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Bicuspid aortic valve (BAV) is a common congenital heart defect (population incidence, 1–2%) 1 – 3 that frequently presents with ascending aortic aneurysm (AscAA) 4 . BAV/AscAA shows autosomal dominant inheritance with incomplete penetrance and male predominance. Causative gene mutations are known for ≤1% of nonsyndromic BAV cases with/without AscAA (e.g. NOTCH1 , SMAD6 ) 5 – 8 , impeding mechanistic insight and development of therapeutic strategies. We report the identification of mutations in ROBO4 , encoding a factor known to contribute to endothelial performance, that segregate with disease in two families. Targeted sequencing of ROBO4 revealed enrichment for rare variants in BAV/AscAA probands compared to controls. Targeted silencing of ROBO4 or mutant ROBO4 expression in endothelial cell lines results in impaired barrier function and a synthetic repertoire suggestive of endothelial-to-mesenchymal transition (EnMT); concordant BAV/AscAA-associated findings are observed in patients and animal models deficient for ROBO4. These data identify a novel endothelial etiology for this common human disease phenotype.

Bicuspid aortic valve (BAV) is the most common congenital heart defect. Although many BAV patients remain asymptomatic, at least 20% develop thoracic aortic aneurysm (TAA). Historically, BAV-related TAA was considered as a hemodynamic consequence of the valve defect. Multiple lines of evidence currently suggest that genetic determinants contribute to the pathogenesis of both BAV and TAA in affected individuals. Despite high heritability, only very few genes have been linked to BAV or BAV/TAA, such as NOTCH1, SMAD6, and MAT2A. Moreover, they only explain a minority of patients. Other candidate genes have been suggested based on the presence of BAV in knockout mouse models (e.g., GATA5, NOS3) or in syndromic (e.g., TGFBR1/2, TGFB2/3) or non-syndromic (e.g., ACTA2) TAA forms. We hypothesized that rare genetic variants in these genes may be enriched in patients presenting with both BAV and TAA. We performed targeted resequencing of 22 candidate genes using Haloplex target enrichment in a strictly defined BAV/TAA cohort (n = 441; BAV in addition to an aortic root or ascendens diameter ≥ 4.0 cm in adults, or a Z-score ≥ 3 in children) and in a collection of healthy controls with normal echocardiographic evaluation (n = 183). After additional burden analysis against the Exome Aggregation Consortium database, the strongest candidate susceptibility gene was SMAD6 (p = 0.002), with 2.5% (n = 11) of BAV/TAA patients harboring causal variants, including two nonsense, one in-frame deletion and two frameshift mutations. All six missense mutations were located in the functionally important MH1 and MH2 domains. In conclusion, we report a significant contribution of SMAD6 mutations to the etiology of the BAV/TAA phenotype.

Background-Venous coronary artery bypass grafts (CABGs) are prone to accelerated atherosclerosis. In atherosclerotic diseases, serum C-reactive protein (CRP) levels have become an important diagnostic and prognostic marker. The origin of CRP in this setting remains to be elucidated. Methods and Results-Monoclonal anti-CRP identified CRP expression in medial and intimal ␣-actin-positive smooth muscle cells (SMCs) of diseased CABGs with type V and VI lesions and also of native saphenous veins of atherosclerotic individuals. In addition, patent coronary arteries with type IV and V but not with type I through III lesions exhibited intense SMC staining for CRP. Calcified desobliterates of occluded coronary arteries with end-stage disease did not show SMC staining for CRP and were consistently negative for CRP mRNA, as detected by means of real-time polymerase chain reaction. However, CRP mRNA was expressed in 11 of 15 diseased CABGs and also in 10 of 15 native veins. By contrast, only 3 of 18 internal mammary and 4 of 12 radial arteries with virtually no atherosclerosis were positive for CRP mRNA. Conclusions-CRP is produced by SMCs of atherosclerotic lesions with active disease but not in end-stage plaques. The role of CRP constitutively expressed by normal vascular tissue in vein graft disease has yet to be elucidated. Key Words: atherosclerosis Ⅲ inflammation Ⅲ restenosis I n recent years, serum C-reactive protein (CRP) has become a powerful marker of future cardiovascular events. 1,2 CRP is linked to vascular inflammation because it attracts monocytes and mediates LDL uptake by macrophages. 3,4 Furthermore, CRP induces adhesion molecule expression but attenuates NO production of human endothelial cells. 5,6 Histological investigations have described an association between intimal CRP deposition and the development of atherosclerotic plaques. 7,8 None of these studies supposed that CRP immunoreactivity resulted from local expression of CRP. We speculated that elevated serum CRP levels do not reflect continuous hepatic CRP synthesis but rather represent local production. This hypothesis has recently been corroborated by findings of detectable CRP mRNA and protein in postmortem cases of aortosclerotic plaques. 9 Yasojima et al 9 described smooth muscle cells (SMCs) and macrophages as sites of CRP production. These data-together with our observation of CRP production by renal epithelial cells 10 -argue against the liver as the only site of CRP formation. The aim of the present study was to examine local generation of CRP in human atherosclerotic lesions. Because we have been interested for years in the increased reocclusion rate of coronary artery venous bypass grafts (CABGs), 11 we investigated samples of diseased CABGs for CRP mRNA and protein expression. The results were compared with patent atherosclerotic coronary arteries and calcified coronary desobliterates as well as with native saphenous veins, internal mammary arteries (IMAs), and radial arteries (RAs). Methods Sample CollectionFor CRP mRNA detection, 10 d...

The structure of the nondilated and dilated aortic wall in bicuspidy and tricuspidy are intrinsically different, with the latter having more aspects of aging. In bicuspidy there is a defective smooth muscle cell differentiation possibly linked to lowered lamin A/C expression. Based on this vessel wall immaturity and increased susceptibility to dilation, different diagnostic and therapeutic approaches are warranted.