Rare Loss-Of-Function Mutations Of Ptgir Identified In Fibromuscular Dysplasia And Spontaneous Coronary Artery Dissection

Background Fibromuscular Dysplasia (FMD) and Spontaneous Coronary Artery Dissection (SCAD) are related, non-atherosclerotic arterial diseases mainly affecting middle-aged women. Little is known about their physiopathological mechanisms. Objectives We aimed to identify rare genetic causes to elucidate molecular mechanisms implicated in FMD and SCAD. Methods We analyzed 29 exomes that included familial and sporadic FMD. Follow-up was conducted by targeted or Sanger sequencing (1,071 FMD and 365 SCAD patients) or lookups in exome (264 FMD) or genome sequences (488 SCAD), all independent and unrelated. We used TRAPD burden test to test for enrichment in patients compared to gnomAD controls. The biological effects of variants on receptor signaling and protein expression were characterized using transient overexpression in human cells. Results We identified one rare loss-of-function variant (LoF) (MAFgnomAD=0.000075) shared by two FMD sisters in the prostaglandin I2 receptor (hIP) gene ( PTGIR ), a key player in vascular remodeling. Follow-up in >1,300 FMD patients revealed four additional LoF allele carriers and a putative enrichment in FMD (PTRAPD=8×10−4), in addition to several rare missense variants. We confirmed the LoFs (Q163X and P17RfsX6) and one missense (L67P) to severely impair hIP function in vitro . Genetic analyses of PTGIR in SCAD revealed one patient who carries Q163X, one with L67P and one carrying a rare splicing mutation (c.768+1C>G), but not a significant enrichment (PTRAPD=0.12) in SCAD. Conclusions Our study shows that rare genetic mutations in PTGIR are enriched among FMD patients and found in SCAD patients, suggesting a role for prostacyclin signaling in non-atherosclerotic stenosis and dissection. Condensed abstract Fibromuscular Dysplasia (FMD) and Spontaneous Coronary Artery Dissection (SCAD) are non-atherosclerotic arterial diseases predominantly affecting women. Their mechanisms and genetic causes are poorly understood. We identified rare loss-of-function mutations of the prostacyclin receptor gene ( PTGIR ) in several FMD and SCAD patients, including two affected sisters, and several unrelated patients. We also showed that a rare missense mutation of PTGIR severely impairs prostacyclin receptor function in vitro . Our data provide evidence for a role for prostacyclin signaling in the etiology of FMD and SCAD providing leads towards this mechanism. ### Competing Interest Statement Dr Azizi reports grants from French Ministry of Health, during the conduct of the study; grants and nonfinancial support from Recor, grants from Idorsia, Novartis, Quantum Genomics, and French Federation of Cardiology; personal fees from CVRx and Novartis, for work unrelated to this work. Dr Ganesh is a non-compensated member of the Medical Advisory Board of the Fibromuscular Dysplasia Society of America, a non-profit organization. Dr Adlam has received research funding from Abbott vascular to support a clinical research fellow, funding from Astra Zeneca inc. for unrelated research and has conducted unrelated consultancy for GE inc. The remaining authors have no disclosures to declare. ### Funding Statement The French studies are supported by a European Research Council grant (ERC-Stg-ROSALIND-716628) to N B-N. The ARCADIA study was sponsored by the Assistance Publique-Hôpitaux de Paris and funded by a grant from the French Ministry of Health (Programme Hospitalier de Recherche Clinique 2009, AOM 08192) and the Fondation de Recherche sur l’Hypertension Artérielle. The French SCAD study is supported by the French Society of Cardiology foundation "Coeur et recherche", the French Coronary Atheroma and Interventional Cardiology Group (GACI). The DEFINE-FMD is supported by the US National Institutes of Health (R01HL130423, R01HL135093, T32HL007824). The University of Michigan study is supported by NHLBI (R01HL139672), Doris Duke Charitable Foundation, University of Michigan Frankel Cardiovascular Center, the University of Michigan Taubman Institute, sequencing services by the Northwest Genomics Center at the University of Washington, Department of Genome Sciences, under U.S. Federal Government contract number HHSN268201j0037C from the NHLBI. The Cleveland Clinic FMD Biorepository was supported in part by the NIH, National Center for Research Resources, CTSA 1UL1RR024989, Cleveland, Ohio. GeneBank was supported in part by grants from NHLBI and Office of Dietary Supplements (P01 HL076491, P01 HL147823, R01HL128300 and R01HL103866) to S.L.H. The UK SCAD study was supported by BeatSCAD, the British Heart Foundation PG/13/96/30608 and the Leicester NIHR Biomedical Research Centre ### Author Declarations All relevant ethical guidelines have been followed; any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript. Yes All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data reported are individual mutations describes in a small sample of patients and are described in detail and made available in the manuscript. All raw data of the in vitro experiments is available to be shared if requested. * FMD : Fibromuscular dysplasia SCAD : Spontaneous Coronary Artery Dissection LoF : loss-of-function mutation hIP : human prostacyclin receptor PTGIR : prostacyclin I2 receptor gene TP : Thromboxane A2 Receptor cAMP : cyclic adenosine mono-phosphate SMC : smooth muscle cell