Danny Huylebroeck

Aim Aortic aneurysms (AA) frequently involve dysregulation of transforming growth factor β (TGF-β)-signaling in the aorta. Here, FURIN was tested as aneurysm predisposition gene given its role as proprotein convertase in pro-TGF-β maturation. Methods and results Rare FURIN variants were detected by whole-exome sequencing of 781 unrelated aortic aneurysm patients and affected relatives. Thirteen rare heterozygous FURIN variants occurred in 3.7% (29) unrelated index AA patients, of which 72% had multiple aneurysms or a dissection. FURIN maturation and activity of these variants were decreased in vitro. Patient-derived fibroblasts showed decreased pro-TGF-β processing, phosphorylation of downstream effector SMAD2 and kinases ERK1/2, and steady-state mRNA levels of the TGF-β-responsive ACTA2 gene. In aortic tissue, collagen and fibrillin fibers were affected. One variant (R745Q), observed in 10 unrelated cases, affected TGF-β signaling variably, indicating effect modification by individual genetic backgrounds. Conclusion FURIN is a novel, frequent genetic predisposition for abdominal-, thoracic-, and multiple aortic or middle sized artery aneurysms in older patients, by affecting intracellular TGF-β signaling, depending on individual genetic backgrounds.