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Merritt JK, Fang X, Caylor RC, Skinner SA, Friez MJ, Percy AK, Neul JL. Normalized Clinical Severity Scores Reveal a Correlation between X Chromosome Inactivation and Disease Severity in Rett Syndrome. Genes (Basel) 2024; 15:594. [PMID: 38790223 PMCID: PMC11120815 DOI: 10.3390/genes15050594] [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: 03/29/2024] [Revised: 05/01/2024] [Accepted: 05/05/2024] [Indexed: 05/26/2024] Open
Abstract
Rett Syndrome (RTT) is a severe neurodevelopmental disorder predominately diagnosed in females and primarily caused by pathogenic variants in the X-linked gene Methyl-CpG Binding Protein 2 (MECP2). Most often, the disease causing the MECP2 allele resides on the paternal X chromosome while a healthy copy is maintained on the maternal X chromosome with inactivation (XCI), resulting in mosaic expression of one allele in each cell. Preferential inactivation of the paternal X chromosome is theorized to result in reduced disease severity; however, establishing such a correlation is complicated by known MECP2 genotype effects and an age-dependent increase in severity. To mitigate these confounding factors, we developed an age- and genotype-normalized measure of RTT severity by modeling longitudinal data collected in the US Rett Syndrome Natural History Study. This model accurately reflected individual increase in severity with age and preserved group-level genotype specific differences in severity, allowing for the creation of a normalized clinical severity score. Applying this normalized score to a RTT XCI dataset revealed that XCI influence on disease severity depends on MECP2 genotype with a correlation between XCI and severity observed only in individuals with MECP2 variants associated with increased clinical severity. This normalized measure of RTT severity provides the opportunity for future discovery of additional factors contributing to disease severity that may be masked by age and genotype effects.
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Affiliation(s)
- Jonathan K. Merritt
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN 37232, USA;
| | - Xiaolan Fang
- Department of Pathology, Henry Ford Health System, Detroit, MI 48202, USA;
- Greenwood Genetic Center, Greenwood, SC 29646, USA; (R.C.C.); (S.A.S.); (M.J.F.)
| | - Raymond C. Caylor
- Greenwood Genetic Center, Greenwood, SC 29646, USA; (R.C.C.); (S.A.S.); (M.J.F.)
| | - Steven A. Skinner
- Greenwood Genetic Center, Greenwood, SC 29646, USA; (R.C.C.); (S.A.S.); (M.J.F.)
| | - Michael J. Friez
- Greenwood Genetic Center, Greenwood, SC 29646, USA; (R.C.C.); (S.A.S.); (M.J.F.)
| | - Alan K. Percy
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL 35294, USA;
| | - Jeffrey L. Neul
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN 37232, USA;
- Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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2
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Zade K, Campbell C, Bach S, Fernandes H, Tropea D. Rett syndrome in Ireland: a demographic study. Orphanet J Rare Dis 2024; 19:34. [PMID: 38291497 PMCID: PMC10829226 DOI: 10.1186/s13023-024-03046-8] [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: 09/04/2023] [Accepted: 01/19/2024] [Indexed: 02/01/2024] Open
Abstract
BACKGROUND Rett syndrome (RTT) is a rare neurodevelopmental condition associated with mutations in the gene coding for the methyl-CpG-binding protein 2 (MECP2). It is primarily observed in girls and affects individuals globally. The understanding of the neurobiology of RTT and patient management has been improved by studies that describe the demographic and clinical presentation of individuals with RTT. However, in Ireland, there is a scarcity of data regarding individuals with RTT, which impedes the ability to fully characterize the Irish RTT population. Together with the Rett Syndrome Association of Ireland (RSAI), we prepared a questionnaire to determine the characteristics of RTT individuals in Ireland. Twenty-five families have participated in the study to date, providing information about demographics, genetics, familial history, clinical features, and regression. RESULTS The results show that Irish individuals with RTT have comparable presentation with respect to individuals in other countries; however, they had a better response to anti-epileptic drugs, and fewer skeletal deformities were reported. Nonetheless, seizures, involuntary movements and regression were more frequently observed in Irish individuals. One of the main findings of this study is the limited genetic information available to individuals to support the clinical diagnosis of RTT. CONCLUSIONS Despite the limited sample size, this study is the first to characterize the RTT population in Ireland and highlights the importance of having a swift access to genetic testing to sharpen the characterization of the phenotype and increase the visibility of Irish individuals in the international RTT community.
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Affiliation(s)
- Komal Zade
- Department of Psychiatry, School of Medicine, Trinity Centre for Health Sciences, Trinity College Dublin, St James Hospital, Dublin, D08 W9RT, Ireland
| | - Ciara Campbell
- Department of Psychiatry, School of Medicine, Trinity Centre for Health Sciences, Trinity College Dublin, St James Hospital, Dublin, D08 W9RT, Ireland
| | - Snow Bach
- Department of Psychiatry, School of Medicine, Trinity Centre for Health Sciences, Trinity College Dublin, St James Hospital, Dublin, D08 W9RT, Ireland
| | - Hazel Fernandes
- Consultant Child and Adolescent Psychiatrist, Barnet, Enfield and Haringey Mental Health NHS Trust, London, UK
| | - Daniela Tropea
- Department of Psychiatry, School of Medicine, Trinity Centre for Health Sciences, Trinity College Dublin, St James Hospital, Dublin, D08 W9RT, Ireland.
- 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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3
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Hong H, Yoon SB, Park JE, Lee JI, Kim HY, Nam HJ, Cho H. MeCP2 dysfunction prevents proper BMP signaling and neural progenitor expansion in brain organoid. Ann Clin Transl Neurol 2023. [PMID: 37302988 DOI: 10.1002/acn3.51799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 04/26/2023] [Accepted: 05/10/2023] [Indexed: 06/13/2023] Open
Abstract
OBJECTIVES Sporadic mutations in MeCP2 are a hallmark of Rett syndrome (RTT). Many RTT brain organoid models have exhibited pathogenic phenotypes such as decreased spine density and small size of soma with altered electrophysiological signals. However, previous models are mainly focused on the phenotypes observed in the late phase and rarely provide clues for the defect of neural progenitors which generate different types of neurons and glial cells. METHODS We newly established the RTT brain organoid model derived from MeCP2-truncated iPS cells which were genetically engineered by CRISPR/Cas9 technology. By immunofluorescence imaging, we studied the development of NPC pool and its fate specification into glutamatergic neurons or astrocytes in RTT organoids. By total RNA sequencing, we investigated which signaling pathways were altered during the early brain development in RTT organoids. RESULTS Dysfunction of MeCP2 caused the defect of neural rosette formation in the early phase of cortical development. In total transcriptome analysis, BMP pathway-related genes are highly associated with MeCP2 depletion. Moreover, levels of pSMAD1/5 and BMP target genes are excessively increased, and treatment of BMP inhibitors partially rescues the cell cycle progression of neural progenitors. Subsequently, MeCP2 dysfunction reduced the glutamatergic neurogenesis and induced overproduction of astrocytes. Nevertheless, early inhibition of BMP pathway rescued VGLUT1 expression and suppressed astrocyte maturation. INTERPRETATION Our results demonstrate that MeCP2 is required for the expansion of neural progenitor cells by modulating BMP pathway at early stages of development, and this influence persists during neurogenesis and gliogenesis at later stages of brain organoid development.
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Affiliation(s)
- Hyowon Hong
- Therapeutics & Biotechnology Division, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea
| | - Sae-Bom Yoon
- Therapeutics & Biotechnology Division, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea
| | - Jung Eun Park
- Therapeutics & Biotechnology Division, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea
| | - Jung In Lee
- Therapeutics & Biotechnology Division, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea
| | - Hyun Young Kim
- Therapeutics & Biotechnology Division, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea
| | - Hye Jin Nam
- Therapeutics & Biotechnology Division, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea
| | - Heeyeong Cho
- Therapeutics & Biotechnology Division, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea
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4
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Wen Y, Wang J, Zhang Q, Yang X, Wei L, Bao X. MECP2 germline mosaicism plays an important part in the inheritance of Rett syndrome: a study of MECP2 germline mosaicism in males. BMC Med 2023; 21:155. [PMID: 37081442 PMCID: PMC10120091 DOI: 10.1186/s12916-023-02846-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 03/23/2023] [Indexed: 04/22/2023] Open
Abstract
BACKGROUND Germline mosaicisms could be inherited to offspring, which considered as "de novo" in most cases. Paternal germline MECP2 mosaicism has been reported in fathers of girls with Rett syndrome (RTT) previously. For further study, we focused on MECP2 germline mosaicism in males, not only RTT fathers. METHODS Thirty-two fathers of RTT girls with MECP2 pathogenic mutations and twenty-five healthy adult males without history and family history of RTT or other genetic disorders were recruited. Sperm samples were collected and ten MECP2 hotspot mutations were detected by micro-droplet digital PCR (mDDPCR). And routine semen test was performed at the same time if the sample was sufficient. Additionally, blood samples were also detected for those with sperm MECP2 mosaicisms. RESULTS Nine fathers with RTT daughters (28.1%, 9/32) were found to have MECP2 mosaicism in their sperm samples, with the mutant allele fractions (MAFs) ranging from 0.05% to 7.55%. Only one father with MECP2 c.806delG germline mosaicism (MAF 7.55%) was found to have mosaicism in the blood sample, with the MAF was 0.28%. In the group of healthy adult males, MECP2 mosaicism was found in 7 sperm samples (28.0%, 7/25), with the MAFs ranging from 0.05% to 0.18%. None of the healthy adult males with MECP2 germline mosaicisms were found with MECP2 mosaicism in blood samples. There were no statistical differences in age, or the incidence of asthenospermia between fathers with RTT daughters and healthy adult males with MECP2 germline mosaicisms. Additionally, there was no linear correlation between MAFs of MECP2 mosaicisms and the age of males with germline MECP2 mosaicisms. CONCLUSIONS Germline MECP2 mosaicism could be found not only in fathers with RTT daughters but also in healthy adult males without family history of RTT. As germline mosaic mutations may be passed on to offspring which commonly known as "de novo", more attention should be paid to germline mosaicism, especially in families with a proband diagnosed with genetic disorders.
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Affiliation(s)
- Yongxin Wen
- Department of Pediatrics, Peking University First Hospital, Beijing, China
- Department of Pediatric Neurology, Guangdong Women and Children Hospital, Guangzhou, Guangdong Province, China
| | - Jiaping Wang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Qingping Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Xiaoxu Yang
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China
| | - Liping Wei
- Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China
| | - Xinhua Bao
- Department of Pediatrics, Peking University First Hospital, Beijing, China.
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5
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Shaheen G, Fleischman D. A case of JOAG in a patient with Rett syndrome. Am J Ophthalmol Case Rep 2023; 29:101762. [DOI: 10.1016/j.ajoc.2022.101762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 11/16/2022] [Accepted: 11/26/2022] [Indexed: 12/05/2022] Open
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6
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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: 0.5] [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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7
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Bouzroud W, Tazzite A, Berrada S, Gazzaz B, Dehbi H. R306X Mutation in the MECP2 Gene Causes an Atypical Rett Syndrome in a Moroccan Patient: A Case Report. CLINICAL PATHOLOGY (THOUSAND OAKS, VENTURA COUNTY, CALIF.) 2022; 15:2632010X221124269. [PMID: 36147795 PMCID: PMC9486266 DOI: 10.1177/2632010x221124269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 08/18/2022] [Indexed: 11/16/2022]
Abstract
Rett syndrome (RTT) is a rare X-linked syndrome that predominantly affects girls.
It is characterized by a severe and progressive neurodevelopmental disorder with
neurological regression and autism spectrum features. The Rett syndrome is
associated with a broad phenotypic spectrum. It ranges from a classical Rett
syndrome defined by well-established criteria to atypical cases with symptoms
similar to other syndromes, such as Angelman syndrome. The first case of a
Moroccan female child carrying a R306X mutation in the MECP2
(Methyl-CpG-Binding Protein 2) gene, with an unusual manifestation of Rett
syndrome, is presented here. She showed autistic regression, behavioral
stagnation, epilepsy, unmotivated laughter, and craniofacial dysmorphia. Whole
exome sequencing revealed a nonsense mutation (R306X), resulting in a truncated,
nonfunctional MECP2 protein. The overlapping phenotypic spectrums between Rett
and Angelman syndromes have been described, and an interaction between the
MECP2 gene and the UBE3A (Ubiquitin
Protein Ligase E3A) gene pathways is possible but has not yet been proven. An
extensive genetic analysis is highly recommended in atypical cases to ensure an
accurate diagnosis and to improve patient management and genetic counseling.
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Affiliation(s)
- Wafaa Bouzroud
- Medical Genetics Laboratory, Ibn Rochd University Hospital, Casablanca, Morocco
| | - Amal Tazzite
- Laboratory of Cellular and Molecular Pathology, Faculty of Medicine and Pharmacy, Hassan II University, Casablanca, Morocco
| | - Sarah Berrada
- Medical Genetics Laboratory, Ibn Rochd University Hospital, Casablanca, Morocco
| | - Bouchaïb Gazzaz
- Laboratory of Cellular and Molecular Pathology, Faculty of Medicine and Pharmacy, Hassan II University, Casablanca, Morocco.,Genetics Analysis Institute, Royal Gendarmerie, Rabat, Morocco
| | - Hind Dehbi
- Medical Genetics Laboratory, Ibn Rochd University Hospital, Casablanca, Morocco.,Laboratory of Cellular and Molecular Pathology, Faculty of Medicine and Pharmacy, Hassan II University, Casablanca, Morocco
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8
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MECP2-related conditions in males: A systematic literature review and 8 additional cases. Eur J Paediatr Neurol 2021; 34:7-13. [PMID: 34271245 DOI: 10.1016/j.ejpn.2021.05.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 02/25/2021] [Accepted: 05/25/2021] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To present a cohort of 8 males and perform a systematic review of all published cases with a single copy of MECP2 carrying a pathogenic variant. METHODS We reviewed medical records of males with a single copy of MECP2 carrying a pathogenic variant. We searched in Medline (Pubmed) and Embase to collect all articles which included well-characterized males with a single copy of MECP2 carrying a pathogenic or likely pathogenic variant in MECP2 (1999-2020). RESULTS The literature search yielded a total of 3,185 publications, of which 58 were included in our systematic review. We were able to collect information on 27 published patients with severe neonatal encephalopathy, 47 individuals with isolated or familial mental retardation X-linked 13 (XLMR13), as well as 24 individuals with isolated or familial Pyramidal signs, parkinsonism, and macroorchidism (PPM-X). In our cohort, we met eight individuals aged 4 to 19-year-old at the last evaluation. Three MECP2-associated phenotypes were seen in male carriers of a single copy of the gene: severe neonatal encephalopathy (n = 5); X-linked intellectual deficiency 13 (n = 2); and pyramidal signs, parkinsonism, and macroorchidism (PPM-X) (n = 1). Two novel de novo variants [p.(Gly252Argfs∗7) and p.(Tyr132Cys)] were detected. CONCLUSION In males, the MECP2 pathogenic variants can be associated with different phenotypes, including neonatal severe encephalopathy, intellectual deficiency, or late-onset parkinsonism and spasticity. The typical RS phenotype is not expected in males, except in those with Klinefelter syndrome or somatic mosaicism for MECP2.
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9
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Brand BA, Blesson AE, Smith-Hicks CL. The Impact of X-Chromosome Inactivation on Phenotypic Expression of X-Linked Neurodevelopmental Disorders. Brain Sci 2021; 11:brainsci11070904. [PMID: 34356138 PMCID: PMC8305405 DOI: 10.3390/brainsci11070904] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/16/2021] [Accepted: 06/20/2021] [Indexed: 12/20/2022] Open
Abstract
Nearly 20% of genes located on the X chromosome are associated with neurodevelopmental disorders (NDD) due to their expression and role in brain functioning. Given their location, several of these genes are either subject to or can escape X-chromosome inactivation (XCI). The degree to which genes are subject to XCI can influence the NDD phenotype between males and females. We provide a general review of X-linked NDD genes in the context of XCI and detailed discussion of the sex-based differences related to MECP2 and FMR1, two common X-linked causes of NDD that are subject to XCI. Understanding the effects of XCI on phenotypic expression of NDD genes may guide the development of stratification biomarkers in X-linked disorders.
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Affiliation(s)
- Boudewien A Brand
- Center for Autism and Related Disorders, Kennedy Krieger Institute, Baltimore, MD 21205, USA; (B.A.B.); (A.E.B.)
| | - Alyssa E Blesson
- Center for Autism and Related Disorders, Kennedy Krieger Institute, Baltimore, MD 21205, USA; (B.A.B.); (A.E.B.)
| | - Constance L. Smith-Hicks
- Department of Neurology and Developmental Medicine, Kennedy Krieger Institute, Baltimore, MD 21205, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
- Correspondence:
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10
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Vermudez SAD, Gogliotti RG, Arthur B, Buch A, Morales C, Moxley Y, Rajpal H, Conn PJ, Niswender CM. Profiling beneficial and potential adverse effects of MeCP2 overexpression in a hypomorphic Rett syndrome mouse model. GENES, BRAIN, AND BEHAVIOR 2021; 21:e12752. [PMID: 34002468 PMCID: PMC8599502 DOI: 10.1111/gbb.12752] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 05/15/2021] [Accepted: 05/16/2021] [Indexed: 01/03/2023]
Abstract
De novo loss-of-function mutations in methyl-CpG-binding protein 2 (MeCP2) lead to the neurodevelopmental disorder Rett syndrome (RTT). Despite promising results from strategies aimed at increasing MeCP2 levels, additional studies exploring how hypomorphic MeCP2 mutations impact the therapeutic window are needed. Here, we investigated the consequences of genetically introducing a wild-type MECP2 transgene in the Mecp2 R133C mouse model of RTT. The MECP2 transgene reversed the majority of RTT-like phenotypes exhibited by male and female Mecp2 R133C mice. However, three core symptom domains were adversely affected in female Mecp2R133C/+ animals; these phenotypes resemble those observed in disease contexts of excess MeCP2. Parallel control experiments in Mecp2Null/+ mice linked these adverse effects to the hypomorphic R133C mutation. Collectively, these data provide evidence regarding the safety and efficacy of genetically overexpressing functional MeCP2 in Mecp2 R133C mice and suggest that personalized approaches may warrant consideration for the clinical assessment of MeCP2-targeted therapies.
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Affiliation(s)
- Sheryl Anne D. Vermudez
- Department of Pharmacology and Warren Center for Neuroscience Drug DiscoveryVanderbilt UniversityNashvilleTennesseeUSA
| | - Rocco G. Gogliotti
- Department of Molecular Pharmacology and NeuroscienceLoyola University ChicagoChicagoIllinoisUSA
| | - Bright Arthur
- Department of Pharmacology and Warren Center for Neuroscience Drug DiscoveryVanderbilt UniversityNashvilleTennesseeUSA
| | - Aditi Buch
- Department of Pharmacology and Warren Center for Neuroscience Drug DiscoveryVanderbilt UniversityNashvilleTennesseeUSA
| | - Clarissa Morales
- Department of Pharmacology and Warren Center for Neuroscience Drug DiscoveryVanderbilt UniversityNashvilleTennesseeUSA
| | - Yuta Moxley
- Department of Pharmacology and Warren Center for Neuroscience Drug DiscoveryVanderbilt UniversityNashvilleTennesseeUSA
| | - Hemangi Rajpal
- Department of Pharmacology and Warren Center for Neuroscience Drug DiscoveryVanderbilt UniversityNashvilleTennesseeUSA
| | - P. Jeffrey Conn
- Department of Pharmacology and Warren Center for Neuroscience Drug DiscoveryVanderbilt UniversityNashvilleTennesseeUSA,Vanderbilt Kennedy CenterVanderbilt UniversityNashvilleTennesseeUSA,Vanderbilt Institute of Chemical BiologyVanderbilt UniversityNashvilleTennesseeUSA
| | - Colleen M. Niswender
- Department of Pharmacology and Warren Center for Neuroscience Drug DiscoveryVanderbilt UniversityNashvilleTennesseeUSA,Vanderbilt Kennedy CenterVanderbilt UniversityNashvilleTennesseeUSA,Vanderbilt Institute of Chemical BiologyVanderbilt UniversityNashvilleTennesseeUSA
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11
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Gu Y, Xiang B, Zhu L, Ma X, Chen X, Cai T. Three intellectual disability-associated de novo mutations in MECP2 identified by trio-WES analysis. BMC MEDICAL GENETICS 2020; 21:99. [PMID: 32393352 PMCID: PMC7216709 DOI: 10.1186/s12881-020-01042-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 05/04/2020] [Indexed: 11/10/2022]
Abstract
BACKGROUND To date, at least 746 genes have been identified to cause intellectual disability (ID). Among them, mutations in the Methyl CpG binding protein 2 (MECP2) gene are the leading cause of Rett syndrome and associated ID. METHODS Considering the large number of ID-associated genes, we applied trio-based whole-exome sequencing (trio-WES) and in silico analysis for genetic diagnosis of 294 children with ID. RESULTS Three de novo heterozygous mutations [NM_004992.3: c.502C > T, p.(Arg168*), c.916C > T, p.(Arg306Cys), and c.879C > G, p.(Ile293Met)] in MECP2 were identified in three unrelated girls. The first two mutations were detected in two patients who were diagnosed as typical Rett syndrome, X-linked ID and psychomotor retardation. The third mutation (c.879C > G), a previously unreported, was found in a 6-year-old girl with ID, microcephaly, severe underweight and psychomotor retardation. Particularly, this extremely rare de novo mutation (DNM) is located in the transcriptional repression domain (TRD) of MECP2, where at least 62 different causal mutations are identified. CONCLUSIONS We identified three DNMs in MECP2 in a cohort of 294 individuals with ID. The novel c.879C > G mutation, as a likely pathogenic allele, may become a risk factor associated with X-linked ID, microcephaly and psychomotor retardation.
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Affiliation(s)
- Yi Gu
- Department of Psychiatry, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, 100045, China.,Experimental Medicine Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Bingwu Xiang
- Physical Medicine and Rehabilitation Center, The Second Affiliated Hospital and Yuying Children's Hospital, Wenzhou Medical University, Wenzhou, 325027, Zhejiang, China
| | - Lina Zhu
- Department of Neurology, Bayi Children's Hospital, General Military Hospital of Beijing, Beijing, 10007, China
| | - Xiuwei Ma
- Department of Neurology, Bayi Children's Hospital, General Military Hospital of Beijing, Beijing, 10007, China
| | - Xiang Chen
- Physical Medicine and Rehabilitation Center, The Second Affiliated Hospital and Yuying Children's Hospital, Wenzhou Medical University, Wenzhou, 325027, Zhejiang, China
| | - Tao Cai
- Experimental Medicine Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20892, USA.
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12
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Xiol C, Vidal S, Pascual-Alonso A, Blasco L, Brandi N, Pacheco P, Gerotina E, O'Callaghan M, Pineda M, Armstrong J. X chromosome inactivation does not necessarily determine the severity of the phenotype in Rett syndrome patients. Sci Rep 2019; 9:11983. [PMID: 31427717 PMCID: PMC6700087 DOI: 10.1038/s41598-019-48385-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 08/05/2019] [Indexed: 11/24/2022] Open
Abstract
Rett syndrome (RTT) is a severe neurological disorder usually caused by mutations in the MECP2 gene. Since the MECP2 gene is located on the X chromosome, X chromosome inactivation (XCI) could play a role in the wide range of phenotypic variation of RTT patients; however, classical methylation-based protocols to evaluate XCI could not determine whether the preferentially inactivated X chromosome carried the mutant or the wild-type allele. Therefore, we developed an allele-specific methylation-based assay to evaluate methylation at the loci of several recurrent MECP2 mutations. We analyzed the XCI patterns in the blood of 174 RTT patients, but we did not find a clear correlation between XCI and the clinical presentation. We also compared XCI in blood and brain cortex samples of two patients and found differences between XCI patterns in these tissues. However, RTT mainly being a neurological disease complicates the establishment of a correlation between the XCI in blood and the clinical presentation of the patients. Furthermore, we analyzed MECP2 transcript levels and found differences from the expected levels according to XCI. Many factors other than XCI could affect the RTT phenotype, which in combination could influence the clinical presentation of RTT patients to a greater extent than slight variations in the XCI pattern.
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Affiliation(s)
- Clara Xiol
- Molecular and Genetics Medicine Section, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Silvia Vidal
- Molecular and Genetics Medicine Section, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Ainhoa Pascual-Alonso
- Molecular and Genetics Medicine Section, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Laura Blasco
- Molecular and Genetics Medicine Section, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Núria Brandi
- Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain
| | - Paola Pacheco
- Molecular and Genetics Medicine Section, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Edgar Gerotina
- Molecular and Genetics Medicine Section, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Mar O'Callaghan
- Neurology Service, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Mercè Pineda
- Institut de Recerca Pediàtrica, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Judith Armstrong
- Molecular and Genetics Medicine Section, Hospital Sant Joan de Déu, Barcelona, Spain. .,Institut de Recerca Pediàtrica, Hospital Sant Joan de Déu, Barcelona, Spain. .,CIBER-ER (Biomedical Network Research Center for Rare Diseases), Instituto de Salud Carlos III, Madrid, Spain.
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13
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Treating Rett syndrome: from mouse models to human therapies. Mamm Genome 2019; 30:90-110. [PMID: 30820643 PMCID: PMC6606665 DOI: 10.1007/s00335-019-09793-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 02/09/2019] [Indexed: 02/06/2023]
Abstract
Rare diseases are very difficult to study mechanistically and to develop therapies for because of the scarcity of patients. Here, the rare neuro-metabolic disorder Rett syndrome (RTT) is discussed as a prototype for precision medicine, demonstrating how mouse models have led to an understanding of the development of symptoms. RTT is caused by mutations in the X-linked gene methyl-CpG-binding protein 2 (MECP2). Mecp2-mutant mice are being used in preclinical studies that target the MECP2 gene directly, or its downstream pathways. Importantly, this work may improve the health of RTT patients. Clinical presentation may vary widely among individuals based on their mutation, but also because of the degree of X chromosome inactivation and the presence of modifier genes. Because it is a complex disorder involving many organ systems, it is likely that recovery of RTT patients will involve a combination of treatments. Precision medicine is warranted to provide the best efficacy to individually treat RTT patients.
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Genomic mosaicism in the pathogenesis and inheritance of a Rett syndrome cohort. Genet Med 2018; 21:1330-1338. [PMID: 30405208 PMCID: PMC6752670 DOI: 10.1038/s41436-018-0348-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Accepted: 10/17/2018] [Indexed: 01/01/2023] Open
Abstract
PURPOSE To determine the role of mosaicism in the pathogenesis and inheritance of Rett and Rett-like disorders. METHODS We recruited 471 Rett and Rett-like patients. Panel-sequencing targeting MECP2, CDKL5, and FOXG1 was performed. Mosaicism was quantified in 147 patients by a Bayesian genotyper. Candidates were validated by amplicon sequencing and digital PCR. Germline mosaicism of 21 fathers with daughters carrying pathogenic MECP2 variants was further quantified. RESULTS Pathogenic variants of MECP2/CDKL5/FOXG1 were found in 324/471 (68.7%) patients. Somatic MECP2 mosaicism was confirmed in 5/471 (1.1%) patients, including 3/18 males (16.7%) and 2/453 females (0.4%). Three of the five patients with somatic MECP2 mosaicism had mosaicism at MECP2-Arg106. Germline MECP2 mosaicism was detected in 5/21 (23.8%) fathers. CONCLUSION This is the first systematic screening of somatic and paternal germline MECP2 mosaicism at a cohort level. Our findings indicate that somatic MECP2 mosaicism contributes directly to the pathogenicity of Rett syndrome, especially in male patients. MECP2-Arg106 might be a mosaic hotspot. The high proportion of paternal germline MECP2 mosaicism indicates an underestimated mechanism underlying the paternal origin bias of MECP2 variants. Finally, this study provides an empirical foundation for future studies of genetic disorders caused by de novo variations of strong paternal origin.
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Zhang Q, Zhao Y, Bao X, Luo J, Zhang X, Li J, Wei L, Wu X. Familial cases and male cases with MECP2 mutations. Am J Med Genet B Neuropsychiatr Genet 2017; 174:451-457. [PMID: 28394482 PMCID: PMC5485058 DOI: 10.1002/ajmg.b.32534] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 02/06/2017] [Indexed: 12/03/2022]
Abstract
This is the first report of Chinese familial cases with Rett syndrome (RTT) or X-linked mental retardation (XLMR). RTT is a neurodevelopmental disorder that almost exclusively affects females. Most RTT cases are sporadic. We have studied eight cases with MECP2 mutations in six Chinese families, including three females and five males with RTT or XLMR. All shared identical MECP2 mutations with their mothers. The three females fulfilled the diagnostic criteria for RTT, while the five males were XLMR. A random X-chromosome inactive (XCI) pattern was seen in all the three female patients and two mothers while a skewed XCI in the rest four mothers. The clinical manifestations and pathogenic gene spectrum between male and female patients were different. The different MECP2 mutations and different XCI pattern may be the determinants of the phenotypic heterogeneity between the family members.
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Affiliation(s)
- Qingping Zhang
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Ying Zhao
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Xinhua Bao
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Jinjun Luo
- Departments of Neurology and PharmacologyLewis Katz School of Medicine at Temple UniversityPhiladelphiaPennsylvania
| | - Xiaoying Zhang
- Department of PediatricsPeking University First HospitalBeijingChina
| | - Jiarui Li
- State Key Laboratory of Protein and Plant Gene ResearchSchool of Life SciencesPeking University, Center for BioinformaticsBeijingChina
| | - Liping Wei
- State Key Laboratory of Protein and Plant Gene ResearchSchool of Life SciencesPeking University, Center for BioinformaticsBeijingChina
| | - Xiru Wu
- Department of PediatricsPeking University First HospitalBeijingChina
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