Differential DNA methylation at the promoter regions of 12 genes (DCC, KCNA3, KCNA2, RIMS2, HOXB7, PNOC, IRX1, JSRP1, TBX1, OPCML, CECR1, SCN4B) has been detected between periodontitis and clinically healthy tissues [41]. The gene discussed is KCNA2; the disease is periodontitis.