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Gomathi M, Padmapriya S, Balachandar V. Drug Studies on Rett Syndrome: From Bench to Bedside. J Autism Dev Disord 2020; 50:2740-2764. [PMID: 32016693 DOI: 10.1007/s10803-020-04381-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Drug studies on Rett syndrome (RTT) have drastically increased over the past few decades. This review aims to provide master data on bench-to-bedside drug studies involving RTT. A comprehensive literature review was performed by searching in PUBMED, MEDLINE and Google Scholar, international, national and regional clinical trial registries and pharmaceutical companies using the keywords "Rett syndrome treatment and/or drug or compound or molecule". Seventy drugs were investigated in non-clinical (N = 65 animal/cell line-based studies; N = 5 iPSC-based study) and clinical trials (N = 34) for ameliorating the symptoms of RTT. Though there is good progress in both clinical and non-clinical studies, none of these drugs entered phase III/IV for being launched as a therapeutic agent for RTT.
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Affiliation(s)
- Mohan Gomathi
- Human Molecular Genetics and Stem Cell Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore, Tamil Nadu, 641046, India
| | | | - Vellingiri Balachandar
- Human Molecular Genetics and Stem Cell Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore, Tamil Nadu, 641046, India.
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Saikusa T, Kawaguchi M, Tanioka Tetsu T T, Nabatame Shin N S, Takahashi S, Yuge K, Nagamitsu SI, Takahashi T, Yamashita Y, Kobayashi Y, Hirayama C, Kakuma T, Matsuishi T, Itoh M. Meaningful word acquisition is associated with walking ability over 10 years in Rett syndrome. Brain Dev 2020; 42:705-712. [PMID: 32684376 DOI: 10.1016/j.braindev.2020.06.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 05/29/2020] [Accepted: 06/22/2020] [Indexed: 10/23/2022]
Abstract
PURPOSE To investigate walking ability in Japanese patients with Rett syndrome (RTT). METHODS Walking ability was assessed in 100 female Japanese patients with RTT using univariate and multivariate analysis in all age groups, and in patients over 10 years of age. We analyzed walking ability and confounding factors including prenatal-perinatal histories, developmental milestones, somatic and head growth, anthropometric data, body mass index, age of loss of purposeful hand use, age at onset of stereotypic hand movement, history of autistic behavior, age at regression, presence or absence of seizures, and the results of MECP2 genetic examination from the Japanese Rett syndrome database. RESULTS Univariate analysis revealed that acquisition of walking in all age groups was significantly correlated with the acquisition of meaningful words, microcephaly, and crawling (P < 0.0001, P = 0.005, P < 0.0001, respectively). Univariate analysis revealed that walking ability over 10 years of age was significantly correlated with acquisition of meaningful words, microcephaly, and body mass index (P < 0,0001, P = 0.005, P = 0.0018, respectively). MECP2 mutations R306C, R133C, and R294X were significantly associated with different acquisition of crawling (P = 0.004) and walking (P = 0.01). Multivariate analysis revealed that only acquisition of meaningful words was significantly correlated with walking ability over 10 years of age. This trend excluded the genetic effects of R306C, R133C, and R294X. CONCLUSIONS Meaningful word acquisition was robustly associated with walking ability over 10 years. Prognosis of walking ability may be predicted by the acquisition of meaningful words. This information is potentially useful for early intervention and the planning of comprehensive treatment for young children with RTT.
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Affiliation(s)
- Tomoko Saikusa
- Department of Pediatrics and Child Health, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
| | - Machiko Kawaguchi
- Biostatistics Center, Kurume University, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
| | | | - Shin Nabatame Shin N
- Department of Pediatrics, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Satoru Takahashi
- Department of Pediatrics, Asahikawa University, Asahikawa 078-8510, Japan
| | - Kotaro Yuge
- Department of Pediatrics and Child Health, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
| | - Shin-Ichiro Nagamitsu
- Department of Pediatrics and Child Health, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
| | - Tomoyuki Takahashi
- Department of Pediatrics and Child Health, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
| | - Yushiro Yamashita
- Department of Pediatrics and Child Health, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
| | - Yasuyuki Kobayashi
- Japan Rett Syndrome Association, 2-29-20-101 Kamiigusa, Suginami, Tokyo 167-002, Japan
| | - Chisato Hirayama
- Sakuranbokai-Rett Syndrome, 63-2-101 Kawatsu, Iizuka, Fukuoka, Japan
| | - Tatsuyuki Kakuma
- Biostatistics Center, Kurume University, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
| | - Toyojiro Matsuishi
- Research Center for Children, Research Center for Rett Syndrome, St. Mary's Hospital, Kurume, Fukuoka 830-8543, Japan.
| | - Masayuki Itoh
- Department of Mental Retardation and Birth Defect Research, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi-machi, Kodaira, Tokyo 187-8502, Japan
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Le Thi Thanh H, Do Thi Diem T, Duy CV, Thanh HLT, Phuong HBT, Thanh LN. Spectrum of MECP2 mutations in Vietnamese patients with RETT syndrome. BMC MEDICAL GENETICS 2018; 19:137. [PMID: 30081849 PMCID: PMC6090653 DOI: 10.1186/s12881-018-0658-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 07/30/2018] [Indexed: 11/29/2022]
Abstract
Background Rett syndrome (RTT) is a severe neurodevelopmental disorder in children characterized by a normal neurodevelopmental process in the first 6–18 months followed by a period of motor and vocal deterioration with stereotypic hand movements. Incidence of RTT is mostly due to de novo mutation in the MECP2 gene (methyl-CpG-binding protein 2). Methods The study assessed 27 female patients presented with classical RTT phenotype age range from 18 months to 48 months. Specialist carried out the clinical evaluation and diagnosis according to RTT diagnosis criteria. Blood samples from patients were then collected for genomic DNA extraction. We next performed MECP2 gene amplification and sequencing of the whole coding region to screen for mutations. Result MECP2 mutation was found in 20 patients (74%) including: 2 missense, 4 nonsense, 6 frameshift and 2 deletion mutation. The study identified 14 pathogenic mutations which we found 4 mutation, to our knowledge and extensive search, not priory reported in any mutation database or publication: c.1384-1385DelGT, c.1205insT, c.717delC and c.1132_1207del77. High percentage of C > T (70%) in CpG sites mutation was found. Conclusion Our result reveals a high percentage of C > T mutation in CpG hot spot, which is more prone to modification and more likely to be detected in RTT as a disorder is strictly due to de novo mutations. The study is the first to identify the mutation spectrum of MECP2 gene in Vietnamese patients and also an important step toward better diagnosis and care for RTT patients in Vietnam.
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Affiliation(s)
- Huong Le Thi Thanh
- Department of Gene Technology - Vinmec Research Institute of Stem cell and Gene Technology, 458 Minh Khai Street, Hanoi, Hai Ba Trung district, Vietnam.
| | - Trinh Do Thi Diem
- Department of Gene Technology - Vinmec Research Institute of Stem cell and Gene Technology, 458 Minh Khai Street, Hanoi, Hai Ba Trung district, Vietnam
| | - Chinh Vu Duy
- Vinmec International Hospital, 458 Minh Khai Street, Hai Ba Trung District, Hanoi, Vietnam
| | - Ha Ly Thi Thanh
- Department of Gene Technology - Vinmec Research Institute of Stem cell and Gene Technology, 458 Minh Khai Street, Hanoi, Hai Ba Trung district, Vietnam
| | - Hoa Bui Thi Phuong
- Department of Gene Technology - Vinmec Research Institute of Stem cell and Gene Technology, 458 Minh Khai Street, Hanoi, Hai Ba Trung district, Vietnam
| | - Liem Nguyen Thanh
- Department of Gene Technology - Vinmec Research Institute of Stem cell and Gene Technology, 458 Minh Khai Street, Hanoi, Hai Ba Trung district, Vietnam
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Are dopamine receptor and transporter changes in Rett syndrome reflected in Mecp2-deficient mice? Exp Neurol 2018; 307:74-81. [PMID: 29782864 DOI: 10.1016/j.expneurol.2018.05.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 04/27/2018] [Accepted: 05/17/2018] [Indexed: 11/20/2022]
Abstract
We tested the claim that the dopaminergic dysfunction of Rett Syndrome (RTT) also occurs in Mecp2-deficient mice that serve as a model of the syndrome. We used positron emission tomography (PET) to image dopamine D2 receptors (D2R) and transporters (DAT) in women with RTT and in Mecp2-deficient mice, and D1R and D2R density was measured in postmortem human tissue by autoradiography. Results showed 1) significantly reduced D2R density in the striatum of women with RTT compared to control subjects. 2) PET imaging of mouse striatum similarly demonstrated significant reductions in D2R density of 7-10 week-old hemizygous (Mecp2-null) and heterozygous (HET) mice compared to wild type (WT) mice. With age, the density of D2R declined in WT mice but not HET mice. 3) In contrast, postmortem autoradiography revealed no group differences in the density of D1R and D2R in the caudate and putamen of RTT versus normal control subjects. 4) In humans and in the mouse model, PET revealed only marginal group differences in DAT. The results confirm that dopaminergic dysfunction in RTT is also present in Mecp2-deficient mice and that reductions in D2R more likely explain the impaired ambulation and progressive rigidity observed rather than alterations in DAT.
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Park MJ, Aja S, Li Q, Degano AL, Penati J, Zhuo J, Roe CR, Ronnett GV. Anaplerotic triheptanoin diet enhances mitochondrial substrate use to remodel the metabolome and improve lifespan, motor function, and sociability in MeCP2-null mice. PLoS One 2014; 9:e109527. [PMID: 25299635 PMCID: PMC4192301 DOI: 10.1371/journal.pone.0109527] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Accepted: 09/11/2014] [Indexed: 01/13/2023] Open
Abstract
Rett syndrome (RTT) is an autism spectrum disorder (ASD) caused by mutations in the X-linked MECP2 gene that encodes methyl-CpG binding protein 2 (MeCP2). Symptoms range in severity and include psychomotor disabilities, seizures, ataxia, and intellectual disability. Symptom onset is between 6-18 months of age, a critical period of brain development that is highly energy-dependent. Notably, patients with RTT have evidence of mitochondrial dysfunction, as well as abnormal levels of the adipokines leptin and adiponectin, suggesting overall metabolic imbalance. We hypothesized that one contributor to RTT symptoms is energy deficiency due to defective nutrient substrate utilization by the TCA cycle. This energy deficit would lead to a metabolic imbalance, but would be treatable by providing anaplerotic substrates to the TCA cycle to enhance energy production. We show that dietary therapy with triheptanoin significantly increased longevity and improved motor function and social interaction in male mice hemizygous for Mecp2 knockout. Anaplerotic therapy in Mecp2 knockout mice also improved indicators of impaired substrate utilization, decreased adiposity, increased glucose tolerance and insulin sensitivity, decreased serum leptin and insulin, and improved mitochondrial morphology in skeletal muscle. Untargeted metabolomics of liver and skeletal muscle revealed increases in levels of TCA cycle intermediates with triheptanoin diet, as well as normalizations of glucose and fatty acid biochemical pathways consistent with the improved metabolic phenotype in Mecp2 knockout mice on triheptanoin. These results suggest that an approach using dietary supplementation with anaplerotic substrate is effective in improving symptoms and metabolic health in RTT.
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Affiliation(s)
- Min Jung Park
- The Center for Metabolism and Obesity Research, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Department of Neuroscience, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
| | - Susan Aja
- The Center for Metabolism and Obesity Research, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Department of Neuroscience, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- * E-mail:
| | - Qun Li
- The Center for Metabolism and Obesity Research, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Department of Neuroscience, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
| | - Alicia L. Degano
- The Center for Metabolism and Obesity Research, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Department of Neuroscience, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Departamento de Química Biológica, CIQUIBIC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Judith Penati
- Department of Neuroscience, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
| | - Justin Zhuo
- Department of Neuroscience, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
| | - Charles R. Roe
- The Center for Metabolism and Obesity Research, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Department of Neuroscience, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
| | - Gabriele V. Ronnett
- The Center for Metabolism and Obesity Research, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Department of Neuroscience, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Department of Neurology, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Department of Biological Chemistry, The Johns Hopkins University, School of Medicine, Baltimore, MD, United States of America
- Department of Brain Sciences, DGIST, Daegu, South Korea
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Tsai SJ. Peripheral administration of brain-derived neurotrophic factor to Rett syndrome animal model: a possible approach for the treatment of Rett syndrome. Med Sci Monit 2012; 18:HY33-36. [PMID: 22847207 PMCID: PMC3560688 DOI: 10.12659/msm.883251] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Rett syndrome (RTT) is a postnatal, severe, disabling neurodevelopmental disorder occurring almost exclusively in females and is the second most common cause for genetic mental retardation in girls. In the majority of cases it is caused by mutations in gene (MECP2) encoding methyl-CpG-binding protein 2. Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor playing a major role in neuronal survival, neurogenesis and plasticity. Animal studies suggested that abnormalities in BDNF homeostasis may contribute to the pathogenesis in Mecp2 null mice, and BDNF administration in the Mecp2 mutant brain led to later onset/slower disease progression, suggesting that increased BDNF in the brain could be therapeutic for this disease. Mature BDNF is a 14 kDa protein that may have poor blood-brain barrier penetrability. However, recent animal studies demonstrated that peripheral administration of BDNF, either by intravenous injection or intranasal delivery, could increase BDNF levels in the brain. Thus it is proposed that peripheral administration of BDNF in the early stage could have therapeutic potential for RTT subjects. Furthermore, the combination use of mannitol may temporarily open the blood-brain barrier and facilitate the entry of BDNF into brain. The potential therapeutic effect of peripheral BDNF administration could be tested in RTT animal models such as Mecp2 KO mice, which may provide a new intervention for this devastating disease.
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Affiliation(s)
- Shih-Jen Tsai
- Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan
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Han ZA, Jeon HR, Kim SW, Park JY, Chung HJ. Clinical characteristics of children with rett syndrome. Ann Rehabil Med 2012; 36:334-9. [PMID: 22837968 PMCID: PMC3400872 DOI: 10.5535/arm.2012.36.3.334] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 04/02/2012] [Indexed: 11/24/2022] Open
Abstract
Objective To identify the clinical characteristics and investigate function related aspects of Korean children with Rett syndrome. Method A total of 26 patients diagnosed as Rett syndrome were clinically observed until the age of five or over. We surveyed past history, developmental history, and presence of typical clinical features of Rett syndrome. Furthermore, we investigated differences in clinical characteristics according to functional status and changes in clinical features related to growth. Results There were no problems related to gestational, perinatal or neonatal history. Only 12 patients had an ultimate head circumference of less than 3 percentile. Developmental regression was definite in all patients. At final assessment, only 14 patients were able to walk. Twenty patients had an epileptic history requiring medication. Sixteen patients with scoliosis showed progression during serial follow-up. The percentage of patients who were able to walk before 16 months was higher in the high function group than the low function group. The age of regression was 5.4 and 4.0 years in the high and low function group respectively, but the difference was not statistically significant. Scoliosis was more severe and seizure onset age was younger in the low function group. Conclusion We investigated 26 clinical characteristics in Korean children with Rett syndrome. Their clinical features change according to age, and we believe such knowledge could be utilized in rehabilitation to minimize their disabilities.
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Affiliation(s)
- Zee-A Han
- Department of Physical Medicine and Rehabilitation, National Health Insurance Corporation Ilsan Hostpital, Goyang 410-719, Korea
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Pan CH, Tsai S. Early intervention with psychostimulants or antidepressants to increase methyl-CpG-binding protein 2 (MeCP2) expressions: a potential therapy for Rett syndrome. Med Sci Monit 2012; 18:HY1-3. [PMID: 22207122 PMCID: PMC3560675 DOI: 10.12659/msm.882183] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Rett syndrome (RTT) is a severe X-linked postnatal neurodevelopmental disorder. The syndrome is caused primarily by mutations in the methyl CpG binding protein 2 (MeCP2) gene on Xq28. Most individuals with RTT are female, and female RTT is normally heterozygous for mutations in MeCP2. Patients with RTT display a normal period of development prior to the onset of symptoms, at which point they undergo a period of regression. Currently, no effective medication is available for this disorder, although animal studies have suggested that RTT symptoms are potentially reversible. For females with RTT, the severity of symptoms and progression of the disease varies a great deal, despite its homogenous genetic origin. These differences could be attributed to differences in the mutation points of MeCP2 and the skew caused by X-chromosome inactivation. Thus, the increased expression in the normal MeCP2 gene could decrease the severity of the disease. Based on findings from studies on animals indicating that fluoxetine (an antidepressant) and cocaine (a psychostimulant) can increase MeCP2 expression in the brain, it is suggested that early intervention with antidepressants or psychostimulants could increase the normal MeCP2 expression in females with RTT, who are normally heterozygous. This therapeutic hypothesis could be tested in an RTT animal model. Following the identification of the antidepressants or psychostimulants with the greatest influence on MeCP2 expression, a combination of early detection of the disorder with early intervention may result in improved therapeutic outcomes. Furthermore, a trial investigating the effects of antidepressants or psychostimulants on MeCP2 expression in lymphocyte culture from patients with RTT is suggested for clinical therapeutic prediction.
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Affiliation(s)
- Chia-Ho Pan
- Department of Psychiatry, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan
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Yao J, Mu Y, Gage FH. Neural stem cells: mechanisms and modeling. Protein Cell 2012; 3:251-61. [PMID: 22549585 PMCID: PMC4875476 DOI: 10.1007/s13238-012-2033-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 02/21/2012] [Indexed: 12/17/2022] Open
Abstract
In the adult brain, neural stem cells have been found in two major niches: the dentate gyrus and the subventricular zone [corrected]. Neurons derived from these stem cells contribute to learning, memory, and the autonomous repair of the brain under pathological conditions. Hence, the physiology of adult neural stem cells has become a significant component of research on synaptic plasticity and neuronal disorders. In addition, the recently developed induced pluripotent stem cell technique provides a powerful tool for researchers engaged in the pathological and pharmacological study of neuronal disorders. In this review, we briefly summarize the research progress in neural stem cells in the adult brain and in the neuropathological application of the induced pluripotent stem cell technique.
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Affiliation(s)
- Jun Yao
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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Loss of MeCP2 in aminergic neurons causes cell-autonomous defects in neurotransmitter synthesis and specific behavioral abnormalities. Proc Natl Acad Sci U S A 2009; 106:21966-71. [PMID: 20007372 DOI: 10.1073/pnas.0912257106] [Citation(s) in RCA: 187] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Rett syndrome (RTT) is characterized by specific motor, cognitive, and behavioral deficits. Because several of these abnormalities occur in other disease states associated with alterations in aminergic neurotransmitters, we investigated the contribution of such alterations to RTT pathogenesis. We found that both individuals with RTT and Mecp2-null mice have lower-than-normal levels of aminergic metabolites and content. Deleting Mecp2 from either TH-positive dopaminergic and noradrenergic neurons or PET1-positive serotonergic neurons in mice decreased corresponding neurotransmitter concentration and specific phenotypes, likely through MeCP2 regulation of rate-limiting enzymes involved in aminergic neurotransmitter production. These data support a cell-autonomous, MeCP2-dependent mechanism for the regulation of aminergic neurotransmitter synthesis contributing to unique behavioral phenotypes.
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Postnatal changes in serotonergic innervation to the hippocampus of methyl-CpG-binding protein 2-null mice. Neuroscience 2009; 165:1254-60. [PMID: 19932741 DOI: 10.1016/j.neuroscience.2009.11.036] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 11/03/2009] [Accepted: 11/13/2009] [Indexed: 11/23/2022]
Abstract
Rett syndrome is a progressive neurodevelopmental disorder caused by mutations in the methyl-CpG-binding protein 2 (MeCP2) gene. Previous reports have revealed serotonergic function to be altered in the medullas of patients with Rett syndrome and in an animal model of the disease. However, it has remained unclear whether a genetic loss of MeCP2 disrupts serotonergic innervation to the forebrain. In this study, we measured levels of monoamines by high-performance liquid chromatography with electrochemical detection in selected regions of the forebrains of Mecp2-null mice (Mecp2-/y) and wild-type mice (Mecp2+/y) on postnatal day (P) 14, P28, P42 and P56. The levels of hippocampal serotonin (5-HT) and its main metabolite, 5-hydroxyindoleacetic acid (5-HIAA), were significantly lower in Mecp2-null mice than in age-matched wild-type mice on P28, P42 and P56. Immunohistochemical analysis revealed a loss of 5-HT-immunoreactive fibers in the Mecp2-null hippocampus on P56. By contrast, in the raphe region of Mecp2-null mice, there were significant decreases in 5-HT and noradrenaline levels, but these differences later disappeared and there was no change in the number of 5-HT-immunoreactive neuronal cell bodies. Furthermore, we conducted an experiment comparing HPLC measurements in presymptomatic heterozygous females (Mecp2+/-) and wild-type female littermates (Mecp2+/+) on P56. Significant decreases in hippocampal 5-HT and 5-HIAA contents in Mecp2-heterozygous mice were revealed, and these were not accompanied by changes in 5-HT or noradrenaline contents in the raphe region. Therefore, these results indicated decreases in serotonergic innervation to the hippocampus in Mecp2-null males and Mecp2 heterozygous females. We speculate that disturbances in serotonergic neurotransmission in the hippocampus may be linked to the behavioral abnormalities seen in Rett syndrome, such as increased anxiety-like behaviors and reduced exploratory locomotion. MeCP2 may be required for stable serotonergic homeostasis and serotonergic innervation to the hippocampus during postnatal development.
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Roux JC, Villard L. Biogenic amines in Rett syndrome: the usual suspects. Behav Genet 2009; 40:59-75. [PMID: 19851857 DOI: 10.1007/s10519-009-9303-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Accepted: 10/07/2009] [Indexed: 12/25/2022]
Abstract
Rett syndrome (RTT) is a severe postnatal neurological disorder caused by mutations in the methyl-CpG binding protein 2 (MECP2) gene. In affected children, most biological parameters, including brain structure, are normal (although acquired microcephaly is usually present). However, in recent years, a deficit in bioaminergic metabolism has been identified at the cellular and molecular levels, in more than 200 patients. Recently available transgenic mouse strains with a defective Mecp2 gene also show abnormalities, strongly suggesting that there is a direct link between the function of the MECP2 protein and the metabolism of biogenic amines. Biogenic amines appear to have an important role in the pathophysiology of Rett syndrome, for several reasons. Firstly, biogenic amines modulate a large number of autonomic and cognitive functions. Secondly, many of these functions are affected in RTT patients. Thirdly, biogenic amines are the only neurotransmitters that have repeatedly been found to be altered in RTT patients. Importantly, pharmacological interventions can be envisaged to try to counteract the deficits observed. Here, we review the available human and mouse data and present how they have been and could be used in the development of pharmacological treatments for children affected by the syndrome. Given our current knowledge and the tools available, modulating biogenic amine metabolism may prove to be the most promising strategy for improving the life quality of Rett syndrome patients in the short term.
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Lalley PM. Post-inspiratory discharges are the centrepiece of respiratory disrhythmia in a gene knockout model of Rett syndrome. J Physiol 2007; 579:565. [PMID: 17234704 PMCID: PMC2151375 DOI: 10.1113/jphysiol.2007.128249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Peter M Lalley
- Department of Physiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
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SEGAWA M. Epochs of development of the sleep-wake cycle reflect the modulation of the higher cortical function particular for each epoch. Sleep Biol Rhythms 2006. [DOI: 10.1111/j.1479-8425.2006.00205.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Niblock MM, Luce CJ, Belliveau RA, Paterson DS, Kelly ML, Sleeper LA, Filiano JJ, Kinney HC. Comparative anatomical assessment of the piglet as a model for the developing human medullary serotonergic system. ACTA ACUST UNITED AC 2005; 50:169-83. [PMID: 16043226 DOI: 10.1016/j.brainresrev.2005.05.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2005] [Revised: 05/10/2005] [Accepted: 05/13/2005] [Indexed: 10/25/2022]
Abstract
Because the piglet is frequently used as a model for developmental disorders of the medullary serotonergic (5-HT) system in the human infant, this review compares the topography and developmental profile of selected 5-HT markers between humans in the first year of life and piglets in the first 60 days of life. The distribution of tryptophan hydroxylase-immunoreactive 5-HT neurons in the human infant medulla is very similar, but not identical, to that in the piglet. One notable difference is the presence of compact clusters of 5-HT neurons at the ventral surface of the piglet medulla. While it lacks these distinctive clusters, the human infant medulla contains potentially homologous 5-HT neurons scattered along the ventral surface embedded in the arcuate nucleus. Each species shows evidence of age-related changes in the 5-HT system, but the changes are different in nature; in the human infant, statistically significant age-related changes are observed in the proportional distribution of medullary 5-HT cells, while in the piglet, statistically significant age-related changes are observed in the levels of 5-HT receptor binding in certain medullary nuclei. Analyses of 5-HT receptor binding profiles in selected nuclei in the two species suggest that the equivalent postnatal ages for 5-HT development in piglets and human infants are, respectively, 4 days and 1 month, 12 days and 4 months, 30 days and 6 months, and 60 days and 12 months. Collectively, when certain species differences are considered, these data support the use of the piglet as a model for the human infant medullary 5-HT system.
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Affiliation(s)
- Mary M Niblock
- Department of Physiology, Dartmouth Medical School, 1 Medical Center Drive, Lebanon, NH 03756, USA.
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Larsson G, Lindström B, Engerström IW. Rett syndrome from a family perspective: The Swedish Rett Center survey. Brain Dev 2005; 27 Suppl 1:S14-S19. [PMID: 16182488 DOI: 10.1016/j.braindev.2005.03.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2005] [Revised: 01/27/2005] [Accepted: 03/05/2005] [Indexed: 11/16/2022]
Abstract
The aim of this study was to make a description of the early development in individuals with the diagnosis Rett syndrome using parents' information. Information received from 125 cases of Rett syndrome in Sweden in 1997 provided us with families' description of early development in gross motor function, fine motor function and communication/social interplay. Best abilities before regression were presented, 62% lost their best abilities, 22% kept them and 5% kept them with deterioration. Seventy-three percent learnt to walk, 20% stopped walking and 2% retrained walking. Concerning feeding, 69% learnt to feed themselves, 57% lost this ability, 7% retrained the ability and 5% learnt to feed after regression. Sixty-four percent were one year or younger when there was a deviation in development. Sixty answers reported the girl was late in developing functions while 35 reported sudden loss of reached abilities. Seventy-four percent developed a scoliosis and 83% reported other deformities; of these, deformities in feet were the most common. Postural control was poor since all but 15 girls/women learnt in different directions when sitting. Transitional movements were difficult to perform. In 80% of cases, the families were those who suspected early that something was wrong in the child's development. Because of this it is essential that medical staff is aware of the different ways RS develops in order to give families early appropriate support and a plan for intervention. Since there is not only loss of function in this group but also kept abilities, retrained abilities and abilities achieved after regression, more research has to be focused on management and treatment to help persons with Rett syndrome keep and develop abilities according to their individual resources.
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Affiliation(s)
- Gunilla Larsson
- Swedish Rett Center, Frösö Strand, Box 601, SE-832 23 Frösön, Sweden.
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Segawa M. Early motor disturbances in Rett syndrome and its pathophysiological importance. Brain Dev 2005; 27 Suppl 1:S54-S58. [PMID: 16182486 DOI: 10.1016/j.braindev.2004.11.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2004] [Accepted: 11/01/2004] [Indexed: 11/18/2022]
Abstract
Assessment of the development of motor function of Rett syndrome (RTT) revealed hypotonia with failure of crawling and disturbance in skillful hand manipulation are shown as early motor signs. Clinical evaluation has revealed the former as postural hypotonia with failure in locomotion and neurophysiological examinations have showed this to be due to hypofunction of the aminergic neurons of the brainstem. The latter signs are considered to indicate dysfunction of the corticospinal tract at higher levels. As the signs appear along with deceleration of head growth, dysfunction of the noradrenergic neuron, which is involved in synaptogenesis in the cerebral cortex, is postulated as the cause. The characteristic stereotyped hand movements appear in early childhood after loss of purposeful hand use and are underlain by rigid hypertonus. Neurophysiological examinations have indicated that these are due to hypofunction of the nigrostriatal (NS) dopamine (DA) neuron. By comparison with animal experimental work the neurohistochemical changes in the substantia nigra of the autopsied brain of RTT suggest a lesion caused by the dysfunction of the pedunculopontine nucleus, induced by dysfunction of the brainstem aminergic neurons which modulate postural tone and locomotion. Hypofunction of the aminergic neurons also cause 'leakage' of atonia into non-REM stages which lead to disturbances in the autonomic nervous system through inhibition of the reflex system. The grade of disturbance of locomotion closely matches the grade in abnormalities of higher cortical function as indicated by the development of meaningful words. The loci of missense mutation of methyl CPG binding domain of MECP 2gene which affect locomotion severely also markedly impaired their effects on the formation of the heterochromatin. Thus, dysfunction of the aminergic neurons of the brainstem which regulate postural tone and locomotion is proposed as the primary lesion.
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Affiliation(s)
- Masaya Segawa
- Segawa Neurological Clinic for Children, 2-8 Surugarai Kanda, Chiyoda-ku, Tokyo 101 0062, Japan.
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Nomura Y. Early behavior characteristics and sleep disturbance in Rett syndrome. Brain Dev 2005; 27 Suppl 1:S35-S42. [PMID: 16182496 DOI: 10.1016/j.braindev.2005.03.017] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 11/30/2004] [Accepted: 03/05/2005] [Indexed: 11/29/2022]
Abstract
This paper reviews the early features of Rett syndrome (RTT). The behavioral characteristics of RTT were analyzed retrospectively by taking history and asking about early infancy behaviors. The earliest behavioral characteristics are thought to be autistic features and hypotonia of trunkal muscles. Analysis of sleep-wake rhythm and all-night polysomnography suggested that the initial lesion is serotonergic and noradrenargic hypofunction at brainstem level. Dopaminergic (DA) hypofunction associated with DA receptor supersensitivity follows as the brain matures. Characteristic symptoms developing at specific age ranges are based on the neuronal connections of the brainstem aminergic neurons and DA neurons with the pedunculo-pontine nuclei, projecting to specific cortical areas.
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Affiliation(s)
- Yoshiko Nomura
- Segawa Neurological Clinic for Children, 2-8 Surugadai Kanda Chiyodaku, Tokyo 101-0062, Japan.
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Lotan M, Shapiro M. Management of young children with Rett disorder in the controlled multi-sensory (Snoezelen) environment. Brain Dev 2005; 27 Suppl 1:S88-S94. [PMID: 16182498 DOI: 10.1016/j.braindev.2005.03.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2004] [Revised: 10/12/2004] [Accepted: 03/02/2005] [Indexed: 11/20/2022]
Abstract
Rett syndrome is a neurological disorder resulting from an X-linked dominant mutation. It is characterized by a variety of physical and perceptual disabilities, resulting in a need for constant therapy programs to be administered on a regular basis throughout the client's life. As the child with Rett disorder (RD) is entering the more obvious, hectic phase of this syndrome (stage II), signs of extreme agitation and discomfort are usually exhibited. This behavior is suspected to reflect damaging chaotic processes accruing in the brain at that time. Experts advise that calming techniques might be helpful for children with Rett during this period. This may be our earliest opportunity to change the course of the disorder. Now that our knowledge of RD has increased and children are being diagnosed at a substantially earlier age, new intervention methods should be introduced for parents and therapists. This may ensure more suitable treatment. The multi-sensory environment may provide a soothing haven, which appeals to the child with RD. This article provides a short review of RD typical phenotype and suggests suitable activities that could take place in the multi-sensory environment with this population at the early stages of appearance of the Rett disorder.
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Affiliation(s)
- Meir Lotan
- Therapeutic Department, Zvi Quittman Residential Center, The Millie Shime Campus, Israel Elwyn, Jerusalem, Israel.
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Abstract
Rett syndrome is a unique neurodevelopmental disorder, with onset of hypotonia, autistic tendency, and abnormalities of fine finger movements and gross movements of the arms in early infancy. Clinical features include specific age-dependent symptoms. Studies of early and late signs correlated locomotive dysfunction to language disability and stereotypy to regression of higher cortical functions. Studies of sleep parameters revealed early hypofunction of brainstem aminergic neurons and late occurrence of hypofunction of dopaminergic neurons, followed by receptor supersensitivity. The syndrome's pathophysiology suggests that early hypofunction of aminergic neurons interferes with the development of higher neuronal systems. Particular symptoms surface at different ages throughout the natural course of Rett syndrome, with regressional and static periods.
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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
Studies on sleep parameters of Rett syndrome revealed hypoactivity of the noradrenaline (NA) and the serotonin (5HT) neuron in early infancy while preserving the function of the dopamine (DA) and the cholinergic neurons of the pons normally. The sleep-wake cycle remains in its development at the level of 4 months of age. Polysomnographies also showed a decrease of the function of the nigrostriatal (NS)-DA neuron in early childhood and suggested the development of receptor supersensitivity in late childhood. Neurohistochemical and neuroimaging (PET) studies revealed the hypofunction of the NS-DA neuron with receptor supersensitivity and of involvement of the cholinergic neurons to the cortical pathology, whereas no substantial pathological or histochemical abnormalities were observed in the NA and the 5HT neurons in the brainstem. The decrease of tyrosine hydroxylase without neurodegenerative changes observed in the substantia nigra of Rett syndrome had similarity to the pathology caused by excitotoxic lesion of the pedunculopontine nuclei (PPN) observed in an animal experiments. Clinically the grade of disability of locomotion was shown to correlate to the grade of the disabilities of language. These clinical manifestations were also correlated to the specific loci of the mutation in the methyl binding domain of the MECP2 gene. In rodents the axons of the brainstem 5HT neuron involved in the morphogenesis of the brain in the early developmental course disappear in neonates without apoptotic or degenerative changes in the neurons. This period corresponds to the first 1.5-2 years in humans. Thus, in Rett syndrome, the primary lesion appears in the brainstem NA and 5HT neurons which affects development of synaptogenesis of the cortex and also dysfunction of the PPN. The latter causes dysfunction of the DA neuron and the cholinergic neuron in the midbrain. The mutation of the MECP2 gene may cause early transcription of the genes which prune the axons of the aminergic neurons for the developmental morphogenesis of the central nervous system in early infancy.
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Affiliation(s)
- M Segawa
- Segawa Neurological Clinic for Children, 2-8 Surugadai, Kanda Chiyodaku, 101-0062, Tokyo, Japan.
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