Fragile X syndrome occurs as a result of a mutation of the fragile X mental retardation 1 (FMR1) gene on the bottom of the X chromosome (Pic. 1), which encodes fragile X mental retardation protein (FMRP). This protein, most commonly found in the brain, is essential for normal cognitive development and female reproductive function. The CGG triplet that means gene segment consisting of a cytosine...

KEY POINTS Layer 2/3 neurons of the prefrontal cortex display higher gain of somatic excitability, responding with a higher number of action potentials for a given stimulus, in fmr1-/y mice. In fmr1-/y L2/3 neurons, action potentials are taller, faster and narrower. Outside-out patch clamp recordings revealed that the maximum Na+ conductance density is higher in fmr1-/y L2/3 neurons. Measuremen...

BACKGROUND Fragile X syndrome is caused by the expansion of a CGG trinucleotide repeat at the 5' untranslated region of the fragile X mental retardation 1 gene (FMR1). When expanded to >200 repeats (full mutation), the repeat region and the adjacent promoter CpG island become hypermethylated, rendering FMR1 transcriptionally inactive. Conventional molecular diagnosis of fragile X syndrome invol...

BACKGROUND The FMR1 premutation is associated with overt primary ovarian insufficiency (POI). However, its prevalence in women with occult POI (i.e. menstrual cycles, but impaired ovarian response) has not been examined. We hypothesized that both the FMR1 premutation and intermediate allele is more frequent in infertile women with occult POI than in controls, and that a repeat length cutoff mig...

Submit Manuscript | http://medcraveonline.com Abbreviations: FXS: Fragile X syndrome; PVET: Passive-Viewing Eye Tracking Task; MSEL: Mullen Scales of Early Learning; PLS: Preschool Language Scale; FMR1: Fragile X Mental Retardation 1; FMRP: FMR1 Protein; SSRI: Selective Serotonin Reuptake Inhibitor; ASD: Autism Spectrum Disorder; CA: Chronological Age; MA: Mental Age; CDI: MacArthur-Bates Commu...

BACKGROUND In premature ovarian failure (POF), cessation of menstruation occurs before the expected age of menopause. Approximately 1% of women are affected. FMR1 premutation was reported to be responsible for up to 3.3%-6.7% of sporadic POF and 13% of familial cases in Caucasians, while the data was absent in Chinese population. Therefore, the impact of FMR1 CGG repeat on ovarian reserve is ne...

Bennett CE, Conway GS, Macpherson JN, Jacobs PA, Murray A. Intermediate sized CGG repeats are not a common cause of idiopathic premature ovarian failure. Hum Reprod 2010;25:1335–1338. Chen LS, Tassone F, Sahota P, Hagerman PJ. The (CGG)n repeat element within the 5′ untranslated region of the FMR1 message provides both positive and negative cis effects on in vivo translation of a downstream rep...

Variability among individuals in the severity of fragile X syndrome (FXS) is influenced by epigenetic methylation mosaicism, which may also be common in other complex disorders. The epigenetic signal of dense promoter DNA methylation is usually associated with gene silencing, as was initially reported for FMR1 alleles in individuals with FXS. A paradox arose when significant levels of FMR1 mRNA...

Expansion of a trinucleotide (CGG) repeat element within the 5' untranslated region (5'UTR) of the human FMR1 gene is responsible for a number of heritable disorders operating through distinct pathogenic mechanisms: gene silencing for fragile X syndrome (>200 CGG) and RNA toxic gain-of-function for FXTAS (∼ 55-200 CGG). Existing models have focused almost exclusively on post-transcriptional mec...

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by the loss-of-function of fragile X mental retardation protein (FMRP). The loss of FMRP function in neurons abolishes its suppression on mGluR1/5-dependent dendritic protein translation, enhancing mGluR1/5-dependent synaptic plasticity and other disease phenotypes in FXS. In this study, we describe a new activation function of FM...