Rare Variants in HTRA1, SGTB, and RBM12 Confer Risk of Atherosclerotic Cardiovascular Disease Independent of Traditional Cardiovascular Risk Factors

BACKGROUND: Atherosclerosis is a pathophysiological process common to a range of cardiovascular diseases. We reasoned that considering clinical presentations of atherosclerosis across the coronary, peripheral, and cerebrovasculature as a single entity would enhance statistical power to identify rare genetic variation driving pathological processes across multiple vascular beds. METHODS: We performed an exome-wide association study of atherosclerotic cardiovascular disease in 434 438 UK Biobank participants of European ancestry. RESULTS: We identified rare, predicted damaging variants in HTRA1, SGTB, and RBM12 to be associated with risk of atherosclerotic cardiovascular disease, independent of known risk factors. Both SGTB and HTRA1 were downregulated in the aorta of patients with coronary artery disease compared with controls. Loss-of-function variants in the RNA-binding protein RBM12 increased the risk of coronary, cerebrovascular, and peripheral vascular diseases to a similar extent. SGTB increased the risk of atherosclerotic cardiovascular disease in the coronary and peripheral circulations but not the cerebrovasculature. While loss-of-function variants in HTRA1 are known to cause monogenic stroke syndromes, we found that damaging missense variants in HTRA1 are associated with increased risk of disease in both the cerebrovascular and coronary circulation. Surprisingly, the increased risk of coronary artery disease was driven predominantly by a single missense variant (p.R227W; minor allele frequency, 0.009). In vitro, the R227W mutant HTRA1 efficiently proteolyzed the disordered substrate casein but not aggregated α-synuclein. In contrast, a stroke risk-raising variant (D320N) could not efficiently process any of the tested substrates. CONCLUSIONS: We identified novel genetic variants predisposing to atherosclerotic cardiovascular diseases that act independently of established cardiovascular risk factors. The observed phenotypic and functional heterogeneities between HTRA1 variants suggest that distinct biochemical mechanisms drive HTRA1-related vascular disease in the brain and heart.