This study may also inform general strategies for epistasis investigations: given that one putatively interacting locus is in a region previously associated with asthma or lung function (ADAM33/HSPA12B), and the other is highly biologically plausible (GLI2), this study provides evidence in support of investigational strategies that restrict the epistasis search space to features with prior disease relevance. Here, HSPA12B is linked to asthma.