CHRNA3 and chronic obstructive pulmonary disease: Previous GWAS have identified three loci associated with COPD susceptibility: HHIP on chromosome 4q31 [12], [13], FAM13A on chromosome 4q22 [11], and a region on chromosome 15q25 encompassing candidate genes CHRNA5, CHRNA3 and IREB2, among others [12], [36].