Jeunemaı̂tre, Xavier

Introduction: Fibromuscular dysplasia (FMD) is a non-atherosclerotic arteriopathy of unknown etiology, afflicting mostly middle-aged women. It is characterized by stenotic lesions of the vascular wall in middle-size arteries, sometimes associated with dissection, aneurysm or tortuosity. Renovascular hypertension is a major presentation of FMD and 50–85% of FMD patients are hypertensive. Methods & Results: We report results from the first genome-wide association meta-analysis of six studies including 1556 FMD cases and 7100 controls. We identified four robustly associated loci (PHACTR1, LRP1, ATP2B1, and LIMA1). Using colocalization and transcriptome-wide association analysis with arterial expression datasets, we found PHACTR1, LRP1 and ATP2B1 as target genes at FMD loci and identified one additional locus (SLC24A3). We analysed chromatin accessibility in artery-derived primary cells and found that FMD associated variants were located in arterial specific regulatory elements active in smooth muscle cells. Target genes were broadly involved in mechanisms related to actin cytoskeleton and intracellular calcium homeostasis, central to vascular contraction. All FMD loci were also associated to at least one blood pressure trait. Colocalization analysis supported the same genetic variants to cause association to FMD and systolic blood pressure at PHACTR1, ATP2B1 and LIMA1 loci, and for FMD and pulse pressure at PHACTR1, LRP1 and ATP2B1 loci. Using genome-wide genetic correlation, we found a significant association between FMD and blood pressure. Mendelian Randomization analysis supported genetically determined systolic blood pressure to significantly increase the risk of FMD. However, we confirmed using adjusted and stratified analyses that hypertension status alone was not driving the association with FMD at top loci. We also report an important genetic overlap of FMD with migraine, intracranial aneurysm, coronary artery disease and myocardial infarction. Conclusion: Our study confirms FMD as a polygenic disease following a complex genetic mode of inheritance. We find that FMD shares an important part of its genetic basis with blood pressure regulation, involving in particular several genes related to intracellular calcium homeostasis and vascular smooth muscle contraction. These results are consistent with previous studies showing systemic alterations in vascular contraction in FMD patients, even outside of affected arterial beds. While the mechanisms through which FMD may cause renovascular hypertension are well known, further studies will be required to determine how alterations in vascular contraction may lead to the arterial remodeling observed in FMD.

Abstract Aims Mitral valve prolapse (MVP) is a common valvular heart disease with a prevalence of >2% in the general adult population. Despite this high incidence, there is a limited understanding of the molecular mechanism of this disease, and no medical therapy is available for this disease. We aimed to elucidate the genetic basis of MVP in order to better understand this complex disorder. Methods and results We performed a meta-analysis of six genome-wide association studies that included 4884 cases and 434 649 controls. We identified 14 loci associated with MVP in our primary analysis and 2 additional loci associated with a subset of the samples that additionally underwent mitral valve surgery. Integration of epigenetic, transcriptional, and proteomic data identified candidate MVP genes including LMCD1, SPTBN1, LTBP2, TGFB2, NMB, and ALPK3. We created a polygenic risk score (PRS) for MVP and showed an improved MVP risk prediction beyond age, sex, and clinical risk factors. Conclusion We identified 14 genetic loci that are associated with MVP. Multiple analyses identified candidate genes including two transforming growth factor-β signalling molecules and spectrin β. We present the first PRS for MVP that could eventually aid risk stratification of patients for MVP screening in a clinical setting. These findings advance our understanding of this common valvular heart disease and may reveal novel therapeutic targets for intervention.

Fibromuscular dysplasia (FMD) is a nonatherosclerotic vascular disease leading to arterial stenosis, aneurysm and dissection, mainly in renal and carotid arteries. FMD has higher prevalence in females (80-90%) and is associated with hypertension and stroke. The pathophysiology of FMD is unclear and a genetic origin is suspected. We performed a genetic association study in European ancestry individuals. The discovery included 249 cases and 689 controls, in which we analyzed ∼26K common variants (MAF>0.05) using an exome-chip array. We followed up 13 loci (P<10-4) in 393 cases and 2537 controls and replicated a signal on Chr6. Three additional studies (combined Ncases=512, Ncontrols=669) confirmed this association, with an overall OR of 1.39, (P=7.4х10e-10 , All Ncases=1154, All Ncontrols=3895). The FMD risk variant is intronic to the phosphatase and actin regulator 1 gene (PHACTR1), involved in angiogenesis and cell migration. PHACTR1 is a risk locus for coronary artery disease, migraine, and cervical artery dissection, which may occur in FMD. We found a significant association between the risk allele and higher central pulse pressure (P=0.0009), increased intima media thickness (P=0.001) and wall cross-sectional area (P=0.003) of carotids assessed by echotracking in 3800 population-based individuals. The correlation of genotypes with the expression of PHACTR1 in primary cultured human fibroblasts showed higher expression in FMD risk allele carriers, compared to non carriers (N=57, P=0.02). Finally, Phactr1 knockdown of zebrafish showed significantly dilated vessels (P=0.003) indicating impaired vascular development. In conclusion, we report the first risk locus for FMD with the largest genetic association study conducted so far. Our data reveal a common genetic variant at PHACTR1 providing indices of shared pathophysiology between FMD and other cardiovascular and neurovascular diseases.

Abstract Objective: Fibromuscular dysplasia (FMD) is an arteriopathy that presents mainly by hypertension, stroke or dissection. Diagnosis is often made in middle-aged women with few cardiovascular risk factors. We aim at identifying common genetic variants associated to FMD. Design and method: We tested ∼6.5 million common genetic variants (MAF > 0.01) in 1962 cases and 7100 controls from 6 studies using variants and gene-based association analyses. Participants were of European ancestry, with similar characteristics (91% multifocal, 88% women), diagnosis methods and inclusion/exclusion criteria. Transcriptome-wide association (TWAS), eQTL, gene expression by sex and colocalization analyses used expression data in arteries from GTEx and/or FMD patients and matched controls. Open chromatin regions were defined using ATAC-Seq on primary human fibroblasts, smooth muscle and endothelial cells. Genetic correlations were assessed using summary statistics from UKBiobank and/or published studies by linkage disequilibrium score regression and multi-trait-based conditional and joint analyses (mtCOJO). Results: We confirmed the previously identified PHACTR1 locus and identified three new loci (LRP1, ATP2B1, and LIMA1) associated with FMD. TWAS in arteries identified one additional locus (SLC24A3). Through integration of annotation datasets, we provided prioritization of variants and genes. These are consistently and specifically expressed in fibroblasts, smooth muscle cells, and arterial tissues. PHACTR1 and SLC24A3 showed sex differences in gene expressions consistent with the direction of effects of FMD risk alleles. FMD genes are involved in regulatory mechanisms related to actin cytoskeleton and intracellular calcium homeostasis, two mechanisms central to vascular contraction. We found significant genetic overlaps between FMD and blood pressure traits, for the associated loci and globally at the genome level, but demonstrated that hypertension is not driving the genetic association with FMD. We also found positive genetic correlations with migraine and intracranial aneurysm, and an inverse correlation with coronary artery disease, independently from the genetics of blood pressure. Conclusions: We describe robustly associated loci and genes with FMD and provide several new leads toward understanding biological mechanisms of stenosis and dissection in young women in the absence of atherosclerosis, which shares part of its genetic basis with more common cardiovascular and neurovascular diseases.