Rare variants in ANO1, encoding a calcium-activated chloride channel, predispose to moyamoya disease.

Moyamoya disease, a cerebrovascular disease leading to strokes in children and young adults, is characterized by progressive occlusion of the distal internal carotid arteries and the formation of collateral vessels. Altered genes play a prominent role in the aetiology of moyamoya disease, but a causative gene is not identified in the majority of cases. Exome sequencing data from 151 individuals from 84 unsolved families were analysed to identify further genes for moyamoya disease, then candidate genes assessed in additional cases (150 probands). Two families had the same rare variant in ANO1, which encodes a calcium-activated chloride channel, anoctamin-1. Haplotype analyses found the families were related, and ANO1 p.Met658Val segregated with moyamoya disease in the family with an LOD score of 3.3. Six additional ANO1 rare variants were identified in moyamoya disease families. The ANO1 rare variants were assessed using patch-clamp recordings, and the majority of variants, including ANO1 p.Met658Val, displayed increased sensitivity to intracellular Ca2+. Patients harbouring these gain-of-function ANO1 variants had classic features of moyamoya disease, but also had aneurysm, stenosis and/or occlusion in the posterior circulation. Our studies support that ANO1 gain-of-function pathogenic variants predispose to moyamoya disease and are associated with unique involvement of the posterior circulation.

Phenotypic variability in 446 CADASIL patients: Impact of NOTCH3 gene mutation location in addition to the effects of age, sex and vascular risk factors.

The recent discovery that the prevalence of cysteine mutations in the NOTCH3 gene responsible for CADASIL was more than 100 times higher in the general population than that estimated in patients highlighted that the mutation location in EGFr-like-domains of the NOTCH3 receptor could have a major effect on the phenotype of the disease. The exact impact of such mutations locations on the multiple facets of the disease has not been fully evaluated. We aimed to describe the phenotypic spectrum of a large population of CADASIL patients and to investigate how this mutation location influenced various clinical and imaging features of the disease. Both a supervised and a non-supervised approach were used for analysis. The results confirmed that the mutation location is strongly related to clinical severity and showed that this effect is mainly driven by a different development of the most damaging ischemic tissue lesions at cerebral level. These effects were detected in addition to those of aging, male sex, hypertension and hypercholesterolemia. The exact mechanisms relating the location of mutations along the NOTCH3 receptor, the amount or properties of the resulting NOTCH3 products accumulating in the vessel wall, and their final consequences at cerebral level remain to be determined.

Elderly CADASIL patients with intact neurological status.

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is one of the most devastating cerebral small vessel diseases. However, despite its progression with aging, some patients remain neurologically intact (Nint) even when they get older. Their main characteristics are poorly known. We aimed to delineate their clinical, imaging, and molecular features. METHODS: Individuals aged over 65 years were selected from a cohort of 472 CADASIL patients. Subjects who had no focal deficit, cognitive impairment, or disability were considered Nint. Their demographic, genetic, clinical, and imaging features were compared to those with permanent neurological symptoms (Nps). RESULTS: Among 129 patients, 23 (17.8%) individuals were considered Nint. The frequency of vascular risk factors and NOTCH3 cysteine mutations in epidermal growth factor-like repeat (EGFr) domains 7-34 did not differ between Nint and Nps patients but Nint patients had less stroke events and were more likely to have migraine with aura. The number of lacunes and microbleeds and degree of brain atrophy were lower in the Nint group, but the volume of white matter hyperintensities did not differ between the two groups. CONCLUSIONS: Nearly one in five CADASIL patients can remain Nint after the age of 65 years. Their clinical and imaging profile differed from that of other age-matched CADASIL patients. The location of NOTCH3 mutation inside or outside EGFr domains 1-6 cannot fully explain this discrepancy. The factors involved in their relative preservation of brain tissue from severe damage despite aging remain to be determined.

Natural history of Myhre syndrome.

BACKGROUND: Myhre syndrome (MS) is a rare genetic disease characterized by skeletal disorders, facial features and joint limitation, caused by a gain of function mutation in SMAD4 gene. The natural history of MS remains incompletely understood. METHODS: We recruited in a longitudinal retrospective study patients with molecular confirmed MS from the French reference center for rare skeletal dysplasia. We described natural history by chaining data from medical reports, clinical data warehouse, medical imaging and photographies. RESULTS: We included 12 patients. The median age was 22 years old (y/o). Intrauterine and postnatal growth retardation were consistently reported. In preschool age, neurodevelopment disorders were reported in 80% of children. Specifics facial and skeletal features, thickened skin and joint limitation occured mainly in school age children. The adolescence was marked by the occurrence of pulmonary arterial hypertension (PAH) and vascular stenosis. We reported for the first time recurrent strokes from the age of 26 y/o, caused by a moyamoya syndrome in one patient. Two patients died at late adolescence and in their 20 s respectively from PAH crises and mesenteric ischemia. CONCLUSION: Myhre syndrome is a progressive disease with severe multisystemic impairement and life-threathning complication requiring multidisciplinary monitoring.

Moyamoya angiopathy in PHACE syndrome not associated with RNF213 variants.

Moyamoya angiopathy is a rare vasculopathy with stenosis and/or occlusion of bilateral intracranial parts of internal carotid arteries and/or proximal parts of middle and anterior cerebral arteries. PHACE syndrome is characterized by large segmental hemangiomas in the cervical-facial region. Both conditions are known to be associated in rare cases. Recently, it was discussed in the literature that RNF213 variants could be etiologically involved in this association. Here, we describe a childhood case with this rare co-occurrence in which we did not identify any rare RNF213 variant. The clinical and genetic backgrounds are discussed.

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.

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.

De novo mutations in CBL causing early-onset paediatric moyamoya angiopathy.

BACKGROUND: Moyamoya angiopathy (MMA) is characterised by a progressive stenosis of the terminal part of the internal carotid arteries and the development of abnormal collateral deep vessels. Its pathophysiology is unknown. MMA can be the sole manifestation of the disease (moyamoya disease) or be associated with various conditions (moyamoya syndrome) including some Mendelian diseases. We aimed to investigate the genetic basis of moyamoya using a whole exome sequencing (WES) approach conducted in sporadic cases without any overt symptom suggestive of a known Mendelian moyamoya syndrome. METHODS: A WES was performed in four unrelated early-onset moyamoya sporadic cases and their parents (trios). Exome data were analysed under dominant de novo, autosomal recessive and X-linked hypotheses. A panel of 17 additional sporadic cases with early-onset moyamoya was available for mutation recurrence analysis. RESULTS: We identified two germline de novo mutations in CBL in two out of the four trio probands, two girls presenting with an infancy-onset severe MMA. Both mutations were predicted to alter the ubiquitin ligase activity of the CBL protein that acts as a negative regulator of the RAS pathway. These two germline CBL mutations have previously been described in association with a developmental Noonan-like syndrome and susceptibility to juvenile myelomonocytic leukaemia (JMML). Notably, the two mutated girls never developed JMML and presented only subtle signs of RASopathy that did not lead to evoke this diagnosis during follow-up. CONCLUSIONS: These data suggest that CBL gene screening should be considered in early-onset moyamoya, even in the absence of obvious signs of RASopathy.

Influence of Nucleoshuttling of the ATM Protein in the Healthy Tissues Response to Radiation Therapy: Toward a Molecular Classification of Human Radiosensitivity.

PURPOSE: Whereas post-radiation therapy overreactions (OR) represent a clinical and societal issue, there is still no consensual radiobiological endpoint to predict clinical radiosensitivity. Since 2003, skin biopsy specimens have been collected from patients treated by radiation therapy against different tumor localizations and showing a wide range of OR. Here, we aimed to establish quantitative links between radiobiological factors and OR severity grades that would be relevant to radioresistant and genetic hyperradiosensitive cases. METHODS AND MATERIALS: Immunofluorescence experiments were performed on a collection of skin fibroblasts from 12 radioresistant, 5 hyperradiosensitive, and 100 OR patients irradiated at 2 Gy. The numbers of micronuclei, γH2AX, and pATM foci that reflect different steps of DNA double-strand breaks (DSB) recognition and repair were assessed from 10 minutes to 24 hours after irradiation and plotted against the severity grades established by the Common Terminology Criteria for Adverse Events and the Radiation Therapy Oncology Group. RESULTS: OR patients did not necessarily show a gross DSB repair defect but a systematic delay in the nucleoshuttling of the ATM protein required for complete DSB recognition. Among the radiobiological factors, the maximal number of pATM foci provided the best discrimination among OR patients and a significant correlation with each OR severity grade, independently of tumor localization and of the early or late nature of reactions. CONCLUSIONS: Our results are consistent with a general classification of human radiosensitivity based on 3 groups: radioresistance (group I); moderate radiosensitivity caused by delay of nucleoshuttling of ATM, which includes OR patients (group II); and hyperradiosensitivity caused by a gross DSB repair defect, which includes fatal cases (group III).

Moyamoya disease and syndromes: from genetics to clinical management.

Moyamoya angiopathy is characterized by a progressive stenosis of the terminal portion of the internal carotid arteries and the development of a network of abnormal collateral vessels. This chronic cerebral angiopathy is observed in children and adults. It mainly leads to brain ischemic events in children, and to ischemic and hemorrhagic events in adults. This is a rare condition, with a marked prevalence gradient between Asian countries and Western countries. Two main nosological entities are identified. On the one hand, moyamoya disease corresponds to isolated moyamoya angiopathy, defined as being "idiopathic" according to the Guidelines of the Research Committee on the Pathology and Treatment of Spontaneous Occlusion of the Circle of Willis. This entity is probably multifactorial and polygenic in most patients. On the other hand, moyamoya syndrome is a moyamoya angiopathy associated with an underlying condition and forms a very heterogeneous group with various clinical presentations, various modes of inheritance, and a variable penetrance of the cerebrovascular phenotype. Diagnostic and evaluation techniques rely on magnetic resonance imaging (MRI), magnetic resonance angiography (MRA) conventional angiography, and cerebral hemodynamics measurements. Revascularization surgery can be indicated, with several techniques. Characteristics of genetic moyamoya syndromes are presented, with a focus on recently reported mutations in BRCC3/MTCP1 and GUCY1A3 genes. Identification of the genes involved in moyamoya disease and several monogenic moyamoya syndromes unraveled different pathways involved in the development of this angiopathy. Studying genes and pathways involved in monogenic moyamoya syndromes may help to give insights into pathophysiological models and discover potential candidates for medical treatment strategies.