The genetic etiology is a relevant cause of central precocious puberty.

OBJECTIVES: The etiology of central precocious puberty (CPP) has expanded with identification of new genetic causes, including the monogenic deficiency of Makorin-Ring-Finger-Protein-3 (MKRN3). We aimed to assess the prevalence of CPP causes and the predictors of genetic involvement in this phenotype. DESIGN: A retrospective cohort study for an etiological survey of patients with CPP from a single academic center. METHODS: All patients with CPP had detailed medical history, phenotyping, and brain magnetic resonance imaging (MRI); those with negative brain MRI (apparently idiopathic) were submitted to genetic studies, mainly DNA sequencing studies, genomic microarray, and methylation analysis. RESULTS: We assessed 270 patients with CPP: 50 (18.5%) had CPP-related brain lesions (34 [68%] congenital lesions), whereas 220 had negative brain MRI. Of the latter, 174 (165 girls) were included for genetic studies. Genetic etiologies were identified in 22 patients (20 girls), indicating an overall frequency of genetic CPP of 12.6% (22.2% in boys and 12.1% in girls). The most common genetic defects were MKRN3, Delta-Like-Non-Canonical-Notch-Ligand-1 (DLK1), and Methyl-CpG-Binding-Protein-2 (MECP2) loss-of-function mutations, followed by 14q32.2 defects (Temple syndrome). Univariate logistic regression identified family history (odds ratio [OR] 3.3; 95% CI 1.3-8.3; P = .01) and neurodevelopmental disorders (OR 4.1; 95% CI 1.3-13.5; P = .02) as potential clinical predictors of genetic CPP. CONCLUSIONS: Distinct genetic causes were identified in 12.6% patients with apparently idiopathic CPP, revealing the genetic etiology as a relevant cause of CPP in both sexes. Family history and neurodevelopmental disorders were suggested as predictors of genetic CPP. We originally proposed an algorithm to investigate the etiology of CPP including genetic studies.

Genomic analysis in Chilean patients with suspected Rett syndrome: keep a broad differential diagnosis.

Introduction: Rett syndrome (RTT, MIM #312750) is a rare genetic disorder that leads to developmental regression and severe disability and is caused by pathogenic variants in the MECP2 gene. The diagnosis of RTT is based on clinical features and, depending on resources and access, on molecular confirmation. There is scarce information on molecular diagnosis from patients in Latin America, mostly due to limited availability and coverage of genomic testing. This pilot study aimed to implement genomic testing and characterize clinical and molecular findings in a group of Chilean patients with a clinical diagnosis of RTT. Methods: Twenty-eight patients with suspected RTT underwent characterization of phenotypic manifestations and molecular testing using Clinical Exome SolutionTM CES_V2 by SOPHiA Genetics. Data was analyzed using the commercial bioinformatics platform, SOPHiA DDMTM. A virtual panel of 34 genes, including MECP2 and other genes that are in the differential diagnosis of RTT, was used to prioritize initial analyses, followed by evaluation of the complete exome sequence data. Results: Twelve patients (42.8% of participants) had variants in MECP2, of which 11 (39.2%) were interpreted as pathogenic/likely pathogenic (P/LP), thus confirming the diagnosis of RTT in them. Eight additional patients (28.5%) harbored ten variants in nine other genes. Four of these variants were interpreted as P/LP (14.2%) (GRIN2B, MADD, TRPM3 and ZEB2) resulting in alternative neurodevelopmental diagnoses, and six were considered of uncertain significance. No evident candidate variant was found for eight patients. Discussion: This study allowed to reach a diagnosis in half of the participants. The diagnosis of RTT was confirmed in over a third of them, while others were found to have alternative neurodevelopmental disorders. Further evaluation is needed to identify the cause in those with negative or uncertain results. This information is useful for the patients, families, and clinicians to guide clinical management, even more so since the development of novel therapies for RTT. We also show the feasibility of implementing a step-wide approach to genomic testing in a setting with limited resources.

Aspectos neurobiológicos del Síndrome de Rett

El Síndrome de Rett es un trastorno monogénico ligado al cromosoma X, de carácter progresivo que afecta el neurodesarrollo principalmente de niñas durante las primeras etapas del ciclo vital. Su etiología se debe principalmente a las mutaciones de cambio de nucleótido único con pérdida de función del gen MECP2. Este gen codifica para la proteína del mismo nombre cuya principal función es actuar como un represor global de la transcripción mediante el reconocimiento de zonas metiladas de islas CpG y el reclutamiento de factores correpresores que modulan la expresión génica desacetilando histonas. Dentro de las principales alteraciones estructurales asociadas al síndrome se encuentran una morfología neuronal atípica con tamaño del soma neuronal y número de espinas dendríticas reducido, además de alteraciones neuroquímicas sobre todo en la señalización GABAérgica llevando a una desregulación entre señales excitatorias e inhibitorias, causando epilepsia. También se han descrito una serie de alteraciones metabólicas, oxidativas e inflamatorias. El tratamiento hasta ahora se ha enfocado más en buscar un alivio sintomático para las manifestaciones del síndrome pero se ha desarrollado recientemente terapia génica con el objetivo de tratar desde sus bases neurogenéticas la patología y evitar así el desarrollo alterado durante la niñez.

Rett Syndrome is a monogenic disorder linked to the X chromosome, of a progressive nature that affects neurodevelopment mainly in girls during the first stages of the life cycle. Its etiology is mainly due to loss-of-function single nucleotide change mutations of the MECP2 gene. This gene codes for the protein of the same name whose main function is to act as a global repressor of transcription through the recognition of methylated areas of CpG islands and the recruitment of corepressor factors that modulate gene expression by deacetylating histones. Among the main structural alterations associated with the syndrome are an atypical neuronal morphology with a size of the neuronal soma and a reduced number of dendritic spines, in addition to neurochemical alterations, especially in the GABAergic signal, leading to dysregulation between excitatory and inhibitory signals, causing epilepsy. A series of metabolic, oxidative, and inflammatory disorders have also been described. Until now, treatment has focused more on seeking symptomatic relief for the manifestations of the syndrome, but gene therapy has recently been developed with the aim of treating the pathology from its neurogenetic bases and thus avoiding altered development during childhood.

Methyl-CpG binding protein 2 is associated with the prognosis and mortality of elderly patients with hip fractures.

OBJECTIVES: To investigate the expression level and clinical significance of Methyl-CpG binding Protein 2 (MECP2) in elderly patients with hip fractures. METHODS: This prospective observational study included 367 elderly patients with hip fractures between April 2016 and December 2018. All the patients were treated with internal fixation or joint replacement. In addition, 50 healthy elderly individuals were enrolled as healthy controls. The serum levels of MECP2 and inflammatory factors Interleukin (IL)-1ß, IL-6, IL-8, and Tumor Necrosis Factor (TNF)-α was determined by enzyme-linked immunosorbent assay. Data on patients' basic characteristics and postoperative complications were collected. The Harris score was used to assess hip function at 1-month, 3-months, and 6-months after surgery. Patient quality of life was measured using the Barthel Index (BI) score 3-months after surgery. The 1-year mortality was analyzed using the Kaplan-Meier curve, and logical regression was used to analyze the risk factors for mortality. RESULTS: No significant differences were observed in the basic clinical characteristics of all patients. The serum MECP2 levels were remarkably high in patients with hip fractures and negatively correlated with serum IL-1ß, IL-6, and TNF-α levels. Patients with higher MECP2 predicted higher dynamic Harris scores, lower postoperative complications, lower 1-year mortality, and higher BI scores. Logical regression showed that age was the only independent risk factor for postoperative 1-year mortality in elderly patients with hip fractures. CONCLUSION: Lower MECP2 predicted poor prognosis and higher 1-year mortality in elderly patients with hip fractures.

Clinical significance of methyl-CpG binding protein 2 in postherpetic neuralgia: an observational study / Importancia clínica de la proteína 2 de unión a metil-CpG (MECP2) en la neuralgia posherpética: un estudio observacional

Abstract The present study was aimed to investigate the clinical significance of methyl-CpG binding protein 2 (MECP2) in patients with postherpetic neuralgia (PHN). This prospective case control study enrolled 319 cases of PHN patients from April 2017~December 2019. The patients' sleep quality and quality of life were evaluated using the Pittsburgh sleep quality score and the SF- 36 scale, respectively. The serum levels of MECP2, CRP, IL -6 and TNF-α were tested using enzyme linked immunosorbent assay (ELISA). The pain condition of the patients was evaluated using the visual analogue scale (VAS). The levels of MECP2 were significantly increased in PHN patients compared with the patients without PHN. Serum MECP2 levels were the highest in patients with severe pain, and were the lowest in patients with mild pain. Similarly, the frequency of severe pain in patients with low expression of MECP2 was significantly lower than the patients with higher MECP2 expression. Besides, serum levels of inflammatory factors CRP, IL -6 and TNF-α were markedly increased in PHN patients, which were also increased with the increase of the severity of pain. CRP, IL -6 and TNF-α were positively correlated with serum levels of MECP2 in PHN patients. Before the study, patients with lower MECP2 levels showed a significantly higher SF-36 score and lower Pittsburgh and VAS scores than patients with higher levels of MECP2. However, after one month, no significant difference was found between the patients. ROC curve showed MECP2 had the potential as a diagnostic biomarker for PHN. In conclusion, higher serum MECP2 levels are associated with a more severe pain condition and increased release of inflammatory factors.

Resumen El objetivo de este estudio fue investigar la importancia clínica de la MECP2 en pacientes con neuralgia posherpética (NPH). Este estudio observacional prospectivo incluyó 319 pacientes con NPH entre abril de 2017 y diciembre de 2019. La calidad del sueño y la calidad de vida de los pacientes se evaluaron con la escala de calidad del sueño de Pittsburgh y la escala SF - 36, respectivamente. Los niveles séricos de MECP2, PCR, IL -6 y TNF-α fueron determinados por ELISA. Se utilizó la escala visual analógica (EVA) para evaluar la intensidad del dolor. Los niveles de MECP2 en pacientes con NPH aumentaron significativamente en comparación con los pacientes sin NPH. El nivel sérico de MECP2 fue más alto en pacientes con dolor grave y el más bajo en pacientes con dolor leve. Además, la incidencia de dolor grave en pacientes con baja expresión de MECP2 fue significativamente menor que en pacientes con alta expresión de MECP2. Además, los niveles séricos de PCR, IL -6 y TNF-α aumentaron significativamente en pacientes con NPH, y se incrementaron con el aumento del grado de dolor. Los niveles séricos de PCR, IL -6 y TNF-α en pacientes con NPH se correlacionaron positivamente con los niveles séricos de MECP2. Antes del estudio, los pacientes con niveles más bajos de MECP2 tenían puntuaciones significativamente más altas de SF - 36, y puntuaciones más bajas de Pittsburgh y EVA que los pacientes con niveles más altos de MECP2. Sin embargo, no se encontraron diferencias significativas entre los pacientes un mes después. Las curvas ROC mostraron que la MECP2 podría ser un biomarcador de diagnóstico para la NPH. En general, los niveles séricos más altos de la MECP2 se asociaron con condiciones de dolor más graves y un aumento de la liberación de factores inflamatorios.

Ancestry-dependent genetic structure of the Xq28 risk haplotype in the Mexican population and its association with childhood-onset systemic lupus erythematosus.

Objective: Here we aimed to investigate the association of the Xq28 risk haplotype (H1) with susceptibility to childhood-onset systemic lupus erythematosus (SLE), and to compare its frequency and genetic structure in the Mexican population with those in other continental populations. Methods: We genotyped 15 single-nucleotide variants (SNVs) that form the H1 haplotype, using TaqMan real-time PCR. The association analysis [case-control and transmission disequilibrium test (TDT)] included 376 cases and 400 adult controls, all of whom were mestizos (MEZ). To identify risk alleles in Mexican Indigenous individuals, SNVs were imputed from whole-exome sequencing data of 1,074 individuals. The allelic frequencies determined in MEZ and Indigenous individuals were compared with those of the continental populations from the 1,000 Genomes database phase 3. Linkage disequilibrium (LD) analysis of risk alleles was performed on all populations. Interleukin-1 receptor associated kinase 1 (IRAK1) and methyl CpG binding protein 2 (MECP2) mRNA levels were determined using real-time PCR. Results: Case-control analysis revealed genetic association with childhood-onset SLE for all 15 SNVs (OR = 1.49-1.75; p = 0.0095 to 1.81 × 10-4) and for the Xq28 risk haplotype (OR = 1.97, p = 4 × 10-6). Comparing with individuals of European ancestry (0.14-0.16), the frequencies of the risk alleles were significantly higher in the MEZ individuals (0.55-0.68) and even higher in Indigenous individuals (0.57-0.83). LD analysis indicated a differential haplotype structure within the Indigenous groups, which was inherited to the MEZ population as a result of genetic admixture. Individuals homozygous for the Xq28 risk haplotype exhibited decreased levels of both MECP2A and B transcripts. Conclusion: We found that the H1 risk haplotype differs in its conformation in the Mexican population. This difference could be attributed to positive selection within the Indigenous population, with its inheritance now having an autoimmune health impact in both the Mexican Indigenous and MEZ populations.

Methyl-CpG binding protein 2 is associated with the prognosis and mortality of elderly patients with hip fractures

ABSTRACT Objectives To investigate the expression level and clinical significance of Methyl-CpG binding Protein 2 (MECP2) in elderly patients with hip fractures. Methods This prospective observational study included 367 elderly patients with hip fractures between April 2016 and December 2018. All the patients were treated with internal fixation or joint replacement. In addition, 50 healthy elderly individuals were enrolled as healthy controls. The serum levels of MECP2 and inflammatory factors Interleukin (IL)-1β, IL-6, IL-8, and Tumor Necrosis Factor (TNF)-α was determined by enzyme-linked immunosorbent assay. Data on patients' basic characteristics and postoperative complications were collected. The Harris score was used to assess hip function at 1-month, 3-months, and 6-months after surgery. Patient quality of life was measured using the Barthel Index (BI) score 3-months after surgery. The 1-year mortality was analyzed using the Kaplan-Meier curve, and logical regression was used to analyze the risk factors for mortality. Results No significant differences were observed in the basic clinical characteristics of all patients. The serum MECP2 levels were remarkably high in patients with hip fractures and negatively correlated with serum IL-1β, IL-6, and TNF-α levels. Patients with higher MECP2 predicted higher dynamic Harris scores, lower postoperative complications, lower 1-year mortality, and higher BI scores. Logical regression showed that age was the only independent risk factor for postoperative 1-year mortality in elderly patients with hip fractures. Conclusion Lower MECP2 predicted poor prognosis and higher 1-year mortality in elderly patients with hip fractures.

Molecular and clinical insights into complex genomic rearrangements related to MECP2 duplication syndrome.

MECP2 duplication syndrome (MDS) is caused by copy number variation (CNV) spanning the MECP2 gene at Xq28 and is a major cause of intellectual disability (ID) in males. Herein, we describe two unrelated males harboring non-recurrent complex Xq28 rearrangements associated with MDS. Copy number gains were initially detected by quantitative real-time polymerase chain reaction and further delineated by high-resolution array comparative genomic hybridization, familial segregation, expression analysis and X-chromosome inactivation (XCI) evaluation in a carrier mother. SNVs within the rearrangements and/or fluorescent in situ hybridization (FISH) were used to assess the parental origin of the rearrangements. Patient 1 exhibited an intrachromosomal rearrangement, whose structure is consistent with a triplicated segment presumably embedded in an inverted orientation between two duplicated sequences (DUP-TRP/INV-DUP). The rearrangement was inherited from the carrier mother, who exhibits extreme XCI skewing and subtle psychiatric symptoms. Patient 2 presented a de novo (X;Y) unbalanced translocation resulting in duplication of Xq28 and deletion of Yp, originated in the paternal gametogenesis. Neurodevelopmental trajectory and non-neurological symptoms were consistent with previous reports, with the exception of cerebellar vermis hypoplasia in patient 2. Although both patients share the core MDS phenotype, patient 1 showed MECP2 transcript levels in blood similar to controls. Understanding the molecular mechanisms related to MDS is essential for designing targeted therapeutic strategies.

[Rett syndrome: report of a new pathogenic variant and review of the literature regarding two clinical cases.] / Síndrome de Rett: reporte de una nueva variante patogénica y revisión de la literatura a propósito de dos casos clínicos.

INTRODUCCIÓN: El síndrome de Rett es un trastorno del neurodesarrollo con una frecuencia estimada de 1/10,000 recién nacidos vivos, el cual se presenta con un modelo de herencia ligado al cromosoma X. Las variantes patogénicas en el gen MECP2, el cual codifica para una proteína que participa en el desarrollo y la diferenciación del sistema nervioso central, causan este síndrome. El objetivo de este trabajo fue describir dos casos de síndrome de Rett, uno de ellos con una nueva variante del gen MECP2. CASOS CLÍNICOS: El primer caso se trata de una paciente de 5 años con microcefalia y regresión del neurodesarrollo desde los 3 años. Clínicamente se diagnosticó de síndrome de Rett en estadio III. Se realizó la secuenciación del gen MECP2 y se identificó una variante probablemente patogénica en estado heterocigoto, c.606delC (p.Thr203Argfs*7), que no ha sido reportada previamente. El segundo caso es una paciente de 17 años, referida por discapacidad intelectual grave, que se encontró clínicamente en estadio IV. Se realizó la secuenciación de MECP2 y se identificó una variante patogénica [c.880C>T(p.Arg294*)] ya descrita previamente. CONCLUSIONES: El diagnóstico clínico de síndrome de Rett se llevó a cabo con criterios establecidos. La confirmación diagnóstica fue mediante la secuenciación de MECP2. Para el correcto abordaje de los trastornos del neurodesarrollo es primordial conocer el fenotipo de síndrome de Rett, así como optar por el análisis molecular para la confirmación del diagnóstico. Los pacientes con síndrome de Rett requieren un seguimiento interdisciplinario para disminuir el impacto de las complicaciones. BACKGROUND: Rett syndrome is an X-linked neurodevelopmental disorder with an estimated frequency of 1/10,000 live births caused by hetereozygous pathogenic variants in the MECP2 gene, whose protein participates in the development and differentiation of the central nervous system. This study aimed to describe two cases with Rett syndrome diagnosis, one of them with a new variant of the MECP2 gene. CASE REPORTS: We first describe the case of a 5-year-old female with microcephaly and neurodevelopmental regression starting at 3 years old, clinically corresponding to stage III Rett syndrome. Sequencing of the MECP2 gene identified a heterozygous likely pathogenic variant [c.606delC (p.Thr203Argfs*7)] not reported previously. The second case is a 17-year-old female, referred due to severe intellectual disability, clinically found on stage IV. MECP2 sequencing was performed identifying a pathogenic variant previously described [c.880C> T (p.Arg294 *)]. CONCLUSIONS: Rett syndrome clinical diagnosis was carried out based on established criteria. MECP2 sequencing confirmed the diagnosis. For neurodevelopmental disorders approach, it is essential to know the phenotype of Rett syndrome and select the molecular tool for the diagnosis. Patients with Rett syndrome require interdisciplinary follow-up for reducing the impact of complications.

Síndrome de Rett: reporte de una nueva variante patogénica y revisión de la literatura a propósito de dos casos clínicos / Rett syndrome: report of a new pathogenic variant and review of the literature regarding two clinical cases

Resumen Introducción: El síndrome de Rett es un trastorno del neurodesarrollo con una frecuencia estimada de 1/10,000 recién nacidos vivos, el cual se presenta con un modelo de herencia ligado al cromosoma X. Las variantes patogénicas en el gen MECP2, el cual codifica para una proteína que participa en el desarrollo y la diferenciación del sistema nervioso central, causan este síndrome. El objetivo de este trabajo fue describir dos casos de síndrome de Rett, uno de ellos con una nueva variante del gen MECP2. Casos clínicos: El primer caso se trata de una paciente de 5 años con microcefalia y regresión del neurodesarrollo desde los 3 años. Clínicamente se diagnosticó de síndrome de Rett en estadio III. Se realizó la secuenciación del gen MECP2 y se identificó una variante probablemente patogénica en estado heterocigoto, c.606delC (p.Thr203Argfs*7), que no ha sido reportada previamente. El segundo caso es una paciente de 17 años, referida por discapacidad intelectual grave, que se encontró clínicamente en estadio IV. Se realizó la secuenciación de MECP2 y se identificó una variante patogénica [c.880C>T(p.Arg294*)] ya descrita previamente. Conclusiones: El diagnóstico clínico de síndrome de Rett se llevó a cabo con criterios establecidos. La confirmación diagnóstica fue mediante la secuenciación de MECP2. Para el correcto abordaje de los trastornos del neurodesarrollo es primordial conocer el fenotipo de síndrome de Rett, así como optar por el análisis molecular para la confirmación del diagnóstico. Los pacientes con síndrome de Rett requieren un seguimiento interdisciplinario para disminuir el impacto de las complicaciones.

Abstract Background: Rett syndrome is an X-linked neurodevelopmental disorder with an estimated frequency of 1/10,000 live births caused by hetereozygous pathogenic variants in the MECP2 gene, whose protein participates in the development and differentiation of the central nervous system. This study aimed to describe two cases with Rett syndrome diagnosis, one of them with a new variant of the MECP2 gene. Case reports: We first describe the case of a 5-year-old female with microcephaly and neurodevelopmental regression starting at 3 years old, clinically corresponding to stage III Rett syndrome. Sequencing of the MECP2 gene identified a heterozygous likely pathogenic variant [c.606delC (p.Thr203Argfs*7)] not reported previously. The second case is a 17-year-old female, referred due to severe intellectual disability, clinically found on stage IV. MECP2 sequencing was performed identifying a pathogenic variant previously described [c.880C> T (p.Arg294 *)]. Conclusions: Rett syndrome clinical diagnosis was carried out based on established criteria. MECP2 sequencing confirmed the diagnosis. For neurodevelopmental disorders approach, it is essential to know the phenotype of Rett syndrome and select the molecular tool for the diagnosis. Patients with Rett syndrome require interdisciplinary follow-up for reducing the impact of complications.

Longitudinal Evaluation of the Stability of Hand Function in Rett Syndrome.

OBJECTIVE: To investigate the longitudinal stability of hand function in Rett syndrome and to analyze further the relationships between stability of hand function and genotype, age, and walking ability. STUDY DESIGN: Longitudinal video data of functional abilities of individuals with genetically confirmed Rett syndrome were collected by families of individuals registered with the Australian Rett Syndrome Database. A total of 120 individuals provided 290 recordings from which 170 observation pairs were available for comparison. The Rett Syndrome Hand Function Scale was used to classify a level of hand function observed in each video on a range from unable to grasp, pick up, and hold objects to skillful manipulation of large and small objects. RESULTS: Approximately one-third of the population lost some hand function over time. Younger children (<6 years) rather than adults were at greater risk of deterioration in hand function. Clinical severity, as indicated by walking ability or genotype, played a lesser role. There was no identified pattern between genotype and the stability of hand function skills. Rather, mutations associated with milder (p.Arg133Cys, p.Arg294∗) and greater (p.Arg106Trp, p.Thr158Met) clinical severity were both associated with greater risks of decline. CONCLUSIONS: Genotype was a lesser predictor of loss of hand function beyond the early regression period, and younger children were particularly vulnerable to further loss of hand function compared with adults.

MeCP2 Deficiency Disrupts Kainate-Induced Presynaptic Plasticity in the Mossy Fiber Projections in the Hippocampus.

Methyl cytosine binding protein 2 (MeCP2) is a structural chromosomal protein involved in the regulation of gene expression. Mutations in the gene encoding MeCP2 result in Rett Syndrome (RTT), a pervasive neurodevelopmental disorder. RTT is one of few autism spectrum disorders whose cause was identified as a single gene mutation. Remarkably, abnormal levels of MeCP2 have been associated to other neurodevelopmental disorders, as well as neuropsychiatric disorders. Therefore, many studies have been oriented to investigate the role of MeCP2 in the nervous system. In the present work, we explore cellular and molecular mechanisms affecting synaptic plasticity events in vivo in the hippocampus of MeCP2 mutant mice. While most studies addressed postsynaptic defects in the absence of MeCP2, we took advantage of an in vivo activity-paradigm (seizures), two models of MeCP2 deficiency, and neurobiological assays to reveal novel defects in presynaptic structural plasticity in the hippocampus in RTT rodent models. These approaches allowed us to determine that MeCP2 mutations alter presynaptic components, i.e., disrupts the plastic response of mossy fibers to synaptic activity and results in reduced axonal growth which is correlated with imbalanced trophic and guidance support, associated with aberrant expression of brain-derived neurotrophic factor and semaphorin 3F. Our results also revealed that adult-born granule cells recapitulate maturational defects that have been only shown at early postnatal ages. As these cells do not mature timely, they may not integrate properly into the adult hippocampal circuitry. Finally, we performed a hippocampal-dependent test that revealed defective spatial memory in these mice. Altogether, our studies establish a model that allows us to evaluate the effect of the manipulation of specific pathways involved in axonal guidance, synaptogenesis, or maturation in specific circuits and correlate it with changes in behavior. Understanding the mechanisms underlying the neuronal compromise caused by mutations in MeCP2 could provide information on the pathogenic mechanism of autistic spectrum disorders and improve our understanding of brain development and molecular basis of behavior.

Altered Gene Expression of Thyroid Hormone Transporters and Deiodinases in iPS MeCP2-Knockout Cells-Derived Neurons.

MeCP2 is an X-linked gene; its mutation causes Rett Syndrome (RTT), a severe neurodevelopmental disability that affects mainly girls. Acting as a transcription factor, the MeCP2 protein is able to regulate several hormone-related genes, such as the thyroid hormones (TH), which are known to play an important role in the development of the central nervous system (CNS). Although only a few studies have associated RTT and TH, TH deficit can lead to neurological deregulation by triggering functional deficiencies during adulthood. Here, we used human-induced pluripotent stem cell (iPSC) to generate MeCP2-knockout neuronal progenitor cells and adult neurons. Using this cellular model, we then investigated the expression of genes associated with TH homeostasis, such as the TH transporters (LAT1, LAT2, MCT8, MCT10, and OATP4A1) and deiodinases (DIO1, 2, and 3). Then, we treated the neural cells with THs and analyzed the expression of several genes related to neurodevelopment and functional maintenance. Our results showed that several TH-related genes, such as deiodinases, are altered in RTT samples when compared to WT cells. Moreover, the treatment of the neural cells with THs increased the amount of MAP2 and synapsin-1 expression in RTT cells. Our work provided evidences that TH homeostasis is compromised in RTT-derived neural cells, which could be an important factor to contribute to the imbalance in the neurodevelopmental phenotype presented in this syndrome and can lead us to better understand other neurodevelopmental diseases.

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.

P152R Mutation Within MeCP2 Can Cause Loss of DNA-Binding Selectivity.

MeCP2 is a protein highly expressed in the brain that participates in the genetic expression and RNA splicing regulation. MeCP2 binds preferably to methylated DNA and other nuclear corepressors to alter chromatin. MECP2 gene mutations can cause rett syndrome (RTT), a severe neurological disorder that affects around one in ten thousand girls. In this paper, Molecular Dynamics (MD) simulations were performed to scrutinize how the MeCP2 P152R mutation influences the protein binding to DNA. Also, the Umbrella Sampling technique was used to obtain the potential mean forces (PMFs) of both wild-type and mutated MeCP2 Methyl-CpG-binding domain (MBD) binding to both non-methylated and methylated DNA. P152R is a common missense mutation in MBD associated with RTT; however, there are no studies that explain how it causes protein dysfunction. The results from this study hypothesize that P152R mutation leads to MBD binding more strongly to DNA, while selectively decreasing binding affinity to methylated DNA. These provide an explanation for previous not conclusive experimental results regarding the mechanism of how this mutation affects the binding of the protein to DNA, and subsequently its effects on RTT. Furthermore, the results of this research-in-progress can be used as the basis for further investigations into the molecular basis of RTT and to potentially reveal a target for therapy in the future.

Alterations in the MicroRNA of the Blood of Autism Spectrum Disorder Patients: Effects on Epigenetic Regulation and Potential Biomarkers.

Aims: Autism spectrum disorder (ASD) refers to a group of heterogeneous brain-based neurodevelopmental disorders with different levels of symptom severity. Given the challenges, the clinical diagnosis of ASD is based on information gained from interviews with patients' parents. The heterogeneous pathogenesis of this disorder appears to be driven by genetic and environmental interactions, which also plays a vital role in predisposing individuals to ASD with different commitment levels. In recent years, it has been proposed that epigenetic modifications directly contribute to the pathogenesis of several neurodevelopmental disorders, such as ASD. The microRNAs (miRNAs) comprises a species of short noncoding RNA that regulate gene expression post-transcriptionally and have an essential functional role in the brain, particularly in neuronal plasticity and neuronal development, and could be involved in ASD pathophysiology. The aim of this study is to evaluate the expression of blood miRNA in correlation with clinical findings in patients with ASD, and to find possible biomarkers for the disorder. Results: From a total of 26 miRNA studied, seven were significantly altered in ASD patients, when compared to the control group: miR34c-5p, miR92a-2-5p, miR-145-5p and miR199a-5p were up-regulated and miR27a-3p, miR19-b-1-5p and miR193a-5p were down-regulated in ASD patients. Discussion: The main targets of these miRNAs are involved in immunological developmental, immune response and protein synthesis at transcriptional and translational levels. The up-regulation of both miR-199a-5p and miR92a-2a and down-regulation of miR-193a and miR-27a was observed in AD patients, and may in turn affect the SIRT1, HDAC2, and PI3K/Akt-TSC:mTOR signaling pathways. Furthermore, MeCP2 is a target of miR-199a-5p, and is involved in Rett Syndrome (RTT), which possibly explains the autistic phenotype in male patients with this syndrome.

Síndrome de Rett: revisión de la literatura con primeros casos reportados en Colombia con caracterización clínica y molecular / Rett syndrome: review of the literature and first cases reported in Colombia with clinical characterization and molecular diagnosis

RESUMEN INTRODUCCIÓN: El síndrome de Rett es una condición neurológica severa y la segunda causa genética de retraso mental profundo en mujeres. Se genera por mutaciones en el gen MECP2 y es caracterizada por una pérdida de las ganancias psicomotoras, con una prevalencia general estimada de 1:10.000 niñas, según la extrapolación de algunos estudios europeos. OBJETIVOS: Realizar una revisión de la literatura sobre el síndrome de Rett y presentar una serie de casos diagnosticados en Colombia por clínica y prueba molecular. METODOLOGÍA: Se efectuó una búsqueda bibliográfica y de reportes de casos en 21 bases de datos internacionales, más de 14 revistas del área de la salud y dos motores de búsqueda generales entre 2014 y 2016. Los casos presentados fueron seleccionados de la consulta de genética médica realizada por los autores. HALLAZGOS: No se encontró ningún caso colombiano de síndrome de Rett, ni confirmado con prueba molecular en Latinoamérica. Se reporta así la primera serie de casos nacional y la mayor latinoamericana, conformada por siete pacientes con tipo clásico y tres atípicos, todas con diagnóstico molecular. CONCLUSIONES: Pese a tener una evolución clínica caracterizada, su baja prevalencia y amplio espectro clínico convierten al síndrome de Rett en un reto diagnóstico y terapéutico. La mutación c.749_750insT se reporta por primera vez, la c.473C>G por segunda en la literatura y la c.763C>T se presenta en dos pacientes con fenotipos totalmente distintos, lo que confirma la no correlación genotipo-fenotipo de la enfermedad.

SUMMARY INTRODUCTION: Rett Syndrome is a severe neurological condition and the second genetic cause of profound mental retardation in women. It is generated by mutations in the MECP2 gene and it is characterized by a loss of psychomotor gains, with an estimated overall prevalence of 1:10,000 girls, according to the extrapolation of some European studies. Objectives. To make a review of Rett Syndrome and to present a series of cases diagnosed in Colombia by clinical criteria and molecular tests. METHODOLOGY: We made a bibliographic research in 21 international databases, more than 14 health journals and two general search engines between 2014 and 2016. The cases presented were selected from the Medical Genetics consultation carried out by the authors. FINDINGS: No Colombian case of Rett Syndrome was found nor confirmed with molecular testing in Latin America. We report the first cases in Colombia and the largest in Latin America, consisting of seven patients with classic type and three with atypical type, all with molecular diagnosis. CONCLUSIONS: In spite of having a characterized clinical evolution, its low prevalence and broad clinical spectrum, make Rett Syndrome a diagnostic and therapeutic challenge. We report for the first time the mutation c.749_750insT, the c.473C> G for second time in the literature and the c.763C> T is presented in two patients with totally different phenotypes, confirming the non-correlation genotype-phenotype of the disease.

Mecp2 Mediates Experience-Dependent Transcriptional Upregulation of Ryanodine Receptor Type-3.

Mecp2 is a DNA methylation reader that plays a critical role in experience-dependent plasticity. Increasing evidence supports a role for epigenetic modifications in activity-induced gene expression. Hence, candidate genes related to such phenomena are of great interest. Ryanodine receptors are intracellular calcium channels that contribute to hippocampal synaptic plasticity, dendritic spine remodeling, and participate in learning and memory processes. Here we exposed mice to the enriched environment (EE) paradigm, which through increased stimulation induces experience dependent-plasticity, to explore a role for methyl-cytosines, and Mecp2 in directing Ryanodine receptor 3 (Ryr3) transcriptional activity. EE induced a hippocampal-specific increase in the methylation of discrete cytosines located at a Ryr3 isoform promoter; chromatin immunoprecipitation experiments revealed that EE increased Mecp2 binding to this Ryr3 isoform promoter. Interestingly, the experimental paradigm induced robust Ryr3 upregulation, accompanied by miR132-dependent suppression of p250GAP, a pathway driving synaptogenesis. In contrast to WT mice, Mecp2-null mice showed diminished levels of Ryr3 and displayed impaired EE-induced Ryr3 upregulation, compromising miR132 dependent suppression of p250GAP and experience-dependent structural plasticity. Based on these results, we propose that Mecp2 acts as a transcriptional activator of Ryr3, contributing to experience-dependent plasticity.

Phenotype Differentiation of FOXG1 and MECP2 Disorders: A New Method for Characterization of Developmental Encephalopathies.

OBJECTIVE: To differentiate developmental encephalopathies by creating a novel quantitative phenotyping tool. STUDY DESIGN: We created the Developmental Encephalopathy Inventory (DEI) to differentiate disorders with complex multisystem neurodevelopmental symptoms. We then used the DEI to study the phenotype features of 20 subjects with FOXG1 disorder and 11 subjects with MECP2 disorder. RESULTS: The DEI identified core domains of fine motor and expressive language that were severely impaired in both disorders. Individuals with FOXG1 disorder were overall more severely impaired. Subjects with FOXG1 disorder were less able to walk, had worse fine motor skills, more disability in receptive language and reciprocity, and had more disordered sleep than did subjects with MECP2 disorder (P <.05). Covariance, cluster, and principal component analysis confirmed a relationship between impaired awareness, reciprocity, and language in both disorders. In addition, abnormal ambulation was a first principal component for FOXG1 but not for MECP2 disorder, suggesting that impaired ambulation is a strong differentiating factor clinically between the 2 disorders. CONCLUSIONS: We have developed a novel quantitative developmental assessment tool for developmental encephalopathies and propose this tool as a method to identify and illustrate core common and differential domains of disability in these complex disorders. These findings demonstrate clear phenotype differences between FOXG1 and MECP2 disorders.

Characterization of the Relationship of CDKL5 with MeCP2 and Dnmt1 in PrimaryRat Cortical Neurons

ABSTRACT Cyclin-dependent kinase-like 5 (CDKL5) is a protein kinase that is homologous to mitogen-activated protein kinases (MAPKs) and cyclin-dependent kinases (CDKs). Mutations in the CDKL5 gene cause X-linked infantile spasms and phenotypes that overlap with that of Rett syndrome, which is a neurodevelopmental disorder caused primarily by mutations in the methyl CpG binding protein 2 gene (MECP2). Previous studies in transfected cell lines showed that CDKL5 interacts with MeCP2 and DNA (cytosine-5)-methyltransferase 1 (Dnmt1). However, little is known about the relationships of CDKL5 with interacting proteins in primary neuronal cultures. In this study, we investigated the expression patterns of CDKL5, MeCP2 and Dnmt1, and their interaction in cultured rat cortical neurons. Using real-time PCR analysis, we found that CDKL5, MeCP2 and Dnmt1 have similar expression patterns at the mRNA level. In contrast, the expression patterns of those proteins at the protein level are different and could be inversely correlated, as shown by western blotting. Using co-immunoprecipitation, we further demonstrated that CDKL5 interacts with MeCP2 and Dnmt1 in primary rat cortical neurons. These data suggest that a functional link exists among CDKL5, MeCP2 and Dnmt1 during neuronal development and may provide further insight into the pathogenesis of Rett syndrome.