Rett syndrome is the manifestation of an X linked, mainly female, genetic, neurodevelopmental disorder that usually produces profound intellectual and physical disabilities including abnormal muscle tone, with a tendency to develop limb contractures, scoliosis, epilepsy and irregular respiration. There is characteristic hand stereotypy with· poor voluntary hand use, locomotion is compromised and speech is rare. Although the disorder is not progressive many sequele shorten life especially in the most severely affected. Subtle abnormalities, present from birth, are frequently overlooked because there is some developmental progress until a period of regression at around one year of age when speech and hand use diminish. This thesis gives an account of clinical, physiological and genetic studies carried out between 1982 and 2005 with the aim of recording the natural history of the disorder and understanding its clinical manifestations. The subjects of these studies have been people of all ages, mainly from the British Isles, reported to have Rett syndrome by their physicians and families or carers (British Isles Survey, n=l228). Most have been examined and recorded on video by myself, many repeatedly. Fully informed parental consent and appropriate ethical approval has been given for all procedures. The early manifestations of the disorder were investigated from developmental histories and donated videos (78) taken by families before they were aware of the problem. The abnormal respiratory rhythms were investigated and characterised, using non-invasive measures of respiratory rhythm, carbon dioxide, oxygen, heart rate and blood pressure. The poor control of voluntary movement was investigated using electromagnetic stimulation of the cortex to record conduction in the motor pathways. Stereotyped hand movements were analysed from three-dimensional live recording and informal two-dimensional video. The prevalence of a toe anomaly was estimated, visual evoked potentials were recorded and a reported increase in urinary neopterin was investigated. The health of people in the British Survey was monitored longitudinally from family and physician reports and direct clinical examinations, data being stored on computer. Simple scores were generated to indicate separately the severity of the condition and health of the individual. The survey data has been used to estimate the prevalence of the disorder (I in 10,000 females), natural history from birth to death, the predictive value of the earliest signs, survival at different levels of severity, the impact of scoliosis surgery on health and has provided a foundation for studies relating clinical manifestations to specific mutations on the affected gene MECP 2 (Xq28). The studies have indicated the nature of the Rett disorder to be developmental and non-progressive, with primary impact on the processing functions of the brain, probably beginning in the brain stem before birth.

Rett syndrome is a neurological condition that affects primarily girls. Approximately 40% of Rett syndrome cases arise from nonsense mutations. Several studies have shown that certain aminoglycosides can suppress some types of nonsense mutations in a context dependent manner, and allow the generation of a full length protein. It remains mostly unclear whether different nonsense mutations of MECP2 will be responsive to aminoglycoside treatment. In this study I tested whether some nonsense mutations of MECP2 seen clinically in Rett syndrome girls can be partially suppressed by aminoglycoside administration. My results show that aminoglycosides allow different mutant forms of MECP2 to be overcome in transiently transfected HEK-293 cells, but with differing levels of efficiency. Furthermore, I also show that aminoglycosides increased the prevalence of full length MeCP2 protein in a lymphocyte cell line derived from a Rett girl with R255X mutation. This study establishes the “proof of principle” that some nonsense mutations causing Rett syndrome can be suppressed by drμg treatment.

Rett syndrome is a neurological condition that affects primarily girls. Approximately 40% of Rett syndrome cases arise from nonsense mutations. Several studies have shown that certain aminoglycosides can suppress some types of nonsense mutations in a context dependent manner, and allow the generation of a full length protein. It remains mostly unclear whether different nonsense mutations of MECP2 will be responsive to aminoglycoside treatment. In this study I tested whether some nonsense mutations of MECP2 seen clinically in Rett syndrome girls can be partially suppressed by aminoglycoside administration. My results show that aminoglycosides allow different mutant forms of MECP2 to be overcome in transiently transfected HEK-293 cells, but with differing levels of efficiency. Furthermore, I also show that aminoglycosides increased the prevalence of full length MeCP2 protein in a lymphocyte cell line derived from a Rett girl with R255X mutation. This study establishes the “proof of principle” that some nonsense mutations causing Rett syndrome can be suppressed by drμg treatment.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisors: N. Carolyn Schanen and Mary C. Farach-Carson, Dept. of Biological Sciences. Includes bibliographical references.

MeCP2 was initially identified as an abundant protein in the brain, with an affinity for methylated DNA in vitro. Interestingly, both deficiency and excess of the protein leads to severe neurological problems, such as Rett syndrome, which is the result of mutations in the MECP2 gene. Subsequent transfection experiments showed that MeCP2 can recruit corepressor complexes and inhibit gene expression in vivo. MeCP2 was therefore thought to repress specific gene targets and the aetiology of Rett syndrome was proposed to result from aberrant gene expression in the MeCP2-deficient brain. Although gene expression is perturbed in the Mecp2-null mouse brain, few specific targets have been verified and alternative hypotheses for MeCP2 function have been put forward. Previous binding studies have also failed to clearly identify MeCP2 targets. To shed light on these matters, a novel technique was generated to isolate neuronal and glial nuclei and established that the amount of MeCP2 is unexpectedly high in neurons, with an abundance approaching that of the histone octamer. Chromatin immunoprecipitation experiments on mature mouse brain showed widespread binding of MeCP2, consistent with its high abundance, tracking the methyl-CpG density of the genome. MeCP2 deficiency results in global changes in neuronal chromatin structure, including elevated histone acetylation and a doubling of histone H1. The mutant brain also shows elevated transcription of repetitive elements, which are distributed throughout the mouse genome. Based on this data, we propose that MeCP2 binds genome wide and suppresses spurious transcription through binding in a DNA methylation dependent manner.

Rett syndrome (RTT) is an X-linked neurological disorder primarily caused by mutations in the MECP2 gene. The majority of RTT mutations disrupt the interaction of MeCP2 with DNA or TBL1X/TBL1XR1, which forms the scaffold of NCoR/SMRT co-repressor complex. Patients with RTT show no signs of neuronal death, although they have abnormal neuronal morphology, indicating that it is a neurodevelopmental rather than a neurodegenerative disease. It has been shown that reactivation of silenced MeCP2 in mice rescues the RTT phenotype, which implies that the disease is treatable. The RTT mutations in MeCP2 cluster to two regions - the methyl-CpG-binding domain (MBD) and NCoR/SMRT Interaction Domain (NID). While the interaction between MBD and DNA has been biochemically and structurally characterised, there are no structural data about the interaction between MeCP2 NID and TBL1XR1. The aim of this work was to understand how mutations in the NID cause RTT by characterising the interaction between MeCP2 and TBL1XR1. I have solved the structure of MeCP2 NID bound to TBL1XR1 WD40 domain. I show that a small region of the MeCP2 NID makes extensive contacts with TBL1XR1, and that these contacts are mediated primarily by MeCP2 residues known to be mutated in RTT. I also measured the affinities between TBL1XR1 and MeCP2-derived peptides using fluorescence anisotropy and surface plasmon resonance assays. I determined the affinity between MeCP2 NID peptide and TBL1XR1 to be around 10- 20 μM, and show that mutations in either MeCP2 or TBL1XR1 can abolish this interaction. Taken together, these data strongly suggest that the abolition of the interaction between MeCP2 NID and TBL1XR1 WD40 domain is sufficient to cause RTT. This knowledge can help with the rational design of small drug-like molecules that might be able to mediate the interaction between mutated MeCP2 and TBL1XR1, potentially helping to treat the disease.

Intractable epilepsy remains one of the top issues affecting the quality of living in Rett children. While several MeCP2-deficient mouse models of Rett Syndrome have been established, minimal information exists on how the loss of MeCP2 affects brain network activity. To address this issue, in vivo recordings of the hippocampus and somatosensory cortex of MeCP2-deficient mice were taken during exploration, immobility, and sleep. The frequency of hippocampal theta oscillations was significantly attenuated in MeCP2-deficient mice during exploration. A subset of MeCP2-heterozygotes displayed spontaneous, cortical epileptiform-like discharges in the immobile-awake state. Similar epileptiform-like discharges were observed in one of the four Mecp2-null mice recorded. Aside from these EEG abnormalities, basal network activity was preserved. Further, convulsive seizures were not seen. Collectively, these findings indicate that a deficiency of MeCP2 in mice leads to only subtle alterations in brain wave activity, contrasting the severely abnormal EEG observed in Rett girls.

Intractable epilepsy remains one of the top issues affecting the quality of living in Rett children. While several MeCP2-deficient mouse models of Rett Syndrome have been established, minimal information exists on how the loss of MeCP2 affects brain network activity. To address this issue, in vivo recordings of the hippocampus and somatosensory cortex of MeCP2-deficient mice were taken during exploration, immobility, and sleep. The frequency of hippocampal theta oscillations was significantly attenuated in MeCP2-deficient mice during exploration. A subset of MeCP2-heterozygotes displayed spontaneous, cortical epileptiform-like discharges in the immobile-awake state. Similar epileptiform-like discharges were observed in one of the four Mecp2-null mice recorded. Aside from these EEG abnormalities, basal network activity was preserved. Further, convulsive seizures were not seen. Collectively, these findings indicate that a deficiency of MeCP2 in mice leads to only subtle alterations in brain wave activity, contrasting the severely abnormal EEG observed in Rett girls.

Several years ago a ten year child with a disability died from "severe malnutrition" according to a Coroners Service inquest jury. The inquest evidence shows that approximately one week prior to this child's death three health care providers conducted individual assessments of the child. Using institutional ethnography as a theoretical and methodological framework, the author conducts a textual analysis of the health care providers' documents generated during their provision of service to this child. Obtained as public documents from the Coroners Service, this data includes: the hospital form, the hospice society records and home care nursing records. / Graduate / 0566

abstract: Methyl-CpG binding protein 2 (MECP2) is a widely abundant, multifunctional regulator of gene expression with highest levels of expression in mature neurons. In humans, both loss- and gain-of-function mutations of MECP2 cause mental retardation and motor dysfunction classified as either Rett Syndrome (RTT, loss-of-function) or MECP2 Duplication Syndrome (MDS, gain-of-function). At the cellular level, MECP2 mutations cause both synaptic and dendritic defects. Despite identification of MECP2 as a cause for RTT nearly 16 years ago, little progress has been made in identifying effective treatments. Investigating major cellular and molecular targets of MECP2 in model systems can help elucidate how mutation of this single gene leads to nervous system and behavioral defects, which can ultimately lead to novel therapeutic strategies for RTT and MDS. In the work presented here, I use the fruit fly, Drosophila melanogaster, as a model system to study specific cellular and molecular functions of MECP2 in neurons. First, I show that targeted expression of human MECP2 in Drosophila flight motoneurons causes impaired dendritic growth and flight behavioral performance. These effects are not caused by a general toxic effect of MECP2 overexpression in Drosophila neurons, but are critically dependent on the methyl-binding domain of MECP2. This study shows for the first time cellular consequences of MECP2 gain-of-function in Drosophila neurons. Second, I use RNA-Seq to identify KIBRA, a gene associated with learning and memory in humans, as a novel target of MECP2 involved in the dendritic growth phenotype. I confirm bidirectional regulation of Kibra by Mecp2 in mouse, highlighting the translational utility of the Drosophila model. Finally, I use this system to identify a novel role for the C-terminus in regulating the function of MECP in apoptosis and verify this finding in mammalian cell culture. In summary, this work has established Drosophila as a translational model to study the cellular effects of MECP2 gain-of-function in neurons, and provides insight into the function of MECP2 in dendritic growth and apoptosis. / Dissertation/Thesis / Doctoral Dissertation Neuroscience 2015