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Ziemka-Nalecz M, Pawelec P, Ziabska K, Zalewska T. Sex Differences in Brain Disorders. Int J Mol Sci 2023; 24:14571. [PMID: 37834018 PMCID: PMC10572175 DOI: 10.3390/ijms241914571] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 09/20/2023] [Accepted: 09/22/2023] [Indexed: 10/15/2023] Open
Abstract
A remarkable feature of the brain is its sexual dimorphism. Sexual dimorphism in brain structure and function is associated with clinical implications documented previously in healthy individuals but also in those who suffer from various brain disorders. Sex-based differences concerning some features such as the risk, prevalence, age of onset, and symptomatology have been confirmed in a range of neurological and neuropsychiatric diseases. The mechanisms responsible for the establishment of sex-based differences between men and women are not fully understood. The present paper provides up-to-date data on sex-related dissimilarities observed in brain disorders and highlights the most relevant features that differ between males and females. The topic is very important as the recognition of disparities between the sexes might allow for the identification of therapeutic targets and pharmacological approaches for intractable neurological and neuropsychiatric disorders.
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Affiliation(s)
| | | | | | - Teresa Zalewska
- NeuroRepair Department, Mossakowski Medical Research Institute, Polish Academy of Sciences, 5, A. Pawinskiego Str., 02-106 Warsaw, Poland; (M.Z.-N.); (P.P.); (K.Z.)
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2
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Oluigbo DC. Rett Syndrome: A Tale of Altered Genetics, Synaptic Plasticity, and Neurodevelopmental Dynamics. Cureus 2023; 15:e41555. [PMID: 37554594 PMCID: PMC10405636 DOI: 10.7759/cureus.41555] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/07/2023] [Indexed: 08/10/2023] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder that is a leading cause of severe cognitive and physical impairment. RTT typically occurs in females, although rare cases of males with the disease exist. Its genetic cause, symptoms, and clinical progression timeline have also become well-documented since its initial discovery. However, a relatively late diagnosis and lack of an available cure signify that our understanding of the disease is incomplete. Innovative research methods and tools are thereby helping to fill gaps in our knowledge of RTT. Specifically, mouse models of RTT, video analysis, and retrospective parental analysis are well-established tools that provide valuable insights into RTT. Moreover, current and anticipated treatment options are improving the quality of life of the RTT patient population. Collectively, these developments are creating optimistic future perspectives for RTT.
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Affiliation(s)
- David C Oluigbo
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, USA
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3
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Botta S, de Prisco N, Chemiakine A, Brandt V, Cabaj M, Patel P, Doron‐Mandel E, Treadway CJ, Jovanovic M, Brown NG, Soni RK, Gennarino VA. Dosage sensitivity to Pumilio1 variants in the mouse brain reflects distinct molecular mechanisms. EMBO J 2023; 42:e112721. [PMID: 37070548 PMCID: PMC10233381 DOI: 10.15252/embj.2022112721] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 03/01/2023] [Accepted: 03/14/2023] [Indexed: 04/19/2023] Open
Abstract
Different mutations in the RNA-binding protein Pumilio1 (PUM1) cause divergent phenotypes whose severity tracks with dosage: a mutation that reduces PUM1 levels by 25% causes late-onset ataxia, whereas haploinsufficiency causes developmental delay and seizures. Yet PUM1 targets are derepressed to equal degrees in both cases, and the more severe mutation does not hinder PUM1's RNA-binding ability. We therefore considered the possibility that the severe mutation might disrupt PUM1 interactions, and identified PUM1 interactors in the murine brain. We find that mild PUM1 loss derepresses PUM1-specific targets, but the severe mutation disrupts interactions with several RNA-binding proteins and the regulation of their targets. In patient-derived cell lines, restoring PUM1 levels restores these interactors and their targets to normal levels. Our results demonstrate that dosage sensitivity does not always signify a linear relationship with protein abundance but can involve distinct mechanisms. We propose that to understand the functions of RNA-binding proteins in a physiological context will require studying their interactions as well as their targets.
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Affiliation(s)
- Salvatore Botta
- Department of Genetics and DevelopmentColumbia University Irving Medical CenterNew YorkNYUSA
- Department of Translational Medical ScienceUniversity of Campania Luigi VanvitelliCasertaItaly
| | - Nicola de Prisco
- Department of Genetics and DevelopmentColumbia University Irving Medical CenterNew YorkNYUSA
| | - Alexei Chemiakine
- Department of Genetics and DevelopmentColumbia University Irving Medical CenterNew YorkNYUSA
| | - Vicky Brandt
- Department of Genetics and DevelopmentColumbia University Irving Medical CenterNew YorkNYUSA
| | - Maximilian Cabaj
- Department of Genetics and DevelopmentColumbia University Irving Medical CenterNew YorkNYUSA
| | - Purvi Patel
- Proteomics and Macromolecular Crystallography Shared Resource, Herbert Irving Comprehensive Cancer CenterColumbia University Irving Medical CenterNew YorkNYUSA
| | | | - Colton J Treadway
- Department of Pharmacology and Lineberger Comprehensive Cancer CenterUniversity of North Carolina School of MedicineChapel HillNCUSA
| | - Marko Jovanovic
- Department of Biological SciencesColumbia UniversityNew YorkNYUSA
| | - Nicholas G Brown
- Department of Pharmacology and Lineberger Comprehensive Cancer CenterUniversity of North Carolina School of MedicineChapel HillNCUSA
| | - Rajesh K Soni
- Proteomics and Macromolecular Crystallography Shared Resource, Herbert Irving Comprehensive Cancer CenterColumbia University Irving Medical CenterNew YorkNYUSA
| | - Vincenzo A Gennarino
- Department of Genetics and DevelopmentColumbia University Irving Medical CenterNew YorkNYUSA
- Departments of NeurologyColumbia University Irving Medical CenterNew YorkNYUSA
- Columbia Stem Cell InitiativeColumbia University Irving Medical CenterNew YorkNYUSA
- Initiative for Columbia Ataxia and TremorColumbia University Irving Medical CenterNew YorkNYUSA
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4
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Cooley Coleman JA, Fee T, Bend R, Louie R, Annese F, Stallworth J, Worthington J, Buchanan CB, Everman DB, Skinner S, Friez MJ, Jones JR, Spellicy CJ. Mosaicism of common pathogenic MECP2 variants identified in two males with a clinical diagnosis of Rett syndrome. Am J Med Genet A 2022; 188:2988-2998. [PMID: 35924478 DOI: 10.1002/ajmg.a.62913] [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: 03/22/2022] [Revised: 05/31/2022] [Accepted: 07/07/2022] [Indexed: 01/31/2023]
Abstract
Rett (RTT) syndrome, a neurodevelopmental disorder caused by pathogenic variation in the MECP2 gene, is characterized by developmental regression, loss of purposeful hand movements, stereotypic hand movements, abnormal gait, and loss of spoken language. Due to the X-linked inheritance pattern, RTT is typically limited to females. Recent studies revealed somatic mosaicism in MECP2 in male patients with RTT-like phenotypes. While detecting mosaic variation using Sanger sequencing is theoretically possible for mosaicism over ~15%-20%, several variables, including efficiency of PCR, background noise, and/or human error, contribute to a low detection rate using this technology. Mosaic variants in two males were detected by next generation sequencing (NGS; Case 1) and by Sanger re-sequencing (Case 2). Both had targeted digital PCR (dPCR) to confirm the variants. In this report, we present two males with classic RTT syndrome in whom we identified pathogenic variation in the MECP2 gene in the mosaic state (c.730C > T (p.Gln244*) in Patient 1 and c.397C > T (p.Arg133Cys) in Patient 2). In addition, estimates and measures of mosaic variant fraction were surprisingly similar between Sanger sequencing, NGS, and dPCR. The mosaic state of these variants contributed to a lengthy diagnostic odyssey for these patients. While NGS and even Sanger sequencing may be viable methods of detecting mosaic variation in DNA or RNA samples, applying targeted dPCR to supplement these sequencing technologies would provide confirmation of somatic mosaicism and mosaic fraction.
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Affiliation(s)
| | - Timothy Fee
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | - Renee Bend
- Greenwood Genetic Center, Greenwood, South Carolina, USA.,PreventionGenetics LLC, Marshfield, Wisconsin, USA
| | - Raymond Louie
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | - Fran Annese
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | - Jennifer Stallworth
- Greenwood Genetic Center, Greenwood, South Carolina, USA.,Sanofi, Bridgewater, New Jersey, USA
| | | | | | | | - Steven Skinner
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | | | - Julie R Jones
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | - Catherine J Spellicy
- Greenwood Genetic Center, Greenwood, South Carolina, USA.,Myriad Genetics, Salt Lake City, Utah, USA
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5
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Bach S, Shovlin S, Moriarty M, Bardoni B, Tropea D. Rett Syndrome and Fragile X Syndrome: Different Etiology With Common Molecular Dysfunctions. Front Cell Neurosci 2021; 15:764761. [PMID: 34867203 PMCID: PMC8640214 DOI: 10.3389/fncel.2021.764761] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 10/27/2021] [Indexed: 01/04/2023] Open
Abstract
Rett syndrome (RTT) and Fragile X syndrome (FXS) are two monogenetic neurodevelopmental disorders with complex clinical presentations. RTT is caused by mutations in the Methyl-CpG binding protein 2 gene (MECP2) altering the function of its protein product MeCP2. MeCP2 modulates gene expression by binding methylated CpG dinucleotides, and by interacting with transcription factors. FXS is caused by the silencing of the FMR1 gene encoding the Fragile X Mental Retardation Protein (FMRP), a RNA binding protein involved in multiple steps of RNA metabolism, and modulating the translation of thousands of proteins including a large set of synaptic proteins. Despite differences in genetic etiology, there are overlapping features in RTT and FXS, possibly due to interactions between MeCP2 and FMRP, and to the regulation of pathways resulting in dysregulation of common molecular signaling. Furthermore, basic physiological mechanisms are regulated by these proteins and might concur to the pathophysiology of both syndromes. Considering that RTT and FXS are disorders affecting brain development, and that most of the common targets of MeCP2 and FMRP are involved in brain activity, we discuss the mechanisms of synaptic function and plasticity altered in RTT and FXS, and we consider the similarities and the differences between these two disorders.
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Affiliation(s)
- Snow Bach
- School of Mathematical Sciences, Dublin City University, Dublin, Ireland.,Neuropsychiatric Genetics, Department of Psychiatry, School of Medicine, Trinity College Dublin, Trinity Translational Medicine Institute, St James's Hospital, Dublin, Ireland
| | - Stephen Shovlin
- Neuropsychiatric Genetics, Department of Psychiatry, School of Medicine, Trinity College Dublin, Trinity Translational Medicine Institute, St James's Hospital, Dublin, Ireland
| | | | - Barbara Bardoni
- Inserm, CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, Université Côte d'Azur, Valbonne, France
| | - Daniela Tropea
- Neuropsychiatric Genetics, Department of Psychiatry, School of Medicine, Trinity College Dublin, Trinity Translational Medicine Institute, St James's Hospital, Dublin, Ireland.,Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland.,FutureNeuro, The SFI Research Centre for Chronic and Rare Neurological Diseases, Dublin, Ireland
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6
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Quach TT, Stratton HJ, Khanna R, Kolattukudy PE, Honnorat J, Meyer K, Duchemin AM. Intellectual disability: dendritic anomalies and emerging genetic perspectives. Acta Neuropathol 2021; 141:139-158. [PMID: 33226471 PMCID: PMC7855540 DOI: 10.1007/s00401-020-02244-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 11/04/2020] [Accepted: 11/05/2020] [Indexed: 12/12/2022]
Abstract
Intellectual disability (ID) corresponds to several neurodevelopmental disorders of heterogeneous origin in which cognitive deficits are commonly associated with abnormalities of dendrites and dendritic spines. These histological changes in the brain serve as a proxy for underlying deficits in neuronal network connectivity, mostly a result of genetic factors. Historically, chromosomal abnormalities have been reported by conventional karyotyping, targeted fluorescence in situ hybridization (FISH), and chromosomal microarray analysis. More recently, cytogenomic mapping, whole-exome sequencing, and bioinformatic mining have led to the identification of novel candidate genes, including genes involved in neuritogenesis, dendrite maintenance, and synaptic plasticity. Greater understanding of the roles of these putative ID genes and their functional interactions might boost investigations into determining the plausible link between cellular and behavioral alterations as well as the mechanisms contributing to the cognitive impairment observed in ID. Genetic data combined with histological abnormalities, clinical presentation, and transgenic animal models provide support for the primacy of dysregulation in dendrite structure and function as the basis for the cognitive deficits observed in ID. In this review, we highlight the importance of dendrite pathophysiology in the etiologies of four prototypical ID syndromes, namely Down Syndrome (DS), Rett Syndrome (RTT), Digeorge Syndrome (DGS) and Fragile X Syndrome (FXS). Clinical characteristics of ID have also been reported in individuals with deletions in the long arm of chromosome 10 (the q26.2/q26.3), a region containing the gene for the collapsin response mediator protein 3 (CRMP3), also known as dihydropyrimidinase-related protein-4 (DRP-4, DPYSL4), which is involved in dendritogenesis. Following a discussion of clinical and genetic findings in these syndromes and their preclinical animal models, we lionize CRMP3/DPYSL4 as a novel candidate gene for ID that may be ripe for therapeutic intervention.
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Affiliation(s)
- Tam T Quach
- Institute for Behavioral Medicine Research, Wexner Medical Center, The Ohio State University, Columbus, OH, 43210, USA
- INSERM U1217/CNRS, UMR5310, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | | | - Rajesh Khanna
- Department of Pharmacology, University of Arizona, Tucson, AZ, 85724, USA
| | | | - Jérome Honnorat
- INSERM U1217/CNRS, UMR5310, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France
- French Reference Center on Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis, Hospices Civils de Lyon, Lyon, France
- SynatAc Team, Institut NeuroMyoGène, Lyon, France
| | - Kathrin Meyer
- The Research Institute of Nationwide Children Hospital, Columbus, OH, 43205, USA
- Department of Pediatric, The Ohio State University, Columbus, OH, 43210, USA
| | - Anne-Marie Duchemin
- Department of Psychiatry and Behavioral Health, The Ohio State University, Columbus, OH, 43210, USA.
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7
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Good KV, Vincent JB, Ausió J. MeCP2: The Genetic Driver of Rett Syndrome Epigenetics. Front Genet 2021; 12:620859. [PMID: 33552148 PMCID: PMC7859524 DOI: 10.3389/fgene.2021.620859] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 01/05/2021] [Indexed: 12/24/2022] Open
Abstract
Mutations in methyl CpG binding protein 2 (MeCP2) are the major cause of Rett syndrome (RTT), a rare neurodevelopmental disorder with a notable period of developmental regression following apparently normal initial development. Such MeCP2 alterations often result in changes to DNA binding and chromatin clustering ability, and in the stability of this protein. Among other functions, MeCP2 binds to methylated genomic DNA, which represents an important epigenetic mark with broad physiological implications, including neuronal development. In this review, we will summarize the genetic foundations behind RTT, and the variable degrees of protein stability exhibited by MeCP2 and its mutated versions. Also, past and emerging relationships that MeCP2 has with mRNA splicing, miRNA processing, and other non-coding RNAs (ncRNA) will be explored, and we suggest that these molecules could be missing links in understanding the epigenetic consequences incurred from genetic ablation of this important chromatin modifier. Importantly, although MeCP2 is highly expressed in the brain, where it has been most extensively studied, the role of this protein and its alterations in other tissues cannot be ignored and will also be discussed. Finally, the additional complexity to RTT pathology introduced by structural and functional implications of the two MeCP2 isoforms (MeCP2-E1 and MeCP2-E2) will be described. Epigenetic therapeutics are gaining clinical popularity, yet treatment for Rett syndrome is more complicated than would be anticipated for a purely epigenetic disorder, which should be taken into account in future clinical contexts.
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Affiliation(s)
- Katrina V. Good
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
| | - John B. Vincent
- Molecular Neuropsychiatry & Development (MiND) Lab, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Juan Ausió
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada
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8
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Pejhan S, Rastegar M. Role of DNA Methyl-CpG-Binding Protein MeCP2 in Rett Syndrome Pathobiology and Mechanism of Disease. Biomolecules 2021; 11:75. [PMID: 33429932 PMCID: PMC7827577 DOI: 10.3390/biom11010075] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 01/01/2021] [Accepted: 01/03/2021] [Indexed: 12/16/2022] Open
Abstract
Rett Syndrome (RTT) is a severe, rare, and progressive developmental disorder with patients displaying neurological regression and autism spectrum features. The affected individuals are primarily young females, and more than 95% of patients carry de novo mutation(s) in the Methyl-CpG-Binding Protein 2 (MECP2) gene. While the majority of RTT patients have MECP2 mutations (classical RTT), a small fraction of the patients (atypical RTT) may carry genetic mutations in other genes such as the cyclin-dependent kinase-like 5 (CDKL5) and FOXG1. Due to the neurological basis of RTT symptoms, MeCP2 function was originally studied in nerve cells (neurons). However, later research highlighted its importance in other cell types of the brain including glia. In this regard, scientists benefitted from modeling the disease using many different cellular systems and transgenic mice with loss- or gain-of-function mutations. Additionally, limited research in human postmortem brain tissues provided invaluable findings in RTT pathobiology and disease mechanism. MeCP2 expression in the brain is tightly regulated, and its altered expression leads to abnormal brain function, implicating MeCP2 in some cases of autism spectrum disorders. In certain disease conditions, MeCP2 homeostasis control is impaired, the regulation of which in rodents involves a regulatory microRNA (miR132) and brain-derived neurotrophic factor (BDNF). Here, we will provide an overview of recent advances in understanding the underlying mechanism of disease in RTT and the associated genetic mutations in the MECP2 gene along with the pathobiology of the disease, the role of the two most studied protein variants (MeCP2E1 and MeCP2E2 isoforms), and the regulatory mechanisms that control MeCP2 homeostasis network in the brain, including BDNF and miR132.
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Affiliation(s)
| | - Mojgan Rastegar
- Regenerative Medicine Program, and Department of Biochemistry and Medical Genetics, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, MB R3E 0J9, Canada;
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Pejhan S, Del Bigio MR, Rastegar M. The MeCP2E1/E2-BDNF- miR132 Homeostasis Regulatory Network Is Region-Dependent in the Human Brain and Is Impaired in Rett Syndrome Patients. Front Cell Dev Biol 2020; 8:763. [PMID: 32974336 PMCID: PMC7471663 DOI: 10.3389/fcell.2020.00763] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 07/21/2020] [Indexed: 11/13/2022] Open
Abstract
Rett Syndrome (RTT) is a rare and progressive neurodevelopmental disorder that is caused by de novo mutations in the X-linked Methyl CpG binding protein 2 (MECP2) gene and is subjected to X-chromosome inactivation. RTT is commonly associated with neurological regression, autistic features, motor control impairment, seizures, loss of speech and purposeful hand movements, mainly affecting females. Different animal and cellular model systems have tremendously contributed to our current knowledge about MeCP2 and RTT. However, the majority of these findings remain unexamined in the brain of RTT patients. Based on previous studies in rodent brains, the highly conserved neuronal microRNA “miR132” was suggested to be an inhibitor of MeCP2 expression. The neuronal miR132 itself is induced by Brain Derived Neurotrophic Factor (BDNF), a neurotransmitter modulator, which in turn is controlled by MeCP2. This makes the basis of the MECP2-BDNF-miR132 feedback regulatory loop in the brain. Here, we studied the components of this feedback regulatory network in humans, and its possible impairment in the brain of RTT patients. In this regard, we evaluated the transcript and protein levels of MECP2/MeCP2E1 and E2 isoforms, BDNF/BDNF, and miR132 (both 3p and 5p strands) by real time RT-PCR, Western blot, and ELISA in four different regions of the human RTT brains and their age-, post-mortem delay-, and sex-matched controls. The transcript level of the studied elements was significantly compromised in RTT patients, even though the change was not identical in different parts of the brain. Our data indicates that MeCP2E1/E2-BDNF protein levels did not follow their corresponding transcript trends. Correlational studies suggested that the MECP2E1/E2-BDNF-miR132 homeostasis regulation might not be similarly controlled in different parts of the human brain. Despite challenges in evaluating autopsy samples in rare diseases, our findings would help to shed some light on RTT pathobiology, and obscurities caused by limited studies on MeCP2 regulation in the human brain.
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Affiliation(s)
- Shervin Pejhan
- Regenerative Medicine Program, Department of Biochemistry and Medical Genetics, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Marc R Del Bigio
- Department of Pathology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Mojgan Rastegar
- Regenerative Medicine Program, Department of Biochemistry and Medical Genetics, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
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Takeguchi R, Takahashi S, Kuroda M, Tanaka R, Suzuki N, Tomonoh Y, Ihara Y, Sugiyama N, Itoh M. MeCP2_e2 partially compensates for lack of MeCP2_e1: A male case of Rett syndrome. Mol Genet Genomic Med 2019; 8:e1088. [PMID: 31816669 PMCID: PMC7005616 DOI: 10.1002/mgg3.1088] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 11/12/2019] [Accepted: 11/13/2019] [Indexed: 12/28/2022] Open
Abstract
Background Rett syndrome (RTT) is a neurodevelopmental disorder that predominantly affects girls. Its causative gene is the X‐linked MECP2 encoding the methyl‐CpG‐binding protein 2 (MeCP2). The gene comprises four exons and generates two isoforms, namely MECP2_e1 and MECP2_e2. However, it remains unclear whether both MeCP2 isoforms have similar function in the brain. Methods We report a case of a boy with typical RTT. Male cases with MECP2 variants have been considered inviable, but somatic mosaicism of the variants can cause RTT in males. Whole‐exome sequencing was performed to search for the genetic background. Results A novel nonsense and mosaic variant was identified in exon 1 of MECP2, and the variant allele fraction (VAF) was 28%. Our patient had the same level of VAF as that in reported male cases with mosaic variants in MECP2 exon 3 or 4, but manifested RTT symptoms that were milder in severity compared to those in these patients. Conclusion This is probably because the variants in MECP2 exon 3 or 4 disrupt both isoforms of MeCP2, whereas the variant in exon 1, as presented in this study, disrupts only MeCP2_e1 but not MeCP2_e2. Therefore, our findings indicate that MeCP2_e2 may partially compensate for a deficiency in MeCP2_e1.
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Affiliation(s)
- Ryo Takeguchi
- Department of Pediatrics, Asahikawa Medical University, Hokkaido, Japan
| | - Satoru Takahashi
- Department of Pediatrics, Asahikawa Medical University, Hokkaido, Japan
| | - Mami Kuroda
- Department of Pediatrics, Asahikawa Medical University, Hokkaido, Japan
| | - Ryosuke Tanaka
- Department of Pediatrics, Asahikawa Medical University, Hokkaido, Japan
| | - Nao Suzuki
- Department of Pediatrics, Asahikawa Medical University, Hokkaido, Japan
| | - Yuko Tomonoh
- Department of Pediatrics, Fukuoka University, Fukuoka, Japan
| | - Yukiko Ihara
- Department of Pediatrics, Fukuoka University, Fukuoka, Japan
| | | | - Masayuki Itoh
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
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