CHRNA3 and chronic obstructive pulmonary disease: Genome-wide association studies (GWASs) have demonstrated a strong association between COPD and polymorphisms in the CHRNA3/5 (cholinergic nicotinic receptor alpha 3/5) and IREB2 (iron-responsive element-binding protein 2) genes, both located within the chromosomal region 15q25 [2,3].