FMRP expression as a potential prognostic indicator in fragile X syndrome

Flora Tassone, Randi J Hagerman, David N. Iklé, Pamela N. Dyer, Megan Lampe, Rob Willemsen, Ben A. Oostra, Annette K. Taylor

Research output: Contribution to journalArticlepeer-review

253 Scopus citations


Absence or deficit of FMR1 protein (FMRP) resulting from methylation of full mutation genes is the fundamental defect in fragile X syndrome. We used FMRP immunocytochemistry and detailed phenotypic assessment to investigate the relationship between degree of FMRP expression and the broad clinical spectrum of impairment in 80 individuals affected with fragile X syndrome. FMRP expression correlated with IQ in mosaic males (P=0.043), males with a partially methylated full mutation (P=0.0005), and females with a full mutation (P=0.046). In the females, FMRP expression also correlated with the number of fragile X physical features (P=0.0003). Even modest deficits in FMRP result in some manifestations of fragile X syndrome. In this initial study of 53 males, FMRP expression testing had a very high positive predictive value (100%, confidence interval of 29-100%) for a nonretarded IQ among males with expression of FMRP in ≥50% of lymphocytes (3 males), suggesting that FMRP expression may have potential as a prognostic indicator in males with fragile X syndrome.

Original languageEnglish (US)
Pages (from-to)250-261
Number of pages12
JournalAmerican Journal of Medical Genetics
Issue number3
StatePublished - May 28 1999
Externally publishedYes


  • Activation ratio
  • Clinical correlation
  • FMR1 mutation
  • FMRP
  • Fragile X syndrome
  • Immunocytochemistry
  • Mosaic
  • Partial methylation

ASJC Scopus subject areas

  • Genetics(clinical)


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