Loss of O-GlcNAcylation on MeCP2 at Threonine 203 Leads to Neurodevelopmental Disorders / 神经科学通报·英文版

Mutations of the X-linked methyl-CpG-binding protein 2 (MECP2) gene in humans are responsible for most cases of Rett syndrome (RTT), an X-linked progressive neurological disorder. While genome-wide screens in clinical trials have revealed several putative RTT-associated mutations in MECP2, their causal relevance regarding the functional regulation of MeCP2 at the etiologic sites at the protein level requires more evidence. In this study, we demonstrated that MeCP2 was dynamically modified by O-linked-β-N-acetylglucosamine (O-GlcNAc) at threonine 203 (T203), an etiologic site in RTT patients. Disruption of the O-GlcNAcylation of MeCP2 specifically at T203 impaired dendrite development and spine maturation in cultured hippocampal neurons, and disrupted neuronal migration, dendritic spine morphogenesis, and caused dysfunction of synaptic transmission in the developing and juvenile mouse cerebral cortex. Mechanistically, genetic disruption of O-GlcNAcylation at T203 on MeCP2 decreased the neuronal activity-induced induction of Bdnf transcription. Our study highlights the critical role of MeCP2 T203 O-GlcNAcylation in neural development and synaptic transmission potentially via brain-derived neurotrophic factor.

Clinical and genetic analysis of two rare male patients with Rett syndrome / 中华医学遗传学杂志

OBJECTIVE@#To conduct clinical and genetic analysis of two male patients with atypical Rett syndrome.@*METHODS@#Collection of clinical data in the two patients and these parents; whole exome sequencing (WES) was used to detect the potential variants, which were verified by Sanger sequencing. X chromosome inactivation (XCI) detection is performed in the Patient 1's mother to detect the allelic expression difference of the MECP2 gene.@*RESULTS@#Patient 1, a 5-year and 10-month-old boy, had mental disorders and mild intellectual disability (ID) (IQ: 54), whose mother had ID. Patient 2 was a 9-month and 18-day-old male presented with recurrent infections, respiratory insufficiency, hypotonia and global developmental delay. WES indentified a hemizygous mutation, c.499C>T (p.R167W), in the MECP2 gene in patient 1, which was inherited from his mother. The inactivation of X chromosome is skewed, and the expression ratio of wild-type and mutant MECP2 is 100%:0. Patient 2 was found a de novo splicing mutation, c.62+2_62+3del in the MECP2 gene. They were both reported pathogenic variant related to Rett syndrome. c.499C>T (p.R167W) was defined as likely pathogenic (PS1+PM2+PP3) and c.62+2_62+3del was pathogenic (PVS1+PM2+PM6) based on American College of Medical Genetics and Genomics standards and guidelines.@*CONCLUSION@#Both the two patients were diagnosed with rare male Rett syndrome, which had atypical clinical manifestations and large difference. Above foundings have revealed novel phenotypes in Chinese male patients with Rett syndrome.

Rett syndrome: the Brazilian contribution to the gene discovery / Síndrome de Rett: a contribuição brasileira para a descoberta do gene

ABSTRACT A brief history of the syndrome discovered by Andreas Rett is reported in this paper. Although having been described in 1966, the syndrome was only recognized by the international community after a report by Hagberg et al. in 1983. Soon, its importance was evident as a relatively frequent cause of severe encephalopathy among girls. From the beginning it was difficult to explain the absence of male patients and the almost total predominance of sporadic cases (99%), with very few familial cases. For these reasons, it was particularly difficult to investigate this condition until 1997, when a particular Brazilian family greatly helped in the final discovery of the gene, and in the clarification of its genetic mechanism. Brief references are made to the importance of the MECP2 gene, 18 years later, as well as to its role in synaptogenesis and future prospects.

RESUMO Uma breve história de uma síndrome neurológica descoberta por Andreas Rett é relatada neste artigo. Embora tenha ocorrido em 1966, a síndrome só foi reconhecida pela comunidade internacional após um relato de Hagberget al, em 1983. Logo, sua importância ficou evidente como causa relativamente frequente de encefalopatia grave entre as crianças do sexo feminino. Desde o início, foi difícil explicar a ausência de envolvimento de pacientes do sexo masculino e a quase absoluta preponderância de casos esporádicos (99%), com muitos poucos casos familiares. Por essas razões, foi difícil investigar essa condição até 1997, quando uma família brasileira em particular ajudou muito na descoberta final do gene e no esclarecimento de seu mecanismo genético. São feitas referências sucintas à importância do gene MECP2, dezoito anos depois, bem como ao seu papel na sinaptogênese e nas perspectivas futuras.

Síndrome de Rett: Análisis molecular del gen MECP2 en pacientes chilenas / Rett syndrome: MECP2 gene molecular analysis in Chilean patients

INTRODUCCIÓN: El síndrome de Rett (RTT) es un trastorno neurológico progresivo caracterizado por producir una regresión del desarrollo psicomotor en niñas previamente sanas. La mayoría de los casos son causados por variantes patogénicas en el gen MECP2, que codifica para la proteína methyl CpG- binding protein 2. OBJETIVO: Describir la frecuencia y el tipo de variantes patogénicas en MECP2 en mujeres chilenas con diagnóstico clínico de RTT. PACIENTES Y MÉTODO: Se invitó a participar en este estudio a mujeres chilenas con sospecha clínica de RTT. Se reunió información clínica mediante un cuestionario. Se analizaron variantes patogénicas en MECP2 mediante el método de secuenciación de Sanger y se utilizó Multiple Ligation-dependant Probe Amplification (MLPA) para la detección de duplicaciones y deleciones. RESULTADO: El estudio incluyó 14 pacientes con sospecha de RTT, de las cuales 8 (57%) pacientes tuvieron variantes patogénicas. Las restantes permanecen sin diagnóstico molecular. CONCLUSIÓN: Variantes patogénicas en MECP2 están presentes en pacientes chilenas con RTT. Es probable que haya otros genes o diagnósticos involucrados en las pacientes sin hallazgos en MECP2. A partir de este trabajo, el diagnóstico molecular está disponible en Chile.

INTRODUCTION: Rett syndrome (RTT) is a progressive neurological disorder characterized by regres sion of psychomotor development in previously healthy girls. Most cases are due to pathogenic va riants in the MECP2 gene which encodes for the methyl CpG-binding protein 2. OBJECTIVE: To des cribe the frequency and type of pathogenic variants in the MECP2 gene in Chilean female patients with clinical diagnosis of RTT. PATIENTS AND METHOD: Chilean women with clinical suspicion of RTT were invited to participate in the study. Clinical data were collected through a questionnaire. MECP2 pathogenic variants were analyzed by Sanger sequencing method and Multiplex Ligation-dependent Probe Amplification (MLPA) was used to detect duplications or deletions. RESULTS: The study in cluded 14 patients with suspected RTT, of which eight (57%) patients had pathogenic variants. The other patients remain without molecular diagnosis. CONCLUSIONS: Pathogenic variants in MECP2 are present in Chilean patients with RTT. It is likely that there are other genes or diagnoses involved in patients without MECP2 findings. As of this study, molecular diagnosis is available in Chile.

Bases moleculares del síndrome de Rett, una mirada actual / Molecular basis of Rett syndrome: A current look

El síndrome de Rett (SR) es un trastorno del neurodesarrollo que afecta casi exclusivamente a niñas y cursa secundariamente con autismo. Es poco frecuente y consta de 5 formas clínicas, una clásica y el resto atípicas que comprometen de manera general la habilidad manual, el lenguaje y la motricidad amplia unida a la aparición de estereotipias y epilepsia precoz. Con el objetivo de actualizar la información sobre SR, se aplicaron los descriptores de búsqueda Síndrome de Rett, genes y «Síndrome de Rett¼, «Rett Syndrome gene¼, «Rett Syndrome¼, «Rett Syndrome gene therapy¼ y «Rett Syndrome review¼. Se investigó en los archivos digitales PubMed, Hinari, SCIELO y Medline, y se consultaron los sitios web OMIM, ORPHANET, GeneMap, Genetests, Proteins y Gene, entre otros. Entre 1.348 artículos se seleccionaron 42, los cuales reportan 3 genes causantes del síndrome: MECP2, CDKL5 y FOXG. El gen MECP2 está mutado en el 80% de los pacientes con SR clásico así como en el 40% de los afectados con alguna de sus formas atípicas. El SR con epilepsia precoz y la variante congénita se deben fundamentalmente a variaciones en los genes CDKL5 y FOXG1 respectivamente. Conclusiones: El diagnóstico del SR se basa en criterios clínicos, sin embargo, los avances en la biología molecular y en la genética en particular han abierto el abanico de posibilidades diagnósticas a las diferentes formas clínicas que antes quedaban sin clasificar, a la vez que el análisis molecular permite confirmar el criterio clínico y aportar información en cuanto al pronóstico del paciente.

Rett syndrome (RS) is a neurodevelopmental disorder that exclusively affects girls, and occurs along with autism. It is very uncommon, and has five distinct forms, one classic and the others atypical, which generally compromise manual skills, language, and mobility, and widely associated with the appearance of stereotypy and early epilepsy. With the aim of updating the information about RS, a search was performed in the computer data bases of PubMed, Hinari, SCIELO and Medline, as well as consulting other web sites including OMIM, ORPHANET, GeneMap, Genetests, Proteins and Gene, using the descriptors "Síndrome de Rett", "genes y Síndrome de Rett", "Rett Syndrome gene", "Rett Syndrome", "Rett Syndrome gene therapy", and "Rett Syndrome review". Of the 1,348 articles found, 42 articles were selected, which reported 3 genes causing the syndrome: MECP2, CDKL5 and FOXG. The MECP2 gene is mutated in 80% of patients with classic RS, as well as in 40% of those affected by any of its atypical forms. RS with early epilepsy and the congenital variant are mainly due to variations in the CDKL5 and FOXG1 genes, respectively. Conclusions: The diagnosis of RS is based on clinical criteria. However, the advances in molecular biology and genetics have opened a wide range of possibilities for diagnosing the different clinical forms that could not be classified before. Molecular analysis can help confirm the clinical criteria and provided information as regards the prognosis of the patient.

Impacto da ativação da intenção na prática da atividade física em diabéticos tipo II: ensaio clínico randomizado / Impact of the activation of intention to perform physical activity in type II diabetics: a randomized clinical trial

O diabetes mellitus, tipo II, é uma doença com alta prevalência na população adulta brasileira e que pode ser controlada, dentre outras intervenções, por meio da atividade física. Este estudo teve como objetivo avaliar o impacto de uma estratégia motivacional tradicional, bem como sua associação à estratégia de ativação da intenção, na adesão à atividade física, nos portadores do diabetes mellitus, tipo II, usuários do Sistema Único de Saúde (SUS), por meio de um ensaio clínico randomizado. Os participantes foram alocados em Grupo Controle (GC) e Grupo Intervenção (GI). Ambos os grupos receberam uma estratégia motivacional tradicional, porém, somente o GI recebeu a estratégia de ativação da intenção. Após dois meses de seguimento, observaram-se diferenças estatisticamente significativas entre os grupos, relativas à prática de caminhada (p = 0,0050), número de dias por semana (p = 0,0076), minutos por dia (p = 0,0050) e minutos por semana (p = 0,0015) de caminhada. Ao final das intervenções, observaram-se, também, diferenças na circunferência abdominal (p = 0,0048) entre os grupos. Conclui-se que a estratégia de ativação da intenção teve maior impacto na adesão à prática de atividade física e diminuição da circunferência abdominal de diabéticos, tipo II, do que a estratégia motivacional tradicional.

Type II diabetes mellitus is a highly prevalent disease among the adult Brazilian population, and one that can be controlled by interventions such as physical activity, among others. The aim of this randomized controlled study was to evaluate the impact of a traditional motivational strategy, associated with the activation of intention theory, on adherence to physical activity in patients with type II, diabetes mellitus who are part of the Unified Health System (SUS). Participants were divided into a control group (CG) and an intervention group (IG). In both groups, the traditional motivational strategy was applied, but the activation of intention strategy was only applied to the IG Group. After a two-month follow-up, statistically significant differences were verified between the groups, related to the practice of walking (p = 0.0050), number of days per week (p = 0.0076), minutes per day (p = 0.0050) and minutes walking per week (p = 0.0015). At the end of the intervention, statistically significant differences in abdominal circumference (p = 0.0048) between the groups were observed. The conclusion drawn is that the activation of intention strategy had greater impact on adherence to physical activity and reduction in abdominal circumference in type II diabetics, than traditional motivational strategy.

Autismo y epigenética. Un modelo de explicación para la comprensión de la génesis en los trastornos del espectro autista / [Autism and epigenetics. A model of explanation for the understanding of the genesis in autism spectrum disorders].

Autism spectrum disorders are characterized by impairment of social integration and language development and restricted interests. Autism spectrum disorders manifest during childhood and may have a varying clinical expression over the years related to different therapeutic approaches, behavior-modifying drugs, and environmental factors, among others. So far, the genetic alterations identified are not sufficient to explain the genesis of all these processes, as many of the mutations found are also present in unaffected individuals. Findings on the underlying biological and pathophysiological mechanisms of entities strongly associated with autism spectrum disorders, such as Rett, fragile X, Angelman, and fetal alcohol syndromes, point to the role of epigenetic changes in disorders of neurodevelopment. Epigenetic phenomena are normal biological processes necessary for cell and thus human life, especially related to embryonic development. Different phenomena that affect epigenetic processes (changes that change operation or expression of a gene, without modifying the DNA structure) have also been shown to be important in the genesis of neurodevelopmental disorders. Alterations in the epigenetic mechanism may be reversible, which may explain the variation in the autism phenotype over time. Here we analyze the normal epigenetic mechanisms, autism spectrum disorders, their association with specific entities associated with altered epigenetic mechanisms, and possible therapeutic approaches targeting these alterations.

Genetic and Epileptic Features in Rett Syndrome

PURPOSE: Rett syndrome is a severe neurodevelopmental disorder in females. Most have mutations in the methyl-CpG-binding protein 2 (MECP2) gene (80-90%). Epilepsy is a significant commonly accompanied feature in Rett syndrome. Our study was aimed at comprehensive analysis of genetic and clinical features in Rett syndrome patients, especially in regards to epileptic features. MATERIALS AND METHODS: We retrospectively reviewed 20 patients who were diagnosed with MECP2 mutations at Severance Children's Hospital between January 1995 and July 2010. All patients met clinical criteria for Rett syndrome. Evaluations included clinical features, epilepsy classification, electroencephalography analysis, and treatment of seizures. RESULTS: Ages ranged from 3.6 to 14.3 years (7.7+/-2.6). Fourteen different types of MECP2 mutations were found, including a novel in-frame mutation (1153-1188 del36). Fourteen of these patients (70.0%) had epilepsy, and the average age of seizure onset was 3.0+/-1.8 years. Epilepsy was diverse, including partial seizure in four patients (28.5%), secondarily generalized seizure in six (42.8%), generalized tonic seizure in two (14.3%), Lennox-Gastaut syndrome in one (7.1%), and myoclonic status in non-progressive encephalopathy in one (7.1%). Motor functions were delayed so that only 10 patients (50.0%) were able to walk independently: five (35.8%) in the epilepsy group and five (83.3%) in the non-epilepsy group. Average developmental scale was 33.5+/-32.8 in the epilepsy group and 44.4+/-21.2 in the non-epilepsy group. A clear genotype-phenotype correlation was not found. CONCLUSION: There is a tendency for more serious motor impairment and cognitive deterioration in Rett syndrome patients with epilepsy.

Farmacología del epigenoma: investigaciones sobre usos de utilidad clínica de drogas estabilizantes del ánimo/anticonvulsivantes / Pharmacology of the epigenome: investigations on the use of clinical utility, of mood stabilizers/anticonvulsants

La epigenética es un promisorio campo de la investigación que probablemente contribuya a la comprensión de un amplio rango de enfermedades como la ansiedad, la depresión, la esquizofrenia, la enfermedad de Alzheimer, la enfermedad de Huntington o el síndrome de Rett. Esta área del conocimiento se refiere a las modificaciones en la expresión genética que resultan en cambios heredables y que son independientes de los cambios de la secuencia genética. Esto incluye la metilación del ácido desoxirribonucleico (ADN), las modificaciones de las histonas y más recientemente a la interferencia del ácido ribonucleico (ARN), especialmente a través de la no traducción a proteínas por microARN (miARN) u otros ARN pequeños de interferencia (SIRNA´s). La farmacología de la epigénetica está avanzando en el desarrollo de drogas o probando las utilizadas para otras indicaciones, para modificar las alteraciones del epigenoma que resultan en enfermedades o vulnerabilidades a diversas patologías.Los inhibidores de la deacetilasa de las histonas son un ejemplo de lo anteriormente expuesto. Demostraron tener eficacia como anticancerosos a través de un amplio rango de enfermedades malignas, especialmente las hematológicas. El valproato, un inhibidor de la deacetilasa de las histonas, es una droga que ha sido utilizada por décadas para tratar la epilepsia, los trastornos del estado de ánimo y la migraña y actualmente se lo investiga para otras indicaciones.El objetivo de este capítulo es mostrar los avances realizados en el conocimiento de los mecanismos de acción de drogas utilizadas como estabilizantes del estado de ánimo/anticonvulsivantes, como también sus probables usos por fuera de su indicación específica.

Epigenetics is a promising field of research, which probably contributes to understanding a wide spectrum of disorders such as anxiety, depression, schizophrenia, Alzheimer's Disease, Huntington's Disease or Rett's Syndrome. This area of knowledge refers to modifications in the gene expression, which result in inheritable changes and which are independent of the changes in the gene sequencing. This includes the methylation of deoxyribonucleic acid (DNA), the changes of histones, and, more recently, the role of ribonucleic acid (RNA), particularly, by means of non-protein-coding RNA (miRNA) or other small interfering RNA's (SIRNA's). The pharmacology of epigenetics is progressing in terms of the development of drugs, or the testing of the already used ones form other indications, in order to modify the alterations in the epigenome that result in diseases or vulnerabilities to different pathologies. Histone decetylase inhibitors are an example of the above. They prove to be effective against cancer through a wide spectrum of malignant diseases, especially hematologic diseases. Valprotate, a histone deacetylase inhibitor, is a drug which has been used for decades to treat epilepsy, mood disorders and migraines, and is currently being researched for other indications as well. The purpose of this chapter is to show the advances achieved with respect to the knowledge of the mechanisms of action of drugs used as mood stabilizers/anticonvulsants, as well as their possible uses beyond their possible uses beyond their specific indication.

Animal models of intellectual disability: towards a translational approach

Intellectual disability is a prevalent form of cognitive impairment, affecting 2-3 percent of the general population. It is a daunting societal problem characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social and practical adaptive skills. Intellectual disability is a clinically important disorder for which the etiology and pathogenesis are still poorly understood. Moreover, although tremendous progress has been made, pharmacological intervention is still currently non-existent and therapeutic strategies remain limited. Studies in humans have a very limited capacity to explain basic mechanisms of this condition. In this sense, animal models have been invaluable in intellectual disability investigation. Certainly, a great deal of the knowledge that has improved our understanding of several pathologies has derived from appropriate animal models. Moreover, to improve human health, scientific discoveries must be translated into practical applications. Translational research specifically aims at taking basic scientific discoveries and best practices to benefit the lives of people in our communities. In this context, the challenge that basic science research needs to meet is to make use of a comparative approach to benefit the most from what each animal model can tell us. Intellectual disability results from many different genetic and environmental insults. Taken together, the present review will describe several animal models of potential intellectual disability risk factors.

Genetic studies in children with intellectual disability and autistic spectrum of disorders.

Autism is one of the five disorders that falls under the umbrella of Pervasive Developmental Disorders (PDD) or Autism Spectrum Disorder (ASD), a category of neurological disorders characterized by “severe and pervasive impairment in several areas of development.” ASD is characterized by varying degrees of impairment in communication skills, social interaction and restricted, repetitive stereotyped patterns of behavior. The five disorders under PDD are autistic disorder, Asperger's disorder, childhood disintegrative disorder, Rett's disorder and PDD-not otherwise specified. ASD can often be reliably detected by the age of 3 years and, in some cases, as early as 18 months. The appearance of any warning signs of ASD is reason to have the child evaluated by a professional specializing in these disorders.

Genotype-phenotype correlation in Brazillian Rett syndrome patients / Correlação genótipo-fenótipo em pacientes brasileiras com síndrome de Rett

BACKGROUND: Rett syndrome (RS) is a severe neurodevelopmental X-linked dominant disorder caused by mutations in the MECP2 gene. PURPOSE: To search for point mutations on the MECP2 gene and to establish a correlation between the main point mutations found and the phenotype. METHOD: Clinical evaluation of 105 patients, following a standard protocol. Detection of point mutations on the MECP2 gene was performed on peripheral blood DNA by sequencing the coding region of the gene. RESULTS: Classical RS was seen in 68 percent of the patients. Pathogenic point mutations were found in 64.1 percent of all patients and in 70.42 percent of those with the classical phenotype. Four new sequence variations were found, and their nature suggests patogenicity. Genotype-phenotype correlations were performed. CONCLUSION: Detailed clinical descriptions and identification of the underlying genetic alterations of this Brazilian RS population add to our knowledge of genotype/phenotype correlations, guiding the implementation of mutation searching programs.

INTRODUÇÃO: A síndrome de Rett é uma grave doença do neurodesenvolvimento ligada ao X dominante, causada por mutações no gene MECP2. OBJETIVOS: Identificar mutações de ponto no gene MECP2 e estabelecer uma correlação entre as principais mutações encontradas e o fenótipo. MÉTODO: Avaliação clínica de 105 pacientes, seguindo um protocolo estabelecido. A identificação de mutações de ponto foi realizada em DNA de sangue periférico por sequenciamento da região codificante do gene amplificada por PCR. RESULTADOS: Em 68 por cento dos pacientes observou-se o quadro clássico da síndrome. Mutações de ponto patogênicas foram encontradas em 64,1 por cento dos pacientes e em 70,42 por cento das pacientes com o quadro clássico. Quatro novas variações de seqüência foram identificadas e sua natureza sugere patogenicidade. Correlações genótipo-fenótipo foram estabelecidas. CONCLUSÃO: Descrições clínicas detalhadas desta população brasileira de pacientes acrescenta conhecimento às correlações genótipo-fenótipo nesta grave condição, que podem auxiliar na implantação de programas de triagem de mutações.

Concepts of color, shape, size and position in ten children with Rett syndrome / Conceitos de cor, forma, tamanho e posição em dez crianças com síndrome de Rett

Individuals with Rett syndrome (RS) present severe motor, language and cognitive deficits, as well as spontaneous hand movement loss. On the other hand, there are strong evidence that these individuals use the eyes with intentional purpose. Ten girls aged 4y8m to 12y10m with RS were assessed with a computer system for visual tracking regarding their ability of indicating with eyes the recognition of concepts of color (red, yellow and blue), shape (circle, square and triangle), size (big and small) and spatial position (over and under) to which they were first exposed to. Results from comparing the time of eyes fixation on required and not required concepts did not differ significantly. Children did not show with eyes the recognition of the required concepts when assessed with eye tracking system.

Pessoas com síndrome de Rett (SR) apresentam severos prejuízos psicomotores, verbais, cognitivos e perda das habilidades manuais proposicionais que impedem o conhecimento de suas reais aquisições intelectuais. Entretanto, estudos relatam que essas pessoas utilizam o olhar com finalidade intencional. O objetivo deste estudo foi avaliar se crianças com SR, após terem sido expostas aos conceitos de cor (vermelho, amarelo e azul), forma (círculo, quadrado e triângulo), tamanho (grande e pequeno) e posição espacial (em cima e em baixo), manifestam o reconhecimento desses conceitos com o olhar, avaliado com equipamento computadorizado de rastreamento ocular. Foram avaliadas dez crianças com diagnóstico de SR, com idades entre 4 anos e 8 meses e 12 anos e 10 meses. Os resultados não indicaram diferenças significativas no tempo de fixação do olhar das crianças quando comparados os conceitos solicitados e os não solicitados. Concluiu-se que, com o método utilizado, as crianças não reconheceram os conceitos avaliados.

Análise de mutações no gene MECP2 em uma amostra de pacientes do sexo feminino afetadas pela síndrome de Rett na população brasileira / Analysis of mutations in the MECP2 gene in a sample of female patients affected by Rett syndrome in the Brazilian population

A síndrome de Rett (SR) é uma doença neurológica com herança dominante ligada ao X, com incidência estimada de 1:10.000–15.000 nascidas vivas. Clinicamente caracterizada pelo progressivo comprometimento neuromotor após um período de desenvolvimento aparentemente normal, a SR está associada a mutações no gene MECP2, mapeado em Xq28. Neste estudo foi realizada a análise mutacional do gene MECP2 em 80 pacientes do sexo feminino clinicamente diagnosticadas como portadoras de SR, ou com forte suspeita clínica para tal doença. A partir de amostras de ADN genômico foram amplificados pela técnica de PCR os éxons 2, 3 e 4 do gene, incluindo as regiões intrônicas flanqueadoras. A detecção de mutações foi realizada através de seqüenciamento direto. No caso das pacientes positivas, foi realizada a análise do ADN materno para identificação de possíveis casos familiares. Para validação dos resultados, foram analisadas 100 amostras de ADN controle do sexo feminino. Os resultados obtidos foram comparados aos dados depositados em bancos de dados disponíveis na Internet. Foram detectadas 29 variações em 49 (61,25%) das 80 pacientes analisadas. Das 49 pacientes positivas, 34 (69,39%) são afetadas pela forma clássica da SR e 15 (30,61%) são afetadas por formas atípicas. As variações detectadas foram caracterizadas como 17 mutações patogênicas (5 missense, 4 nonsense, 7 frameshift e 1 deleção in-frame), 4 mutações silenciosas, 6 variações intrônicas, 1 polimorfismo não-sinônimo e 1 variação na região 3 UTR. Das variações detectadas, 18 são previamente descritas e incluem 11 mutações patogênicas e sete polimorfismos. Outras 11 variações detectadas não constam nos bancos de dados consultados e incluem seis mutações patogênicas, uma mutação silenciosa, três variações intrônicas e uma variação na região 3 UTR. As mutações patogênicas mais freqüentes detectadas na amostra estudada foram p.R133C, p.T158M, p.R168X, p.R255X, p.R270X e p.R294X, descritas como hot spots em outras populações. A detecção de variações não descritas no MECP2 sugere que as pacientes com síndrome de Rett na população brasileira podem apresentar diferenças significativas quanto ao espectro mutacional, uma vez que nenhuma das mutações patogênicas não descritas foi verificada em amostras controles analisadas. A não detecção de mutações patogênicas no ADN materno comprovou a baixa freqüência de casos familiares na SR. Embora seja considerada uma das principais causas de retardo mental no sexo feminino, os estudos sobre a SR no Brasil ainda são restritos. Por este motivo, o cruzamento de dados moleculares, clínicos e epidemiológicos é de fundamental importância para analisar o perfil das pacientes brasileiras de SR. Isto permite traçar estratégias de tratamento e reabilitação mais adequadas para a melhoria na qualidade de vida destas pacientes.

Rett syndrome: clinical and molecular characterization of two Brazilian patients

BACKGROUND: Rett syndrome (RS) is recognized as a pan-ethnic condition. Since the identification of mutations in the MECP2 gene, more patients have been diagnosed, and a broad spectrum of phenotypes has been reported. There is a lack of phenotype-genotype studies. OBJECTIVE: To describe two cases of Brazilian patients with identified MECP2 mutations. METHOD: We present two female Brazilian patients with RS. RESULTS: Both patients presented with regression at 2-3 years of age, when stereotypic hand movements, social withdrawal and postnatal deceleration of head growth rate were observed. Both patients presented verbal communication impairment. Case 1 had loss of purposeful hand movements, and severe seizure episodes. Case 2 had milder impairment of purposeful hand movements, and no seizures. They had different mutations, D97Y and R294X, found in exons 3 and 4 of MECP2 gene, respectively. CONCLUSION: Testing for MECP2 mutations is important to confirm diagnosis and to establish genotype/phenotype correlations, and improve genetic counseling.

CONTEXTO: Síndrome de Rett (RS) é doença pan-étnica de fenótipo bastante variado desde que foram identificadas mutações no gene MECP2 e um número maior de pacientes tem sido diagnosticadas. Existe uma demanda por estudos que investiguem a relação genótipo-fenotipo. OBJETIVO: Descrever dois casos brasileiros de RS com mutações identificadas. MÉTODO: Duas pacientes brasileiras com diagnóstico clínico-molecular de RS foram descritas buscando-se correlacionar genótipo-fenótipo. RESULTADOS: Ambas pacientes apresentaram regressão aos 2-3 anos de idade, movimentos esteriotipados de mãos, retraimento social e desaceleração do crescimento encefálico. Ambas apresentaram déficit de comunicação verbal. Caso 1 também apresentou perda dos movimentos manuais intencionados e crises convulsivas graves. Caso 2 apresentou-se com comprometimento parcial dos movimentos manuais e sem história de crise convulsiva. As mutações distintas, D97Y e R294X, foram encontradas respectivamente em exons 3 e 4 do gene MECP2. CONCLUSÃO: A investigacao de mutações no gene MECP2 é importante na confirmação diagnóstica, investigação genótipo-fenótipo, e aconselhamento genético em síndrome de Rett.

Rett syndrome: clinical and epidemiological aspects in a Brazilian institution

Rett syndrome (RS) is a neurodevelopmental disorder, preferentially found in females and specifically involving the functions on which intelligence and its expression depend - learning, hand use and speech - leaving many others intact. Mutations have been identified at Xq28 on the MECP2 gene (methyl-CpG 2), which selectively silences the expression of other genes whose location is still unknown. This is a study on clinical, diagnostic and epidemiological aspects of RS in a Brazilian sample. It included 33 female patients with chronic encephalopathy without known etiology. RS was diagnosed in 24 patients (72.7 percent): 17 (70.8 percent) had classical RS; 5 (20.8 percent), atypical RS and 2 (8.4 percent), potential RS. In 9 girls clinical data and/or laboratory studies excluded diagnosis of RS. Among the atypical RS patients, 4 were form fruste and one, congenital form. Among the girls with other encephalopathies, cerebral malformation was the most frequent finding

Síndrome de Rett / Rett syndrome

A partir do que já se conhece sobre a síndrome de Rett, este artigo focaliza as informações mais recentes da literatura internacional sobre os aspectos genéticos e etiológicos desta condição, bem como sobre a sua identificação clínica e laboratorial, neuropatologia, eletrofisiologia, e evolução clínica (epilepsia, distúrbios respiratórios, distúrbios autonômicos e aspectos nutricionais), enfatizando, ainda, que, embora até recentemente tida como condição que afetava apenas o sexo feminino, também pode estar presente no sexo masculino, ainda que com fenótipo diverso