Fibrillin-1 (FBN1) mutations in patients with thoracic aortic aneurysms.

Mutations in the FBN1 gene are the cause of the Marfan syndrome, an autosomal dominant disorder with skeletal, ocular, and cardiovascular complications. Aneurysms or dissections of the ascending thoracic aorta are the major cardiovascular complications of the disorder. We tested the hypothesis that FBN1 mutations cause thoracic aortic aneurysms or dissections in patients who do not have the Marfan syndrome. The FBN1 gene was screened for mutations by use of genomic DNA from two patients with thoracic aortic aneurysms who did not have the Marfan syndrome. Individual FBN1 exons were amplified with intron-based exon-specific primers; the DNA fragments were screened for mutations using single-stranded conformational polymorphism analysis; and aberrantly migrating bands were sequenced directly. We identified a missense mutation in one patient, D1155N in exon 27. Dermal fibroblasts from the affected individual were used to study the effect of the missense mutation D1155N on fibrillin-1 cellular processing. The mutation decreased the amount of fibrillin-1 deposited into the pericellular matrix. A second putative FBN1 mutation was identified in the second patient, P1837S in exon 44. Although this alteration was not observed in 234 chromosomes from unrelated individuals, the alteration may represent a rare polymorphism. Results of these studies support the hypothesis that FBN1 mutations cause thoracic aortic aneurysms in patients who do not have the Marfan syndrome. This information is important for understanding the pathogenesis of aortic aneurysms and identification of individuals at risk for developing thoracic aortic aneurysms or dissections.