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Nina Xie, He Gong, Joshua A Suhl, Pankaj Chopra, Tao Wang, Stephen T Warren
Fragile X syndrome (FXS) is a common cause of intellectual disability that is most often due to a CGG-repeat expansion mutation in the FMR1 gene that triggers epigenetic gene silencing. Epigenetic modifying drugs can only transiently and modestly induce FMR1 reactivation in the presence of the elongated CGG repeat. As a proof-of-principle, we excised the expanded CGG-repeat in both somatic cell hybrids containing the human fragile X chromosome and human FXS iPS cells using the CRISPR/Cas9 genome editing. We observed transcriptional reactivation in approximately 67% of the CRISPR cut hybrid colonies and in 20% of isolated human FXS iPSC colonies...
2016: PloS One
Amy Krans, Michael G Kearse, Peter K Todd
OBJECTIVE: Repeat associated non-AUG (RAN) translation drives production of toxic proteins from pathogenic repeat sequences in multiple untreatable neurodegenerative disorders. Fragile X-associated tremor/ataxia syndrome (FXTAS) is one such condition, resulting from a CGG trinucleotide repeat expansion in the 5' leader sequence of the FMR1 gene. RAN proteins from the CGG repeat accumulate in ubiquitinated inclusions in FXTAS patient brains and elicit toxicity. In addition to the CGG repeat, an antisense mRNA containing a CCG repeat is also transcribed from the FMR1 locus...
October 19, 2016: Annals of Neurology
Indhu-Shree Rajan-Babu, Samuel S Chong
Fragile X syndrome (FXS) is the most common monogenic cause of intellectual disability and autism. Molecular diagnostic testing of FXS and related disorders (fragile X-associated primary ovarian insufficiency (FXPOI) and fragile X-associated tremor/ataxia syndrome (FXTAS)) relies on a combination of polymerase chain reaction (PCR) and Southern blot (SB) for the fragile X mental retardation 1 (FMR1) CGG-repeat expansion and methylation analyses. Recent advancements in PCR-based technologies have enabled the characterization of the complete spectrum of CGG-repeat mutation, with or without methylation assessment, and, as a result, have reduced our reliance on the labor- and time-intensive SB, which is the gold standard FXS diagnostic test...
October 14, 2016: Genes
Chih-Ping Chen, Chen-Yu Chen, Schu-Rern Chern, Peih-Shan Wu, Yen-Ni Chen, Shin-Wen Chen, Chen-Chi Lee, Dai-Dyi Town, Meng-Shan Lee, Chien-Wen Yang, Wayseen Wang
OBJECTIVE: We present molecular cytogenetic characterization of an Xp22.32→pter deletion and an Xq26.3→qter duplication in a male fetus with congenital malformations and maternal X chromosome pericentric inversion. MATERIALS AND METHODS: A 22-year-old woman underwent amniocentesis at 17 weeks of gestation because of an abnormal maternal serum screening result. Prenatal ultrasound revealed a hypoplastic left heart and short limbs. Amniocentesis revealed a karyotype of 46,Y,der(X) t(X;?)(p22...
October 2016: Taiwanese Journal of Obstetrics & Gynecology
Annie L Shelton, Kim Cornish, Meaghan Clough, Sanuji Gajamange, Scott Kolbe, Joanne Fielding
Executive dysfunction has been demonstrated among premutation (PM) carriers (55-199 CGG repeats) of the Fragile X mental retardation 1 (FMR1) gene. Further, alterations to neural activation patterns have been reported during memory and comparison based functional magnetic resonance imaging (fMRI) tasks in these carriers. For the first time, the relationships between fMRI neural activation during an interleaved ocular motor prosaccade/antisaccade paradigm, and concurrent task performance (saccade measures of latency, accuracy and error rate) in PM females were examined...
October 14, 2016: Human Brain Mapping
Ping Lu, Xiaolong Chen, Yun Feng, Qiao Zeng, Cizhong Jiang, Xianmin Zhu, Guoping Fan, Zhigang Xue
Fragile X syndrome (FXS) patients carry the expansion of over 200 CGG repeats at the promoter of fragile X mental retardation 1 (FMR1), leading to decreased or absent expression of its encoded fragile X mental retardation protein (FMRP). However, the global transcriptional alteration by FMRP deficiency has not been well characterized at single nucleotide resolution, i.e., RNA-seq. Here, we performed in-vitro neuronal differentiation of human induced pluripotent stem (iPS) cells that were derived from fibroblasts of a FXS patient (FXS-iPSC)...
October 11, 2016: Science China. Life Sciences
Rebecca Lyndsey Hardiman, Alison Bratt
Fragile X Syndrome (FXS) is characterised by features including anxiety and autistic-like behaviour, which led to early hypotheses that aberrant physiological arousal may underlie the behavioural phenotype. In line with this, several lines of evidence suggest that the hypothalamic-pituitary-adrenal (HPA) axis may be altered in the syndrome. This review collates evidence to determine the nature of HPA axis baseline activity and reactivity (as measured by glucocorticoid levels) differences in FXS, and its relationship to behaviour...
October 5, 2016: Physiology & Behavior
Yifan Zhou, Daman Kumari, Nicholas Sciascia, Karen Usdin
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...
2016: Molecular Autism
Yasser Vega, Sergio Arias, Irene Paradisi
Martin-Bell syndrome is mainly caused by the expansion of CGG trinucleotide repeats (>200 CGG) in the first exon of the FMR1 gene, leading to hypermethylation of the promoter region and silencing of the FMR1 protein expression. These changes are responsible for a phenotype with varying degrees of mental retardation, a long face with large and protruding ears, macroorchidism and autistic behavior. There may also be, however, patients who exhibit typical features of the syndrome without any expansion in the FMR1 gene; thus, other mechanisms affecting the expression of the FMR1 gene were assessed in 25 out of 29 ascertained patients with the typical phenotype without full mutation...
October 6, 2016: Journal of Human Genetics
Xiao Wang, Yawen Mu, Mengshi Sun, Junhai Han
Homeostatic regulation of the light sensor, rhodopsin, is critical for the maintenance of light sensitivity and survival of photoreceptors. The major fly rhodopsin, Rh1, undergoes light-induced endocytosis and degradation, but its protein and mRNA levels remain constant during light/dark cycles. It is not clear how translation of Rh1 is regulated. Here, we show that adult photoreceptors maintain a constant, abundant quantity of ninaE mRNA, which encodes Rh1. We demonstrate that the Fmr1 protein associates with ninaE mRNA and represses its translation...
October 4, 2016: Journal of Molecular Cell Biology
Yun Tae Hwang, Solange Mabel Aliaga, Marta Arpone, David Francis, Xin Li, Belinda Chong, Howard Robert Slater, Carolyn Rogers, Lesley Bretherton, Matthew Hunter, Robert Heard, David Eugeny Godler
CGG repeat expansion >200 within FMR1, termed full mutation (FM), has been associated with promoter methylation, consequent silencing of gene expression and fragile X syndrome (FXS)-a common cause of intellectual disability and co-morbid autism. Unmethylated premutation (55-199 repeats) and FM alleles have been associated with fragile X related tremor/ataxia syndrome (FXTAS), a late onset neurodegenerative disorder. Here we present a 33-year-old male with FXS, with white matter changes and progressive deterioration in gait with cerebellar signs consistent with probable FXTAS; there was no evidence of any other cerebellar pathology...
October 1, 2016: American Journal of Medical Genetics. Part A
Atefeh Entezari, Mahmoud Shekari Khaniani, Tayyeb Bahrami, Sima Mansoori Derakhshan, Hossein Darvish
Male carriers of an expansion of CGG alleles (with 55-200 CGG repeats) in the FMR1 gene are affected with Fragile X-associated tremor/ataxia syndrome (FXTAS). On the other hand, individuals with Parkinson's disease (PD) or Parkinsonism spectrum disorders may have some clinical features that overlap with FXTAS. To investigate the possible association between PD and FMR1 expanded alleles, we screened a total of 154 male PD patients and 190 gender- and age-matched healthy control subjects from Iran. Eleven intermediate allele carriers (7...
October 1, 2016: Neurological Sciences
Zuzana Musova, Miroslava Hancarova, Marketa Havlovicova, Radka Pourova, Michal Hrdlicka, Josef Kraus, Marie Trkova, David Stejskal, Zdenek Sedlacek
Myotonic dystrophy type 1 (DM1) belongs to the broad spectrum of genetic disorders associated with autism spectrum disorders (ASD). ASD were reported predominantly in congenital and early childhood forms of DM1. We describe dizygotic twin boys with ASD who were referred for routine laboratory genetic testing and in whom karyotyping, FMR1 gene testing, and single nucleotide polymorphism array analysis yielded negative results. The father of the boys was later diagnosed with suspected DM1, and testing revealed characteristic DMPK gene expansions in his genome as well as in the genomes of both twins and their elder brother, who also suffered from ASD...
2016: Neuropsychiatric Disease and Treatment
Roseanne Rosario, Panagiotis Filis, Victoria Tessyman, Hazel Kinnell, Andrew J Childs, Nicola K Gray, Richard A Anderson
Germ cell development and primordial follicle formation during fetal life is critical in establishing the pool of oocytes that subsequently determines the reproductive lifespan of women. Fragile X-associated primary ovarian insufficiency (FXPOI) is caused by inheritance of the FMR1 premutation allele and approximately 20% of women with the premutation allele develop ovarian dysfunction and premature ovarian insufficiency. However, the underlying disease mechanism remains obscure, and a potential role of FMRP in human ovarian development has not been explored...
2016: PloS One
Hagar Mor-Shaked, Rachel Eiges
Fragile X syndrome (FXS) is the most common heritable form of cognitive impairment. It results from a loss-of-function mutation by a CGG repeat expansion at the 5' untranslated region of the X-linked fragile X mental retardation 1 (FMR1) gene. Expansion of the CGG repeats beyond 200 copies results in protein deficiency by leading to aberrant methylation of the FMR1 promoter and the switch from active to repressive histone modifications. Additionally, the CGGs become increasingly unstable, resulting in high degree of variation in expansion size between and within tissues of affected individuals...
2016: Genes
Marc Alexandre Duarte Gigonzac, Lilian Souza Teodoro, Lysa Berandes Minasi, Thaís Cidália Vieira, Aparecido Divino da Cruz
Fragile X Syndrome (FXS) is the most common cause of inherited intellectual disability. The most common etiology of the syndrome is expansion and methylation of a CGG trinucleotide at chromosome region Xq27.3 involving FMR1. This disorder is commonly underdiagnosed in children and adolescents, given the high clinical variability. In Brazil, molecular diagnosis of FXS by capillary electrophoresis does not exist in the public health system. The current standard for separation and identification of DNA fragment sizes is 50 cm capillary electrophoresis, which is uncommon in public genotyping laboratories...
September 26, 2016: Electrophoresis
Sarah A Wolfe, Emily R Workman, Chelcie F Heaney, Farr Niere, Sanjeev Namjoshi, Luisa P Cacheaux, Sean P Farris, Michael R Drew, Boris V Zemelman, R Adron Harris, Kimberly F Raab-Graham
Alcohol promotes lasting neuroadaptive changes that may provide relief from depressive symptoms, often referred to as the self-medication hypothesis. However, the molecular/synaptic pathways that are shared by alcohol and antidepressants are unknown. In the current study, acute exposure to ethanol produced lasting antidepressant and anxiolytic behaviours. To understand the functional basis of these behaviours, we examined a molecular pathway that is activated by rapid antidepressants. Ethanol, like rapid antidepressants, alters γ-aminobutyric acid type B receptor (GABABR) expression and signalling, to increase dendritic calcium...
2016: Nature Communications
Olfa Khalfallah, Marielle Jarjat, Laetitia Davidovic, Nicolas Nottet, Sandrine Cestèle, Massimo Mantegazza, Barbara Bardoni
Fragile X syndrome (FXS) is the most common form of inherited intellectual disability (ID) and a leading cause of autism. FXS is due to the silencing of the Fragile X Mental Retardation Protein (FMRP), an RNA binding protein mainly involved in translational control, dendritic spine morphology and synaptic plasticity. Despite extensive studies, there is currently no cure for FXS. With the purpose to decipher the initial molecular events leading to this pathology, we developed a stem-cell-based disease model by knocking-down the expression of Fmr1 in mouse embryonic stem cells (ESCs)...
September 24, 2016: Stem Cells
Kirsty Sawicka, Alexander Pyronneau, Miranda Chao, Michael V L Bennett, R Suzanne Zukin
Fragile X syndrome (FXS) is the most common heritable cause of intellectual disability and a leading genetic form of autism. The Fmr1 KO mouse, a model of FXS, exhibits elevated translation in the hippocampus and the cortex. ERK (extracellular signal-regulated kinase) and mTOR (mechanistic target of rapamycin) signaling regulate protein synthesis by activating downstream targets critical to translation initiation and elongation and are known to contribute to hippocampal defects in fragile X. Here we show that the effect of loss of fragile X mental retardation protein (FMRP) on these pathways is brain region specific...
October 11, 2016: Proceedings of the National Academy of Sciences of the United States of America
S Y Yau, C A Bostrom, J Chiu, C J Fontaine, S Sawchuk, A Meconi, R C Wortman, E Truesdell, A Truesdell, C Chiu, B N Hryciw, B D Eadie, M Ghilan, B R Christie
Fragile-X syndrome (FXS) is caused by the transcriptional repression of the Fmr1 gene resulting in loss of the Fragile-X mental retardation protein (FMRP). This leads to cognitive impairment in both male and female patients, however few studies have focused on the impact of FXS in females. Significant cognitive impairment has been reported in approximately 35% of women who exhibit a heterozygous Fmr1 gene mutation, however to date there is a paucity of information regarding the mechanistic underpinnings of these deficits...
September 19, 2016: Neurobiology of Disease
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