Fragile X Syndrome in children

Fragile X syndrome is caused by the expansion of CGG triplets in the FMR1 gene, which generates epigenetic changes that silence its expression. The absence of the protein coded by this gene, FMRP, causes cellular dysfunction, leading to impaired brain development and functional abnormalities. The physical and neurologic manifestations of the disease appear early in life and may suggest the diagnosis. However, it must be confirmed by molecular tests. It affects multiple areas of daily living and greatly burdens the affected individuals and their families. Fragile X syndrome is the most common monogenic cause of intellectual disability and autism spectrum disorder; the diagnosis should be suspected in every patient with neurodevelopmental delay. Early interventions could improve the functional prognosis of patients with Fragile X syndrome, significantly impacting their quality of life and daily functioning. Therefore, healthcare for children with Fragile X syndrome should include a multidisciplinary approach.

El síndrome de X frágil es causado por la expansión de tripletas CGG en el gen FMR1, el cual genera cambios epigenéticos que silencian su expresión. La ausencia de la proteína codificada por este gen, la FMRP, causa disfunción celular, llevando a deficiencia en el desarrollo cerebral y anormalidades funcionales. Las manifestaciones físicas y neurológicas de la enfermedad aparecen en edades tempranas y pueden sugerir el diagnóstico. Sin embargo, este debe ser confirmado por pruebas moleculares. El síndrome afecta múltiples aspectos de la vida diaria y representa una alta carga para los individuos afectados y para sus familias. El síndrome de C frágil es la causa monogénica más común de discapacidad intelectual y trastornos del espectro autista; por ende, el diagnóstico debe sospecharse en todo paciente con retraso del neurodesarrollo. Intervenciones tempranas podrían mejorar el pronóstico funcional de pacientes con síndrome de X frágil, impactando significativamente su calidad de vida y funcionamiento. Por lo tanto, la atención en salud de niños con síndrome de X frágil debe incluir un abordaje multidisciplinario.

Effect of CYFIP2 overexpression on biological function and Wnt/β-catenin signaling pathway of bladder cancer cell line T24 / 国际生物医学工程杂志

Objective:To investigate the effects of cytoplasmic fragile X mental retardation protein 1 binding protein 2 (CYFIP2) overexpression on the biological functions and Wnt/β-catenin signaling pathways of bladder cancer T24 cells.Methods:The control group was T24 cells transfected with the empty pcDNA3 vector, and the overexpression group was T24 cells transfected with the CYFIP2 overexpression vector. The expression of CYFIP2 mRNA and protein was detected by reverse transcriptase, quantitative polymerase chain reaction, and Western Blot. The effect of CYFIP2 overexpression on T24 cell proliferation was detected by CCK-8. The effect of CYFIP2 overexpression on T24 cell migration and invasion was detected by Transwell. The effects of CYFIP2 overexpression on Wnt/β-catenin signaling pathway in T24 cells were detected by Western Blot.Results:Compared with the control group, the expression levels of CYFIP2 mRNA and protein were increased in the overexpression group (all P < 0.001), and the cell proliferation, migration, and invasion abilities were reduced (all P < 0.01). β-catenin, c-Myc, and Cyclin D1 protein expression were down-regulated in CYFIP2 overexpressed T24 cells (all P < 0.05), while the protein levels of p-β-catenin were increased ( P < 0.05). Conclusions:CYFIP2 overexpression can inhibit T24 cell proliferation, migration, and invasion, and its possible molecular mechanism is related to the inhibition of Wnt/β-catenin signaling pathway.

Advances in the molecular mechanism and diagnosis and treatment of fragile X syndrome / 中国医师杂志

Fragile X syndrome (FXS) is the most common monogenic disease that causes intellectual disability and autism spectrum disorder (ASD),causing moderate to severe mental retardation with unusual facial features and connective tissue abnormalities.Fragile X syndrome is caused by the mutation of FMR1 gene,resulting in the reduction or loss of its product,fragile X mental retardation protein (FMRP).The diagnosis is mainly based on the detection of FMR1 gene,and there is no effective treatment for fragile X syndrome.Therefore,it is very important to strengthen genetic counseling and prenatal diagnosis,and effectively reduce the incidence of fragile X syndrome.

Prenatal diagnosis and genetic counseling of fragile X syndrome in four pedigrees by using high-resolution multiplex polymerase chain reaction / 中华围产医学杂志

Objectives To provide prenatal diagnosis and genetic counseling for four athigh-risk pregnant women with a suspected family or personal history of fragile X syndrome (FXS) by genetic screening of fragile X mental retardation (FMR1) gene.Methods This study was conducted on four pregnant women (No.l to 4) who received outpatient treatment in Peking University First Hospital from August 2014 to June 2016.Genomic DNA was extracted from peripheral blood samples of the pregnant women and six of their family members,four of which were suspected or confirmed FXS and the other two were FMR1 gene carriers.Amplide X kits were used to detect CGG repeat size in FMR1 gene.Two amniocytes and one chorionic villi samples were collected from three pregnant women to extract DNAs for FMR1 gene and karyotyping analyses.Results There were patients diagnosed with FXS in all the families by detecting CGG repeat numbers in FMR1 gene.The pregnant woman No.1 was a permutation carrier;No.2 carried normal FMR1 alleles while her brother had a mutation with over 20 CGG repeats in FMRI gene at chromosome X.No.3 and 4 were full mutation carriers with over 200 CGG repeats in FMR1 gene.After genetic counseling,No.3 decided to terminate the pregnancy due to abnormal fetal karyotype (47,XY,+21) and full mutation of FMR1 alleles.No.1 and 4 continued to pregnancy as their fetuses were normal in FMR1 alleles and karyotype.No.2 continued to pregnancy as her fetus was free of FXS risk.Conclusions Prenatal diagnosis and genetic counseling should be conducted on women at highrisk for FXS to avoid birth defects.People with a family history of FXS should be tested for FMR1 gene carrier status.

Altered Translational Control of Fragile X Mental Retardation Protein on Myelin Proteins in Neuropsychiatric Disorders

Myelin is a specialized structure of the nervous system that both enhances electrical conductance and insulates neurons from external risk factors. In the central nervous system, polarized oligodendrocytes form myelin by wrapping processes in a spiral pattern around neuronal axons through myelin-related gene regulation. Since these events occur at a distance from the cell body, post-transcriptional control of gene expression has strategic advantage to fine-tune the overall regulation of protein contents in situ. Therefore, many research interests have been focused to identify RNA binding proteins and their regulatory mechanism in myelinating compartments. Fragile X mental retardation protein (FMRP) is one such RNA binding protein, regulating its target expression by translational control. Although the majority of works on FMRP have been performed in neurons, it is also found in the developing or mature glial cells including oligodendrocytes, where its function is not well understood. Here, we will review evidences suggesting abnormal translational regulation of myelin proteins with accompanying white matter problem and neurological deficits in fragile X syndrome, which can have wider mechanistic and pathological implication in many other neurological and psychiatric disorders.

Fragile X Syndrome / Síndrome de X Frágil

Fragile X Syndrome (FXS) is a genetic disease due to a CGG trinucleotide expansion, named full mutation (greater than 200 CGG repeats), in the FMR1 gene locus Xq27.3; which leads to an hypermethylated region in the gene promoter therefore silencing it and lowering the expression levels of FMRP, a protein involved in synaptic plasticity and maturation. Individuals with FXS present with intellectual disability, autism, hyperactivity, long face, large or prominent ears and macroorchidism at puberty and thereafter. Most of the young children with FXS will present with language delay, sensory hyper arousal and anxiety. Girls are less affected than boys, only 25% have intellectual disability. Given the genomic features of the syndrome, there are patients with a number of triplet repeats between 55 and 200, known as premutation (PM) carriers. Most carriers have a normal IQ but some have developmental problems. The diagnosis of FXS has evolved from karyotype with special culture medium, to molecular techniques that are more sensitive and specific including PCR and Southern Blot. During the last decade, the advances in the knowledge of FXS, has led to the development of investigations on pharmaceutical management or targeted treatments for FXS. Minocycline and sertraline have shown efficacy in children.

El Síndrome de X Frágil (SXF), es una enfermedad genética debida a una expansión del trinucleótido CGG, nombrada mutación completa (más de 200 repeticiones de CGG) en el gen FMR1, locus Xq27.3; la cual lleva a una hipermetilación de la región promotora del gen, silenciándolo y disminuyendo los niveles de expresión de la proteína FMRP relacionada con la plasticidad y maduración neuronal. Los individuos con SXF presentan retardo mental, autismo, hiperactividad, cara alargada, orejas grandes o prominentes y macroorquidismo desde la pubertad. La mayoría de niños con SXF presentan retraso en el lenguaje, hiperactivación sensorial y ansiedad. Las niñas se afectan menos que los varones, solo el 25% presenta retardo mental. Dadas las características genómicas del síndrome, existen pacientes con un número de repetición de la tripleta entre 55 y 200 que se denominan portadores de la premutación. La mayoría de los portadores tienen un coeficiente intelectual normal, pero presentan problemas en el desarrollo. El diagnóstico en SXF ha evolucionado del cariotipo con medio especial de cultivo, a pruebas moleculares más sensibles y específicas incluyendo PCR y Southern blot. Durante la última década, los avances en el conocimiento sobre el SXF han permitido el desarrollo de investigaciones sobre el manejo farmacológico o tratamientos específicos para el SXF. La minociclina y la sertralina han demostrado eficacia en niños.

Effects of Fragile Mental Retardation Protein on Cerebellar Neuron Development and Migration in Mouse Model / 中国医科大学学报

Objective To investigate the effects of fragile X mental retardation protein（FMRP）on the development and migration of cerebellar neurons in mouse model.Methods Plasmids containing FMRPmutant-EGFP or EGFP were established and transfected into the lateral ventricle of the embryo mouse.Fragile X syndrome（FXS）genotype of the mouse model was identified.Nissl staining and immunofluorescence staining were conducted to assess the changes in neuron development and migration.Results In the experimental group,Nissl staining showed that the deep cerebellar neuclei contracted and divided by white matter,and the non-polarized Purkinje cells retained in internal granular layer;while immunofluorescence staining showed that Tbr2-positive unipolar brush cells changed the migration pathway and accumulated in the ventricular zone.Conclusion Cerebellar neurons showed abnormal formation and migration with the absence of FMRP.

Síndrome de tremor e ataxia associada ao X frágil: rastreamento por PCR em amostra de idosos / Fragile X-associated tremor/ataxia syndrome: PCR-based screening in a sample of elderly men

Introdução: A presença de sequências repetidas de DNA já foi identificada como marcadoras de certas doenças neuropsiquiátricas. O gene FMR1 possui sequência rica em repetições CGG, sujeito a expansão quando transmitido por via materna. Alelos pré-mutados (55200 repetições CGG). Na mutação completa, o gene é inativado determinando a síndrome do X frágil (FRAX). Os portadores da pré-mutação não apresentam deficiência cognitiva associada à FRAX, porém, um subgrupo desses indivíduos com mais de 50 anos de idade desenvolve uma síndrome neurológica progressiva, a síndrome de tremor/ataxia associada ao X frágil (Fragile X-associated Tremor/Ataxia Syndrome–FXTAS). Objetivos: Este estudo investigou as características clínicas e moleculares dos familiares de quatro homens com mais de 50 anos de idade, familiares de indivíduos FRAX, uma vez que esses indivíduos possuem risco elevado de desenvolver o quadro de FXTAS. Resultados: Nenhum dos pacientes avaliados possuía FXTAS. Conclusão: A síndrome FXTAS foi recentemente descrita e é pouco conhecida no meio clínico e científico. Dessa forma, a avaliação de familiares de indivíduos FRAX pode contribuir para o melhor entendimento da doença e permitir a determinação de sua incidência na população brasileira.

Introduction: The presence of repeated sequences was already identified as markers of neuropsychiatric diseases. The FMR1 gene shelters a CGGrich sequence which is vulnerable to expansion when transmitted through maternal lineage. Premutated alleles (55 200 CGG repeats). In the full mutation range, the gene is inactivated causing the fragile X syndrome (FRAX). Premutation carriers do not present mental retardation, however a subgroup of permutation carriers older than 50 years can develop a progressive neurological syndrome, the Fragile X-associated Tremor/Ataxia Syndrome (FXTAS). Objectives: This approach had investigated clinical and molecular features offour males - relatives of FRAX individuals – due to the high risk of developing FXTAS. Results: None of the investigated patients had FXTAS. Conclusion: This syndrome was recently described and there is little knowledge about it by clinicians and scientists. Thus, evaluation of people in this condition can contribute to the better understanding of the disease and its incidence in the Brazilian population.

Fragile X Syndrome in Korea: A Case Series and a Review of the Literature

The purposes of this study were to present DNA analysis findings of our case series of fragile X syndrome (FXS) based on methylation-specific polymerase chain reaction (MS-PCR), PCR, and Southern blotting alongside developmental characteristics including psychological profiles and to review the literature on FXS in Korea. The reports of 65 children (male:female, 52:13; age, 6.12+/-4.00 yrs) referred for the diagnosis of FXS over a 26-months period were retrospectively reviewed for the identification of full mutation or premutation of fragile X mental retardation 1 (FMR1). Among the 65 children, there were 4 boys with full mutation, and one boy showed premutation of FMR1, yielding a 6.15% positive rate of FXS. All 4 children with full mutation showed significant developmental delay, cognitive dysfunction, and varying degrees of autistic behaviors. The boys with premutation showed also moderate mental retardation, severe drooling, and behavioral problems as severe as the boys with full mutation. Thirteen articles on FXS in Korea have been published since 1993, and they were reviewed. The positive rate of FXS was in the range of 0.77-8.51%, depending on the study groups and the method of diagnosis. Finally, the population-based prevalence study on FXS in Korea is required in the near future.

Cloning,expression and purification of fragile X mental retardation protein / 基础医学与临床

Objective Explore the conditions of the cloning,expression and purification of FMRP.Methods The plasmid pET22b(+)-FMR1,constructed by molecular cloning,was transformed into E.coli BL21(DE3) competent cells and induced to express FMRP by IPTG.Recombinant FMRP was purified by affinity chromatography,verified by Western-blot,and tested for its RNA binding ability.Results FMR1 cDNA was successfully cloned into pET22b(+) vector and expressed in E.coli BL21(DE3).A protein with Mr 79 000 was purified and confirmed to be FMRP.This protein retained the RNA binding ability of FMRP.Conclusion We successfully expressed recombinant hFMRP with high purity and activity in E.coli,which provided a reliable material to study the function of FMRP.