Exome sequencing in seven families and gene-based association studies indicate genetic heterogeneity and suggest possible candidates for fibromuscular dysplasia

Moyamoya Vasculopathy and Moyamoya-Related Systemic Vasculopathy: A Review With Histopathological and Genetic Viewpoints

Systemic vasculopathy has occasionally been reported in cases of moyamoya disease (MMD). Since the pathological relationship between moyamoya vasculopathy (MMV) and moyamoya-related systemic vasculopathy (MMRSV) remains unclear, it was examined herein by a review of histopathologic studies in consideration of clinicopathological and genetic viewpoints. Although luminal stenosis was a common finding in MMV and MMRSV, histopathologic findings of vascular remodeling markedly differed. MMV showed intimal hyperplasia, marked medial atrophy, and redundant tortuosity of the internal elastic lamina, with outer diameter narrowing called negative remodeling. MMRSV showed hyperplasia, mainly in the intima and sometimes in the media, with disrupted stratification of the internal elastic lamina. Systemic vasculopathy has also been observed in patients with non-MMD carrying the RNF213 (ring finger protein 213) mutation, leading to the concept of RNF213 vasculopathy. RNF213 vasculopathy in patients with non-MMD was histopathologically similar to MMRSV. Cases of MMRSV have sometimes been diagnosed with fibromuscular dysplasia. Fibromuscular dysplasia is similar to MMD not only in the histopathologic findings of MMRSV but also from clinicopathological and genetic viewpoints. The significant histopathologic difference between MMV and MMRSV may be attributed to a difference in the original vascular wall structure and its resistance to pathological stress between the intracranial and systemic arteries. To understand the pathogeneses of MMD and MMRSV, a broader perspective that includes RNF213 vasculopathy and fibromuscular dysplasia as well as an examination of the 2- or multiple-hit theory consisting of genetic factors, vascular structural conditions, and vascular environmental factors, such as blood immune cells and hemodynamics, are needed.

The complex genetic basis of fibromuscular dysplasia, a systemic arteriopathy associated with multiple forms of cardiovascular disease

Artery stenosis is a common cause of hypertension and stroke and can be due to atherosclerosis accumulation in the majority of cases and in a small fraction of patients to arterial fibromuscular dysplasia (FMD). Artery stenosis due to atherosclerosis is widely studied with known risk factors (e.g. increasing age, male gender, and dyslipidemia) to influence its etiology, including genetic factors. However, the causes of noninflammatory and nonatherosclerotic stenosis in FMD are less understood. FMD occurs predominantly in early middle-age women, a fraction of the population where cardiovascular risk is different and understudied. FMD arteriopathies are often diagnosed in the context of hypertension and stroke and co-occur mainly with spontaneous coronary artery dissection, an atypical cause of acute myocardial infarction. In this review, we provide a comprehensive overview of the recent advances in the understanding of molecular origins of FMD. Data were obtained from genetic studies using complementary methodological approaches applied to familial, syndromic, and sporadic forms of this intriguing arteriopathy. Rare variation analyses point toward mechanisms related to impaired prostacyclin signaling and defaults in fibrillar collagens. The study of common variation, mainly through a recent genome-wide association study, describes a shared genetic link with blood pressure, in addition to point at potential risk genes involved in actin cytoskeleton and intracellular calcium homeostasis supporting impaired vascular contraction as a key mechanism. We conclude this review with future strategies and approaches needed to fully understand the genetic and molecular mechanisms related to FMD.

Novel Multifaceted Roles for RNF213 Protein

Ring Finger Protein 213 (RNF213), also known as Mysterin, is the major susceptibility factor for Moyamoya Arteriopathy (MA), a progressive cerebrovascular disorder that often leads to brain stroke in adults and children. Although several rare RNF213 polymorphisms have been reported, no major susceptibility variant has been identified to date in Caucasian patients, thus frustrating the attempts to identify putative therapeutic targets for MA treatment. For these reasons, the investigation of novel biochemical functions, substrates and unknown partners of RNF213 will help to unravel the pathogenic mechanisms of MA and will facilitate variant interpretations in a diagnostic context in the future. The aim of the present review is to discuss novel perspectives regarding emerging RNF213 roles in light of recent literature updates and dissect their relevance for understanding MA and for the design of future research studies. Since its identification, RNF213 involvement in angiogenesis and vasculogenesis has strengthened, together with its role in inflammatory signals and proliferation pathways. Most recent studies have been increasingly focused on its relevance in antimicrobial activity and lipid metabolism, highlighting new intriguing perspectives. The last area could suggest the main role of RNF213 in the proteasome pathway, thus reinforcing the hypotheses already previously formulated that depict the protein as an important regulator of the stability of client proteins involved in angiogenesis. We believe that the novel evidence reviewed here may contribute to untangling the complex and still obscure pathogenesis of MA that is reflected in the lack of therapies able to slow down or halt disease progression and severity.

Ring Finger Protein 213 in Moyamoya Disease With Pulmonary Arterial Hypertension: A Mini-Review

Moyamoya disease (MMD), most often diagnosed in children and adolescents, is a chronic cerebrovascular disease characterized by progressive stenosis at the terminal portion of the internal carotid artery and an abnormal vascular network at the base of the brain. Recently, many investigators show a great interest in MMD with pulmonary arterial hypertension (PAH). Ring finger protein 213 (RNF213) is a major susceptibility gene for MMD and also has strong correlations with PAH. Therefore, this review encapsulates current cases of MMD with PAH and discusses MMD with PAH in the aspects of epidemiology, pathology, possible pathogenesis, clinical manifestations, diagnosis, and treatment.

Renovascular hypertension in pediatric patients: update on diagnosis and management

Renovascular hypertension (RVH) is defined as an elevated blood pressure caused by kidney hypoperfusion, generally as a result of anatomic stenosis of the renal artery with consequent activation of the Renin Angiotensin-Aldosterone System. The main causes include genetic and inflammatory disorders, extrinsic compression, and idiopathic alterations. RVH is often asymptomatic and should be suspected in any child with refractory hypertension, especially if other suggestive findings are present, including those with severe hypertension, abdominal bruit, and abrupt fall of glomerular filtration rate after administration of angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers. There is a consensus that digital subtraction angiography is the gold standard method for the diagnosis of RVH. Nevertheless, the role of non-invasive imaging studies such as Doppler ultrasound, magnetic resonance angiography, or computed tomographic angiography remains controversial, especially due to limited pediatric evidence. The therapeutic approach should be individualized, and management options include non-surgical pharmacological therapy and revascularization with percutaneous transluminal renal angioplasty (PTRA) or surgery. The prognosis is related to the procedure performed, and PTRA has a higher restenosis rate compared to surgery, although a decreased risk of complications. This review summarizes the causes, physiopathology, diagnosis, treatment, and prognosis of RVH in pediatric patients. Further studies are required to define the best approach for RVH in children.

Genetics of Intracranial Aneurysms

Rupture of an intracranial aneurysm leads to aneurysmal subarachnoid hemorrhage, a severe type of stroke which is, in part, driven by genetic variation. In the past 10 years, genetic studies of IA have boosted the number of known genetic risk factors and improved our understanding of the disease. In this review, we provide an overview of the current status of the field and highlight the latest findings of family based, sequencing, and genome-wide association studies. We further describe opportunities of genetic analyses for understanding, prevention, and treatment of the disease.

Spontaneous coronary artery dissection: presentation and management options

Coronary artery dissection is a serious, life-threatening heart condition. It can occur spontaneously or due to traumatic or iatrogenic causes. Spontaneous coronary artery dissection (SCAD) is often misdiagnosed as most patients present with symptoms resembling those of an acute coronary syndrome. Clinical sequelae of SCAD include debilitating morbidities such as myocardial infarction, myocardial ischaemia, sudden cardiac death, ventricular arrhythmias amongst many other myocardial ischaemia associated complications. There are two main methods of managing patients with SCAD; conservative management with medical therapy or revascularisation by percutaneous coronary intervention or coronary artery bypass grafting.

[Fibromuscular dysplasia and its neurological manifestations]

The authors present the current data on the classification, epidemiology, etiology, neurological manifestations, prognosis, diagnosis, and treatment of patients with fibromuscular dysplasia (FMD). The review is based on the selection of publications by searching PubMed for keywords from the first sources until March 2019. FMD is a segmental non-atherosclerotic and non-inflammatory disease of large- and medium-caliber arteries leading to their stenosis. The disease occurs mostly in women (90%), and manifests itself in the 5th decade of life. In the cerebrovascular form of FMD, the extracranial internal carotid artery and the vertebral artery are usually affected. Diagnosis is based on the identification of alternation of narrowing and dilation of arteries using angiography (the string of beads sign (multifocal form)). Neurological manifestations include headache, tinnitus, and ischemic stroke, usually due to the dissection or stenosis, rarely, intracerebral or subarachnoid hemorrhages. The prognosis in most cases is favorable, relapses of strokes are rare. Treatment includes antiplatelet agents, if they are ineffective to prevent recurrence of ischemic stroke, endovascular treatment is carried out. Approaches to the treatment of intracranial aneurysms do not differ from those in patients without FMD.

Spontaneous Coronary Artery Dissection and Fibromuscular Dysplasia: Vasculopathies With a Predilection for Women

The burden of cardiovascular disease in women is being increasingly appreciated. Nevertheless, both clinicians and the general public are largely unaware that cardiovascular disease is the leading cause of death worldwide in women in all countries and that outcomes after a heart attack are worse for women than men. Of note, certain types of cardiovascular disease have a predilection for women, including spontaneous coronary artery dissection (SCAD) and fibromuscular dysplasia (FMD). Although uncommon, SCAD is being increasingly recognised as the cause of an acute coronary syndrome (ACS) and can recur. It is a potentially fatal, under-diagnosed condition that affects relatively young women, who often have few traditional risk factors, and is the commonest cause of a myocardial infarction associated with pregnancy. In contrast, FMD often remains silent but when manifested can also cause major sequelae, including renal infarction, stroke, cervical artery dissection and gut infarction. Here we provide an update on the diagnosis, aetiology and management of these important disorders that overwhelmingly affect women.

Rare loss-of-function mutations of PTGIR are enriched in fibromuscular dysplasia

Aims

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. We aimed to identify rare genetic causes to elucidate molecular mechanisms implicated in FMD and SCAD.

Methods and results

We analysed 29 exomes that included familial and sporadic FMD. We identified one rare loss-of-function variant (LoF) (frequency_gnomAD = 0.000075) shared by two FMD sisters in the prostaglandin I₂ receptor gene (PTGIR), a key player in vascular remodelling. Follow-up was conducted by targeted or Sanger sequencing (1071 FMD and 363 SCAD patients) or lookups in exome (264 FMD) or genome sequences (480 SCAD), all independent and unrelated. It revealed four additional LoF allele carriers, in addition to several rare missense variants, among FMD patients, and two LoF allele carriers among SCAD patients, including one carrying a rare splicing mutation (c.768 + 1C>G). We used burden test to test for enrichment in patients compared to gnomAD controls, which detected a putative enrichment in FMD (P_TRAPD = 8 × 10⁻⁴), but not a significant enrichment (P_TRAPD = 0.12) in SCAD. The biological effects of variants on human prostaclycin receptor (hIP) signalling and protein expression were characterized using transient overexpression in human cells. We confirmed the LoFs (Q163X and P17RfsX6) and one missense (L67P), identified in one FMD and one SCAD patient, to severely impair hIP function in vitro.

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 signalling in non-atherosclerotic stenosis and dissection.

Fibromuscular Dysplasia and Its Neurologic Manifestations: A Systematic Review

Importance

Data on neurologic manifestations of fibromuscular dysplasia (FMD) are rare, and current knowledge remains limited.

Objectives

To present a comprehensive review of the epidemiologic characteristics, management, and prognosis of the neurologic manifestations associated with cerebrovascular FMD (ie, involving cervical or intracranial arteries) and to guide future research priorities.

Evidence Review

References were identified through searches of PubMed from inception to December 2017 using both the medical subject headings and text words. Additional sources were also identified by reviewing reference lists of relevant articles and through searches of the authors' personal files. Selected articles described at least 1 clinical or radiologic feature and/or outcome of cerebrovascular FMD. Isolated case reports could be included if they described interesting or noteworthy manifestations of FMD.

Findings

A total of 84 relevant references were identified. Diagnosis of cerebrovascular FMD is based on the appearance of alternating arterial dilatation and constriction ("string of beads") or of focal narrowing, with no sign of atherosclerotic or inflammatory lesions. Although the diagnosis is easily apparent on results of radiographic imaging, making a diagnosis can be challenging in children or individuals with atypical phenotypes, such as purely intracranial FMD and arterial diaphragm. Involvement of multiple arteries is common, and there is increased incidence of cervical artery dissection and intracranial aneurysms. A variant in the PHACTR1 gene has been associated with FMD as well as cervical artery dissection and migraine, although less than 5% of cases of FMD are familial. Headaches, mainly of the migraine type, are observed in up to 70% of patients with FMD. Cerebrovascular FMD is mostly asymptomatic, but the most frequent neurologic manifestations include transient ischemic attack and ischemic stroke, notably in the presence of associated cervical artery dissection. Other conditions associated with FMD include subarachnoid hemorrhage and, rarely, intracranial hemorrhage. Management relies on observational data and expert opinion. Antiplatelet therapy is considered reasonable to prevent thromboembolic complications. Endovascular therapy is typically restricted to cases with symptomatic stenosis despite optimal medical therapy or in those with rupture of an intracranial aneurysm.

Conclusions and Relevance

Longitudinal cohort studies of individuals of multiple ethnicities with biosampling are needed to better understand the risk factors, pathophysiological features, and outcomes of FMD. Patient advocacy groups could assist researchers in answering patient-centered questions regarding FMD.

The Genetic Landscape of Cerebral Steno-Occlusive Arteriopathy and Stroke in Sickle Cell Anemia

Sickle cell disease (SCD) is one of the most common autosomal recessive diseases in humans, occurring at a frequency of 1 in 365 African-American and 1 in 50 sub-Saharan African births. Despite progress in managing complications of SCD, these remain a major health burden worldwide. Stroke is a common and serious complication of SCD, most often associated with steno-occlusive cerebral arteriopathy, but little is known about its pathogenesis. Transcranial Doppler ultrasonography is currently the only predictive test for future development of stroke in patients with sickle cell anemia and is used to guide preventative treatment. However, transcranial Doppler ultrasonography does not identify all patients at increased risk for stroke, and progressive arteriopathy may occur despite preventative treatment. While sibling studies have shown a strong genetic contribution to the development of steno-occlusive arteriopathy (SOA) in SCD, the only genome-wide association study compared a relatively small cohort of 177 patients with stroke to 335 patients with no history of stroke. This single study detected variants in only 2 genes, ENPP1 and GOLGB1, and only one of these was confirmed in a subsequent independent study. Thus, the underlying genes and pathogenesis of SOA in SCD remain poorly understood, greatly limiting the ability to develop more effective preventive therapies. Dissecting the molecular causes of stroke in SCD will provide valuable information that can be used to better prevent stroke, stratify risk of SOA, and optimize personalized medicine approaches.

Unraveling obscurins in heart disease

Obscurins, expressed from the single OBSCN gene, are a family of giant, modular, cytoskeletal proteins that play key structural and regulatory roles in striated muscles. They were first implicated in the development of heart disease in 2007 when two missense mutations were found in a patient diagnosed with hypertrophic cardiomyopathy (HCM). Since then, the discovery of over a dozen missense, frameshift, and splicing mutations that are linked to various forms of cardiomyopathy, including HCM, dilated cardiomyopathy (DCM), and left ventricular non-compaction (LVNC), has highlighted OBSCN as a potential disease-causing gene. At this time, the functional consequences of the identified mutations remain largely elusive, and much work has yet to be done to characterize the disease mechanisms of pathological OBSCN variants. Herein, we describe the OBSCN mutations known to date, discuss their potential impact on disease development, and provide future directions in order to better understand the involvement of obscurins in heart disease.

Genomics of Fibromuscular Dysplasia

Fibromuscular Dysplasia (FMD) is &ldquo;an idiopathic, segmental, non-atherosclerotic and non-inflammatory disease of the musculature of arterial walls, leading to stenosis of small and medium-sized arteries&rdquo; (Persu, et al; 2014). FMD can lead to hypertension, arterial dissections, subarachnoid haemorrhage, stroke or mesenteric ischemia. The pathophysiology of the disease remains elusive. While familial cases are rare (<5%) in contemporary FMD registries, there is evidence in favour of the existence of multiple genetic factors involved in this vascular disease. Recent collaborative efforts allowed the identification of a first genetic locus associated with FMD. This intronic variant located in the phosphatase and actin regulator 1 gene (PHACTR1) may influence the transcription activity of the endothelin-1 gene (EDN1) located nearby on chromosome 6. Interestingly, the PHACTR1 locus has also been involved in vascular hypertrophy in normal subjects, carotid dissection, migraine and coronary artery disease. National and international registries of FMD patients, with deep and harmonised phenotypic and genetic characterisation, are expected to be instrumental to improve our understanding of the genetic basis and pathophysiology of this intriguing vascular disease.

Low frequency of cervicocranial artery involvement in Japanese with renal artery fibromuscular dysplasia compared with that of Caucasians

BACKGROUND

Fibromuscular dysplasia (FMD), which usually affects the renal artery, also affects the carotid, vertebral, and intracranial arteries. Previous studies have shown a high prevalence of concomitant renal artery and cervicocranial lesions in FMD patients. However, the analyzed subjects were mostly Caucasians in Western countries.

METHOD

We performed a retrospective analysis to examine the prevalence of cervicocranial vascular lesions in Japanese FMD patients with renal artery involvement at a single institution. The presence of cervicocranial lesions was evaluated by Doppler echography and magnetic resonance angiography. We compared this prevalence with that reported in the literature.

RESULT

Thirty-one Japanese FMD patients with renal artery lesions were studied. The mean age was 30 ± 12 years, 71% were women, and 16% were smokers; all patients were Asians and had hypertension. Multifocal, tubular, and unifocal types of renal lesions were found in 52, 35, and 13% of patients, respectively. Bilateral renal lesions were found in 13% of patients. None of the patients had a cervical vascular lesion associated with FMD. Only two patients (8%) had a lesion in the intracranial artery, of which one was a known case of moyamoya disease.

CONCLUSION

These findings suggest that cervical artery involvement and intracranial artery involvement are not common in renal FMD patients in Japan, which is in contrast to the data reported for Caucasian patients in Western countries. Ethnic differences could influence the occurrence of cervicocranial lesions. A study with a larger sample size should be performed to validate these findings.

Identification of genomic aberrations associated with lymph node metastasis in diffuse-type gastric cancer

Diffuse-type gastric cancer (DGC) is a GC subtype with heterogeneous clinical outcomes. Lymph node metastasis of DGC heralds a dismal progression, which hampers the curative treatment of patients. However, the genomic heterogeneity of DGC remains unknown. To identify genomic variations associated with lymph node metastasis in DGC, we performed whole exome sequencing on 23 cases of DGC and paired non-tumor tissues and compared the mutation profiles according to the presence (N3, n = 13) or absence (N0, n = 10) of regional lymph node metastasis. Overall, we identified 185 recurrently mutated genes in DGC, which included a significant novel mutation at CMTM2, as well as previously known mutations at CDH1, RHOA, and TP53. Noticeably, CMTM2 expression could predict the prognostic outcomes of DGC but not intestinal-type GC (IGC), indicating pivotal roles of CMTM2 in DGC progression. In addition, we identified a recurrent loss of heterozygosity (LOH) of DNA copy numbers at the 3p12-pcen locus in DGC. A comparison of N0 and N3 tumors showed that N3 tumors exhibited more frequent DNA copy number aberrations, including copy-neutral LOH and mutations of CpTpT trinucleotides, than N0 tumors (P = 0.2 × 10^-3). In conclusion, DGCs have distinct profiles of somatic mutations and DNA copy numbers according to the status of lymph node metastasis, and this might be helpful in delineating the pathobiology of DGC.

Rare RNF213 variants in the C-terminal region encompassing the RING-finger domain are associated with moyamoya angiopathy in Caucasians

Moyamoya angiopathy (MMA) is a cerebral angiopathy affecting the terminal part of internal carotid arteries. Its prevalence is 10 times higher in Japan and Korea than in Europe. In East Asian countries, moyamoya is strongly associated to the R4810K variant in the RNF213 gene that encodes for a protein containing a RING-finger and two AAA+ domains. This variant has never been detected in Caucasian MMA patients, but several rare RNF213 variants have been reported in Caucasian cases. Using a collapsing test based on exome data from 68 European MMA probands and 573 ethnically matched controls, we showed a significant association between rare missense RNF213 variants and MMA in European patients (odds ratio (OR)=2.24, 95% confidence interval (CI)=(1.19-4.11), P=0.01). Variants specific to cases had higher pathogenicity predictive scores (median of 24.2 in cases versus 9.4 in controls, P=0.029) and preferentially clustered in a C-terminal hotspot encompassing the RING-finger domain of RNF213 (P<10^-3). This association was even stronger when restricting the analysis to childhood-onset and familial cases (OR=4.54, 95% CI=(1.80-11.34), P=1.1 × 10^-3). All clinically affected relatives who were genotyped were carriers. However, the need for additional factors to develop MMA is strongly suggested by the fact that only 25% of mutation carrier relatives were clinically affected.

A Review of the Genetics of Intracranial Berry Aneurysms and Implications for Genetic Counseling

Here we review the current understanding of the genetic architecture of intracranial berry aneurysms (IBA) to aid in the genetic counseling of patients at risk for this condition. The familial subtype of IBA, familial intracranial aneurysms (FIA), is associated with increased frequency of IBA, increased risk of rupture, and increased morbidity and mortality after rupture. Family history is the strongest predictor for the development of IBA. However, a genetic test is not yet available to assess risk within a family. Studies using linkage analysis, genome-wide association, and next-generation sequencing have found several candidate loci and genes associated with disease onset, but have not conclusively implicated a single gene. In addition to family history, a separate or concurrent diagnosis of autosomal dominant polycystic kidney disease is a strong genetic risk factor for IBA formation. We also discuss the relative risk for developing IBA in several Mendelian syndromes including vascular Ehlers-Danlos syndrome, Marfan syndrome, Neurofibromatosis Type I, and Loeys-Dietz syndrome.

Loss-of-Function Mutations in YY1AP1 Lead to Grange Syndrome and a Fibromuscular Dysplasia-Like Vascular Disease

Fibromuscular dysplasia (FMD) is a heterogeneous group of non-atherosclerotic and non-inflammatory arterial diseases that primarily involves the renal and cerebrovascular arteries. Grange syndrome is an autosomal-recessive condition characterized by severe and early-onset vascular disease similar to FMD and variable penetrance of brachydactyly, syndactyly, bone fragility, and learning disabilities. Exome-sequencing analysis of DNA from three affected siblings with Grange syndrome identified compound heterozygous nonsense variants in YY1AP1, and homozygous nonsense or frameshift YY1AP1 variants were subsequently identified in additional unrelated probands with Grange syndrome. YY1AP1 encodes yin yang 1 (YY1)-associated protein 1 and is an activator of the YY1 transcription factor. We determined that YY1AP1 localizes to the nucleus and is a component of the INO80 chromatin remodeling complex, which is responsible for transcriptional regulation, DNA repair, and replication. Molecular studies revealed that loss of YY1AP1 in vascular smooth muscle cells leads to cell cycle arrest with decreased proliferation and increased levels of the cell cycle regulator p21/WAF/CDKN1A and disrupts TGF-β-driven differentiation of smooth muscle cells. Identification of YY1AP1 mutations as a cause of FMD indicates that this condition can result from underlying genetic variants that significantly alter the phenotype of vascular smooth muscle cells.

RNF213 Is Associated with Intracranial Aneurysms in the French-Canadian Population

Intracranial aneurysms (IAs) are the result of focal weakness in the artery wall and have a complex genetic makeup. To date, genome-wide association and sequencing studies have had limited success in identifying IA risk factors. Distinct populations, such as the French-Canadian (FC) population, have increased IA prevalence. In our study, we used exome sequencing to prioritize risk variants in a discovery cohort of six FC families affected by IA, and the analysis revealed an increased variation burden for ring finger protein 213 (RNF213). We resequenced RNF213 in a larger FC validation cohort, and association tests on further identified variants supported our findings (SKAT-O, p = 0.006). RNF213 belongs to the AAA+ protein family, and two variants (p.Arg2438Cys and p.Ala2826Thr) unique to affected FC individuals were found to have increased ATPase activity, which could lead to increased risk of IA by elevating angiogenic activities. Common SNPs in RNF213 were also extracted from the NeuroX SNP-chip genotype data, comprising 257 FC IA-affected and 1,988 control individuals. We discovered that the non-ancestral allele of rs6565666 was significantly associated with the affected individuals (p = 0.03), and it appeared as though the frequency of the risk allele had changed through genetic drift. Although RNF213 is a risk factor for moyamoya disease in East Asians, we demonstrated that it might also be a risk factor for IA in the FC population. It therefore appears that the function of RNF213 can be differently altered to predispose distinct populations to dissimilar neurovascular conditions, highlighting the importance of a population's background in genetic studies of heterogeneous disease.

PHACTR1 Is a Genetic Susceptibility Locus for Fibromuscular Dysplasia Supporting Its Complex Genetic Pattern of Inheritance

Fibromuscular dysplasia (FMD) is a nonatherosclerotic vascular disease leading to stenosis, dissection and aneurysm affecting mainly the renal and cerebrovascular arteries. FMD is often an underdiagnosed cause of hypertension and stroke, has higher prevalence in females (~80%) but its pathophysiology is unclear. We analyzed ~26K common variants (MAF>0.05) generated by exome-chip arrays in 249 FMD patients and 689 controls. We replicated 13 loci (P<10-4) in 402 cases and 2,537 controls and confirmed an association between FMD and a variant in the phosphatase and actin regulator 1 gene (PHACTR1). Three additional case control cohorts including 512 cases and 669 replicated this result and overall reached the genomic level of significance (OR = 1.39, P = 7.4×10-10, 1,154 cases and 3,895 controls). The top variant, rs9349379, is intronic to PHACTR1, a risk locus for coronary artery disease, migraine, and cervical artery dissection. The analyses of geometrical parameters of carotids from ~2,500 healthy volunteers indicate higher intima media thickness (P = 1.97×10-4) and wall to lumen ratio (P = 0.002) in rs9349379-A carriers, suggesting indices of carotid hypertrophy previously described in carotids of FMD patients. Immunohistochemistry detected PHACTR1 in endothelium and smooth muscle cells of FMD and normal human carotids. The expression of PHACTR1 by genotypes in primary human fibroblasts showed higher expression in rs9349379-A carriers (N = 86, P = 0.003). Phactr1 knockdown in zebrafish resulted in dilated vessels indicating subtle impaired vascular development. We report the first susceptibility locus for FMD and provide evidence for a complex genetic pattern of inheritance and indices of shared pathophysiology between FMD and other cardiovascular and neurovascular diseases.

Clinical characteristics and treatment of renal artery fibromuscular dysplasia with percutaneous transluminal angioplasty: a long-term follow-up study

BACKGROUND

Renal artery fibromuscular dysplasia (RAFMD) is a non-atherosclerotic cause of renal artery stenosis often affecting the young. Percutaneous transluminal renal angioplasty (PTRA) is the treatment of choice but there are few studies of the outcome of the procedure.

METHODS

This retrospective analysis included 64 patients (56.2 % female; mean age at diagnosis, 28.0 years) with RAFMD who underwent PTRA between November 2003 and August 2015. Technical and clinical success rates and restenosis rates were evaluated.

RESULTS

Seventy-six procedures were performed on 64 RAFMD patients. Technical success was 96.9 %, as defined by <30 % residual stenosis, with stent placement required in 11 patients (17.2 %). In the short term (1 month), the majority (79.7 %) had an immediate clinical benefit, with cure of hypertension in 35.9 %, and improvement in hypertension and a lower requirement for antihypertensive medications in 43.8 %. In the long term (mean, 47.5 months; range, 5-141 months), the survival rate was 96.9 %, freedom from restenosis was 84.4 %, and 76.6 % of patients showed a sustained clinical benefit (cure rate 40.6 %, improvement rate 35.9 %). Eight patients were treated with a second procedure and two had a third procedure, with half of these patients showing an improvement in hypertension.

CONCLUSION

PTRA for symptomatic RAFMD is safe and clinically successful. More than half of patients experience an immediate clinical benefit with sustained long-term effects. For patients with restenosis, there was a good response to a second PTRA.

[Fibromuscular dysplasia of renal arteries]

Fibromuscular dysplasia is non-atherosclerotic, non-inflammatory disease of the medium caliber arteries causing segmental stenosis, and sometimes aneurysm and/or dissection. Renal involvement is either asymptomatic or revealed by hypertension, rarely acute complications (renal infarction/hemorrhage). Cross-sectional imaging or angiography differentiates multifocal fibromuscular dysplasia (pearl necklace appearance) and focal fibromuscular dysplasia (tubular stenosis). Several differential diagnoses are to be mentioned. Carotid and vertebral involvement are possible. Smoking cessation must be encouraged. Selected patients benefit from renal revascularization. The best indications are recent or resistant hypertension, and progressive renal atrophy. Angioplasty without stent revascularization is the technique of choice in purely stenotic forms.