Methylation of novel markers of fragile X alleles is inversely correlated with FMRP expression and FMR1 activation ratio

David Eugeny Godler, Flora Tassone, Danuta Zuzanna Loesch, Annette Kimball Taylor, Freya Gehling, Randi J Hagerman, Trent Burgess, Devika Ganesamoorthy, Debbie Hennerich, Lavinia Gordon, Andrew Evans, K. H. Choo, Howard Robert Slater

Research output: Contribution to journalArticlepeer-review

78 Scopus citations


The fragile X syndrome (FXS) is caused by silencing of the fragile X mental retardation gene (FMR1) and the absence of its product, fragile X mental retardation protein (FMRP), resulting from CpG island methylation associated with large CGG repeat expansions (more than 200) termed full mutation (FM). We have identified a number of novel epigenetic markers for FXS using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), naming the most informative fragile X-related epigenetic element 1 (FREE1) and 2 (FREE2). Methylation of both regions was correlated with that of the FMR1 CpG island detected using Southern blot (FREE1 R = 0.97; P < 0.00001, n = 23 and FREE2 R = 0.93; P < 0.00001, n = 23) and nega- tively correlated with lymphocyte expression of FMRP (FREE1 R 520.62; P = 0.01, n = 15 and FREE2 R 520.55; P = 0.03, n = 15) in blood of partially methylated 'high functioning' FM males. In blood of FM carrier females, methylation of both markers was inversely correlated with the FMR1 activation ratio (FREE1 R 520.93; P < 0.0001, n = 12 and FREE2 R 520.95; P < 0.0001, n = 9). In a sample set of 49 controls, 18 grey zone (GZ 40-54 repeats), 22 premutation (PM 55-170 repeats) and 22 (affected) FXS subjects, the FREE1 methylation pattern was consistent between blood and chorionic villi as a marker of methylated FM alleles and could be used to differentiate FXS males and females from controls, as well as from carriers of GZ/PM alleles, but not between GZ and PM alleles and controls. Considering its high-throughput and speci- ficity for pathogenic FM alleles, low cost and minimal DNA requirements, FREE MALDI-TOF MS offers a unique tool in FXS diagnostics and newborn population screening.

Original languageEnglish (US)
Article numberddq037
Pages (from-to)1618-1632
Number of pages15
JournalHuman Molecular Genetics
Issue number8
StatePublished - Jan 29 2010

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)
  • Molecular Biology


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