FURIN and aneurysm: 10 We selected FURIN as a candidate gene because it is expressed in the aorta, and is involved in TGF-β signalling.11,12 While the candidate gene approach has been used successfully to find novel susceptibility genes for other polygenic diseases such as obesity, it has not been used previously in aneurysm research.13 This approach is preferred over gene burden analyses, given that disease alleles also occur in unaffected individuals (non-penetrance) in the general population that would serve as the control group.