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A Hexanucleotide Repeat Expansion in C9ORF72 Is the Cause of Chromosome 9p21-Linked ALS-FTD

Alan Renton et al.Sep 22, 2011

The chromosome 9p21 amyotrophic lateral sclerosis-frontotemporal dementia (ALS-FTD) locus contains one of the last major unidentified autosomal-dominant genes underlying these common neurodegenerative diseases. We have previously shown that a founder haplotype, covering the MOBKL2b, IFNK, and C9ORF72 genes, is present in the majority of cases linked to this region. Here we show that there is a large hexanucleotide (GGGGCC) repeat expansion in the first intron of C9ORF72 on the affected haplotype. This repeat expansion segregates perfectly with disease in the Finnish population, underlying 46.0% of familial ALS and 21.1% of sporadic ALS in that population. Taken together with the D90A SOD1 mutation, 87% of familial ALS in Finland is now explained by a simple monogenic cause. The repeat expansion is also present in one-third of familial ALS cases of outbred European descent, making it the most common genetic cause of these fatal neurodegenerative diseases identified to date.

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Clinical diagnosis of progressive supranuclear palsy: The movement disorder society criteria

Günter Höglinger et al.May 3, 2017

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Neurological and neuropsychiatric complications of COVID-19 in 153 patients: a UK-wide surveillance study

Aravinthan Varatharaj et al.Jun 25, 2020

Concerns regarding potential neurological complications of COVID-19 are being increasingly reported, primarily in small series. Larger studies have been limited by both geography and specialty. Comprehensive characterisation of clinical syndromes is crucial to allow rational selection and evaluation of potential therapies. The aim of this study was to investigate the breadth of complications of COVID-19 across the UK that affected the brain.

Internal Medicine

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Frequency of the C9orf72 hexanucleotide repeat expansion in patients with amyotrophic lateral sclerosis and frontotemporal dementia: a cross-sectional study

Elisa Majounie et al.Mar 9, 2012

We aimed to accurately estimate the frequency of a hexanucleotide repeat expansion in C9orf72 that has been associated with a large proportion of cases of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).We screened 4448 patients diagnosed with ALS (El Escorial criteria) and 1425 patients with FTD (Lund-Manchester criteria) from 17 regions worldwide for the GGGGCC hexanucleotide expansion using a repeat-primed PCR assay. We assessed familial disease status on the basis of self-reported family history of similar neurodegenerative diseases at the time of sample collection. We compared haplotype data for 262 patients carrying the expansion with the known Finnish founder risk haplotype across the chromosomal locus. We calculated age-related penetrance using the Kaplan-Meier method with data for 603 individuals with the expansion.In patients with sporadic ALS, we identified the repeat expansion in 236 (7·0%) of 3377 white individuals from the USA, Europe, and Australia, two (4·1%) of 49 black individuals from the USA, and six (8·3%) of 72 Hispanic individuals from the USA. The mutation was present in 217 (39·3%) of 552 white individuals with familial ALS from Europe and the USA. 59 (6·0%) of 981 white Europeans with sporadic FTD had the mutation, as did 99 (24·8%) of 400 white Europeans with familial FTD. Data for other ethnic groups were sparse, but we identified one Asian patient with familial ALS (from 20 assessed) and two with familial FTD (from three assessed) who carried the mutation. The mutation was not carried by the three Native Americans or 360 patients from Asia or the Pacific Islands with sporadic ALS who were tested, or by 41 Asian patients with sporadic FTD. All patients with the repeat expansion had (partly or fully) the founder haplotype, suggesting a one-off expansion occurring about 1500 years ago. The pathogenic expansion was non-penetrant in individuals younger than 35 years, 50% penetrant by 58 years, and almost fully penetrant by 80 years.A common Mendelian genetic lesion in C9orf72 is implicated in many cases of sporadic and familial ALS and FTD. Testing for this pathogenic expansion should be considered in the management and genetic counselling of patients with these fatal neurodegenerative diseases.Full funding sources listed at end of paper (see Acknowledgments).

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Differentiation of atypical parkinsonian syndromes with routine MRI

Anette Schrag et al.Feb 8, 2000

To evaluate the use of routine MRI in differentiating between patients with progressive supranuclear palsy (PSP), multiple system atrophy (MSA), corticobasal degeneration (CBD) and control subjects.Two neuroradiologists rated blindly and independently axial T2-weighted and proton density MR images of 54 patients with MSA, 35 patients with PSP, 5 patients with CBD, and 44 control subjects.More than 70% of patients with PSP and more than 80% of patients with cerebellar predominant MSA could be classified correctly with 0.5-T or 1.5-T scans, and no patient in these groups was misclassified. In the remaining patients an unequivocal differentiation could not be made. However, only approximately 50% of patients with parkinsonism-predominant MSA could be classified correctly, and 19% of them (all of whom had had 0.5-T scans) were misclassified.Characteristic findings on routine MRI, either 1.5 T or 0.5 T, can contribute to the identification of MSA and PSP. However, in a minority of patients no unequivocal diagnosis can be made using MRI findings alone.

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Corticobasal degeneration and progressive supranuclear palsy share a common tau haplotype

Henry Houlden et al.Jun 26, 2001

To analyze the association of polymorphisms in the tau gene with pathologically confirmed corticobasal degeneration (CBD).The authors previously described an extended tau haplotype (H1) that covers the human tau gene and is associated with the development of progressive supranuclear palsy (PSP). The authors now extend this analysis to CBD, a neurodegenerative condition with clinical and neuropathologic similarities to PSP. Like PSP, CBD is associated with accumulation of aggregates containing the 4-repeat isoforms of tau. Because of difficulty in diagnosis of CBD, the authors only analyzed cases with pathologically confirmed CBD.The authors collected 57 unrelated, neuropathologically confirmed cases of CBD. Tau sequencing in these cases failed to show the presence of pathogenic mutations. Polymorphisms that spanned the tau gene were analyzed in all CBD cases and controls.Analyzing tau polymorphisms in CBD cases showed that the frequency of H1 and H1/H1 was significantly increased when analyzing all cases and when separating by country of origin. H1 frequency in all CBD cases was 0.921, compared with a control frequency of 0.766 (X(2) = 9.1, p = 0.00255 [1df], OR 3.56 [8.43 > CI 95% > 1.53]). The H1/H1 frequency was also significantly higher at 0.842 compared with 0.596 in age-matched controls (X(2) = 17.42, p = 0.00016, 2df), OR 3.61 [7.05 > CI 95% > 1.85]).The CBD tau association described here suggests that PSP and CBD share a similar cause, although the pathogenic mechanism behind the two diseases leads to a different clinical and pathologic phenotype.

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Excessive burden of lysosomal storage disorder gene variants in Parkinson’s disease

Laurie Robak et al.Oct 12, 2017

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Unbiased screen for interactors of leucine-rich repeat kinase 2 supports a common pathway for sporadic and familial Parkinson disease

A Beilina et al.Feb 7, 2014

Significance Understanding loci nominated by genome-wide association studies (GWASs) is challenging. Here, we show, using the specific example of Parkinson disease, that identification of protein–protein interactions can help determine the most likely candidate for several GWAS loci. This result illustrates a significant general principle that will likely apply across multiple diseases.

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Parkinson's disease age at onset genome‐wide association study: Defining heritability, genetic loci, and α‐synuclein mechanisms

Cornelis Blauwendraat et al.Apr 7, 2019

Abstract Background Increasing evidence supports an extensive and complex genetic contribution to PD. Previous genome‐wide association studies (GWAS) have shed light on the genetic basis of risk for this disease. However, the genetic determinants of PD age at onset are largely unknown. Objectives To identify the genetic determinants of PD age at onset. Methods Using genetic data of 28,568 PD cases, we performed a genome‐wide association study based on PD age at onset. Results We estimated that the heritability of PD age at onset attributed to common genetic variation was ∼0.11, lower than the overall heritability of risk for PD (∼0.27), likely, in part, because of the subjective nature of this measure. We found two genome‐wide significant association signals, one at SNCA and the other a protein‐coding variant in TMEM175 , both of which are known PD risk loci and a Bonferroni‐corrected significant effect at other known PD risk loci, GBA , INPP5F/BAG3, FAM47E/SCARB2 , and MCCC1 . Notably, SNCA, TMEM175, SCARB2, BAG3 , and GBA have all been shown to be implicated in α‐synuclein aggregation pathways. Remarkably, other well‐established PD risk loci, such as GCH1 and MAPT , did not show a significant effect on age at onset of PD. Conclusions Overall, we have performed the largest age at onset of PD genome‐wide association studies to date, and our results show that not all PD risk loci influence age at onset with significant differences between risk alleles for age at onset. This provides a compelling picture, both within the context of functional characterization of disease‐linked genetic variability and in defining differences between risk alleles for age at onset, or frank risk for disease. © 2019 International Parkinson and Movement Disorder Society

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Genome-wide Pleiotropy Between Parkinson Disease and Autoimmune Diseases

Aree Witoelar et al.Jul 1, 2017

Recent genome-wide association studies (GWAS) and pathway analyses supported long-standing observations of an association between immune-mediated diseases and Parkinson disease (PD). The post-GWAS era provides an opportunity for cross-phenotype analyses between different complex phenotypes.To test the hypothesis that there are common genetic risk variants conveying risk of both PD and autoimmune diseases (ie, pleiotropy) and to identify new shared genetic variants and their pathways by applying a novel statistical framework in a genome-wide approach.Using the conjunction false discovery rate method, this study analyzed GWAS data from a selection of archetypal autoimmune diseases among 138 511 individuals of European ancestry and systemically investigated pleiotropy between PD and type 1 diabetes, Crohn disease, ulcerative colitis, rheumatoid arthritis, celiac disease, psoriasis, and multiple sclerosis. NeuroX data (6927 PD cases and 6108 controls) were used for replication. The study investigated the biological correlation between the top loci through protein-protein interaction and changes in the gene expression and methylation levels. The dates of the analysis were June 10, 2015, to March 4, 2017.The primary outcome was a list of novel loci and their pathways involved in PD and autoimmune diseases.Genome-wide conjunctional analysis identified 17 novel loci at false discovery rate less than 0.05 with overlap between PD and autoimmune diseases, including known PD loci adjacent to GAK, HLA-DRB5, LRRK2, and MAPT for rheumatoid arthritis, ulcerative colitis and Crohn disease. Replication confirmed the involvement of HLA, LRRK2, MAPT, TRIM10, and SETD1A in PD. Among the novel genes discovered, WNT3, KANSL1, CRHR1, BOLA2, and GUCY1A3 are within a protein-protein interaction network with known PD genes. A subset of novel loci was significantly associated with changes in methylation or expression levels of adjacent genes.The study findings provide novel mechanistic insights into PD and autoimmune diseases and identify a common genetic pathway between these phenotypes. The results may have implications for future therapeutic trials involving anti-inflammatory agents.

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