The genes contributing most to the periodontitis group, with highest significance, were MUC4, MMP7, interleukin 19 (IL19), and immunoglobulin heavy variable 3–43 (IGHV3-43), while the corresponding genes in the healthy subjects were collagen type X alpha 1 (COL10A1), WNT1-inducible signaling pathway protein 2 (WISP2), and Sp7 transcription factor (SP7) (Fig. 2d). The gene discussed is MMP7; the disease is periodontitis.