CGG-repeat dynamics and FMR1 gene silencing in fragile X syndrome stem cells and stem cell-derived neurons / Y. ZHOU in Molecular Autism, 7 (2016)  

Public ISBD [article]  inMolecular Autism > 7 (2016) . - 42p. Titre : CGG-repeat dynamics and FMR1 gene silencing in fragile X syndrome stem cells and stem cell-derived neurons Type de document : Texte imprimé et/ou numérique Auteurs : Y. ZHOU, Auteur ; D. KUMARI, Auteur ; N. SCIASCIA, Auteur ; K. USDIN, Auteur Article en page(s) : 42p. Langues : Anglais (eng) Mots-clés : 5' Untranslated Regions  Alleles  Cell Differentiation  Cell Line  DNA Methylation  Embryonic Stem Cells/metabolism/pathology  Fragile X Mental Retardation Protein/genetics/metabolism  Fragile X Syndrome/genetics/metabolism/pathology  Gene Silencing  Humans  Induced Pluripotent Stem Cells/metabolism/pathology  Male  Neurons/metabolism/pathology  Primary Cell Culture  Time Factors  Trinucleotide Repeat Expansion  Fragile X syndrome  Repeat contractions  Repeat expansion mutation  Repeat-mediated gene silencing  Stem cells Index. décimale : PER Périodiques Résumé : BACKGROUND: Fragile X syndrome (FXS), a common cause of intellectual disability and autism, results from the expansion of a CGG-repeat tract in the 5' untranslated region of the FMR1 gene to >200 repeats. Such expanded alleles, known as full mutation (FM) alleles, are epigenetically silenced in differentiated cells thus resulting in the loss of FMRP, a protein important for learning and memory. The timing of repeat expansion and FMR1 gene silencing is controversial. METHODS: We monitored the repeat size and methylation status of FMR1 alleles with expanded CGG repeats in patient-derived induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs) that were grown for extended period of time either as stem cells or differentiated into neurons. We used a PCR assay optimized for the amplification of large CGG repeats for sizing, and a quantitative methylation-specific PCR for the analysis of FMR1 promoter methylation. The FMR1 mRNA levels were analyzed by qRT-PCR. FMRP levels were determined by western blotting and immunofluorescence. Chromatin immunoprecipitation was used to study the association of repressive histone marks with the FMR1 gene in FXS ESCs. RESULTS: We show here that while FMR1 gene silencing can be seen in FXS embryonic stem cells (ESCs), some silenced alleles contract and when the repeat number drops below ~400, DNA methylation erodes, even when the repeat number remains >200. The resultant active alleles do not show the large step-wise expansions seen in stem cells from other repeat expansion diseases. Furthermore, there may be selection against large active alleles and these alleles do not expand further or become silenced on neuronal differentiation. CONCLUSIONS: Our data support the hypotheses that (i) large expansions occur prezygotically or in the very early embryo, (ii) large unmethylated alleles may be deleterious in stem cells, (iii) methylation can occur on alleles with >400 repeats very early in embryogenesis, and (iv) expansion and contraction may occur by different mechanisms. Our data also suggest that the threshold for stable methylation of FM alleles may be higher than previously thought. A higher threshold might explain why some carriers of FM alleles escape methylation. It may also provide a simple explanation for why silencing has not been observed in mouse models with >200 repeats. En ligne : http://dx.doi.org/10.1186/s13229-016-0105-9 Permalink : https://www.cra-rhone-alpes.org/cid/opac_css/index.php?lvl=notice_display&id=329 [article] CGG-repeat dynamics and FMR1 gene silencing in fragile X syndrome stem cells and stem cell-derived neurons [Texte imprimé et/ou numérique] / Y. ZHOU, Auteur ; D. KUMARI, Auteur ; N. SCIASCIA, Auteur ; K. USDIN, Auteur . - 42p. Langues : Anglais (eng) in Molecular Autism > 7 (2016) . - 42p. Mots-clés : 5' Untranslated Regions  Alleles  Cell Differentiation  Cell Line  DNA Methylation  Embryonic Stem Cells/metabolism/pathology  Fragile X Mental Retardation Protein/genetics/metabolism  Fragile X Syndrome/genetics/metabolism/pathology  Gene Silencing  Humans  Induced Pluripotent Stem Cells/metabolism/pathology  Male  Neurons/metabolism/pathology  Primary Cell Culture  Time Factors  Trinucleotide Repeat Expansion  Fragile X syndrome  Repeat contractions  Repeat expansion mutation  Repeat-mediated gene silencing  Stem cells Index. décimale : PER Périodiques Résumé : BACKGROUND: Fragile X syndrome (FXS), a common cause of intellectual disability and autism, results from the expansion of a CGG-repeat tract in the 5' untranslated region of the FMR1 gene to >200 repeats. Such expanded alleles, known as full mutation (FM) alleles, are epigenetically silenced in differentiated cells thus resulting in the loss of FMRP, a protein important for learning and memory. The timing of repeat expansion and FMR1 gene silencing is controversial. METHODS: We monitored the repeat size and methylation status of FMR1 alleles with expanded CGG repeats in patient-derived induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs) that were grown for extended period of time either as stem cells or differentiated into neurons. We used a PCR assay optimized for the amplification of large CGG repeats for sizing, and a quantitative methylation-specific PCR for the analysis of FMR1 promoter methylation. The FMR1 mRNA levels were analyzed by qRT-PCR. FMRP levels were determined by western blotting and immunofluorescence. Chromatin immunoprecipitation was used to study the association of repressive histone marks with the FMR1 gene in FXS ESCs. RESULTS: We show here that while FMR1 gene silencing can be seen in FXS embryonic stem cells (ESCs), some silenced alleles contract and when the repeat number drops below ~400, DNA methylation erodes, even when the repeat number remains >200. The resultant active alleles do not show the large step-wise expansions seen in stem cells from other repeat expansion diseases. Furthermore, there may be selection against large active alleles and these alleles do not expand further or become silenced on neuronal differentiation. CONCLUSIONS: Our data support the hypotheses that (i) large expansions occur prezygotically or in the very early embryo, (ii) large unmethylated alleles may be deleterious in stem cells, (iii) methylation can occur on alleles with >400 repeats very early in embryogenesis, and (iv) expansion and contraction may occur by different mechanisms. Our data also suggest that the threshold for stable methylation of FM alleles may be higher than previously thought. A higher threshold might explain why some carriers of FM alleles escape methylation. It may also provide a simple explanation for why silencing has not been observed in mouse models with >200 repeats. En ligne : http://dx.doi.org/10.1186/s13229-016-0105-9 Permalink : https://www.cra-rhone-alpes.org/cid/opac_css/index.php?lvl=notice_display&id=329

Mouse models of the fragile X premutation and fragile X-associated tremor/ataxia syndrome / Robert F. BERMAN in Journal of Neurodevelopmental Disorders, 6-1 (December 2014)  

Public ISBD [article]  inJournal of Neurodevelopmental Disorders > 6-1 (December 2014) . - p.25 Titre : Mouse models of the fragile X premutation and fragile X-associated tremor/ataxia syndrome Type de document : Texte imprimé et/ou numérique Auteurs : Robert F. BERMAN, Auteur ; R. A. BUIJSEN, Auteur ; K. USDIN, Auteur ; E. PINTADO, Auteur ; F. KOOY, Auteur ; D. PRETTO, Auteur ; I. N. PESSAH, Auteur ; D. L. NELSON, Auteur ; Z. ZALEWSKI, Auteur ; N. CHARLET-BERGEURAND, Auteur ; R. WILLEMSEN, Auteur ; R. K. HUKEMA, Auteur Article en page(s) : p.25 Langues : Anglais (eng) Mots-clés : CGG trinucleotide repeat  Fmr1  Fmrp  Fxtas  Fragile X premutation  Intranuclear inclusions  Mouse models  RNA toxicity Index. décimale : PER Périodiques Résumé : Carriers of the fragile X premutation (FPM) have CGG trinucleotide repeat expansions of between 55 and 200 in the 5'-UTR of FMR1, compared to a CGG repeat length of between 5 and 54 for the general population. Carriers were once thought to be without symptoms, but it is now recognized that they can develop a variety of early neurological symptoms as well as being at risk for developing the late onset neurodegenerative disorder fragile X-associated tremor/ataxia syndrome (FXTAS). Several mouse models have contributed to our understanding of FPM and FXTAS, and findings from studies using these models are summarized here. This review also discusses how this information is improving our understanding of the molecular and cellular abnormalities that contribute to neurobehavioral features seen in some FPM carriers and in patients with FXTAS. Mouse models show much of the pathology seen in FPM carriers and in individuals with FXTAS, including the presence of elevated levels of Fmr1 mRNA, decreased levels of fragile X mental retardation protein, and ubiquitin-positive intranuclear inclusions. Abnormalities in dendritic spine morphology in several brain regions are associated with neurocognitive deficits in spatial and temporal memory processes, impaired motor performance, and altered anxiety. In vitro studies have identified altered dendritic and synaptic architecture associated with abnormal Ca(2+) dynamics and electrical network activity. FPM mice have been particularly useful in understanding the roles of Fmr1 mRNA, fragile X mental retardation protein, and translation of a potentially toxic polyglycine peptide in pathology. Finally, the potential for using these and emerging mouse models for preclinical development of therapies to improve neurological function in FXTAS is considered. En ligne : http://dx.doi.org/10.1186/1866-1955-6-25 Permalink : https://www.cra-rhone-alpes.org/cid/opac_css/index.php?lvl=notice_display&id=346 [article] Mouse models of the fragile X premutation and fragile X-associated tremor/ataxia syndrome [Texte imprimé et/ou numérique] / Robert F. BERMAN, Auteur ; R. A. BUIJSEN, Auteur ; K. USDIN, Auteur ; E. PINTADO, Auteur ; F. KOOY, Auteur ; D. PRETTO, Auteur ; I. N. PESSAH, Auteur ; D. L. NELSON, Auteur ; Z. ZALEWSKI, Auteur ; N. CHARLET-BERGEURAND, Auteur ; R. WILLEMSEN, Auteur ; R. K. HUKEMA, Auteur . - p.25. Langues : Anglais (eng) in Journal of Neurodevelopmental Disorders > 6-1 (December 2014) . - p.25 Mots-clés : CGG trinucleotide repeat  Fmr1  Fmrp  Fxtas  Fragile X premutation  Intranuclear inclusions  Mouse models  RNA toxicity Index. décimale : PER Périodiques Résumé : Carriers of the fragile X premutation (FPM) have CGG trinucleotide repeat expansions of between 55 and 200 in the 5'-UTR of FMR1, compared to a CGG repeat length of between 5 and 54 for the general population. Carriers were once thought to be without symptoms, but it is now recognized that they can develop a variety of early neurological symptoms as well as being at risk for developing the late onset neurodegenerative disorder fragile X-associated tremor/ataxia syndrome (FXTAS). Several mouse models have contributed to our understanding of FPM and FXTAS, and findings from studies using these models are summarized here. This review also discusses how this information is improving our understanding of the molecular and cellular abnormalities that contribute to neurobehavioral features seen in some FPM carriers and in patients with FXTAS. Mouse models show much of the pathology seen in FPM carriers and in individuals with FXTAS, including the presence of elevated levels of Fmr1 mRNA, decreased levels of fragile X mental retardation protein, and ubiquitin-positive intranuclear inclusions. Abnormalities in dendritic spine morphology in several brain regions are associated with neurocognitive deficits in spatial and temporal memory processes, impaired motor performance, and altered anxiety. In vitro studies have identified altered dendritic and synaptic architecture associated with abnormal Ca(2+) dynamics and electrical network activity. FPM mice have been particularly useful in understanding the roles of Fmr1 mRNA, fragile X mental retardation protein, and translation of a potentially toxic polyglycine peptide in pathology. Finally, the potential for using these and emerging mouse models for preclinical development of therapies to improve neurological function in FXTAS is considered. En ligne : http://dx.doi.org/10.1186/1866-1955-6-25 Permalink : https://www.cra-rhone-alpes.org/cid/opac_css/index.php?lvl=notice_display&id=346

The multiple molecular facets of fragile X-associated tremor/ataxia syndrome / C. SELLIER in Journal of Neurodevelopmental Disorders, 6-1 (December 2014)  

Public ISBD [article]  inJournal of Neurodevelopmental Disorders > 6-1 (December 2014) . - p.23 Titre : The multiple molecular facets of fragile X-associated tremor/ataxia syndrome Type de document : Texte imprimé et/ou numérique Auteurs : C. SELLIER, Auteur ; K. USDIN, Auteur ; C. PASTORI, Auteur ; V. J. PESCHANSKY, Auteur ; F. TASSONE, Auteur ; N. CHARLET-BERGUERAND, Auteur Article en page(s) : p.23 Langues : Anglais (eng) Index. décimale : PER Périodiques Résumé : Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset inherited neurodegenerative disorder characterized by intentional tremor, gait ataxia, autonomic dysfunction, and cognitive decline. FXTAS is caused by the presence of a long CGG repeat tract in the 5' UTR of the FMR1 gene. In contrast to Fragile X syndrome, in which the FMR1 gene harbors over 200 CGG repeats but is transcriptionally silent, the clinical features of FXTAS arise from a toxic gain of function of the elevated levels of FMR1 transcript containing the long CGG tract. However, how this RNA leads to neuronal cell dysfunction is unknown. Here, we discuss the latest advances in the current understanding of the possible molecular basis of FXTAS. En ligne : http://dx.doi.org/10.1186/1866-1955-6-23 Permalink : https://www.cra-rhone-alpes.org/cid/opac_css/index.php?lvl=notice_display&id=346 [article] The multiple molecular facets of fragile X-associated tremor/ataxia syndrome [Texte imprimé et/ou numérique] / C. SELLIER, Auteur ; K. USDIN, Auteur ; C. PASTORI, Auteur ; V. J. PESCHANSKY, Auteur ; F. TASSONE, Auteur ; N. CHARLET-BERGUERAND, Auteur . - p.23. Langues : Anglais (eng) in Journal of Neurodevelopmental Disorders > 6-1 (December 2014) . - p.23 Index. décimale : PER Périodiques Résumé : Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset inherited neurodegenerative disorder characterized by intentional tremor, gait ataxia, autonomic dysfunction, and cognitive decline. FXTAS is caused by the presence of a long CGG repeat tract in the 5' UTR of the FMR1 gene. In contrast to Fragile X syndrome, in which the FMR1 gene harbors over 200 CGG repeats but is transcriptionally silent, the clinical features of FXTAS arise from a toxic gain of function of the elevated levels of FMR1 transcript containing the long CGG tract. However, how this RNA leads to neuronal cell dysfunction is unknown. Here, we discuss the latest advances in the current understanding of the possible molecular basis of FXTAS. En ligne : http://dx.doi.org/10.1186/1866-1955-6-23 Permalink : https://www.cra-rhone-alpes.org/cid/opac_css/index.php?lvl=notice_display&id=346

Use of model systems to understand the etiology of fragile X-associated primary ovarian insufficiency (FXPOI) / S. L. SHERMAN in Journal of Neurodevelopmental Disorders, 6-1 (December 2014)  

Public ISBD [article]  inJournal of Neurodevelopmental Disorders > 6-1 (December 2014) . - p.26 Titre : Use of model systems to understand the etiology of fragile X-associated primary ovarian insufficiency (FXPOI) Type de document : Texte imprimé et/ou numérique Auteurs : S. L. SHERMAN, Auteur ; E. C. CURNOW, Auteur ; C. A. EASLEY, Auteur ; P. JIN, Auteur ; R. K. HUKEMA, Auteur ; M. I. TEJADA, Auteur ; R. WILLEMSEN, Auteur ; K. USDIN, Auteur Article en page(s) : p.26 Langues : Anglais (eng) Mots-clés : CGG repeat  Fertility  Fragile X syndrome  Premature ovarian failure  Primary ovarian insufficiency  Repeat expansion disorder Index. décimale : PER Périodiques Résumé : Fragile X-associated primary ovarian insufficiency (FXPOI) is among the family of disorders caused by the expansion of a CGG repeat sequence in the 5' untranslated region of the X-linked gene FMR1. About 20% of women who carry the premutation allele (55 to 200 unmethylated CGG repeats) develop hypergonadotropic hypogonadism and cease menstruating before age 40. Some proportion of those who are still cycling show hormonal profiles indicative of ovarian dysfunction. FXPOI leads to subfertility and an increased risk of medical conditions associated with early estrogen deficiency. Little progress has been made in understanding the etiology of this clinically significant disorder. Understanding the molecular mechanisms of FXPOI requires a detailed knowledge of ovarian FMR1 mRNA and FMRP's function. In humans, non-invasive methods to discriminate the mechanisms of the premutation on ovarian function are not available, thus necessitating the development of model systems. Vertebrate (mouse and rat) and invertebrate (Drosophila melanogaster) animal studies for the FMR1 premutation and ovarian function exist and have been instrumental in advancing our understanding of the disease phenotype. For example, rodent models have shown that FMRP is highly expressed in oocytes where it is important for folliculogenesis. The two premutation mouse models studied to date show evidence of ovarian dysfunction and, together, suggest that the long repeat in the transcript itself may have some pathological effect quite apart from any effect of the toxic protein. Further, ovarian morphology in young animals appears normal and the primordial follicle pool size does not differ from that of wild-type animals. However, there is a progressive premature decline in the levels of most follicle classes. Observations also include granulosa cell abnormalities and altered gene expression patterns. Further comparisons of these models are now needed to gain insight into the etiology of the ovarian dysfunction. Premutation model systems in non-human primates and those based on induced pluripotent stem cells show particular promise and will complement current models. Here, we review the characterization of the current models and describe the development and potential of the new models. Finally, we will discuss some of the molecular mechanisms that might be responsible for FXPOI. En ligne : http://dx.doi.org/10.1186/1866-1955-6-26 Permalink : https://www.cra-rhone-alpes.org/cid/opac_css/index.php?lvl=notice_display&id=346 [article] Use of model systems to understand the etiology of fragile X-associated primary ovarian insufficiency (FXPOI) [Texte imprimé et/ou numérique] / S. L. SHERMAN, Auteur ; E. C. CURNOW, Auteur ; C. A. EASLEY, Auteur ; P. JIN, Auteur ; R. K. HUKEMA, Auteur ; M. I. TEJADA, Auteur ; R. WILLEMSEN, Auteur ; K. USDIN, Auteur . - p.26. Langues : Anglais (eng) in Journal of Neurodevelopmental Disorders > 6-1 (December 2014) . - p.26 Mots-clés : CGG repeat  Fertility  Fragile X syndrome  Premature ovarian failure  Primary ovarian insufficiency  Repeat expansion disorder Index. décimale : PER Périodiques Résumé : Fragile X-associated primary ovarian insufficiency (FXPOI) is among the family of disorders caused by the expansion of a CGG repeat sequence in the 5' untranslated region of the X-linked gene FMR1. About 20% of women who carry the premutation allele (55 to 200 unmethylated CGG repeats) develop hypergonadotropic hypogonadism and cease menstruating before age 40. Some proportion of those who are still cycling show hormonal profiles indicative of ovarian dysfunction. FXPOI leads to subfertility and an increased risk of medical conditions associated with early estrogen deficiency. Little progress has been made in understanding the etiology of this clinically significant disorder. Understanding the molecular mechanisms of FXPOI requires a detailed knowledge of ovarian FMR1 mRNA and FMRP's function. In humans, non-invasive methods to discriminate the mechanisms of the premutation on ovarian function are not available, thus necessitating the development of model systems. Vertebrate (mouse and rat) and invertebrate (Drosophila melanogaster) animal studies for the FMR1 premutation and ovarian function exist and have been instrumental in advancing our understanding of the disease phenotype. For example, rodent models have shown that FMRP is highly expressed in oocytes where it is important for folliculogenesis. The two premutation mouse models studied to date show evidence of ovarian dysfunction and, together, suggest that the long repeat in the transcript itself may have some pathological effect quite apart from any effect of the toxic protein. Further, ovarian morphology in young animals appears normal and the primordial follicle pool size does not differ from that of wild-type animals. However, there is a progressive premature decline in the levels of most follicle classes. Observations also include granulosa cell abnormalities and altered gene expression patterns. Further comparisons of these models are now needed to gain insight into the etiology of the ovarian dysfunction. Premutation model systems in non-human primates and those based on induced pluripotent stem cells show particular promise and will complement current models. Here, we review the characterization of the current models and describe the development and potential of the new models. Finally, we will discuss some of the molecular mechanisms that might be responsible for FXPOI. En ligne : http://dx.doi.org/10.1186/1866-1955-6-26 Permalink : https://www.cra-rhone-alpes.org/cid/opac_css/index.php?lvl=notice_display&id=346

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