CD9 and asthma: We identified several significant mediation genes (Table 2 and Additional file 2: Table S8) including INAGL1, SERPINE1, TLR5, SLC9A3 and CD9 for asthma severity and INAGL1, TLR5, CD9 for FEV1 (Table 2 and Additional file 2: Table S9), suggesting potential regulation effect of DNAm on gene expression in asthma.