Figure 2

Relationships between intragenic DNA methylation in buccal epithelial cells and FSIQ. (a) Organization of the Xq27.3 sequence encompassing specific FREE2 CpG sites at the FMR1 exon 1/intron 1 boundary (GenBank L29074 L38501) targeted by MALDI-TOF MS methylation analysis. The CTCF box indicates 5′ CTCF binding sites from UCSF Chip-Seq which overlap with FREE2 CpG10-12; the RNA:DNA hybrid box indicates locations of forward and reverse primers used in ChiRP to show formation of RNA:DNA hybrids denoted as fP(200-400) in Colak et al.32. (b) Relationships between corrected FSIQ, obtained through extrapolation using the Whitaker and Gordon method (cFSIQ), and FREE2 DNA methylation at the FMR1 intron 1/exon 1 boundary, measured in buccal epithelial cells (BEC). (c) Relationships between FREE2 DNA methylation in BEC and standardized FSIQ (FSIQ) only (open circles) with invalid scores omitted; and dFSIQ (crosses), which include FSIQ and invalid scores included as default of FSIQ of 40. Note: black broken lines represent lines of best fit from linear regression analyses. The parallel grey broken line highlights the FSIQ of 40 as the floor of standardized FSIQ scores.