroscience, Soochow University, Suzhou City, China
| | - Xingshun Xu
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China.
- The Institute of Neuroscience, Soochow University, Suzhou City, China.
- Department of Neurology, The First Affiliated Hospital of Soochow University, Suzhou, 215000, China.
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Randol JL, Kim K, Ponzini MD, Tassone F, Falcon AK, Hagerman RJ, Hagerman PJ. Variation of FMRP Expression in Peripheral Blood Mononuclear Cells from Individuals with Fragile X Syndrome. Genes (Basel) 2024; 15:356. [PMID: 38540415 PMCID: PMC10969917 DOI: 10.3390/genes15030356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 03/02/2024] [Accepted: 03/08/2024] [Indexed: 04/07/2024] Open
Abstract
Fragile X syndrome (FXS) is the most common heritable cause of intellectual disability and autism spectrum disorder. The syndrome is often caused by greatly reduced or absent protein expression from the fragile X messenger ribonucleoprotein 1 (FMR1) gene due to expansion of a 5'-non-coding trinucleotide (CGG) element beyond 200 repeats (full mutation). To better understand the complex relationships among FMR1 allelotype, methylation status, mRNA expression, and FMR1 protein (FMRP) levels, FMRP was quantified in peripheral blood mononuclear cells for a large cohort of FXS (n = 154) and control (n = 139) individuals using time-resolved fluorescence resonance energy transfer. Considerable size and methylation mosaicism were observed among individuals with FXS, with FMRP detected only in the presence of such mosaicism. No sample with a minimum allele size greater than 273 CGG repeats had significant levels of FMRP. Additionally, an association was observed between FMR1 mRNA and FMRP levels in FXS samples, predominantly driven by those with the lowest FMRP values. This study underscores the complexity of FMR1 allelotypes and FMRP expression and prompts a reevaluation of FXS therapies aimed at reactivating large full mutation alleles that are likely not capable of producing sufficient FMRP to improve cognitive function.
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Affiliation(s)
- Jamie L. Randol
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Kyoungmi Kim
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
- Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Matthew D. Ponzini
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
- Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
| | - Alexandria K. Falcon
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Randi J. Hagerman
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
- Department of Pediatrics, School of Medicine, University of California, Davis, Sacramento, CA 95817, USA
| | - Paul J. Hagerman
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
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Kumari D, Lokanga RA, McCann C, Ried T, Usdin K. The fragile X locus is prone to spontaneous DNA damage that is preferentially repaired by nonhomologous end-joining to preserve genome integrity. iScience 2024; 27:108814. [PMID: 38303711 PMCID: PMC10831274 DOI: 10.1016/j.isci.2024.108814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 10/26/2023] [Accepted: 01/02/2024] [Indexed: 02/03/2024] Open
Abstract
A long CGG-repeat tract in the FMR1 gene induces the epigenetic silencing that causes fragile X syndrome (FXS). Epigenetic changes include H4K20 trimethylation, a heterochromatic modification frequently implicated in transcriptional silencing. Here, we report that treatment with A-196, an inhibitor of SUV420H1/H2, the enzymes responsible for H4K20 di-/trimethylation, does not affect FMR1 transcription, but does result in increased chromosomal duplications. Increased duplications were also seen in FXS cells treated with SCR7, an inhibitor of Lig4, a ligase essential for NHEJ. Our study suggests that the fragile X (FX) locus is prone to spontaneous DNA damage that is normally repaired by NHEJ. We suggest that heterochromatinization of the FX allele may be triggered, at least in part, in response to this DNA damage.
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Affiliation(s)
- Daman Kumari
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Rachel Adihe Lokanga
- Section of Cancer Genomics, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Cai McCann
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Thomas Ried
- Section of Cancer Genomics, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Karen Usdin
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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Hnoonual A, Plong-On O, Worachotekamjorn J, Charalsawadi C, Limprasert P. Clinical and molecular characteristics of FMR1 microdeletion in patient with fragile X syndrome and review of the literature. Clin Chim Acta 2024; 553:117728. [PMID: 38142803 DOI: 10.1016/j.cca.2023.117728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/09/2023] [Accepted: 12/16/2023] [Indexed: 12/26/2023]
Abstract
BACKGROUND Fragile X syndrome (FXS) is mainly caused by FMR1 CGG repeat expansions. Other types of mutations, particularly deletions, are also responsible for FXS phenotypes, however these mutations are often missed by routine clinical testing. MATERIALS AND METHODS Molecular diagnosis in cases of suspected FXS was a combination of PCR and Southern blot. Measurement of the FMRP protein level was useful for detecting potentially deleterious impact. RESULTS PCR analysis and Southern blot revealed a case with premutation and suspected deletion alleles. Sanger sequencing showed that the deletion involved 313 bp upstream of repeats and some parts of CGG repeat tract, leaving transcription start site. FMRP was detected in 5.5 % of blood lymphocytes. CONCLUSION According to our review of case reports, most patients carrying microdeletion and full mutation had typical features of FXS. To our knowledge, our case is the first to describe mosaicism of a premutation and microdeletion in the FMR1 gene. The patient was probably protected from the effects of the deletion by mosaicism with premutation allele, leading to milder phenotype. It is thus important to consider appropriate techniques for detecting FMR1 variants other than repeat expansions which cannot be detected by routine FXS diagnosis.
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Affiliation(s)
- Areerat Hnoonual
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Oradawan Plong-On
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | | | - Chariyawan Charalsawadi
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Pornprot Limprasert
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.
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Handley RR, Reid SJ, Burch Z, Jacobsen JC, Gillis T, Correia K, Rudiger SR, McLaughlin CJ, Bawden CS, MacDonald ME, Wheeler VC, Snell RG. Somatic CAG Repeat Stability in a Transgenic Sheep Model of Huntington's Disease. J Huntingtons Dis 2024; 13:33-40. [PMID: 38393920 DOI: 10.3233/jhd-231516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2024]
Abstract
Somatic instability of the huntingtin (HTT) CAG repeat mutation modifies age-at-onset of Huntington's disease (HD). Understanding the mechanism and pathogenic consequences of instability may reveal therapeutic targets. Using small-pool PCR we analyzed CAG instability in the OVT73 sheep model which expresses a full-length human cDNA HTT transgene. Analyses of five- and ten-year old sheep revealed the transgene (CAG)69 repeat was remarkably stable in liver, striatum, and other brain tissues. As OVT73 sheep at ten years old have minimal cell death and behavioral changes, our findings support instability of the HTT expanded-CAG repeat as being required for the progression of HD.
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Affiliation(s)
- Renee R Handley
- Centre for Brain Research, School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Suzanne J Reid
- Centre for Brain Research, School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Zoe Burch
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Jessie C Jacobsen
- Centre for Brain Research, School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Tammy Gillis
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Kevin Correia
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Skye R Rudiger
- Molecular Biology and Reproductive Technology, Laboratories, South Australian Research and Development Institute, Adelaide, SA, Australia
| | - Clive J McLaughlin
- Molecular Biology and Reproductive Technology, Laboratories, South Australian Research and Development Institute, Adelaide, SA, Australia
| | - C Simon Bawden
- Molecular Biology and Reproductive Technology, Laboratories, South Australian Research and Development Institute, Adelaide, SA, Australia
| | - Marcy E MacDonald
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Neurology, Harvard Medical School, Boston, MA, USA
| | - Vanessa C Wheeler
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Neurology, Harvard Medical School, Boston, MA, USA
| | - Russell G Snell
- Centre for Brain Research, School of Biological Sciences, The University of Auckland, Auckland, New Zealand
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Madera D, Alonso-Gómez A, Delgado MJ, Valenciano AI, Alonso-Gómez ÁL. Gene Characterization of Nocturnin Paralogues in Goldfish: Full Coding Sequences, Structure, Phylogeny and Tissue Expression. Int J Mol Sci 2023; 25:54. [PMID: 38203224 PMCID: PMC10779419 DOI: 10.3390/ijms25010054] [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: 10/30/2023] [Revised: 12/05/2023] [Accepted: 12/14/2023] [Indexed: 01/12/2024] Open
Abstract
The aim of this work is the full characterization of all the nocturnin (noc) paralogues expressed in a teleost, the goldfish. An in silico analysis of the evolutive origin of noc in Osteichthyes is performed, including the splicing variants and new paralogues appearing after teleostean 3R genomic duplication and the cyprinine 4Rc. After sequencing the full-length mRNA of goldfish, we obtained two isoforms for noc-a (noc-aa and noc-ab) with two splice variants (I and II), and only one for noc-b (noc-bb) with two transcripts (II and III). Using the splicing variant II, the prediction of the secondary and tertiary structures renders a well-conserved 3D distribution of four α-helices and nine β-sheets in the three noc isoforms. A synteny analysis based on the localization of noc genes in the patrilineal or matrilineal subgenomes and a phylogenetic tree of protein sequences were accomplished to stablish a classification and a long-lasting nomenclature of noc in goldfish, and valid to be extrapolated to allotetraploid Cyprininae. Finally, both goldfish and zebrafish showed a broad tissue expression of all the noc paralogues. Moreover, the enriched expression of specific paralogues in some tissues argues in favour of neo- or subfunctionalization.
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Affiliation(s)
| | | | | | | | - Ángel Luis Alonso-Gómez
- Departamento de Genética, Fisiología y Microbiología, Universidad Complutense de Madrid, 28040 Madrid, Spain; (D.M.); (A.A.-G.); (M.J.D.); (A.I.V.)
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Ciobanu CG, Nucă I, Popescu R, Antoci LM, Caba L, Ivanov AV, Cojocaru KA, Rusu C, Mihai CT, Pânzaru MC. Narrative Review: Update on the Molecular Diagnosis of Fragile X Syndrome. Int J Mol Sci 2023; 24:9206. [PMID: 37298158 PMCID: PMC10252420 DOI: 10.3390/ijms24119206] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 04/30/2023] [Accepted: 05/20/2023] [Indexed: 06/12/2023] Open
Abstract
The diagnosis and management of fragile X syndrome (FXS) have significantly improved in the last three decades, although the current diagnostic techniques are not yet able to precisely identify the number of repeats, methylation status, level of mosaicism, and/or the presence of AGG interruptions. A high number of repeats (>200) in the fragile X messenger ribonucleoprotein 1 gene (FMR1) results in hypermethylation of promoter and gene silencing. The actual molecular diagnosis is performed using a Southern blot, TP-PCR (Triplet-Repeat PCR), MS-PCR (Methylation-Specific PCR), and MS-MLPA (Methylation-Specific MLPA) with some limitations, with multiple assays being necessary to completely characterise a patient with FXS. The actual gold standard diagnosis uses Southern blot; however, it cannot accurately characterise all cases. Optical genome mapping is a new technology that has also been developed to approach the diagnosis of fragile X syndrome. Long-range sequencing represented by PacBio and Oxford Nanopore has the potential to replace the actual diagnosis and offers a complete characterization of molecular profiles in a single test. The new technologies have improved the diagnosis of fragile X syndrome and revealed unknown aberrations, but they are a long way from being used routinely in clinical practice.
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Affiliation(s)
- Cristian-Gabriel Ciobanu
- Medical Genetics Department, Faculty of Medicine, “Grigore T. Popa” University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania; (C.-G.C.)
| | - Irina Nucă
- Medical Genetics Department, Faculty of Medicine, “Grigore T. Popa” University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania; (C.-G.C.)
- Investigatii Medicale Praxis, St. Moara de Vant No 35, 700376 Iasi, Romania
| | - Roxana Popescu
- Medical Genetics Department, Faculty of Medicine, “Grigore T. Popa” University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania; (C.-G.C.)
- Medical Genetics Department, “Saint Mary” Emergency Children’s Hospital, St. Vasile Lupu No 62, 700309 Iasi, Romania
| | - Lucian-Mihai Antoci
- Medical Genetics Department, Faculty of Medicine, “Grigore T. Popa” University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania; (C.-G.C.)
| | - Lavinia Caba
- Medical Genetics Department, Faculty of Medicine, “Grigore T. Popa” University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania; (C.-G.C.)
| | - Anca Viorica Ivanov
- Pediatrics Department, “Grigore T. Popa” University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
| | - Karina-Alexandra Cojocaru
- Department of Biochemistry, Faculty of Dental Medicine, “Grigore T. Popa” University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
| | - Cristina Rusu
- Medical Genetics Department, Faculty of Medicine, “Grigore T. Popa” University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania; (C.-G.C.)
- Medical Genetics Department, “Saint Mary” Emergency Children’s Hospital, St. Vasile Lupu No 62, 700309 Iasi, Romania
| | | | - Monica-Cristina Pânzaru
- Medical Genetics Department, Faculty of Medicine, “Grigore T. Popa” University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania; (C.-G.C.)
- Medical Genetics Department, “Saint Mary” Emergency Children’s Hospital, St. Vasile Lupu No 62, 700309 Iasi, Romania
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