Neurovascular complications in adults with Neurofibromatosis type 1: A national referral center experience.

Neurofibromatosis type 1 (NF1) is associated with a range of vascular abnormalities. To assess the frequency, clinical and imaging spectrum of vascular complications in an adult cohort of NF1 patients, we reviewed 2068 adult NF1 patient records seen in our service between 2009 and 2019, to determine presence of vascular abnormalities, age at detection, associated symptoms and management. A literature review of the range of vascular abnormalities associated with NF1 was also undertaken. 1234 patients had magnetic resonance imaging cranial imaging. The frequency of vascular abnormalities associated with NF1 patients who had cranial imaging in this cohort was 3.5% (n = 43), the majority (n = 26, 60%) were symptomatic. Stroke and cerebral arterial stenosis were the commonest vascular complication. Eight patients (0.65%) had more than one type of vascular abnormality. One death due to a vascular complication was identified and significant morbidity resulted from other complications. We conclude that clinicians caring for patients with NF1 need to be cognizant that rapid onset of new neurological symptoms or signs may be the result of a vascular complication of NF1 and require urgent investigation and management, ideally within specialist teams who have experience of managing vascular complications of NF1.

Parkinson's disease-linked mutations in VPS35 induce dopaminergic neurodegeneration.

Mutations in the vacuolar protein sorting 35 homolog (VPS35) gene at the PARK17 locus, encoding a key component of the retromer complex, were recently identified as a new cause of late-onset, autosomal dominant Parkinson's disease (PD). Here we explore the pathogenic consequences of PD-associated mutations in VPS35 using a number of model systems. VPS35 exhibits a broad neuronal distribution throughout the rodent brain, including within the nigrostriatal dopaminergic pathway. In the human brain, VPS35 protein levels and distribution are similar in tissues from control and PD subjects, and VPS35 is not associated with Lewy body pathology. The common D620N missense mutation in VPS35 does not compromise its protein stability or localization to endosomal and lysosomal vesicles, or the vesicular sorting of the retromer cargo, sortilin, SorLA and cation-independent mannose 6-phosphate receptor, in rodent primary neurons or patient-derived human fibroblasts. In yeast we show that PD-linked VPS35 mutations are functional and can normally complement VPS35 null phenotypes suggesting that they do not result in a loss-of-function. In rat primary cortical cultures the overexpression of human VPS35 induces neuronal cell death and increases neuronal vulnerability to PD-relevant cellular stress. In a novel viral-mediated gene transfer rat model, the expression of D620N VPS35 induces the marked degeneration of substantia nigra dopaminergic neurons and axonal pathology, a cardinal pathological hallmark of PD. Collectively, these studies establish that dominant VPS35 mutations lead to neurodegeneration in PD consistent with a gain-of-function mechanism, and support a key role for VPS35 in the development of PD.

Hereditary leukoencephalopathy with axonal spheroids: a spectrum of phenotypes from CNS vasculitis to parkinsonism in an adult onset leukodystrophy series.

BACKGROUND: Hereditary diffuse leukoencephalopathy with neuroaxonal spheroids (HDLS) is a hereditary, adult onset leukodystrophy which is characterised by the presence of axonal loss, axonal spheroids and variably present pigmented macrophages on pathological examination. It most frequently presents in adulthood with dementia and personality change. HDLS has recently been found to be caused by mutations in the colony stimulating factor-1 receptor (CSF1R) gene. METHODS: In this study, we sequenced the CSF1R gene in a cohort of 48 patients from the UK, Greece and Ireland with adult onset leukodystrophy of unknown cause. RESULTS: Five pathogenic mutations were found, including three novel mutations. The presentations ranged from suspected central nervous system (CNS) vasculitis to extrapyramidal to cognitive phenotypes. The case histories and imaging are presented here, in addition to neuropathological findings from two cases with novel mutations. CONCLUSION: We estimate that CSF1R mutations account for 10% of idiopathic adult onset leukodystrophies and that genetic testing for CSF1R mutations is essential in adult patients presenting with undefined CNS vasculitis or a leukodystrophy with prominent neuropsychiatric signs or dementia.

Mutations in ANO3 cause dominant craniocervical dystonia: ion channel implicated in pathogenesis.

In this study, we combined linkage analysis with whole-exome sequencing of two individuals to identify candidate causal variants in a moderately-sized UK kindred exhibiting autosomal-dominant inheritance of craniocervical dystonia. Subsequent screening of these candidate causal variants in a large number of familial and sporadic cases of cervical dystonia led to the identification of a total of six putatively pathogenic mutations in ANO3, a gene encoding a predicted Ca(2+)-gated chloride channel that we show to be highly expressed in the striatum. Functional studies using Ca(2+) imaging in case and control fibroblasts demonstrated clear abnormalities in endoplasmic-reticulum-dependent Ca(2+) signaling. We conclude that mutations in ANO3 are a cause of autosomal-dominant craniocervical dystonia. The locus DYT23 has been reserved as a synonym for this gene. The implication of an ion channel in the pathogenesis of dystonia provides insights into an alternative mechanism that opens fresh avenues for further research.

Glycine receptor antibodies in PERM and related syndromes: characteristics, clinical features and outcomes.

The clinical associations of glycine receptor antibodies have not yet been described fully. We identified prospectively 52 antibody-positive patients and collated their clinical features, investigations and immunotherapy responses. Serum glycine receptor antibody endpoint titres ranged from 1:20 to 1:60 000. In 11 paired samples, serum levels were higher than (n = 10) or equal to (n = 1) cerebrospinal fluid levels; there was intrathecal synthesis of glycine receptor antibodies in each of the six pairs available for detailed study. Four patients also had high glutamic acid decarboxylase antibodies (>1000 U/ml), and one had high voltage-gated potassium channel-complex antibody (2442 pM). Seven patients with very low titres (<1:50) and unknown or alternative diagnoses were excluded from further study. Three of the remaining 45 patients had newly-identified thymomas and one had a lymphoma. Thirty-three patients were classified as progressive encephalomyelitis with rigidity and myoclonus, and two as stiff person syndrome; five had a limbic encephalitis or epileptic encephalopathy, two had brainstem features mainly, two had demyelinating optic neuropathies and one had an unclear diagnosis. Four patients (9%) died during the acute disease, but most showed marked improvement with immunotherapies. At most recent follow-up, (2-7 years, median 3 years, since first antibody detection), the median modified Rankin scale scores (excluding the four deaths) decreased from 5 at maximal severity to 1 (P < 0.0001), but relapses have occurred in five patients and a proportion are on reducing steroids or other maintenance immunotherapies as well as symptomatic treatments. The glycine receptor antibodies activated complement on glycine receptor-transfected human embryonic kidney cells at room temperature, and caused internalization and lysosomal degradation of the glycine receptors at 37°C. Immunoglobulin G antibodies bound to rodent spinal cord and brainstem co-localizing with monoclonal antibodies to glycine receptor-α1. Ten glycine receptor antibody positive samples were also identified in a retrospective cohort of 56 patients with stiff person syndrome and related syndromes. Glycine receptor antibodies are strongly associated with spinal and brainstem disorders, and the majority of patients have progressive encephalomyelitis with rigidity and myoclonus. The antibodies demonstrate in vitro evidence of pathogenicity and the patients respond well to immunotherapies, contrasting with earlier studies of this syndrome, which indicated a poor prognosis. The presence of glycine receptor antibodies should help to identify a disease that responds to immunotherapies, but these treatments may need to be sustained, relapses can occur and maintenance immunosuppression may be required.

Paroxysmal dyskinesias revisited: a review of 500 genetically proven cases and a new classification.

Paroxysmal movement disorders are a heterogeneous group of conditions manifesting as episodic dyskinesia with sudden onset and lasting a variable duration. Based on the difference of precipitating factors, three forms are clearly recognized, namely, paroxysmal kinesigenic (PKD), non-kinesigenic (PNKD), and exercise induced (PED). The elucidation of the genetic cause of various forms of paroxysmal dyskinesia has led to better clinical definitions based on genotype-phenotype correlations in the familial forms. However, it has been increasingly recognized that (1) there is a marked pleiotropy of mutations in such genes with still expanding clinical spectra; and (2) not all patients clinically presenting with either PKD, PNKD, or PED have mutations in these genes. We aimed to review the clinical features of 500 genetically proven cases published to date. Based on our results, it is clear that there is not a complete phenotypic-genotypic correlation, and therefore we suggest an algorithm to lead the genetic analyses. Given the fact that the reliability of current clinical categorization is not entirely valid, we further propose a novel classification for paroxysmal dyskinesias, which takes into account the recent genetic discoveries in this field.

Analysis of Parkinson's disease brain-derived DNA for alpha-synuclein coding somatic mutations.

BACKGROUND: Although alpha-synuclein (SNCA) is crucial to the pathogenesis of Parkinson's disease (PD) and dementia with Lewy bodies (DLB), mutations in the gene appear to be rare. We have recently hypothesized that somatic mutations in early development could contribute to PD. METHODS: Expanding on our recent negative small study, we used high-resolution melting (HRM) analysis to screen SNCA coding exons for somatic point mutations in DNA from 539 PD and DLB cerebellar samples, with two additional regions (frontal cortex, substantia nigra) for 20 PD cases. We used artificial mosaics to determine sensitivity where possible. RESULTS: We did not detect any evidence of somatic coding mutations. Three cases were heterozygous for known silent polymorphisms. The protocol we used was sensitive enough to detect 5% to 10% mutant DNA. CONCLUSION: Using DNA predominantly from cerebellum, but also from frontal cortex and substantia nigra (n = 20 each), we have not detected any somatic coding SNCA point mutations.

The phenotypic spectrum of DYT24 due to ANO3 mutations.

Genes causing primary dystonia are rare. Recently, pathogenic mutations in the anoctamin 3 gene (ANO3) have been identified to cause autosomal dominant craniocervical dystonia and have been assigned to the dystonia locus dystonia-24 (DYT24). Here, we expand on the phenotypic spectrum of DYT24 and provide demonstrative videos. Moreover, tremor recordings were performed, and back-averaged electroencephalography, sensory evoked potentials, and C-reflex studies were carried out in two individuals who carried two different mutations in ANO3. Ten patients from three families are described. The age at onset ranged from early childhood to the forties. Cervical dystonia was the most common site of onset followed by laryngeal dystonia. The characteristic feature in all affected individuals was the presence of tremor, which contrasts DYT24 from the typical DYT6 phenotype. Tremor was the sole initial manifestation in some individuals with ANO3 mutations, leading to misdiagnosis as essential tremor. Electrophysiology in two patients with two different mutations showed co-contraction of antagonist muscles, confirming dystonia, and a 6-Hz arm tremor at rest, which increased in amplitude during action. In one of the studied patients, clinically superimposed myoclonus was observed. The duration of the myoclonus was in the range of 250 msec at about 3 Hz, which is more consistent with subcortical myoclonus. In summary, ANO3 causes a varied phenotype of young-onset or adult-onset craniocervical dystonia with tremor and/or myoclonic jerks. Patients with familial cervical dystonia who also have myoclonus-dystonia as well as patients with prominent tremor and mild dystonia should be tested for ANO3 mutations.

Primary progressive multiple sclerosis developing in the context of young onset Parkinson's disease.

We report a patient with young onset Parkinson's disease (PD) and a heterozygous point mutation in parkin (c.1000C>T; p.Arg334Cys). After 8 years he developed pyramidal signs and reinvestigation demonstrated MRI and laboratory findings supportive of a diagnosis of multiple sclerosis (MS) with a primary progressive (PP) clinical course. This is a previously un-described association of young onset PD with PPMS. Imaging clearly dates the occurrence of each disease as chronologically separate phenomena. There is not currently evidence for shared causation or pathogenesis between the two neurological disorders but we will follow with interest the emerging genetic characterization of parkin in both PD and MS.

Imputation of sequence variants for identification of genetic risks for Parkinson's disease: a meta-analysis of genome-wide association studies.

BACKGROUND: Genome-wide association studies (GWAS) for Parkinson's disease have linked two loci (MAPT and SNCA) to risk of Parkinson's disease. We aimed to identify novel risk loci for Parkinson's disease. METHODS: We did a meta-analysis of datasets from five Parkinson's disease GWAS from the USA and Europe to identify loci associated with Parkinson's disease (discovery phase). We then did replication analyses of significantly associated loci in an independent sample series. Estimates of population-attributable risk were calculated from estimates from the discovery and replication phases combined, and risk-profile estimates for loci identified in the discovery phase were calculated. FINDINGS: The discovery phase consisted of 5333 case and 12 019 control samples, with genotyped and imputed data at 7 689 524 SNPs. The replication phase consisted of 7053 case and 9007 control samples. We identified 11 loci that surpassed the threshold for genome-wide significance (p<5×10(-8)). Six were previously identified loci (MAPT, SNCA, HLA-DRB5, BST1, GAK and LRRK2) and five were newly identified loci (ACMSD, STK39, MCCC1/LAMP3, SYT11, and CCDC62/HIP1R). The combined population-attributable risk was 60·3% (95% CI 43·7-69·3). In the risk-profile analysis, the odds ratio in the highest quintile of disease risk was 2·51 (95% CI 2·23-2·83) compared with 1·00 in the lowest quintile of disease risk. INTERPRETATION: These data provide an insight into the genetics of Parkinson's disease and the molecular cause of the disease and could provide future targets for therapies. FUNDING: Wellcome Trust, National Institute on Aging, and US Department of Defense.

Lack of evidence for a role of genetic variation in TMEM230 in the risk for Parkinson's disease in the Caucasian population.

Mutations in TMEM230 have recently been associated to Parkinson's disease (PD). To further understand the role of this gene in the Caucasian population, we interrogated our large repository of next generation sequencing data from unrelated PD cases and controls, as well as multiplex families with autosomal dominant PD. We identified 2 heterozygous missense variants in 2 unrelated PD cases and not in our control database (p.Y106H and p.I162V), and a heterozygous missense variant in 2 PD cases from the same family (p.A163T). However, data presented herein is not sufficient to support the role of any of these variants in PD pathology. A series of unified sequence kernel association tests also failed to show a cumulative effect of rare variation in this gene on the risk of PD in the general Caucasian population. Further evaluation of genetic data from different populations is needed to understand the genetic role of TMEM230 in PD etiology.

Advances in the Genetics of Parkinson's Disease: A Guide for the Clinician.

Over the last 16 years, insights in clinical and genetic characteristics of Parkinson's disease (PD) have increased substantially. We summarize the clinical, genetic, and pathological findings of autosomal dominant PD linked to mutations in SNCA, leucine-rich repeat kinase 2, vacuolar protein sorting-35, and eukaryotic translation initiation factor 4 gamma 1 and autosomal recessive PD linked to parkin,PINK1, and DJ-1, as well as autosomal recessive complicated parkinsonian syndromes caused by mutations in ATP13A2,FBXO7,PLA2G6,SYNJ1, and DNAJC6. We also review the advances in high- and low-risk genetic susceptibility factors and present multisystem disorders that may present with parkinsonism as the major clinical feature and provide recommendations for prioritization of genetic testing. Finally, we consider the challenges of future genetic research in PD.

ALS2 mutations: juvenile amyotrophic lateral sclerosis and generalized dystonia.

OBJECTIVE: To determine the genetic etiology in 2 consanguineous families who presented a novel phenotype of autosomal recessive juvenile amyotrophic lateral sclerosis associated with generalized dystonia. METHODS: A combination of homozygosity mapping and whole-exome sequencing in the first family and Sanger sequencing of candidate genes in the second family were used. RESULTS: Both families were found to have homozygous loss-of-function mutations in the amyotrophic lateral sclerosis 2 (juvenile) (ALS2) gene. CONCLUSIONS: We report generalized dystonia and cerebellar signs in association with ALS2-related disease. We suggest that the ALS2 gene should be screened for mutations in patients who present with a similar phenotype.

A multicenter study of glucocerebrosidase mutations in dementia with Lewy bodies.

IMPORTANCE: While mutations in glucocerebrosidase (GBA1) are associated with an increased risk for Parkinson disease (PD), it is important to establish whether such mutations are also a common risk factor for other Lewy body disorders. OBJECTIVE: To establish whether GBA1 mutations are a risk factor for dementia with Lewy bodies (DLB). DESIGN We compared genotype data on patients and controls from 11 centers. Data concerning demographics, age at onset, disease duration, and clinical and pathological features were collected when available. We conducted pooled analyses using logistic regression to investigate GBA1 mutation carrier status as predicting DLB or PD with dementia status, using common control subjects as a reference group. Random-effects meta-analyses were conducted to account for additional heterogeneity. SETTING: Eleven centers from sites around the world performing genotyping. PARTICIPANTS: Seven hundred twenty-one cases met diagnostic criteria for DLB and 151 had PD with dementia. We compared these cases with 1962 controls from the same centers matched for age, sex, and ethnicity. MAIN OUTCOME MEASURES: Frequency of GBA1 mutations in cases and controls. RESULTS We found a significant association between GBA1 mutation carrier status and DLB, with an odds ratio of 8.28 (95% CI, 4.78-14.88). The odds ratio for PD with dementia was 6.48 (95% CI, 2.53-15.37). The mean age at diagnosis of DLB was earlier in GBA1 mutation carriers than in noncarriers (63.5 vs 68.9 years; P < .001), with higher disease severity scores. CONCLUSIONS AND RELEVANCE: Mutations in GBA1 are a significant risk factor for DLB. GBA1 mutations likely play an even larger role in the genetic etiology of DLB than in PD, providing insight into the role of glucocerebrosidase in Lewy body disease.

Study of the genetic variability in a Parkinson's Disease gene: EIF4G1.

Chartier-Harlin and colleagues [2] recently reported mutations in the eukaryotic translation initiation factor 4-gamma (EIF4G1) gene in families with parkinsonism. Large-scale screening found two mutations (p.R1205H and p.A502V) only in affected individuals, although their relative frequency was very low. The aim of this study was to investigate EIF4G1 parkinsonism-related variants in two separate cohorts and study coding variability across the gene. We first screened a series of familial Parkinson's Disease (PD) patients in an attempt to confirm previous results by showing segregation. Then, to determine the extent of coding variation in the gene, we first screened a cohort of sub-Saharan African individuals from the Centre d'Etude du Polymorphisme Humain - Human Genome Diversity Cell Line Panel (HGDP) [1] and then analyzed data from 5350 individuals National Heart, Lung, and Blood Institute (NHLBI) exome sequencing project. We failed to identify any PD-related mutations in the familial samples. Conversely we found the p.A502V variant in the NHLBI population. We observed a high number of coding polymorphism in the exons where the two PD variants have been previously reported. We conclude that either EIF4G1 variants are an extremely rare cause of familial PD in Caucasian cohorts, or that A502V is in fact a rare benign variant not involved in PD aetiology. Our data also suggests that the protein can tolerate some extent of variability particularly at this point of the gene.

Screening for VPS35 mutations in Parkinson's disease.

Recently 2 groups have independently identified a mutation in the gene 'vacuolar protein sorting 35 homolog' (VPS35 c.1858G>A; p.Asp620Asn) as a possible cause of autosomal dominant Parkinson's disease (PD). In order to assess the frequency of the reported mutation and to search for other possible disease-causing variants in this gene, we sequenced all 17 exons of VPS35 in 96 familial PD cases, and exon 15 (in which the reported mutation is found) in an additional 64 familial PD cases, 175 young-onset PD cases, and 262 sporadic, neuropathologically confirmed PD cases. We identified 1 individual with the p.Asp620Asn mutation and an autosomal dominant family history of PD. Subsequent follow-up of the family confirmed an affected sibling and cousin who also carried the same mutation. No other potentially disease-causing mutations were identified. We conclude that the VPS35 c.1858G>A mutation is an uncommon cause of familial Parkinson's disease in our population.

Tau acts as an independent genetic risk factor in pathologically proven PD.

MAPT has been repeatedly linked with Parkinson's disease (PD) in association studies. Although tau deposition may be seen in PD, its relevance to the pathogenesis of the condition remains unclear. The presence of tau-positive inclusions is, however, the defining feature of progressive supranuclear palsy (PSP), which may often be clinically misdiagnosed as idiopathic PD. On a genetic level, variants in MAPT are the strongest risk factor for PSP. These facts raise the question whether the MAPT association in PD results from contamination with unrecognized cases of PSP. Using only neuropathologically proven PD, we show that the MAPT association remains and is independent of the PSP Association.