A síndrome de Rett (SR) é um distúrbio neurológico progressivo de causa genética que afeta quase exclusivamente o sexo feminino. É causada por mutações, geralmente esporádicas, do gene MECP2, localizado no cromossomo X. Apresenta como características principais: estagnação no desenvolvimento neuropsicomotor, perda de comunicação, do contato visual, do interesse por pessoas e objetos e estereotipias manuais. Em conseqüência do grave comprometimento cognitivo e motor, as portadoras de SR têm muita dificuldade em realizar as tarefas do dia-a-dia. O objetivo desse trabalho foi avaliar as habilidades funcionais e averiguar as necessidades de assistência do cuidador, conforme determinadas pelo Inventário de Avaliação Pediátrica de Incapacidade (PEDI). Esse instrumento de avaliação, que possui 197 itens nas áreas de autocuidado, mobilidade e função social, foi aplicado em 64 portadoras de SR que preenchiam os critérios para a forma clássica da doença. Elas tinham idade entre 2 e 26 anos, com média de 10 anos. Entre as 73 atividades da área de autocuidado do PEDI, 52 (71,2%) não foram realizadas por qualquer criança; na área de mobilidade, entre as 59 atividades propostas, 8 (13,5%) não foram feitas pelas portadoras de SR; e finalmente na área de função social, nenhuma das 50 (76,9%) entre 65 atividades foi realizada. O desempenho médio ajustado em escala de 0 a 100 para a área de autocuidado foi de 8,9/100, variando de 0 a 26; para a de mobilidade, foi em média de 30,2/100, variando de 1,7 a 74,5; e a de função social foi de 5,2/100, com variação de 0 a 21,5. A necessidade de assistência foi, de forma complementar, maior nas áreas de autocuidado e função social do que na de mobilidade. Não encontramos, em nossa amostra, uma relação entre a idade e o grau de incapacidade, sugerindo que as portadoras de SR apresentam um nível de comprometimento que é, desde o início, bastante grave. Infelizmente, o menor comprometimento da mobilidade, comparado com as áreas de autocuidado e função social, não traz vantagens adaptativas ou maior independência às portadoras de SR. / Rett syndrome (RS) is a progressive neurological disturbance of genetic cause that affects females almost exclusively. It is caused by mutations, usually sporadic, of the MECP2 gene located in the X chromosome. Presented as main characteristics: stagnation in neuromotor development; losses of communication, visual contact, interest for people and objects; and manual stereotypes. In consequence to the serious cognitive and motor compromise, the RS patients have great difficulty in accomplishing day-to-day tasks. The objective of this work was to evaluate the functional abilities and to discover the needs of assistance by the caregiver, conforming to the established Pediatric Evaluation of Disability Inventory (PEDI). That evaluation instrument, which possesses 197 items in the areas of self-care, mobility and social function, was applied to 64 individuals with RS that matched the criteria for the classic form of the disease. Their ages ranged between 2 years and 26 years, with an average of 10 years. Among the 73 PEDI activities in the area of self-care, 52 (71.2%) were not accomplished by any child; in the area of mobility, among the 59 proposed activities, 8 (13.5%) were not done by any RS patient; and finally in the area of social function, none of the 50 (76.9%) activities among 65 were accomplished. The average performance adjusted in a scale from 0 to 100 for the area of self-care was of 8.9/100, varying from 0 to 26; for mobility, it was an average of 30.2/100, varying from 1.7 to 74.5; and of social function was 5.2/100, with variation from 0 to 21.5. The need of attendance was, in a complementary way, greater in the self-care areas and social function than in mobility. We didn\'t find, in our sample, a relationship between the age and the degree of incapacity, suggesting that RS individual present a compromising level that is from the beginning quite serious. Unfortunately, the smallest compromise of mobility, compared with the areas of self-care and social function, doesn\'t bring adaptive advantages or greater independence to the RS patients.

Das Rett-Syndrom ist eine postnatale neurologische Entwicklungsstörung, der eine Mutation im Methyl-CPG-bindenden Protein 2 (MECP2) zugrunde liegt. Es betrifft überwiegend Mädchen und geht mit kognitiven Beeinträchtigungen, motorischen Stereotypien und Atmungsstörungen einher. Es existieren vielfältige Hinweise dafür, dass die Pathogenese des Rett-Syndroms im Zusammenhang mit einer beeinträchtigten Mitochondrienfunktion steht. Genetische Untersuchungen des Rett-Genoms zeigten, dass eine Untereinheit des Komplex III der Atmungskette dysreguliert ist und die innere Mitochondrienmembran ein Protonenleck aufweist. Weiterhin fanden sich Hinweise für erhöhten oxidativen Stress in Blut- und Liquoruntersuchungen. Um den intrazellulären Redox-Status zu quantifzieren, wurde die genetisch kodierte optische Sonde roGFP1 verwendet, die semiquantitative Messungen reaktiver Sauerstoffspezies ermöglichte. Es zeigte sich, dass Mecp2(-/y)-Hirnschnitte bereits unter Ruhebedingungen erhöhtem oxidativen Stress ausgesetzt sind. Auf der Suche nach der Ursache wurden die intrazellulären antioxidativen Schutzenzyme Superoxid-Dismutase und Katalase sowie das Glutathionsystem überprüft. Alle drei Enzymsysteme zeigten Funktionsstörungen und waren nicht in der Lage, extern applizierten oxidativen Stress im gleichen Umfang zu kompensieren wie die Enzyme der Wildtyp-Vergleichsgruppe. Um die zytosolischen Redox-Verhältnisse zu beeinflussen, wurden Untersuchungen mit den Antioxidantien Ascorbat, Trolox und Melatonin vorgenommen. Dabei zeigte sich, dass Antioxidantien eine potentielle pharmakologische Maßnahme darstellen, um die zu oxidativen Verhältnissen verschobene Redox-Homöostase in Mecp2(-/y)-Hippokampi zu senken und folglich zu normalisieren. Vor allem das Vitamin E-Derivat Trolox stellte sich als wirkungsvoller Radikalfänger heraus und bietet sich für weitere detaillierte Untersuchungen hinsichtlich einer therapeutischen Option des Rett-Syndroms an. Die externe Störung der mitochondrialen Funktion durch die Induktion einer transienten Hypoxie sowie die gezielte Inhibition verschiedener Atmungskettenkomplexe zeigte eine deutlich erhöhte Hypoxieempfindlichkeit der Mecp2(-/y)-Hippokampi und war mit einer erhöhten ROS-Produktion verbunden. In der Arbeit gelang es erstmals, die bereits mehrfach postulierte Störung der Redox-Homöostase im Rett-Syndrom direkt auf zellulärer Ebene nachzuweisen. Die erhobenen Befunde liefern mögliche mechanistische Erklärungsansätze für die Störung der synaptischen Plastizität im Rett-Syndrom, da es klare Verbindungen zwischen dem zellulären Redox-Status und dem Kalziumhaushalt gibt, der durch redoxsensitive Proteine mitreguliert wird. Somit konnte eine zentrale Dysregulation der Erkrankung identifziert werden, die unter Umständen auch neue pharmakologische Angriffspunkt aufzeigt, um die Symptomatik des Rett-Syndroms zu mildern.

Rett Syndrome (RTT) is a neurodevelopmental disorder affecting 1 out of 10,000 females worldwide. Mutations of the X-linked MECP2 gene encoding methyl CpG binding protein 2 (MeCP2) accounts for >90% of RTT cases. People with RTT and mice with Mecp2 disruption show autonomic dysfunction, especially life-threatening breathing disorders, which involves defects in brainstem neurons for breathing controls, including neurons in the locus coeruleus (LC). Accumulating evidence obtained from Mecp2−/Y mice suggests that imbalanced excitation/inhibition or the impaired synaptic communications in central neurons plays a major role. LC neurons in Mecp2−/Ymice are hyperexcited, attributable to the deficiency in GABA synaptic inhibition. Several previous studies indicate that augmenting synaptic GABA receptors (GABARs) leads to a relief of RTT-like symptoms in mice. The extrasynaptic GABARs located outside synaptic cleft, which have the capability to produce sustained inhibition, and may be a potential therapeutic target for the rebalance of excitation/inhibition in RTT. In contrast to the rich information of the synaptic GABARs in RTT research, however, whether Mecp2 gene disruption affects the extrasynaptic GABARs remains unclear. In this study, we show evidence that the extrasynaptic GABAR mediated tonic inhibition of LC neurons was enhanced in Mecp2−/Ymice, which seems attributable to the augmented δ subunit expression. Low-dose THIP exposure, an agonist specific to δ subunit containing extrasynaptic GABARs, extended the lifespan, alleviated breathing abnormalities, enhanced motor function, and improved social behaviors of Mecp2−/Ymice. Such beneficial effects were associated with stabilization of brainstem neuronal hyperexcitability, including neurons in the LC and the mesencephalic trigeminal V nucleus (Me5), and improvement of norepinephrine (NE) biosynthesis. Such phenomena were found in symptomatic Mecp2+/− (sMecp2+/−) female mice model as well, in which the THIP exposure alleviated the hyperexcitability of both LC and Me5 neurons to a similar level as their counterparts in Mecp2−/Y mice, and improved breathing function. In identified LC neurons of sMecp2+/− mice, the hyperexcitability appeared to be determined by both MeCP2 expression and their environmental cues. In conclusion, intervention to extrasynaptic GABAAR by chronic treatment with THIP might be a therapeutic approach to RTT-like symptoms in both Mecp2−/Y and Mecp2+/− mice models and perhaps in people with RTT as well.

No description available.

Induced pluripotent stem (iPS) cells generated from patients hold great promise for studying diseases that affect the central nervous system, as differentiation into the neuronal lineage creates a limitless supply of affected cells for disease study. Rett syndrome (RTT) is a neurodevelopmental autism spectrum disorder primarily caused by mutations in the methyl-CpG-binding protein 2 (MECP2) gene. Due to the inaccessibility of patient neurons, most of what is known about underlying phenotypes has been described using mouse models. iPS cells provide a potential solution, but reprogramming of patient cells is hampered by low efficiency, and early methods of identifying iPS cells involve transgenic techniques that are not translatable to human patient samples. The first part of this thesis describes the generation and characterization of a pluripotency reporter to address this issue. The EOS lentiviral reporter allows real-time observation of pluripotency changes during reprogramming, and is a useful tool for more efficient isolation of reprogrammed cell lines. Further, the EOS selection system can be used in a disease context to reproducibly mark and maintain disease-specific iPS cell lines for future use in disease modelling. Though iPS cells have been used to study RTT in vitro, extensive assessments of neuron function and electrophysiology have not yet been performed. In the second part of this thesis, iPS cell lines generated from a RTT mouse model were tested for their ability to model disease in vitro. Directed differentiation of multiple Mecp2-deficient and wild-type iPS cell lines to glutamatergic neurons revealed neurons that lack Mecp2 have a smaller soma size, diminished sodium currents, and are less excitable, firing fewer, prolonged action potentials that are smaller in magnitude. This deficiency in intrinsic excitability was accompanied by a dysfunction at excitatory glutamatergic synapses, which together recapitulate changes previously observed in the Mecp2-deficient mouse brain. Having accumulated counts and recordings from hundreds of neurons with consistent responses among lines, the iPS cell system is a representative model of the neuronal and synaptic defects in RTT. These results illustrate the requirement of MeCP2 in normal neuronal function, and suggest altered neuronal homeostasis or aberrant network circuitry may underlie RTT pathogenesis.

Patients with Rett Syndrome (RTT) show severe breathing disorders in addition to other neuropathological features, contributing to the high incidence of sudden unexplained death and abnormal brain development. However, the molecular and cellular mechanisms underlying the breathing disorders are still unknown. Recent studies indicate that the dysfunction of brainstem norepinephrine (NE) systems are closely associated with breathing disorders in RTT patients as well as its mice model, the Mecp2-null (Mecp2─/Y) mice. This as well as the fact the major group of NE-ergic neurons in the locus coeruleus (LC) is CO2 chemosensitive suggests that the breathing disorders in RTT may be related these LC neurons. To test this hypothesis, we took a multidisciplinary approach and systematically studied these neurons using molecular biology, in-vitro brain slices, acutely dissociated neurons, immunocytochemistry, and whole-body plethysmograph. To facilitate the electrophysiological studies, we developed a new strain of transgenic mice with GFP expression selectively in the LC neurons of both WT and Mecp2─/Y mice. Breathing activity of the Mecp2─/Y mice showed selective disruptions in responses to mild hypercapnia. The defect was alleviated with the NE uptake blocker desipramine, suggesting the involvement of NE in central CO2 chemosensitivity. In the LC region, the expressions of tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) at both protein and mRNA levels reduced by ~50% in Mecp2─/Y mice. No evidence was found for selective deficiency in TH- or DBH-containing neurons in Mecp2─/Y mice, and no major loss of NE-ergic LC cells were found, indicating that the NE defect is likely to result from deficient expression of biosynthetic enzymes rather than a loss of neurons in the LC. Several intrinsic membrane properties were abnormal in Mecp2─/Y LC neurons in comparison to wild type cells, including stronger inward rectification, shorter time constant, extended action potential duration, smaller amplitude of medium afterhyperpolarization (AHP) and over-expression of fast AHP. These abnormalities seem to be associated with the altered K+ and Na+ currents. Most importantly, Mecp2─/Y LC neurons displayed defective CO2 chemosensitivity in agreement of in vivo CO2 response, likely due to excessive expression of the homomeric Kir4.1 channel. Thus, it seems that the global effect of MeCP2 on the A6 NE system contributes to the impaired systemic CO2 response as well as the breathing irregularities in Mecp2─/Y mice. Such an alteration allowed CO2 to be detected only when hypercapnia became severe, leading to periodical hyper- and hypoventilation. These findings not only provide a novel etiology for the breathing disturbances of Mecp2─/Y mice but also show direct evidence for the first time on a molecular mechanism for the central CO2 chemosensitivity.

Rett syndrome (RTT) is a rare, severe neurodevelopmental disorder, which partly develops in a predictable way, and influences many bodily functions. Regression, i.e. loss of earlier achieved abilities, is one of the clinical criteria for RTT. Research on motor function has to some extent focused on this loss, and less on the possibility to keep, regain or develop abilities. RTT is mainly verified in girls/women, and the prevalence of classic RTT in Sweden for girls born between 1965 and 1976 was 1 in 10.000-12.000. Clinical criteria are used for diagnosis, but since 1999 RTT can be confirmed by a genetic test. As there is no cure so far, development of clinical intervention and management is important, and with good treatment it is possible to improve quality of life. The main aim was to acquire more knowledge about motor development in RTT, both, early development, and development over time. Another aim was to study if there were deviating orthostatic reactions when rising from sitting to standing, and during standing, compared with normally developed, healthy people, matched by sex and age. Clinical experience as well as reports from parents showed that some people with RTT had lost abilities, some had been able to keep abilities, and some had been able to learn new abilities after regression. For good results, the person with RTT had to be motivated, and the intervention jointly planned; it was also important to realize that dyspraxia causes dependence on other people’s initiatives. Information about one person with RTT, collected over several years, showed the possibility to develop in some areas over time and the tendency to deteriorate in other areas. Studying orthostatic reactions when rising to standing, and standing for three minutes, revealed that those with RTT mainly had the same reactions as the healthy controls. The quicker initial drop in systolic blood pressure in people with RTT, when rising, has not been documented earlier.   In conclusion, this thesis shows that it is possible for some people with RTT to keep abilities, regain abilities, and also learn new abilities after regression. Since those with RTT recovered their blood pressure in the same way as the healthy controls, there is no reason to recommend limitations in standing, though the quicker initial drop in systolic blood pressure should be noted. The deterioration in walking found in our previous studies does not seem to be due to deviation in orthostatic reactions. Individual analysis, as well as good knowledge about the development of the disorder and variation in its expression, is essential. Since many people with RTT live to adulthood, planning for lifelong intervention and care is most important.

Rett syndrome is a congenital neurological syndrome, which in the classic phenotype only affects girls. The symptoms include lack of speech, stereotypic movements of hands, dyspraxia and mental retardation, and these symptoms lead to communicative impairments. The purpose of this study was to examine whether the intervention method Intensive Imitation affected interaction/communication and initiative in a girl with Rett syndrome. The design of the study was a Single Subject Experimental Design with a three-week long intervention period where the girl participated daily in 30- minute sessions of Intensive Imitation together with the test conductor. Interaction, communication and initiatives were observed and analyzed before (Baseline A), during and after (Baseline B) the intervention period. The results showed that the girl’s total amount of communicative contributions increased between Baseline A and Baseline B, especially regarding the amount of produced vocalizations. However, there were some variations in the amount of contributions during the entire period. The girl increased her eye gazing towards her communicative partner, especially during the intervention sessions. There were no increase in the amount of communicative initiatives between Baseline A and Baseline B. However, the amount of initiatives increased between the first and the last observation. Intensive Imitation had a positive effect on eye gazing, vocalizations and communicative contributions, but this study cannot show any stable improvement regarding the girl’s communication and interaction. / Rett syndrom är ett medfött neurologiskt syndrom som i den klassiska varianten enbart drabbar flickor. Till symtombilden hör avsaknad av tal, handstereotypier, dyspraxi och utvecklingsstörning som tillsammans innebär kommunikativa begränsningar för individen. Syftet med föreliggande studie var att undersöka om behandlingsmetoden Intensiv Imitation påverkade samspel/kommunikation och initiativförmåga hos en flicka med Rett syndrom. Studien utformades som en Single Subject Design och innehöll en tre veckor lång interventionsperiod där den deltagande flickan dagligen deltog i 30-minuterssessioner med Intensiv Imitation tillsammans med en testledare. Mätningar av samspel, kommunikation och initiativförmåga utfördes före (Baseline A), under och efter (Baseline B) interventionsperioden. Resultaten visade att flickans totala antal kommunikativa bidrag ökade mellan Baseline A och Baseline B, i synnerhet vad gällde antalet producerade ljud. Andelen ögonkontakt flickan sökte med sin samtalspartner var högre vid behandlingssessionerna än vid de vardagliga pedagogiska situationerna. Antalen initiativ ökade inte mellan Baseline A och Baseline B, men däremot uppvisades relativt stora variationer mellan den första och den sista observationen. Den Intensiva Imitationen har således haft en positiv påverkan på vissa kommunikativa beteenden hos den deltagande flickan, men studien har inte kunnat påvisa någon stabil förändring vad gäller hennes samspel/kommunikation och initiativförmåga.

Das Rett-Syndrom ist eine postnatal progressiv verlaufende neurologische Entwicklungsstörung, die x-chromosomal vererbt. Das klassische Rett-Syndrom entsteht durch eine spontane Mutation des MECP2-Gens, welches für die Kodierung des Transkriptionsfaktors MeCP2 (methyl CpG binding protein 2) verantwortlich ist. Das Krankheitsbild verläuft in vier Stadien und ist vor allem von geistiger Retadierung, motorischer Dysfunktion und Unregelmäßigkeiten der Atmung geprägt. In verschiedenen Untersuchungen wurden bereits verschiedene zelluläre Dysfunktionen und Beeinträchtigungen der Mitochondrien bestätigt, weshalb wir weitere Untersuchungen anstrebten. Ziel dieser Dissertation war es, mögliche Einflüsse verschiedener Enzyme auf die ROS-Produktion zu untersuchen und somit die Erkenntnisse aus vorangegangenen Arbeiten zu erweitern. Im Fokus dieser Untersuchungen lagen zum einen die mitochondriale ROS-Produktion sowie die extramitochondriale ROS-Produktion. Durch unterschiedliche pharmakologische Modulationen wurden beide Systeme beeinflusst, um den jeweiligen Beitrag zur gesamten ROS-Produktion abzuschätzen.

Rett Syndrome (RTT) is a neurodevelopmental disorder primarily caused by mutations in the X-linked gene methyl-CpG-binding protein 2 (MECP2). The mosaic brain environment in heterozygous (MECP2+/-) females consists of both MeCP2-wildtype (MeCP2+) and Mecp2-mutant (MeCP2-) neurons. To separate possible cell autonomous and cell non-autonomous effects three-dimensional morphological analysis was performed on individually genotyped layer V pyramidal neurons in the primary motor cortex of heterozygous (Mecp2+/-) and wild-type (Mecp2+/+) mature female mice (>8 months old) from the Mecp2tm1.1Jae line. Mecp2+/+ neurons and Mecp2+ were found to be indistinguishable while Mecp2- neurons have significantly reduced basal dendritic length (p<0.05), predominantly in the region 70-130 μm from the cell body, culminating in a total reduction of 15%. Mecp2- neurons have three (17%) fewer total branch points, lost specifically at the second and third branch orders. Thus the reduced total dendritic length in Mecp2- neurons is a result of fewer higher-order branches. Soma and nuclear areas of 30 Mecp2+/- female mice (5-21 months) with X chromosome inactivation (XCI) ratios ranging from 12% to 56% were analyzed. On average Mecp2- somata and nuclei were 15% and 13% smaller than Mecp2+ neurons respectively. The variation observed in the soma and nuclear sizes of Mecp2- neurons was not due to age, but was found to be correlated with the XCI ratio. Animals with a balanced XCI ratio (approximately 50% Mecp2-) were found to have Mecp2- neurons with a less severe cellular phenotype (11-17% smaller than Mecp2+). Animals with a highly skewed XCI ratio favouring expression of the wild-type allele (less than 30% Mecp2-) were found to have a more severe Mecp2- cellular phenotype (17-22% smaller than Mecp2+). These data support indicate that mutations in Mecp2 exert both cell autonomous and cell non- autonomous effects on neuronal morphology. / Graduate