title: Examination of the effect of the polymorphic CGG repeat in the FMR1 gene on cognitive performance.
abstract: A CGG repeat sequence located in the 5' untranslated region of the FMR1 gene is polymorphic with respect to size and stability of the repeat during parent-offspring transmission. When expanded to over 200 repeats, the gene is hypermethylated and silenced, leading to fragile X syndrome (FXS). Recently, alleles with large unmethylated repeat tracts (premutations) have been associated with ovarian failure and a late-onset tremor/ataxia syndrome, symptoms unrelated to FXS. To further investigate the phenotype consequence of high repeat alleles, we have analyzed Wechsler adult intelligence scales-III (WAIS-III) measures on 66 males and 217 females with a wide range of repeat sizes. Among females only, we found that FMR1 repeat size and transcript level significantly explained approximately 4% of the variance in the Verbal IQ summary measure, suggesting that this polymorphism is one of many factors that influence variation in cognitive performance. Because of the well established association of increasing repeat size with decreasing age at menopause, we also investigated the reproductive stage and use of hormone replacement therapy (HRT) as a covariate to model verbal intelligence quotient (VIQ). We found that it explained an additional 5% of the variance in VIQ, but did not interact with FMR1 repeat and transcript level.
authors.affiliation: Emory University, Atlanta, GA 30322, USA,
authors.forename: Emily Graves
authors.initials: EG
authors.lastname: Allen
authors.forename: Stephanie
authors.initials: S
authors.lastname: Sherman
authors.forename: Ann
authors.initials: A
authors.lastname: Abramowitz
authors.forename: Mary
authors.initials: M
authors.lastname: Leslie
authors.forename: Gloria
authors.initials: G
authors.lastname: Novak
authors.forename: Michele
authors.initials: M
authors.lastname: Rusin
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Scott
authors.forename: Richard
authors.initials: R
authors.lastname: Letz
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology; D003071:Cognition; D003430:Cross-Sectional Studies; D005260:Female; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics*; D005600:Fragile X Syndrome / Q000235:genetics; D020249:Hormone Replacement Therapy; D006801:Humans; D007360:Intelligence / Q000235:genetics*; D007361:Intelligence Tests; D007802:Language; D008279:Magnetic Resonance Imaging; D008297:Male; D008593:Menopause; D008875:Middle Aged; D010641:Phenotype; D018911:Trinucleotide Repeats
chemical_list: D051860:Fragile X Messenger Ribonucleoprotein 1; C497683:FMR1 protein, human