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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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Variation spectrum of MECP2 in Korean patients with Rett and Rett-like syndrome: a literature review and reevaluation of variants based on the ClinGen guideline. J Hum Genet 2022; 67:601-606. [PMID: 35606502 DOI: 10.1038/s10038-022-01044-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/09/2022]
Abstract
Rett syndrome (RTT) is a progressive neurodevelopmental disorder caused by variants in MECP2. Emerging evidence of ethnic specificity of genetic variations has allowed precise diagnostic approaches with tailored therapies. In this study, we reviewed the variation spectrum of MECP2 in Korean RTT(-like) patients and compared it with previous reports in multiple ethnic groups. We reevaluated variants found in Korean RTT patients according to the new Clinical Genome Resource guideline to reinterpret and reclassify variants of uncertain significance in MECP2. Among 377 cases, 56 (14.9%) showed pathogenic variants, and three novel variants, p.(Ala277Argfs*7), p.(Ala378Glyfs*8), and p.(Arg270_Ser332del), were identified. Comprehensive data from Korea revealed an overall consistent variation spectrum with those from other ethnicities. Through the reevaluation of variants, nine that previously had insufficient evidence for pathogenicity were reclassified into pathogenic variants. Our study provided insight on the genetic contribution of MECP2 in RTT and a useful background for genetic counseling in the Korean population.
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Mullegama SV, Klein SD, Signer RH, Vilain E, Martinez-Agosto JA. Mutations in STAG2 cause an X-linked cohesinopathy associated with undergrowth, developmental delay, and dysmorphia: Expanding the phenotype in males. Mol Genet Genomic Med 2018; 7:e00501. [PMID: 30447054 PMCID: PMC6393687 DOI: 10.1002/mgg3.501] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 09/27/2018] [Accepted: 10/10/2018] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The cohesin complex is a multi-subunit protein complex which regulates sister chromatid cohesion and separation during cellular division. In addition, this evolutionarily conserved protein complex plays an integral role in DNA replication, DNA repair, and the regulation of transcription. The core complex is composed of four subunits: RAD21, SMC1A, SMC3, and STAG1/2. Mutations in these proteins have been implicated in human developmental disorders collectively termed "cohesinopathies." METHODS Using clinical exome sequencing, we have previously identified three female cases with heterozygous STAG2 mutations and overlapping syndromic phenotypes. Subsequently, a familial missense variant was identified in five male family members. RESULTS We now present the case of a 4-year-old male with developmental delay, failure to thrive, short stature, and polydactyly with a likely pathogenic STAG2 de novo missense hemizygous variant, c.3027A>T, p.Lys1009Asn. Furthermore, we compare the phenotypes of the four previously reported STAG2 variants with our case. CONCLUSION We conclude that mutations in STAG2 cause a novel constellation of sex-specific cohesinopathy-related phenotypes and are furthermore, essential for neurodevelopment, human growth, and behavioral development.
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Affiliation(s)
- Sureni V Mullegama
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas
| | - Steven D Klein
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Rebecca H Signer
- Division of Medical Genetics, Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
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- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Eric Vilain
- Department of Genomic and Precision Medicine, Children's National Hospital, Washington, District of Columbia
| | - Julian A Martinez-Agosto
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.,Division of Medical Genetics, Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.,UCLA Clinical Genomics Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
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Mullegama SV, Klein S, Mulatinho MV, Senaratne T, Singh K, Nguyen D, Gallant N, Strom S, Ghahremani S, Rao PN, Martinez-Agosto JA. De novo loss-of-function variants in STAG2 are associated with developmental delay, microcephaly, and congenital anomalies. Am J Med Genet A 2017; 173:1319-1327. [PMID: 28296084 PMCID: PMC7033032 DOI: 10.1002/ajmg.a.38207] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 02/09/2017] [Accepted: 02/13/2017] [Indexed: 12/26/2022]
Abstract
The cohesin complex is an evolutionarily conserved multi-subunit protein complex which regulates sister chromatid cohesion during mitosis and meiosis. Additionally, the cohesin complex regulates DNA replication, DNA repair, and transcription. The core of the complex consists of four subunits: SMC1A, SMC3, RAD21, and STAG1/2. Loss-of-function mutations in many of these proteins have been implicated in human developmental disorders collectively termed "cohesinopathies." Through clinical exome sequencing (CES) of an 8-year-old girl with a clinical history of global developmental delay, microcephaly, microtia with hearing loss, language delay, ADHD, and dysmorphic features, we describe a heterozygous de novo variant (c.205C>T; p.(Arg69*)) in the integral cohesin structural protein, STAG2. This variant is associated with decreased STAG2 protein expression. The analyses of metaphase spreads did not exhibit premature sister chromatid separation; however, delayed sister chromatid cohesion was observed. To further support the pathogenicity of STAG2 variants, we identified two additional female cases from the DECIPHER research database with mutations in STAG2 and phenotypes similar to our patient. Interestingly, the clinical features of these three cases are remarkably similar to those observed in other well-established cohesinopathies. Herein, we suggest that STAG2 is a dosage-sensitive gene and that heterozygous loss-of-function variants lead to a cohesinopathy.
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Affiliation(s)
- S. V. Mullegama
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
- UCLA Clinical Genomics Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - S. Klein
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - M. V. Mulatinho
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - T.N. Senaratne
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - K. Singh
- Division of Genetic and Genomic Medicine, University of California, Irvine, California, USA, and Miller Children’s and Women’s Hospital Long Beach, Long Beach, California, USA
| | - UCLA Clinical Genomics Center
- UCLA Clinical Genomics Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - D.C. Nguyen
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - N.M. Gallant
- Division of Genetic and Genomic Medicine, University of California, Irvine, California, USA, and Miller Children’s and Women’s Hospital Long Beach, Long Beach, California, USA
| | - S.P. Strom
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
- UCLA Clinical Genomics Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - S. Ghahremani
- Department of Radiology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - P. N. Rao
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - J. A. Martinez-Agosto
- UCLA Clinical Genomics Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
- Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
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Petrinovic MM, Künnecke B. Neuroimaging endophenotypes in animal models of autism spectrum disorders: lost or found in translation? Psychopharmacology (Berl) 2014; 231:1167-89. [PMID: 23852013 DOI: 10.1007/s00213-013-3200-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 06/26/2013] [Indexed: 11/26/2022]
Abstract
RATIONALE Autism spectrum disorder(s) (ASDs) is a neurodevelopmental disorder characterized by stereotyped behaviours and impairments in communication and social interactions. This heterogeneity has been a major obstacle in uncovering the aetiology and biomarkers of ASDs. Rodent models with genetic modifications or environmental insults have been created to study particular endophenotypes and bridge the gap between genetics and behavioural phenotypes. Translational neuroimaging modalities with their ability to screen the brain noninvasively and yield structural, biochemical and functional information provide a unique platform for discovery and evaluation of such endophenotypes in preclinical and clinical research. OBJECTIVES We reviewed literature on translational neuroimaging in rodent models of ASDs. The most prominent models will be described and the respective neuroimaging endophenotypes will be discussed with reference to human data. A perspective on future directions of translational neuroimaging in animal models of ASDs will be given. RESULTS AND CONCLUSIONS To date, we experience a proliferation of rodent models which recapitulate specific liabilities identified in ASDs patients. Translational neuroimaging in these models is emerging but is skewed towards magnetic resonance imaging (MRI) modalities. Volumetric and structural assessments of the brain are dominating and a host of endophenotypes have been reported that allude to findings in ASDs patients but with only few to converge among the models. Caveats of current studies are the diverging biological conditions related to genetic background and age of the animals. It is anticipated that longitudinal and functional assessments will gain much importance and will help elucidating mechanistic relationship between behavioural and structural endophenotypes.
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Affiliation(s)
- Marija M Petrinovic
- F. Hoffmann-La Roche AG, pRED, Pharma Research and Early Development, DTA Neuroscience, Building 68, Room 327A, Grenzacherstrasse 124, 4070, Basel, Switzerland
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Zhang X, Bao X, Zhang J, Zhao Y, Cao G, Pan H, Zhang J, Wei L, Wu X. Molecular characteristics of Chinese patients with Rett syndrome. Eur J Med Genet 2012; 55:677-81. [DOI: 10.1016/j.ejmg.2012.08.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 08/20/2012] [Indexed: 10/27/2022]
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Hadzsiev K, Polgar N, Bene J, Komlosi K, Karteszi J, Hollody K, Kosztolanyi G, Renieri A, Melegh B. Analysis of Hungarian patients with Rett syndrome phenotype for MECP2, CDKL5 and FOXG1 gene mutations. J Hum Genet 2010; 56:183-7. [DOI: 10.1038/jhg.2010.156] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Marco EJ, Skuse DH. Autism-lessons from the X chromosome. Soc Cogn Affect Neurosci 2010; 1:183-93. [PMID: 18985105 DOI: 10.1093/scan/nsl028] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Accepted: 09/18/2006] [Indexed: 02/06/2023] Open
Abstract
Recognized cases of autism spectrum disorders are on the rise. It is unclear whether this increase is attributable to secular trends in biological susceptibility, or to a change in diagnostic practices and recognition. One hint concerning etiological influences is the universally reported male excess (in the range of 4:1 to 10:1). Evidence suggests that genetic influences from the X chromosome play a crucial role in engendering this male vulnerability. In this review, we discuss three categories of genetic disease that highlight the importance of X-linked genes in the manifestation of an autistic phenotype: aneuploides (Turner syndrome and Klinefelter syndrome), trinucleotide expansions (Fragile X syndrome) and nucleotide mutations (Rett Syndrome, Neuroligins 3 & 4, and SLC6A8). The lessons from these diseases include an understanding of autistic features as a broad phenotype rather than as a single clinical entity, the role of multiple genes either alone or in concert with the manifestation of autistic features, and the role of epigenetic factors such as imprinting and X-inactivation in the expression of disease severity. Better understanding of the clinical phenotypes of social cognition and the molecular neurogenetics of X-linked gene disorders will certainly provide additional tools for understanding autism in the years to come.
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Affiliation(s)
- Elysa J Marco
- Behavioral and Brain Sciences Unit, Institute of Child Health, London, UK
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Louise S, Fyfe S, Bebbington A, Bahi-Buisson N, Anderson A, Pineda M, Percy A, Ben Zeev B, Wu XR, Bao X, Mac Leod P, Armstrong J, Leonard H. InterRett, a model for international data collection in a rare genetic disorder. RESEARCH IN AUTISM SPECTRUM DISORDERS 2009; 3:10.1016/j.rasd.2008.12.004. [PMID: 24348750 PMCID: PMC3858578 DOI: 10.1016/j.rasd.2008.12.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Rett syndrome (RTT) is a rare genetic disorder within the autistic spectrum. This study compared socio-demographic, clinical and genetic characteristics of the international database, InterRett, and the population based Australian Rett syndrome database (ARSD). It also explored the strengths and limitations of InterRett in comparison with other studies. A literature review compared InterRett with RTT population-based and case-based studies of thirty or more cases that investigated genotype and/or phenotype relationships. Questionnaire data were used to determine case status and to investigate the comparability of InterRett and ARSD. Twenty four case series, five population based studies and a MECP2 mutation database were identified of which twenty one (70%) collected phenotype and genotype data. Only three studies were representative of their underlying case population and many had low numbers. Of one thousand one hundred and fourteen InterRett subjects, nine hundred and thirty five born after 1976 could be verified as Rett cases and compared with the two hundred and ninety five ARSD subjects. Although more InterRett families had higher education and occupation levels and their children were marginally less severe, the distribution of MECP2 mutation types was similar. The InterRett can be used with confidence to investigate genotype phenotype associations and clinical variation in RTT and provides an exemplary international model for other rare disorders.
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Affiliation(s)
- Sandra Louise
- Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Perth, Western Australia
| | - Sue Fyfe
- Curtin University, Perth, Western Australia
| | - Ami Bebbington
- Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Perth, Western Australia
| | - Nadia Bahi-Buisson
- Université René Descartes - Paris V, Hopital Necker Enfants Malades, Paris, France
| | - Alison Anderson
- Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Perth, Western Australia
| | | | - Alan Percy
- Civitan International Research Centre, University of Alabama, Birmingham, Alabama, USA
| | - Bruria Ben Zeev
- Safra Pediatric Hospital, Sheba Medical Center, Ramat-Gan, Israel
| | - Xi Ru Wu
- Peking University First Hospital, Beijing, China
| | - Xinhua Bao
- Peking University First Hospital, Beijing, China
| | | | | | - Helen Leonard
- Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Perth, Western Australia
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Horská A, Farage L, Bibat G, Nagae LM, Kaufmann WE, Barker PB, Naidu S. Brain metabolism in Rett syndrome: age, clinical, and genotype correlations. Ann Neurol 2009; 65:90-7. [PMID: 19194883 DOI: 10.1002/ana.21562] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Brain metabolism, as studied by magnetic resonance spectroscopy (MRS), has been previously shown to be abnormal in Rett syndrome (RTT). This study reports the relation of MRS findings to age, disease severity, and genotype. METHODS Forty RTT girls (1-14 years old) and 12 age-matched control subjects were examined. Single-voxel proton MRS of left frontal white matter was performed. RESULTS NAA/Cr ratios decreased and myoinositol/Cr ratios increased with age in RTT patients (both p < 0.03), whereas these ratios were stable in control. The mean glutamate and glutamine/Cr ratio was 36% greater in RTT patients than in control (p = 0.043). The mean NAA/Cr ratio was 12.6% lower in RTT patients with seizures compared with those without seizures (p = 0.017). NAA/Cr ratios decreased with increasing clinical severity score (p = 0.031). Compared with patients with T158X, R255X, and R294X mutations, and C-terminal deletions, patients with the R168X mutation tended to have the greatest severity score (0.01 < or = p < or = 0.11) and the lowest NAA/Cr ratio (0.029 < or = p < 0.14). INTERPRETATION Decreasing NAA/Cr and increasing myoinositol/Cr with age are suggestive of progressive axonal damage and astrocytosis in RTT, respectively, whereas increased glutamate and glutamine/Cr ratio may be secondary to increasing glutamate/glutamine cycling at the synaptic level. The relations between NAA/Cr, presence or absence of seizures, and disease severity suggest that MRS provides a noninvasive measure of cerebral involvement in RTT.
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Affiliation(s)
- Alena Horská
- Division of Neuroradiology, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.
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Ward BC, Agarwal S, Wang K, Berger-Sweeney J, Kolodny NH. Longitudinal brain MRI study in a mouse model of Rett Syndrome and the effects of choline. Neurobiol Dis 2008; 31:110-9. [PMID: 18571096 DOI: 10.1016/j.nbd.2008.03.009] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2007] [Revised: 03/26/2008] [Accepted: 03/31/2008] [Indexed: 10/22/2022] Open
Abstract
Rett Syndrome (RTT), the second most common cause of mental retardation in girls, is associated with mutations of an X-linked gene encoding the transcriptional repressor protein MeCP2. Mecp2(1lox) mutant mice express no functional MeCP2 protein and exhibit behavioral abnormalities similar to those seen in RTT patients. Here we monitor the development of both whole brain and regional volumes between 21 and 42 days of age in this model of RTT using MRI. We see decreases in whole brain volumes in both male and female mutant mice. Cerebellar and ventricular volumes are also decreased in RTT males. Previous work has suggested that perinatal choline supplementation alleviates some of the behavioral deficits in both male and female Mecp2(1lox) mutant mice. Here we show that perinatal choline supplementation also positively affects whole brain volume in heterozygous females, and cerebellar volume in male RTT mice.
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Affiliation(s)
- B C Ward
- Neuroscience Program, Wellesley College, USA
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Nag N, Ward B, Berger-Sweeney JE. Nutritional factors in a mouse model of Rett syndrome. Neurosci Biobehav Rev 2008; 33:586-92. [PMID: 18479749 DOI: 10.1016/j.neubiorev.2008.03.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 03/07/2008] [Accepted: 03/19/2008] [Indexed: 11/17/2022]
Abstract
Environmental factors such as nutrition and housing can influence behavioral and anatomical characteristics of several neurological disorders, including Rett syndrome (RTT). RTT is associated with mutations in the X-linked gene encoding MeCP2, a transcriptional repressor that binds methylated DNA. While direct genetic intervention in humans is impossible at this time, motor and cognitive deficits in RTT may be ameliorated through manipulations of epigenetic/environmental factors. For example, studies in rodents suggest that choline nutrient supplementation during critical periods of brain development enhances cholinergic neurotransmission, alters neuronal size and distribution, and facilitates performance of memory and motoric tasks. Recent work in a mouse model of RTT shows that enhancing maternal nutrition through choline supplementation improves both anatomical and behavioral symptoms in the mutant offspring. We describe here cellular and molecular mechanisms that may underlie this specific enhancement and may provide more general insights into mechanisms underlying gene-environment interactions in neurological disorders.
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Affiliation(s)
- Nupur Nag
- Department of Biological Sciences, Wellesley College, 106 Central Street, Wellesley, MA 02481, United States
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Nag N, Berger-Sweeney JE. Postnatal dietary choline supplementation alters behavior in a mouse model of Rett syndrome. Neurobiol Dis 2007; 26:473-80. [PMID: 17395475 DOI: 10.1016/j.nbd.2007.02.003] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 02/05/2007] [Accepted: 02/07/2007] [Indexed: 01/06/2023] Open
Abstract
Rett syndrome (RTT), a neurodevelopmental disorder primarily affecting females, is accompanied by behavioral and neuropathological abnormalities and decreases in brain cholinergic markers. Because the cholinergic system is associated with cognitive and motor functions, cholinergic deficits in RTT may underlie some of the behavioral abnormalities. In rodents, increased choline availability during development enhances transmission at cholinergic synapses and improves behavioral performance throughout life. We examined whether choline supplementation of nursing dams would attenuate deficits in Mecp2(1lox) offspring, a mouse model of RTT. Dams were given choline in drinking water, and pups nursed from birth to weaning. Offspring were assessed on development and behavior. In Mecp2(1lox) males, choline supplementation improved motor coordination and locomotor activity, whereas in females it enhanced grip strength. Choline supplementation did not improve response to fear conditioning. Postnatal choline supplementation attenuates some behavioral deficits in Mecp2(1lox) mice and should be explored further as a therapeutic agent in RTT.
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Affiliation(s)
- Nupur Nag
- Department of Biological Sciences, Wellesley College, Wellesley, MA 02481, USA
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Abstract
PURPOSE OF REVIEW Nearly 70 reports on Rett syndrome were published in 2004. We have selected 51 articles, including clinical reports, on pathophysiology, genotype-phenotype correlation, and clinical and basic molecular biology studies. These articles explain how mutation of the gene (MECP2) for methyl-CpG-binding protein 2 causes the particular disorders of Rett syndrome, and also induces other neurodevelopmental disorders, clarifying the situation for future studies. RECENT FINDINGS The role of X-chromosome inactivation has been clarified in animal experiments. New isoforms of MeCP2 have been discovered and its functional characteristics are under research. Understanding of the influence of the MECP2 mutation on other neurodevelopmental disorders has increased. However, there is no apparent progress in neurophysiological studies. SUMMARY Clinical studies included the pathophysiology of stereotyped movement, and cardiac and respiratory disturbances, and there were four therapeutic trials including one for epilepsy. For genotype-phenotype correlation the role of X-chromosome inactivation was looked at and its basic mechanisms were studied extensively in animals. Characteristics of mutations in the C-terminus and the biological function of the new isoform, exon 1, were introduced. In studies on related neurodevelopmental disorders, a relationship is suggested between the MECP2 gene and autism-related gene, with overlapping pathways, but this is not common to other neurodevelopmental disorders. Developmental studies suggest an important role for MeCP2 in the formation and/or maintenance of synapses, and clarify the molecular biological aspects of Rett syndrome. However, early involvement of the aminergic neurons, suggested as the basic, pathognomonic lesion of Rett syndrome, has unfortunately not been investigated with the MECP2 mutation.
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Affiliation(s)
- Masaya Segawa
- Segawa Neurological Clinic for Children, Tokyo, Japan.
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Abstract
Of the recently discovered group of proteins that interpret DNA methylation signals by preferentially associating with methylated CpG dinucleotides, the methyl-CpG-binding protein 2 (MeCP2) has attracted considerable attention in view of its ability to repress transcription. The interest in MeCP2 dramatically increased following the discovery of mutated forms of the protein in patients with Rett syndrome, a neurodevelopmental disease. A connection with carcino-genesis has also been established. This review attempts to bring together and critically discuss recently acquired information about the molecular biology of the protein and its mechanism of action. A careful overview of the literature reveals the complexity of its activity, which goes well beyond the recognized chromatin connections. Finally, the newly established facts concerning the connection of MeCP2 to human disease are presented. Key words: methyl-CpG-binding proteins, MeCP2, transcription repression, chromatin modification, Rett syndrome, cancer.
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Affiliation(s)
- Jordanka Zlatanova
- Department of Molecular Biology, College of Agriculture, University of Wyoming, Laramie, WY 82071, USA.
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Bapat S, Galande S. Association by guilt: identification of DLX5 as a target for MeCP2 provides a molecular link between genomic imprinting and Rett syndrome. Bioessays 2005; 27:676-80. [PMID: 15954098 DOI: 10.1002/bies.20266] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Rett syndrome (RTT) is an X-linked dominant neurodevelopmental disorder affecting almost exclusively girls. Although mutations in methyl-CpG-binding protein (MeCP2) are known to be associated with RTT, gene expression patterns are not significantly altered in MeCP2-deficient cells. A recent study1 identified MeCP2-mediated histone modification and formation of a higher-order chromatin loop structure specifically associated with silent chromatin at the Dlx5-Dlx6 locus in normal cells, and its absence thereof in RTT patients. This altered expression of Dlx5 through loss of silent chromatin loop formation provides a molecular mechanism underlying RTT and proposes a novel role for MeCP2 in chromatin organization and imprinting.
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Affiliation(s)
- Sharmila Bapat
- National Centre for Cell Science, Ganeshkhind, Pune, India
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