1,721,025 research outputs found
Epigenetic modifications of the FMR1 gene
No full textThe fragile X syndrome (FXS), the most common cause of heritable intellectual disability, is caused by expansion of a CGG repeat located at the 5' UTR of the FMR1 gene and subsequent epigenetic modifications of its promoter. Epigenetic modifications include both methylation of the cytosines of the CpG island in the promoter region and of the expanded CGG triplet, and posttranslational histone changes. The combination of these changes, one structural (expansion) and one epigenetic (methylation and histone modifications), results in transcriptional silencing, even though the coding region of the FMR1 gene remains intact. Here we describe the molecular methods used to study both DNA methylation and histone epigenetic modifications, namely, bisulfite sequencing and quantification of immunoprecipitated DNA after Chromatin Immunoprecipitation (ChIP)
Epigenetics, fragile X syndrome and transcriptional therapy.
No full textEpigenetics refers to the study of heritable changes in gene expression that occur without a change in DNA sequence. Epigenetic mechanisms therefore include all transcriptional controls that determine how genes are expressed during development and differentiation, but also in individual cells responding to environmental stimuli. The purpose of this review is to examine the basic principles of epigenetic mechanisms and their contribution to human disorders with a particular focus on fragile X syndrome (FXS), the most common monogenic form of developmental cognitive impairment. FXS represents a prototype of the so-called repeat expansion disorders due to "dynamic" mutations, namely the expansion (known as "full mutation") of a CGG repeat in the 5'UTR of the FMR1 gene. This genetic anomaly is accompanied by epigenetic modifications (mainly DNA methylation and histone deacetylation), resulting in the inactivation of the FMR1 gene. The presence of an intact FMR1 coding sequence allowed pharmacological reactivation of gene transcription, particularly through the use of the DNA demethylating agent 5'-aza-2'-deoxycytydine and/or inhibitors of histone deacetylases. These treatments suggested that DNA methylation is dominant over histone acetylation in silencing the FMR1 gene. The importance of DNA methylation in repressing FMR1 transcription is confirmed by the existence of rare unaffected males carrying unmethylated full mutations. Finally, we address the potential use of epigenetic approaches to targeted treatment of other genetic conditions
Transcriptional reactivation of the FMR1 Gene. A possible approach to the treatment of the fragile X syndrome
Full text linkFragile X syndrome (FXS) is the most common cause of inherited intellectual disability, caused by CGG expansion over 200 repeats (full mutation, FM) at the 5′ untranslated region (UTR) of the fragile X mental retardation 1 (FMR1) gene and subsequent DNA methylation of the promoter region, accompanied by additional epigenetic histone modifications that result in a block of transcription and absence of the fragile X mental retardation protein (FMRP). The lack of FMRP, involved in multiple aspects of mRNA metabolism in the brain, is thought to be the direct cause of the FXS phenotype. Restoration of FMR1 transcription and FMRP production can be obtained in vitro by treating FXS lymphoblastoid cell lines with the demethylating agent 5-azadeoxycytidine, demonstrating that DNA methylation is key to FMR1 inactivation. This concept is strengthened by the existence of rare male carriers of a FM, who are unable to methylate the FMR1 promoter. These individuals produce limited amounts of FMRP and are of normal intelligence. Their inability to methylate the FMR1 promoter, whose cause is not yet fully elucidated, rescues them from manifesting the FXS. These observations demonstrate that a therapeutic approach to FXS based on the pharmacological reactivation of the FMR1 gene is conceptually tenable and worthy of being further pursued
The role of sevoflurane exposure on systemic inflammation and neuroinflammation: a systematic review and meta-analysis of in vivo and in vitro studies
No full textNeuroinflammation induced by anaesthetics may negatively affect neurocognitive functions after surgery in humans. This systematic review and meta-analysis aimed to evaluate the impact of sevoflurane exposure on systemic inflammation and neuroinflammation and to assess alterations in behavioural/cognitive functions in experimental rodent models not exposed to surgery nor to other inflammatory stimuli. Databases were searched for in vivo and/or in vitro studies examining inflammation after sevoflurane exposure compared to control conditions. Inflammatory biomarkers, including interleukin (IL)-6, IL-1β, and tumour necrosis factor alfa (TNFα), at the peak time of production (primary outcomes) were investigated. The secondary outcome was to evaluate the presence of alterations in behavioural/cognitive tests. Subgroup analyses on young and adult rodents were performed for in vivo studies. Thirty-five in vivo and in vitro studies were selected. Results from meta-analyses demonstrated significant increases in the secretion peak of all inflammatory markers in in vivo models. Significantly higher plasma peaks of IL-6 (SMD: 7.97, 95% CI: 4.76-11.17), IL-1β (SMD: 5.71, 95% CI: 1.88-9.55) and TNFα (SMD: 6.64, 95% CI: 3.73-9.56) were found only in adult rodents exposed to sevoflurane. Similar findings were observed in brain tissue homogenates. Rodents exposed to sevoflurane exhibited significant alterations in behavioural/cognitive tests and significance persisted only in adult rodents. Sevoflurane exposure may trigger systemic inflammation and neuroinflammation in experimental rodent models with marked effects in adult rodents. Alterations in behavioural/cognitive tests suggest a potential role of sevoflurane in the development of postoperative cognitive disorders in the elderly, independently of surgery. Further research is needed in humans
No Correlation between X Chromosome Inactivation Pattern and Autistic Spectrum Disorders in an Italian Cohort of Patients
No full textAutistic spectrum disorders (ASD) occur more frequently in males, suggesting a major pathogenic role for genes located on the X-chromosome. The analysis of X chromosome inactivation (XCI) pattern may help to identify XCI skewing in those families in which such genes are involved, even without identifying the specific genetic mutation. In order to identify such families, we determined the XCI pattern in 40 females with ASD and 58 mothers of children with ASD, as well as in 80 matched control females. We could not detect any skewing in mothers of ASD children nor in ASD females. However, it cannot be ruled out that a different XCI pattern is present in the brain or that other, unexplored X-linked loci might undergo segmental or locus specific XCI skewing
The FRAXopathies: Definition, overview, and update
No full textThe fragile X syndrome, fragile X tremor ataxia syndrome, and premature ovarian insufficiency are conditions related tot he X chromosome folate-sensitive site FRAXA. Threfore, we propose that they are considered as a family of disorders under the general designation of FRAXopathies. The present reviwe will outline the main clinical and molecular features of these disorders, with special emphasis on the pathogenic mechanisms that lead to distinct phenotypes, starting from related mutations. The understanding of these mechanisms is already generating promising therapeutic approache
Epigenetic analysis reveals a euchromatic configuration in the FMR1 unmethylated full mutations.
No full textAssisted reproductive technology and congenital overgrowth:some speculations on a case of Pallister-Killian syndrome
No full textWe report on a boy with Pallister-Killian syndrome (PKS) who was conceived by assisted reproductive technology (ART), specifically in vitro fertilization (IVF) with parents' gametes. A prenatal diagnosis performed elsewhere by CVS failed to detect the presence of the isochromosome 12p that was demonstrated postnatally in approximately 50% of cultured skin fibroblasts. Given that the patient did not show the congenital overgrowth typical of PKS, we speculate that ART might have restricted overgrowth in this particular case. More broadly, we hypothesize that overgrowth might protect from early demise fetuses conceived by ART, a technology known to cause low and very low birth weight
Modest reactivation of the mutatnt FMR1 gene by valproic acid is accompanied by histone modifications but not DNA demethylation.
No full textThe mGluR5 antagonist AFQ056 does not affect methylation and transcription of the mutant FMR1 gene in vitro.
No full textFragile X syndrome (FXS), the leading cause of inherited mental retardation, is due to expansion and methylation of a CGG sequence in the FMR1 gene, which result in its silencing and consequent absence of FMRP protein. This absence causes loss of repression of metabotropic glutamate receptor 5 (mGluR5)-mediated pathways resulting in the behavioral and cognitive impairments associated with FXS. In a randomized, double-blind trial it was recently demonstrated a beneficial effect of AFQ056, a selective inhibitor of metabotrobic glutamate receptor type 5 (mGluR5), on fully methylated FXS patients respect to partially methylated FXS ones.
METHODS: To determine whether AFQ056 may have secondary effects on the methylation and transcription of FMR1, here we treated three FXS lymphoblastoid cell lines and one normal control male line. A quantitative RT-PCR was performed to assess transcriptional reactivation of the FMR1 gene. To assess the methylation status of the FMR1 gene promoter it was carried out a bisulphite sequencing analysis.
RESULTS: Both FMR1-mRNA levels and DNA methylation were unmodified with respect to untreated controls.
CONCLUSIONS: These results demonstrate that the AFQ056 effect on fully methylated FXS patients is not due to a secondary effect on DNA methylation and consequent transcriptional activation of FMR1
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