SSPOP and irritable bowel syndrome: DNA methylation levels were significantly higher in selected CpG (5′‐C‐phosphate‐G‐3′) sites of GSTM5 (glutathione‐S‐transferases mu 5), SSPO (subcommissural organ‐spondin), and TPPP (tubulin polymerization promoting protein) genes in IBS patients compared to controls.