Inheritance of moyamoya disease in a Caucasian family

Whole-exome sequencing in moyamoya patients of Northern-European origin identifies gene variants involved in Nitric Oxide metabolism: A pilot study

Introduction

Moyamoya disease (MMD) is a chronic cerebrovascular steno-occlusive disease of largely unknown etiology. Variants in the RNF213 gene are strongly associated with MMD in East-Asia. In MMD patients of Northern-European origin, no predominant susceptibility variants have been identified so far.

Research question

Are there specific candidate genes associated with MMD of Northern-European origin, including the known RNF213 gene? Can we establish a hypothesis for MMD phenotype and associated genetic variants identified for further research?

Material and methods

Adult patients of Northern-European origin, treated surgically for MMD at Oslo University Hospital between October 2018 to January 2019 were asked to participate. WES was performed, with subsequent bioinformatic analysis and variant filtering. The selected candidate genes were either previously reported in MMD or known to be involved in angiogenesis. The variant filtering was based on variant type, location, population frequency, and predicted impact on protein function.

Results

Analysis of WES data revealed nine variants of interest in eight genes. Five of those encode proteins involved in nitric oxide (NO) metabolism: NOS3, NR4A3, ITGAV, GRB7 and AGXT2. In the AGXT2 gene, a de novo variant was detected, not previously described in MMD. None harboured the p.R4810K missense variant in the RNF213 gene known to be associated with MMD in East-Asian patients.

Discussion and conclusion

Our findings suggest a role for NO regulation pathways in Northern-European MMD and introduce AGXT2 as a new susceptibility gene. This pilot study warrants replication in larger patient cohorts and further functional investigations.

The Genetic Basis of Moyamoya Disease

Moyamoya disease (MMD) is a rare cerebrovascular disease characterized by progressive spontaneous bilateral occlusion of the intracranial internal cerebral arteries (ICA) and their major branches with compensatory capillary collaterals resembling a “puff of smoke” (Japanese: Moyamoya) on cerebral angiography. These pathological alterations of the vessels are called Moyamoya arteriopathy or vasculopathy and a further distinction is made between primary and secondary MMD. Clinical presentation depends on age and population, with hemorrhage and ischemic infarcts in particular leading to severe neurological dysfunction or even death. Although the diagnostic suspicion can be posed by MRA or CTA, cerebral angiography is mandatory for diagnostic confirmation. Since no therapy to limit the stenotic lesions or the development of a collateral network is available, the only treatment established so far is surgical revascularization. The pathophysiology still remains unknown. Due to the early age of onset, familial cases and the variable incidence rate between different ethnic groups, the focus was put on genetic aspects early on. Several genetic risk loci as well as individual risk genes have been reported; however, few of them could be replicated in independent series. Linkage studies revealed linkage to the 17q25 locus. Multiple studies on the association of SNPs and MMD have been conducted, mainly focussing on the endothelium, smooth muscle cells, cytokines and growth factors. A variant of the RNF213 gene was shown to be strongly associated with MMD with a founder effect in the East Asian population. Although it is unknown how mutations in the RNF213 gene, encoding for a ubiquitously expressed 591 kDa cytosolic protein, lead to clinical features of MMD, RNF213 has been confirmed as a susceptibility gene in several studies with a gene dosage-dependent clinical phenotype, allowing preventive screening and possibly the  development of new therapeutic approaches. This review focuses on the genetic basis of primary MMD only.

Clinical and Molecular Features of 5 European Multigenerational Families With Moyamoya Angiopathy

Background and Purpose Moyamoya angiopathy (MMA) is a rare cerebral vasculopathy outside of Asia. In Japanese patients, a vast majority of patients carry the founder p.R4810K variant in the RNF213 gene, and familial cases are around 10%. In European patients, data about familial occurrence are limited. The aim of this study was to characterize the clinical and molecular features of several European families with a parent-to-child transmission of MMA. Methods Out of 126 MMA probands referred, we identified 113 sporadic probands and 13 familial probands. Segregation analysis showed a vertical parent-to-child pattern of inheritance in the families of 5 of these probands. All 5 families were of German or Dutch ancestry. We investigated the clinical features of affected members and used whole-exome sequencing to screen RNF213 and 13 genes involved in Mendelian MMA and to identify genes recurrently mutated in these families. Results Twelve affected MMA patients were identified, including 9 females and 3 males. Age at clinical onset ranged from 11 to 65 years. In 3 of 5 families, associated livedo racemosa was found. We did not detect any deleterious variants in the 13 known MMA genes. RNF213 rare missense variants predicted to be pathogenic were detected in all affected members of 2 of these families, as well as 2 candidate variants of the PALD1 gene. Conclusions Nonsyndromic MMA was identified in 5 European families, including 2 to 3 clinically affected cases segregating with a parent-to-child pattern of inheritance in each family. Molecular screening detected rare deleterious variants within RNF213 and PALD1 in all affected members of 2 of these 5 families, as well as in some clinically unaffected members. Altogether these data raise the difficult and, to date unanswered, question of the medical indication of presymptomatic screening.

Neurology Case Studies: Cerebrovascular Disease

This article discusses interesting vascular neurology cases including the management of intracranial stenosis, migraine headache and stroke risk, retinal artery occlusions associated with impaired hearing, intracranial occlusive disease, a heritable cause of stroke and vascular cognitive impairment, and an interesting clinico-neuroradiologic disorder associated with eclampsia.

Moyamoya angiopathy - Is there a Western phenotype?

Moyamoya disease (MMD) is a chronic cerebrovascular disease involving progressive bilateral stenosis of the intracranial segments of the internal carotid arteries. It results in the development of a rich, but friable collateral supply, prone to rupture. The disease is well described in Japanese literature and was originally thought to be a predozminantly Eastern disease. However, the recent literature describes a Western phenotype that may present with a different clinical course. This review aims to describe the variations in the epidemiology of the MMD between Eastern and Western populations, the possible reasons for them and highlight their implications for clinical practise and future research.

Recent advances in moyamoya disease: pathophysiology and treatment

Moyamoya disease is a progressive intracranial arteriopathy characterized by bilateral stenosis of the distal portion of the internal carotid artery and the proximal anterior and middle cerebral arteries, resulting in transient ischemic attacks or strokes. The pathogenesis of moyamoya disease remains unresolved, but recent advances have suggested exciting new insights into a genetic contribution as well as into other pathophysiological mechanisms. Treatment that may halt progression of the disease or even reverse the intracranial arteriopathy is yet to be found. There are strong indications that neurosurgical intervention, through direct, indirect, or combined revascularization surgery, can reduce the risk of ischemic stroke and possibly also cognitive dysfunction by improving cerebral perfusion, although randomized clinical trials have not been performed. Many questions regarding the indication for and timing of surgery remain unanswered. In this review, we discuss recent developments in the pathogenesis and treatment of moyamoya disease.

Caucasian familial moyamoya syndrome with rare multisystemic malformations

Moyamoya disease is an idiopathic progressive steno-occlusive disorder of the intracranial arteries located at the base of the brain. It is associated with the development of compensatory extensive network of fine collaterals. Moyamoya disease is considered syndromic when certain genetic or acquired disorders such as polycystic kidney disease, neurofibromatosis, or meningitis are also present. Although the genetic contribution in moyamoya is indisputable, its cause and pathogenesis remain under discussion. Herein, we report a rare occurrence of moyamoya syndrome in two European Caucasian siblings in association with unusual multisystemic malformations (polycystic kidney disease in one, and intestinal duplication cyst in the other). The karyotype was normal. No mutation in the RFN213 gene was found, and none of the HLA types linked to moyamoya disease or described in similar familial cases were identified. By describing these multisystemic associations, polycystic kidney disease for the second time, and intestinal malformation for the first time in the literature, our report expands the phenotypic variability of moyamoya syndrome. The coexistence of disparate malformations among close relatives suggests an underlying common genetic background predisposing to structural or physiological abnormalities in different tissues and organs.

Analysis of human leucocyte antigen genes in Caucasian patients with idiopathic moyamoya angiopathy

BACKGROUND

The etiology and genetic susceptibility of Moyamoya angiopathy (MMA) (Moyamoya disease, Moyamoya syndrome and unilateral type of MMA) still remain unclear. In Asian patient cohorts several HLA markers were described to be associated with MMA, but in Caucasians very little is known about genetic susceptibility of this angiopathy.

METHOD

We analysed DNA of 33 Caucasian patients with MMA for HLA-A, HLA-B, HLA-DRB1, and HLA-DQB1 markers, respectively. HLA frequencies of all 33 patients with MMA were compared with HLA-frequencies of Caucasian controls. Additionally, subgroup analysis of 22 patients with Moyamoya disease (MMD) and 11 patients with unilateral type of MMA was performed.

FINDINGS

Significant association was observed for HLA-DRB1*03 and HLA-DRB1*13 in all 33 patients (P (c) < 0.001 and P (c) < 0.001, respectively). Moreover, HLA-A*02 (P (c) = 0.009); HLA-B*08 (P (c) = 0.009), and HLA-DQB1*03 (P (c) = 0.003) frequencies were higher in all patients with MMA when compared with the controls. In addition, in 22 patients with MMD a higher frequency of HLA-DRB1*03 (P (c) < 0.001) was observed when compared with controls.

CONCLUSIONS

The results of this study indicate a putative association of HLA markers with MMA in Caucasian patients. Further studies are needed to elucidate the role of human MHC in the pathogenesis of this angiopathy.