Early Detection of Fragile X Syndrome: Applications of a Novel Approach for Improved Quantitative Methylation Analysis in Venous Blood and Newborn Blood Spots Academic Article uri icon

abstract

  • BACKGROUND:Standard fragile X syndrome (FXS) diagnostic tests that target methylation of the fragile X mental retardation 1 (FMR1) CpG island 5' of the CGG expansion can be used to predict severity of the disease in males from birth, but not in females. METHODS:We describe methylation specific-quantitative melt analysis (MS-QMA) that targets 10 CpG sites, with 9 within FMR1 intron 1, to screen for FXS from birth in both sexes. The novel method combines the qualitative strengths of high-resolution melt and the high-throughput, quantitative real-time PCR standard curve to provide accurate quantification of DNA methylation in a single assay. Its performance was assessed in 312 control (CGG <40), 143 premutation (PM) (CGG 56-170), 197 full mutation (FM) (CGG 200-2000), and 33 CGG size and methylation mosaic samples. RESULTS:In male and female newborn blood spots, MS-QMA differentiated FM from control alleles, with sensitivity, specificity, and positive and negative predictive values between 92% and 100%. In venous blood of FM females between 6 and 35 years of age, MS-QMA correlated most strongly with verbal IQ impairment (P = 0.002). In the larger cohort of males and females, MS-QMA correlated with reference methods Southern blot and MALDI-TOF mass spectrometry (P < 0.05), but was not significantly correlated with age. Unmethylated alleles in high-functioning FM and PM males determined by both reference methods were also unmethylated by MS-QMA. CONCLUSIONS:MS-QMA has an immediate application in FXS diagnostics, with a potential use of its quantitative methylation output for prognosis in both sexes.

authors

  • Inaba, Y
  • Schwartz, CE
  • Bui, QM
  • Li, X
  • Skinner, C
  • Field, M
  • Wotton, T
  • Hagerman, RJ
  • Francis, D
  • Amor, DJ
  • Hopper, JL
  • Loesch, DZ
  • Bretherton, L
  • Slater, HR
  • Godler, DE

publication date

  • 2014

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