Genome-wide association studies of asthma in children and adults have identified polymorphisms for IL33, IL1RL1/IL18R1, HLA-DQ, SMAD3, and IL2RB9 and the locus on chromosome 17q21 including the genes ZPBP2, GSDMB, and ORMDL3 that are implicated in epithelial barrier function and innate and adaptive immune responses in asthma [126,127]. Here, SMAD3 is linked to asthma.