CCDC13 and periodontitis: 15 DEGs had been reported in previous human GWAS on periodontitis with P < 9 × 10−6 (C1orf87, HLA-DOA, BIRC5, CCDC13, GLDC, GPR141, OTOF, IFI16, ETNK2, TTLL11, ATP5S, GRID1, LBP, NIN, and VAV1; Appendix Table 4).