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Zhang X, Smits M, Curfs L, Spruyt K. Sleep and the Social Profiles of Individuals With Rett Syndrome. Pediatr Neurol 2024; 152:153-161. [PMID: 38290182 DOI: 10.1016/j.pediatrneurol.2024.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 12/30/2023] [Accepted: 01/03/2024] [Indexed: 02/01/2024]
Abstract
BACKGROUND This study investigates the distinctive social behaviors observed in individuals with Rett syndrome (RTT), characterized by the loss of spoken language, impaired eye gaze communication, gait abnormalities, and sleep issues. The research aims to identify social profiles in RTT and explore their correlation with sleep, sleep-disordered breathing (SDB), and daytime sleepiness. METHODS Standard overnight sleep macrostructure and respiratory parameters were assessed. Extracting 25 social-related items and one for daytime sleepiness from the Rett Syndrome Behavioral Questionnaire, factor analysis was applied to establish latent social profiles. These profiles were then correlated with sleep parameters. The nonparametric Mann-Whitney U test compared social profiles based on the presence of SDB (defined by an apnea-hypopnea index greater than one per hour) and daytime sleepiness. RESULTS The study involved 12 female subjects with confirmed RTT diagnoses and MECP2 mutations, aged 8.54 ± 5.30 years. The Rett Syndrome Behavioral Questionnaire revealed a total average score of 25.83 ± 12.34, indicating varying degrees of social impairments. Comprising 25 social-related items, factor analysis yielded four social profiles: "interactive motricity," "mood change," "anxiety/agitation," and "gazing." Longer sleep onset latency correlated with increased socio-behavioral impairments, particularly in interactive motricity reduction. Conversely, higher rapid eye movement sleep was associated with fewer interactive socio-motor behaviors. No significant differences in social profiles were found concerning the presence of SDB or daytime sleepiness. CONCLUSIONS The findings suggest four distinct social profiles in RTT individuals, hinting at shared disrupted circuits between sensorimotor functioning and sleep-related neuronal pathways. Despite the absence of differences in SDB or daytime sleepiness, the study highlights the relationship between sleep parameters, such as sleep onset latency and rapid eye movement sleep, and socio-behavioral outcomes in RTT with MECP2 mutations.
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Affiliation(s)
- Xinyan Zhang
- Université Paris Cité, NeuroDiderot - INSERM, Paris, France
| | - Marcel Smits
- Department of Sleep-Wake Disorders and Chronobiology, Hospital Gelderse Vallei Ede, Ede, Netherlands; Governor Kremers Centre, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Leopold Curfs
- Governor Kremers Centre, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Karen Spruyt
- Université Paris Cité, NeuroDiderot - INSERM, Paris, France.
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2
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Farhoomand F, Delaney KR. Long-term cortical plasticity following sensory deprivation is reduced in male Rett model mice. Somatosens Mot Res 2023; 40:133-140. [PMID: 36565289 DOI: 10.1080/08990220.2022.2158799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 12/08/2022] [Indexed: 12/25/2022]
Abstract
PURPOSE/AIM Rett (RTT) syndrome, a neurodevelopmental disorder, results from loss-of-function mutations in methyl-CpG-binding protein 2. We studied activity-dependent plasticity induced by sensory deprivation via whisker trimming in early symptomatic male mutant mice to assess neural rewiring capability. METHODS One whisker was trimmed for 0-14 days and intrinsic optical imaging of the transient reduction of brain blood oxygenation resulting from neural activation by 1 second of wiggling of the whisker stump was compared to that of an untrimmed control whisker. RESULTS Cortical evoked responses to wiggling a non-trimmed whisker were constant for 14 days, reduced for a trimmed whisker by 49.0 ± 4.3% in wild type (n = 14) but by only 22.7 ± 4.6% in mutant (n = 18, p = 0.001). CONCLUSION As the reduction in neural activation following sensory deprivation in whisker barrel cortex is known to be dependent upon evoked and basal neural activity, impairment of cortical re-wiring following whisker trimming provides a paradigm suitable to explore mechanisms underlying deficiencies in the establishment and maintenance of synapses in RTT, which can be potentially targeted by therapeutics.
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Affiliation(s)
| | - Kerry R Delaney
- Department of Biology, University of Victoria, Victoria, B.C, Canada
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Zhang X, Cattoglio C, Zoltek M, Vetralla C, Mozumdar D, Schepartz A. Dose-Dependent Nuclear Delivery and Transcriptional Repression with a Cell-Penetrant MeCP2. ACS CENTRAL SCIENCE 2023; 9:277-288. [PMID: 36844491 PMCID: PMC9951310 DOI: 10.1021/acscentsci.2c01226] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Indexed: 06/13/2023]
Abstract
The vast majority of biologic-based therapeutics operate within serum, on the cell surface, or within endocytic vesicles, in large part because proteins and nucleic acids fail to efficiently cross cell or endosomal membranes. The impact of biologic-based therapeutics would expand exponentially if proteins and nucleic acids could reliably evade endosomal degradation, escape endosomal vesicles, and remain functional. Using the cell-permeant mini-protein ZF5.3, here we report the efficient nuclear delivery of functional Methyl-CpG-binding-protein 2 (MeCP2), a transcriptional regulator whose mutation causes Rett syndrome (RTT). We report that ZF-tMeCP2, a conjugate of ZF5.3 and MeCP2(Δaa13-71, 313-484), binds DNA in a methylation-dependent manner in vitro, and reaches the nucleus of model cell lines intact to achieve an average concentration of 700 nM. When delivered to live cells, ZF-tMeCP2 engages the NCoR/SMRT corepressor complex, selectively represses transcription from methylated promoters, and colocalizes with heterochromatin in mouse primary cortical neurons. We also report that efficient nuclear delivery of ZF-tMeCP2 relies on an endosomal escape portal provided by HOPS-dependent endosomal fusion. The Tat conjugate of MeCP2 (Tat-tMeCP2), evaluated for comparison, is degraded within the nucleus, is not selective for methylated promoters, and trafficks in a HOPS-independent manner. These results support the feasibility of a HOPS-dependent portal for delivering functional macromolecules to the cell interior using the cell-penetrant mini-protein ZF5.3. Such a strategy could broaden the impact of multiple families of biologic-based therapeutics.
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Affiliation(s)
- Xizi Zhang
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Claudia Cattoglio
- Department
of Molecular and Cellular Biology, University
of California, Berkeley, California 94720, United States
- Howard
Hughes Medical Institute, University of
California, Berkeley, California 94720, United States
| | - Madeline Zoltek
- Department
of Molecular and Cellular Biology, University
of California, Berkeley, California 94720, United States
| | - Carlo Vetralla
- Department
of Molecular and Cellular Biology, University
of California, Berkeley, California 94720, United States
- Howard
Hughes Medical Institute, University of
California, Berkeley, California 94720, United States
| | - Deepto Mozumdar
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Department
of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Alanna Schepartz
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Department
of Molecular and Cellular Biology, University
of California, Berkeley, California 94720, United States
- California
Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California 94720, United States
- Chan Zuckerberg
Biohub, San Francisco, California 94158, United States
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Zhang X, Smits M, Curfs L, Spruyt K. An investigation of the sleep macrostructure of girls with Rett syndrome. Sleep Med 2023; 101:77-86. [PMID: 36343395 DOI: 10.1016/j.sleep.2022.10.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 10/16/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022]
Abstract
OBJECTIVE/BACKGROUND Methyl-CpG-binding protein 2 (MeCP2) is of utmost importance in neuronal function. We aim to characterize phenotypic traits in the sleep of individuals with Rett Syndrome (RTT, OMIM # 312750), a rare disorder predominantly caused by mutations of the MECP2 gene. PATIENTS/METHODS An overnight polysomnographic recording was performed. Outcomes investigated were parameters of nocturnal sleep macrostructure, and sample stratification per genetic and clinical characteristics, and six key features of clinical severity was applied. RESULTS The sleep of our 21 RTT female subjects with a mutant MECP2 gene, aged 8.8 ± 5.4 years, showed no significant differences within strata. However, compared to a normative dataset, we found longer duration of wake time after sleep onset and total sleep time (TST) but shorter sleep onset latency, in RTT. Regarding the proportion of sleep stages per TST, higher stage N3 (%) with lower stage N2 (%) and REM (%) were generally seen. Such abnormalities became more uniformly expressed at the severe level of clinical features, particularly for hand functioning and walking. CONCLUSIONS RTT girls with MECP2 mutations in our study demonstrated an increased deep sleep and reduced rapid eye movement sleep proportion, which is mostly allied with their hand dysfunction severity. Poor sleep-on/off switching in RTT since embryogenesis is possibly linked to (psycho)motor impairment in the cases with MECP2 mutations.
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Affiliation(s)
- Xinyan Zhang
- Université de Paris, NeuroDiderot - INSERM, Paris, France.
| | - Marcel Smits
- Department of Sleep-wake Disorders and Chronobiology, Hospital Gelderse Vallei Ede, Netherlands. Governor Kremers Centre, Maastricht University Medical Centre, Netherlands.
| | - Leopold Curfs
- Governor Kremers Centre, Maastricht University Medical Centre, Netherlands.
| | - Karen Spruyt
- Université de Paris, NeuroDiderot - INSERM, Paris, France.
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Damianidou E, Mouratidou L, Kyrousi C. Research models of neurodevelopmental disorders: The right model in the right place. Front Neurosci 2022; 16:1031075. [PMID: 36340790 PMCID: PMC9630472 DOI: 10.3389/fnins.2022.1031075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 10/07/2022] [Indexed: 11/25/2022] Open
Abstract
Neurodevelopmental disorders (NDDs) are a heterogeneous group of impairments that affect the development of the central nervous system leading to abnormal brain function. NDDs affect a great percentage of the population worldwide, imposing a high societal and economic burden and thus, interest in this field has widely grown in recent years. Nevertheless, the complexity of human brain development and function as well as the limitations regarding human tissue usage make their modeling challenging. Animal models play a central role in the investigation of the implicated molecular and cellular mechanisms, however many of them display key differences regarding human phenotype and in many cases, they partially or completely fail to recapitulate them. Although in vitro two-dimensional (2D) human-specific models have been highly used to address some of these limitations, they lack crucial features such as complexity and heterogeneity. In this review, we will discuss the advantages, limitations and future applications of in vivo and in vitro models that are used today to model NDDs. Additionally, we will describe the recent development of 3-dimensional brain (3D) organoids which offer a promising approach as human-specific in vitro models to decipher these complex disorders.
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Affiliation(s)
- Eleni Damianidou
- University Mental Health, Neurosciences and Precision Medicine Research Institute “Costas Stefanis”, Athens, Greece
| | - Lidia Mouratidou
- University Mental Health, Neurosciences and Precision Medicine Research Institute “Costas Stefanis”, Athens, Greece
- First Department of Psychiatry, Medical School, Eginition Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Christina Kyrousi
- University Mental Health, Neurosciences and Precision Medicine Research Institute “Costas Stefanis”, Athens, Greece
- First Department of Psychiatry, Medical School, Eginition Hospital, National and Kapodistrian University of Athens, Athens, Greece
- *Correspondence: Christina Kyrousi,
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Mok RSF, Zhang W, Sheikh TI, Pradeepan K, Fernandes IR, DeJong LC, Benigno G, Hildebrandt MR, Mufteev M, Rodrigues DC, Wei W, Piekna A, Liu J, Muotri AR, Vincent JB, Muller L, Martinez-Trujillo J, Salter MW, Ellis J. Wide spectrum of neuronal and network phenotypes in human stem cell-derived excitatory neurons with Rett syndrome-associated MECP2 mutations. Transl Psychiatry 2022; 12:450. [PMID: 36253345 PMCID: PMC9576700 DOI: 10.1038/s41398-022-02216-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 10/01/2022] [Accepted: 10/03/2022] [Indexed: 11/19/2022] Open
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder primarily caused by heterozygous loss-of-function mutations in the X-linked gene MECP2 that is a global transcriptional regulator. Mutations in the methyl-CpG binding domain (MBD) of MECP2 disrupt its interaction with methylated DNA. Here, we investigate the effect of a novel MECP2 L124W missense mutation in the MBD of an atypical RTT patient with preserved speech in comparison to severe MECP2 null mutations. L124W protein had a limited ability to disrupt heterochromatic chromocenters due to decreased binding dynamics. We isolated two pairs of isogenic WT and L124W induced pluripotent stem cells. L124W induced excitatory neurons expressed stable protein, exhibited increased input resistance and decreased voltage-gated Na+ and K+ currents, and their neuronal dysmorphology was limited to decreased dendritic complexity. Three isogenic pairs of MECP2 null neurons had the expected more extreme morphological and electrophysiological phenotypes. We examined development and maturation of L124W and MECP2 null excitatory neural network activity using micro-electrode arrays. Relative to isogenic controls, L124W neurons had an increase in synchronous network burst frequency, in contrast to MECP2 null neurons that suffered a significant decrease in synchronous network burst frequency and a transient extension of network burst duration. A biologically motivated computational neural network model shows the observed changes in network dynamics are explained by changes in intrinsic Na+ and K+ currents in individual neurons. Our multilevel results demonstrate that RTT excitatory neurons show a wide spectrum of morphological, electrophysiological and circuitry phenotypes that are dependent on the severity of the MECP2 mutation.
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Grants
- R01 MH108528 NIMH NIH HHS
- MOP-133423 CIHR
- R01 MH109885 NIMH NIH HHS
- FDN-154336 CIHR
- R01 MH100175 NIMH NIH HHS
- Col Harland Sanders Rett Syndrome Research Fund at the University of Toronto (to J.E.), SFARI (Research grant #514918 to J.E. and J.M-T), CIHR (MOP-133423 to J.E. and M.W.S.; ERARE Team Grant ERT161303 to J.E.), CIHR foundation grant (FDN-154336 to M.W.S), Ontario Brain Institute (POND Network to J.E.), McLaughlin Centre Accelerator grant (to J.E.), John Evans Leadership Fund & Ontario Research Fund (to J.E), Canada Research Chair in Stem Cell Models of Childhood Disease (to J.E.), Beta Sigma Phi International Endowment Fund (to J.E.).
- BrainsCAN at Western University through the Canada First Research Excellence Fund (CFREF) (to GB, KP, LM, JMT). NSERC Postgraduate Scholarship–Doctoral (PGS-D) Scholarship to KP.
- Trainee support was provided by Restracomp (to LCD).
- National Institutes of Health (NIH) grants # R01MH108528, R01MH109885, and R01MH1000175 to ARM.
- Ontario Rett Syndrome Association to JBV.
- SFARI (Research grant #514918 to J.E. and J.M-T), BrainsCAN at Western University through the Canada First Research Excellence Fund (CFREF) (to GB, KP, LM, JMT)
- CIHR (MOP-133423 to J.E. and M.W.S.; CIHR foundation grant (FDN-154336 to M.W.S),
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Affiliation(s)
- Rebecca S F Mok
- Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 1A8, Canada
- Developmental & Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Wenbo Zhang
- Neurosciences & Mental Health Program, The Hospital for Sick Children, Toronto, M5G 0A4, ON, Canada
| | - Taimoor I Sheikh
- Molecular Neuropsychiatry & Development (MiND) Lab, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON, M5T 1R8, Canada
| | - Kartik Pradeepan
- Department of Physiology and Pharmacology, Department of Psychiatry, Neuroscience Graduate Program, Robarts Research and Brain and Mind Institutes, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5B7, Canada
| | - Isabella R Fernandes
- University of California San Diego, School of Medicine, Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA, 92037-0695, USA
| | - Leah C DeJong
- Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 1A8, Canada
- Developmental & Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Gabriel Benigno
- Department of Applied Mathematics, Robarts Research Institute, Brain and Mind Institute, Western University, London, ON, N6A 5B7, Canada
| | - Matthew R Hildebrandt
- Developmental & Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Marat Mufteev
- Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 1A8, Canada
- Developmental & Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Deivid C Rodrigues
- Developmental & Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Wei Wei
- Developmental & Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Alina Piekna
- Developmental & Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Jiajie Liu
- Developmental & Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
| | - Alysson R Muotri
- University of California San Diego, School of Medicine, Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA, 92037-0695, USA
- Department of Pediatrics/Rady Children's Hospital, Department of Cellular & Molecular Medicine, Center for Academic Research and Training in Anthropogeny, Archealization Center, Kavli Institute, University of California San Diego, La Jolla, CA, 92037, USA
| | - John B Vincent
- Molecular Neuropsychiatry & Development (MiND) Lab, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON, M5T 1R8, Canada
| | - Lyle Muller
- Department of Applied Mathematics, Robarts Research Institute, Brain and Mind Institute, Western University, London, ON, N6A 5B7, Canada
| | - Julio Martinez-Trujillo
- Department of Physiology and Pharmacology, Department of Psychiatry, Neuroscience Graduate Program, Robarts Research and Brain and Mind Institutes, Schulich School of Medicine and Dentistry, Western University, London, ON, N6A 5B7, Canada
| | - Michael W Salter
- Neurosciences & Mental Health Program, The Hospital for Sick Children, Toronto, M5G 0A4, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - James Ellis
- Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 1A8, Canada.
- Developmental & Stem Cell Biology Program, The Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada.
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Zhang XY, Spruyt K. Literature Cases Summarized Based on Their Polysomnographic Findings in Rett Syndrome. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19063422. [PMID: 35329122 PMCID: PMC8955319 DOI: 10.3390/ijerph19063422] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 03/06/2022] [Accepted: 03/11/2022] [Indexed: 12/10/2022]
Abstract
Rett syndrome (RTT) is a severe and rare neurodevelopmental disorder affecting mostly girls. In RTT, an impaired sleep pattern is a supportive criterion for the diagnosis, yet little is known regarding the sleep structure and sleep respiratory events. Aiming to delineate sleep by aggregating RTT case (series) data from published polysomnographic studies, seventy-four RTT cases were collected from eleven studies up until 6 February 2022 (PROSPERO: CRD 42020198099). We compared the polysomnographic data within RTT stratifications and to a typically developing population. MECP2 cases demonstrated shortened total sleep time (TST) with increased stage N3 and decreased REM sleep. In cases with CDKL5 mutations, TST was longer and they spent more time in stage N1 but less in stage N3 than those cases affected by MECP2 mutations and a typically developing population. Sleep-disordered breathing was confirmed by the abnormal apnea/hypopnea index of 11.92 ± 23.67/h TST in these aggregated cases. No association of sleep structure with chronological age was found. In RTT, the sleep macrostructure of MECP2 versus CDKL5 cases showed differences, particularly regarding sleep stage N3. A severe REM sleep propensity reduction was found. Aberrant sleep cycling, possibly characterized by a poor REM ‘on switch’ and preponderance in slow and high-voltage sleep, is proposed.
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Musi CA, Castaldo AM, Valsecchi AE, Cimini S, Morello N, Pizzo R, Renieri A, Meloni I, Bonati M, Giustetto M, Borsello T. JNK signaling provides a novel therapeutic target for Rett syndrome. BMC Biol 2021; 19:256. [PMID: 34911542 PMCID: PMC8675514 DOI: 10.1186/s12915-021-01190-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 11/11/2021] [Indexed: 11/24/2022] Open
Abstract
Background Rett syndrome (RTT) is a monogenic X-linked neurodevelopmental disorder characterized by loss-of-function mutations in the MECP2 gene, which lead to structural and functional changes in synapse communication, and impairments of neural activity at the basis of cognitive deficits that progress from an early age. While the restoration of MECP2 in animal models has been shown to rescue some RTT symptoms, gene therapy intervention presents potential side effects, and with gene- and RNA-editing approaches still far from clinical application, strategies focusing on signaling pathways downstream of MeCP2 may provide alternatives for the development of more effective therapies in vivo. Here, we investigate the role of the c-Jun N-terminal kinase (JNK) stress pathway in the pathogenesis of RTT using different animal and cell models and evaluate JNK inhibition as a potential therapeutic approach. Results We discovered that the c-Jun N-terminal kinase (JNK) stress pathway is activated in Mecp2-knockout, Mecp2-heterozygous mice, and in human MECP2-mutated iPSC neurons. The specific JNK inhibitor, D-JNKI1, promotes recovery of body weight and locomotor impairments in two mouse models of RTT and rescues their dendritic spine alterations. Mecp2-knockout presents intermittent crises of apnea/hypopnea, one of the most invalidating RTT pathological symptoms, and D-JNKI1 powerfully reduces this breathing dysfunction. Importantly, we discovered that also neurons derived from hiPSC-MECP2 mut show JNK activation, high-phosphorylated c-Jun levels, and cell death, which is not observed in the isogenic control wt allele hiPSCs. Treatment with D-JNKI1 inhibits neuronal death induced by MECP2 mutation in hiPSCs mut neurons. Conclusions As a summary, we found altered JNK signaling in models of RTT and suggest that D-JNKI1 treatment prevents clinical symptoms, with coherent results at the cellular, molecular, and functional levels. This is the first proof of concept that JNK plays a key role in RTT and its specific inhibition offers a new and potential therapeutic tool to tackle RTT. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01190-2.
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Affiliation(s)
- Clara Alice Musi
- Department of Pharmacological and Biomolecular Sciences, Milan University, Via Balzaretti 9, 20133, Milan, Italy.,Department of Neuroscience, Istituto di Ricerche Farmacologiche Mario Negri-IRCCS, Via Mario Negri 2, 20156, Milan, Italy
| | - Anna Maria Castaldo
- Department of Pharmacological and Biomolecular Sciences, Milan University, Via Balzaretti 9, 20133, Milan, Italy
| | | | - Sara Cimini
- Department of Neuroscience, Istituto di Ricerche Farmacologiche Mario Negri-IRCCS, Via Mario Negri 2, 20156, Milan, Italy
| | - Noemi Morello
- Department of Neuroscience and National Institute of Neuroscience, University of Turin, Turin, Italy
| | - Riccardo Pizzo
- Department of Neuroscience and National Institute of Neuroscience, University of Turin, Turin, Italy
| | | | | | - Maurizio Bonati
- Department of Public Heath, Istituto di Ricerche Farmacologiche Mario Negri-IRCCS, Milan, Italy
| | - Maurizio Giustetto
- Department of Neuroscience and National Institute of Neuroscience, University of Turin, Turin, Italy
| | - Tiziana Borsello
- Department of Pharmacological and Biomolecular Sciences, Milan University, Via Balzaretti 9, 20133, Milan, Italy. .,Department of Neuroscience, Istituto di Ricerche Farmacologiche Mario Negri-IRCCS, Via Mario Negri 2, 20156, Milan, Italy.
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9
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Quach TT, Stratton HJ, Khanna R, Kolattukudy PE, Honnorat J, Meyer K, Duchemin AM. Intellectual disability: dendritic anomalies and emerging genetic perspectives. Acta Neuropathol 2021; 141:139-158. [PMID: 33226471 PMCID: PMC7855540 DOI: 10.1007/s00401-020-02244-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 11/04/2020] [Accepted: 11/05/2020] [Indexed: 12/12/2022]
Abstract
Intellectual disability (ID) corresponds to several neurodevelopmental disorders of heterogeneous origin in which cognitive deficits are commonly associated with abnormalities of dendrites and dendritic spines. These histological changes in the brain serve as a proxy for underlying deficits in neuronal network connectivity, mostly a result of genetic factors. Historically, chromosomal abnormalities have been reported by conventional karyotyping, targeted fluorescence in situ hybridization (FISH), and chromosomal microarray analysis. More recently, cytogenomic mapping, whole-exome sequencing, and bioinformatic mining have led to the identification of novel candidate genes, including genes involved in neuritogenesis, dendrite maintenance, and synaptic plasticity. Greater understanding of the roles of these putative ID genes and their functional interactions might boost investigations into determining the plausible link between cellular and behavioral alterations as well as the mechanisms contributing to the cognitive impairment observed in ID. Genetic data combined with histological abnormalities, clinical presentation, and transgenic animal models provide support for the primacy of dysregulation in dendrite structure and function as the basis for the cognitive deficits observed in ID. In this review, we highlight the importance of dendrite pathophysiology in the etiologies of four prototypical ID syndromes, namely Down Syndrome (DS), Rett Syndrome (RTT), Digeorge Syndrome (DGS) and Fragile X Syndrome (FXS). Clinical characteristics of ID have also been reported in individuals with deletions in the long arm of chromosome 10 (the q26.2/q26.3), a region containing the gene for the collapsin response mediator protein 3 (CRMP3), also known as dihydropyrimidinase-related protein-4 (DRP-4, DPYSL4), which is involved in dendritogenesis. Following a discussion of clinical and genetic findings in these syndromes and their preclinical animal models, we lionize CRMP3/DPYSL4 as a novel candidate gene for ID that may be ripe for therapeutic intervention.
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Affiliation(s)
- Tam T Quach
- Institute for Behavioral Medicine Research, Wexner Medical Center, The Ohio State University, Columbus, OH, 43210, USA
- INSERM U1217/CNRS, UMR5310, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | | | - Rajesh Khanna
- Department of Pharmacology, University of Arizona, Tucson, AZ, 85724, USA
| | | | - Jérome Honnorat
- INSERM U1217/CNRS, UMR5310, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France
- French Reference Center on Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis, Hospices Civils de Lyon, Lyon, France
- SynatAc Team, Institut NeuroMyoGène, Lyon, France
| | - Kathrin Meyer
- The Research Institute of Nationwide Children Hospital, Columbus, OH, 43205, USA
- Department of Pediatric, The Ohio State University, Columbus, OH, 43210, USA
| | - Anne-Marie Duchemin
- Department of Psychiatry and Behavioral Health, The Ohio State University, Columbus, OH, 43210, USA.
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Overshooting Subcellular Redox-Responses in Rett-Mouse Hippocampus during Neurotransmitter Stimulation. Cells 2020; 9:cells9122539. [PMID: 33255426 PMCID: PMC7760232 DOI: 10.3390/cells9122539] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/16/2020] [Accepted: 11/22/2020] [Indexed: 12/21/2022] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder associated with disturbed neuronal responsiveness and impaired neuronal network function. Furthermore, mitochondrial alterations and a weakened cellular redox-homeostasis are considered part of the complex pathogenesis. So far, overshooting redox-responses of MeCP2-deficient neurons were observed during oxidant-mediated stress, hypoxia and mitochondrial inhibition. To further clarify the relevance of the fragile redox-balance for the neuronal (dys)function in RTT, we addressed more physiological stimuli and quantified the subcellular redox responses to neurotransmitter-stimulation. The roGFP redox sensor was expressed in either the cytosol or the mitochondrial matrix of cultured mouse hippocampal neurons, and the responses to transient stimulation by glutamate, serotonin, dopamine and norepinephrine were characterized. Each neurotransmitter evoked more intense oxidizing responses in the cytosol of MeCP2-deficient than in wildtype neurons. In the mitochondrial matrix the neurotransmitter-evoked oxidizing changes were more moderate and more uniform among genotypes. This identifies the cytosol as an important reactive oxygen species (ROS) source and as less stably redox buffered. Fura-2 imaging and extracellular Ca2+ withdrawal confirmed cytosolic Ca2+ transients as a contributing factor of neurotransmitter-induced redox responses and their potentiation in the cytosol of MeCP2-deficient neurons. Chemical uncoupling demonstrated the involvement of mitochondria. Nevertheless, cytosolic NADPH- and xanthine oxidases interact to play the leading role in the neurotransmitter-mediated oxidizing responses. As exaggerated redox-responses were already evident in neonatal MeCP2-deficient neurons, they may contribute remarkably to the altered neuronal network performance and the disturbed neuronal signaling, which are among the hallmarks of RTT.
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11
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Saby JN, Peters SU, Roberts TPL, Nelson CA, Marsh ED. Evoked Potentials and EEG Analysis in Rett Syndrome and Related Developmental Encephalopathies: Towards a Biomarker for Translational Research. Front Integr Neurosci 2020; 14:30. [PMID: 32547374 PMCID: PMC7271894 DOI: 10.3389/fnint.2020.00030] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 05/04/2020] [Indexed: 12/17/2022] Open
Abstract
Rett syndrome is a debilitating neurodevelopmental disorder for which no disease-modifying treatment is available. Fortunately, advances in our understanding of the genetics and pathophysiology of Rett syndrome has led to the development of promising new therapeutics for the condition. Several of these therapeutics are currently being tested in clinical trials with others likely to progress to clinical trials in the coming years. The failure of recent clinical trials for Rett syndrome and other neurodevelopmental disorders has highlighted the need for electrophysiological or other objective biological markers of treatment response to support the success of clinical trials moving forward. The purpose of this review is to describe the existing studies of electroencephalography (EEG) and evoked potentials (EPs) in Rett syndrome and discuss the open questions that must be addressed before the field can adopt these measures as surrogate endpoints in clinical trials. In addition to summarizing the human work on Rett syndrome, we also describe relevant studies with animal models and the limited research that has been carried out on Rett-related disorders, particularly methyl-CpG binding protein 2 (MECP2) duplication syndrome, CDKL5 deficiency disorder, and FOXG1 disorder.
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Affiliation(s)
- Joni N. Saby
- Lurie Family Foundations MEG Imaging Center, Department of Radiology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Sarika U. Peters
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Timothy P. L. Roberts
- Lurie Family Foundations MEG Imaging Center, Department of Radiology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States,Department of Radiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
| | - Charles A. Nelson
- Laboratories of Cognitive Neuroscience, Division of Developmental Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
| | - Eric D. Marsh
- Division of Neurology and Pediatrics, Children’s Hospital of Philadelphia, Philadelphia, PA, United States,Departments of Neurology and Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States,*Correspondence: Eric D. Marsh
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12
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Sysoeva OV, Smirnov K, Stroganova TA. Sensory evoked potentials in patients with Rett syndrome through the lens of animal studies: Systematic review. Clin Neurophysiol 2019; 131:213-224. [PMID: 31812082 DOI: 10.1016/j.clinph.2019.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 11/07/2019] [Accepted: 11/11/2019] [Indexed: 01/04/2023]
Abstract
OBJECTIVE Systematically review the abnormalities in event related potential (ERP) recorded in Rett Syndrome (RTT) patients and animals in search of translational biomarkers of deficits related to the particular neurophysiological processes of known genetic origin (MECP2 mutations). METHODS Pubmed, ISI Web of Knowledge and BIORXIV were searched for the relevant articles according to PRISMA standards. RESULTS ERP components are generally delayed across all sensory modalities both in RTT patients and its animal model, while findings on ERPs amplitude strongly depend on stimulus properties and presentation rate. Studies on RTT animal models uncovered the abnormalities in the excitatory and inhibitory transmission as critical mechanisms underlying the ERPs changes, but showed that even similar ERP alterations in auditory and visual domains have a diverse neural basis. A range of novel approaches has been developed in animal studies bringing along the meaningful neurophysiological interpretation of ERP measures in RTT patients. CONCLUSIONS While there is a clear evidence for sensory ERPs abnormalities in RTT, to further advance the field there is a need in a large-scale ERP studies with the functionally-relevant experimental paradigms. SIGNIFICANCE The review provides insights into domain-specific neural basis of the ERP abnormalities and promotes clinical application of the ERP measures as the non-invasive functional biomarkers of RTT pathophysiology.
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Affiliation(s)
- Olga V Sysoeva
- The Cognitive Neurophysiology Laboratory, Department of Pediatrics, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, New York, USA; The Cognitive Neurophysiology Laboratory, Ernest J. Del Monte Institute for Neuroscience, Department of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA; The Laboratory of Human Higher Nervous Activity, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
| | - Kirill Smirnov
- Department of Neuroontogenesis, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Science, Moscow, Russia.
| | - Tatiana A Stroganova
- Center for Neurocognitive Research (MEG-Center), Moscow State University of Psychology and Education (MSUPE), Moscow, Russia; Autism Research Laboratory, Moscow State University of Psychology and Education (MSUPE), Moscow, Russia.
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13
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Yang H, Li K, Han S, Zhou A, Zhou ZJ. Leveraging the genetic basis of Rett syndrome to ascertain pathophysiology. Neurobiol Learn Mem 2019; 165:106961. [PMID: 30447288 PMCID: PMC6635128 DOI: 10.1016/j.nlm.2018.11.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 09/18/2018] [Accepted: 11/14/2018] [Indexed: 10/27/2022]
Abstract
Mutations in the methyl-CpG binding protein 2 (MECP2) gene cause Rett syndrome (RTT), a progressive X-linked neurological disorder characterized by loss of developmental milestones, intellectual disability and breathing abnormality. Despite being a monogenic disorder, the pathogenic mechanisms by which mutations in MeCP2 impair neuronal function and underlie the RTT symptoms have been challenging to elucidate. The seemingly simple genetic root and the availability of genetic data from RTT patients have led to the generation and characterization of a series of mouse models recapitulating RTT-associated genetic mutations. This review focuses on the studies of RTT mouse models and describe newly obtained pathogenic insights from these studies. We also highlight the potential of studying pathophysiology using genetics-based modeling approaches in rodents and suggest a future direction to tackle the pathophysiology of intellectual disability with known or complex genetic causes.
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Affiliation(s)
- Hua Yang
- Qingdao Jiaozhou Central Hospital, Jiaozhou City, Shandong Province 266300, China
| | - Kequan Li
- Qingdao Jiaozhou Central Hospital, Jiaozhou City, Shandong Province 266300, China
| | - Song Han
- Jiaozhou People's Hospital, Jiaozhou City, Shandong Province 266300, China
| | - Ailing Zhou
- Jiaozhou People's Hospital, Jiaozhou City, Shandong Province 266300, China
| | - Zhaolan Joe Zhou
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
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14
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Drobnyk W, Rocco K, Davidson S, Bruce S, Zhang F, Soumerai SB. Sensory Integration and Functional Reaching in Children With Rett Syndrome/Rett-Related Disorders. CLINICAL MEDICINE INSIGHTS-PEDIATRICS 2019; 13:1179556519871952. [PMID: 31488957 PMCID: PMC6710672 DOI: 10.1177/1179556519871952] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 07/26/2019] [Indexed: 11/16/2022]
Abstract
Background The loss of functional hand skills is a primary characteristic of Rett syndrome. Stereotypies, dyspraxia, and other sensory processing issues severely limit the individual's ability to reach toward and sustain grasp on objects. This loss of functional reach and grasp severely limits their ability to participate in self-help, play, and school-related activities. We proposed that Ayres Sensory Integration (ASI) treatment would improve sensory processing and motor planning, which would lay the sensory-motor groundwork for improving grasp of objects, an important first step in developing functional hand use. Objective We examined effects of ASI treatment on rate of reaching and grasping for children with Rett syndrome/Rett-related disorders. Methods We used an interrupted time series design to measure changes in outcome variables occurring after intervention initiation and cessation. We analyzed daily video observations during baseline, intervention, and post-intervention periods, over a span of 7 months. Results During baseline, rate of grasping declined moderately. There was a 15% increase in grasping from the end of baseline to end of the post-intervention period. There was no significant change in rate of reaching. Conclusions This study provides preliminary data showing very small improvements in hand grasp of children with Rett syndrome following ASI treatment; larger studies in diverse settings are needed to establish the effectiveness of this approach. This study shows that an interrupted time series research design provides a valid template for evaluating interventions for children with rare disorders.
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Affiliation(s)
- Wendy Drobnyk
- Lynch School of Education, Boston College, Chestnut Hill, MA, USA
| | - Karen Rocco
- Lynch School of Education, Boston College, Chestnut Hill, MA, USA
| | - Sara Davidson
- Lynch School of Education, Boston College, Chestnut Hill, MA, USA
| | - Susan Bruce
- Lynch School of Education, Boston College, Chestnut Hill, MA, USA
| | - Fang Zhang
- Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA, USA
| | - Stephen B Soumerai
- Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA, USA
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15
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Sun Y, Gao Y, Tidei JJ, Shen M, Hoang JT, Wagner DF, Zhao X. Loss of MeCP2 in immature neurons leads to impaired network integration. Hum Mol Genet 2019; 28:245-257. [PMID: 30277526 DOI: 10.1093/hmg/ddy338] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Accepted: 09/18/2018] [Indexed: 12/12/2022] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations or deletions in Methyl-CpG-binding Protein 2 (MeCP2), a brain-enriched transcriptional regulator. MeCP2 is highly expressed during neuronal maturation and its deficiency results in impaired dendritic morphogenesis and reduced dendritic spine numbers in developing neurons. However, whether MeCP2 deficiency impacts the integration of new neurons has not been directly assessed. In this study, we developed a modified rabies virus-mediated monosynaptic retrograde tracing method to interrogate presynaptic integration of MeCP2-deficient new neurons born in the adult hippocampus, a region with lifelong neurogenesis and plasticity. We found that selective deletion of MeCP2 in adult-born new neurons impaired their long-range connectivity to the cortex, whereas their connectivity within the local hippocampal circuits or with subcortical regions was not significantly affected. We further showed that knockdown of MeCP2 in primary hippocampal neurons also resulted in reduced network integration. Interestingly, (1-3) insulin-like growth factor-1 (IGF-1), a small peptide under clinical trial testing for RTT, rescued neuronal integration deficits of MeCP2-deficient neurons in vitro but not in vivo. In addition, (1-3) IGF-1 treatment corrected aberrant excitability and network synchrony of MeCP2-deficient hippocampal neurons. Our results indicate that MeCP2 is essential for immature neurons to establish appropriate network connectivity.
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Affiliation(s)
- Yi Sun
- National Key Research Laboratory of Natural and Biomimetic Drugs.,Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, PR China.,Waisman Center
| | - Yu Gao
- Waisman Center.,Department of Neuroscience
| | | | | | | | | | - Xinyu Zhao
- Waisman Center.,Department of Neuroscience.,Cellular and Molecular Biology Program, University of Wisconsin-Madison, Madison, WI, USA
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16
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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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17
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Tsix-Mecp2 female mouse model for Rett syndrome reveals that low-level MECP2 expression extends life and improves neuromotor function. Proc Natl Acad Sci U S A 2018; 115:8185-8190. [PMID: 30038001 DOI: 10.1073/pnas.1800931115] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder caused by a mutation in the X-linked methyl-CpG-binding protein 2 (MECP2). There is currently no disease-specific treatment, but MECP2 restoration through reactivation of the inactive X (Xi) has been of considerable interest. Progress toward an Xi-reactivation therapy has been hampered by a lack of suitable female mouse models. Because of cellular mosaicism due to random X-chromosome inactivation (XCI), Mecp2+/- heterozygous females develop only mild RTT. Here, we create an improved female mouse model by introducing a mutation in Tsix, the antisense regulator of XCI allelic choice. Tsix-Mecp2 mice show reduced MECP2 mosaicism and closely phenocopy the severely affected Mecp2-null males. Tsix-Mecp2 females demonstrate shortened lifespan, motor weakness, tremors, and gait disturbance. Intriguingly, they also exhibit repetitive behaviors, as is often seen in human RTT, including excessive grooming and biting that result in self-injury. With a Tsix allelic series, we vary MECP2 levels in brain and demonstrate a direct, but nonlinear correlation between MECP2 levels and phenotypic improvement. As little as 5-10% MECP2 restoration improves neuromotor function and extends lifespan five- to eightfold. Our study thus guides future pharmacological strategies and suggests that partial MECP2 restoration could have disproportionate therapeutic benefit.
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18
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Gadalla KKE, Ross PD, Hector RD, Bahey NG, Bailey MES, Cobb SR. Gene therapy for Rett syndrome: prospects and challenges. FUTURE NEUROLOGY 2015. [DOI: 10.2217/fnl.15.29] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Rett syndrome (RTT) is a neurological disorder that affects females and is caused by loss-of-function mutations in the X-linked gene MECP2. Deletion of Mecp2 in mice results in a constellation of neurological features that resemble those seen in RTT patients. Experiments in mice have demonstrated that restoration of MeCP2, even at adult stages, reverses several aspects of the RTT-like pathology suggesting that the disorder may be inherently treatable. This has provided an impetus to explore several therapeutic approaches targeting RTT at the level of the gene, including gene therapy, activation of MECP2 on the inactive X chromosome and read-through and repair of RTT-causing mutations. Here, we review these different strategies and the challenges of gene-based approaches in RTT.
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Affiliation(s)
- Kamal KE Gadalla
- University of Glasgow, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, Glasgow, UK
- Pharmacology Department, Faculty of Medicine, Tanta University, Egypt
| | - Paul D Ross
- University of Glasgow, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, Glasgow, UK
| | - Ralph D Hector
- University of Glasgow, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, Glasgow, UK
| | - Noha G Bahey
- University of Glasgow, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, Glasgow, UK
- Histology Department, Faculty of Medicine, Tanta University, Egypt
| | - Mark ES Bailey
- School of Life Sciences, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Stuart R Cobb
- University of Glasgow, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, Glasgow, UK
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19
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Cellular origins of auditory event-related potential deficits in Rett syndrome. Nat Neurosci 2014; 17:804-6. [PMID: 24777420 PMCID: PMC4038660 DOI: 10.1038/nn.3710] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 03/31/2014] [Indexed: 12/12/2022]
Abstract
Dysfunction in sensory information processing is a hallmark of many neurological disorders including autism spectrum disorders (ASDs), schizophrenia and Rett syndrome (RTT)1. Using mouse models of RTT, a monogenic disorder caused by mutations in MECP22, we demonstrate that the large scale loss of MeCP2 from forebrain GABAergic interneurons leads to deficits in auditory event-related potentials (ERPs) and seizure manifestation; but the restoration of MeCP2 in specific classes of interneurons ameliorates these deficits.
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20
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Zhao YT, Goffin D, Johnson BS, Zhou Z. Loss of MeCP2 function is associated with distinct gene expression changes in the striatum. Neurobiol Dis 2013; 59:257-66. [PMID: 23948639 DOI: 10.1016/j.nbd.2013.08.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 07/05/2013] [Accepted: 08/02/2013] [Indexed: 01/22/2023] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder characterized by developmental regression beginning 6-18months after birth, followed by a lifetime of intellectual disability, stereotyped behaviors, and motor deficits. RTT is caused by mutations in the gene encoding MeCP2, a methyl-CpG binding protein believed to modulate gene transcription. Gene expression studies of individual brain regions have reported that Mecp2 loss-of-function leads to both activation and repression of its gene targets in mice. Conditional deletion of MeCP2 from different brain regions has revealed unique insights into the role of these structures in mediating particular RTT-like phenotypes. However, the function of MeCP2 in the striatum, a major brain region involved in motor control and executive cognitive functions, has yet to be studied. Here, we characterized the gene expression changes in the striatum of Mecp2 mutant mice. We found a number of differentially expressed genes in the striatum of both constitutive Mecp2-null mice and mice lacking MeCP2 only from forebrain GABAergic neurons. These changes only occurred when MeCP2 expression levels had reached mature levels and RTT-like symptoms were manifest, supporting a role for MeCP2 in maintaining proper brain function. Many of the gene expression changes identified in the striatum have not previously been shown to change in the hypothalamus or cerebellum. Bioinformatic analysis of differentially expressed genes in striatum as well as hypothalamus and cerebellum revealed that loss of MeCP2 does not affect the global landscape of gene expression. Additionally, we uncovered a number of differentially expressed genes in the liver of Mecp2-null mice suggesting an important role for MeCP2 in non-neuronal tissues. Collectively, our data suggest that the differential expression of genes following loss of MeCP2 occurs in a tissue- or cell-type specific manner and thus MeCP2 function should be understood in a cellular context.
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Affiliation(s)
- Ying-Tao Zhao
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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21
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Wang ITJ, Reyes ARS, Zhou Z. Neuronal morphology in MeCP2 mouse models is intrinsically variable and depends on age, cell type, and Mecp2 mutation. Neurobiol Dis 2013; 58:3-12. [PMID: 23659895 DOI: 10.1016/j.nbd.2013.04.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2013] [Revised: 04/16/2013] [Accepted: 04/23/2013] [Indexed: 11/16/2022] Open
Abstract
Rett Syndrome (RTT), a progressive neurological disorder characterized by developmental regression and loss of motor and language skills, is caused by mutations in the X-linked gene encoding methyl-CpG binding protein 2 (MECP2). Neurostructural phenotypes including decreased neuronal size, dendritic complexity, and spine density have been reported in postmortem RTT brain tissue and in Mecp2 animal models. How these changes in neuronal morphology are related to RTT-like phenotype and MeCP2 function, and the extent to which restoration of neuronal morphology can be used as a cellular readout in therapeutic studies, however, remain unclear. Here, we systematically examined neuronal morphology in vivo across three Mecp2 mouse models representing Mecp2 loss-of-function, partial loss-of-function, and gain-of-function mutations, at developmental time points corresponding to early- and late-symptomatic RTT-like behavioral phenotypes. We found that in Mecp2 loss-of-function mouse models, dendritic complexity is reduced in a mild, age-dependent, and brain region-specific manner, whereas soma size is reduced consistently throughout development. Neither phenotype, however, is altered in Mecp2 gain-of-function mice. Our results suggest that, in the cell types we examined, the use of dendritic morphology as a cellular readout of RTT phenotype and therapeutic efficacy should be cautioned, as it is intrinsically variable. In contrast, soma size may be a robust and reliable marker for evaluation of MeCP2 function in Mecp2 loss-of-function studies.
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Affiliation(s)
- I-Ting J Wang
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
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