Genetic basis of hereditary thoracic aortic aneurysms and dissections

Recent advances in DNA sequencing technology have identified several causative genes for hereditary thoracic aortic aneurysms and dissections (TAADs), including Marfan syndrome (MFS), Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, and familial non-syndromic TAADs. Syndromic TAADs are typically caused by pathogenic variants in the transforming growth factor-β signal and extracellular matrix-related genes (e.g. FBN1, TGFBR1, TGFBR2, SMAD3, TGFB2, and COL3A1). On the other hand, approximately 20% of the non-syndromic hereditary TAADs result from altered components of the contractile apparatus of vascular smooth muscle cells, which are encoded by ACTA2, MYH11, MYLK, and PRKG1 genes; however, the remaining 80% cannot be explained by previously reported candidate genes. Moreover, the relationship between the genotype and phenotype of TAADs has extensively been reported to investigate better methods for risk stratification and further personalized treatment strategies. With regard to MFS-causing FBN1, recent reports have shown significantly increased risk of aortic events in patients carrying a truncating variant or a variant exhibiting a haploinsufficient-type effect, typically comprising nonsense or small insertions/deletions resulting in out-of-frame effects, compared to those carrying a variant with dominant negative-type effect, typically comprising missense variants. Therefore, cardiologists are required to have sufficient knowledge regarding the genetics of hereditary TAADs for providing the best clinical management, with an appropriate genetic counseling. In the current review, we present current advances in the genetics of hereditary TAADs and discuss the benefits and limitations with respect to the use of this genetic understanding in clinical settings.