Fig 2. Correlation of Small Airway Epithelium (SAE) DNA methylation and gene expression.

Unique genes that show differences in DNA methylation between waterpipe smokers and nonsmokers (p<0.05, fold-change > ±1.5) that also have corresponding gene expression probes on the Affymetrix HG-U133 Plus 2.0 array (673 unique genes from the 727 HpaII probe fragments differentially methylated in waterpipe smokers compared to nonsmokers). The starburst plot shows -log₁₀ p value of waterpipe smokers/nonsmokers plotted for DNA methylation (x-axis) vs gene expression (y-axis) for each gene. Dashed lines, p values = 0.05. Red dots are probesets with differential DNA methylation and gene expression, gray dots are differentially expressed for DNA methylation but not for gene expression. Left upper quadrant—hypomethylated genes with up-regulated gene expression. Right upper quadrant—hypermethylated genes with up-regulated gene expression. Left lower quadrant—hypomethylated genes with down-regulated gene expression. Right lower quadrant—hypermethylated genes with down-regulated gene expression.