Lack of c9orf72 repeat expansion in taiwanese patients with mixed neurodegenerative disorders

Meta-analysis of the association between C9orf72 repeats and neurodegeneration diseases

To conduct a meta-analysis investigating the relationship between the chromosome 9 open reading frame 72 (C9orf72) GGGGCC (G4C2) and neurodegenerative diseases (NDs), including Alzheimer's disease (AD), Parkinson's disease (PD), multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). We searched the EMBASE, PubMed, Web of Science, and Cochrane databases. Twenty-seven case-control studies were included, comprising 7202 AD, 5856 PD, 644 MSA, 439 PSP, and 477 CBD cases. This study demonstrated that C9orf72 repeat expansions (>30) were associated with AD, MSA, PSP, and CBD (AD: OR = 4.88, 95% CI = 2.71-8.78; MSA: OR = 6.98, 95% CI = 1.48-33.01; PSP: OR =10.04, 95% CI = 2.72-37.10; CBD: OR = 28.04, 95% CI = 10.17-77.31). C9orf72 intermediate repeat expansions (20-30) were not associated with AD and MSA (AD: OR = 1.16, 95% CI = 0.39-3.45; MSA: OR = 5.65, 95% CI = 0.69-46.19), while C9orf72 repeat expansions (>30) were not associated with the risk of PD (OR = 1.51, 95% CI = 0.55-4.17), C9orf72 intermediate repeat expansions (20-30) were indeed associated with PD (OR = 2.43, 95% CI = 1.20-4.9). The pathological mechanism of C9orf72 G4C2 repeat expansions differs across various NDs due to the varying number of pathogenic expansions. Measuring the number of C9orf72 G4C2 repeats may be useful in the early-stage differential diagnosis of various NDs.

Distinct sex-specific DNA methylation differences in Alzheimer's disease

BACKGROUND

Sex is increasingly recognized as a significant factor contributing to the biological and clinical heterogeneity in AD. There is also growing evidence for the prominent role of DNA methylation (DNAm) in Alzheimer's disease (AD).

METHODS

We studied sex-specific DNA methylation differences in the blood samples of AD subjects compared to cognitively normal subjects, by performing sex-specific meta-analyses of two large blood-based epigenome-wide association studies (ADNI and AIBL), which included DNA methylation data for a total of 1284 whole blood samples (632 females and 652 males). Within each dataset, we used two complementary analytical strategies, a sex-stratified analysis that examined methylation to AD associations in male and female samples separately, and a methylation-by-sex interaction analysis that compared the magnitude of these associations between different sexes. After adjusting for age, estimated immune cell type proportions, batch effects, and correcting for inflation, the inverse-variance fixed-effects meta-analysis model was used to identify the most consistent DNAm differences across datasets. In addition, we also evaluated the performance of the sex-specific methylation-based risk prediction models for AD diagnosis using an independent external dataset.

RESULTS

In the sex-stratified analysis, we identified 2 CpGs, mapped to the PRRC2A and RPS8 genes, significantly associated with AD in females at a 5% false discovery rate, and an additional 25 significant CpGs (21 in females, 4 in males) at P-value < 1×10^-5. In methylation-by-sex interaction analysis, we identified 5 significant CpGs at P-value < 10^-5. Out-of-sample validations using the AddNeuroMed dataset showed in females, the best logistic prediction model included age, estimated immune cell-type proportions, and methylation risk scores (MRS) computed from 9 of the 23 CpGs identified in AD vs. CN analysis that are also available in AddNeuroMed dataset (AUC = 0.74, 95% CI: 0.65-0.83). In males, the best logistic prediction model included only age and MRS computed from 2 of the 5 CpGs identified in methylation-by-sex interaction analysis that are also available in the AddNeuroMed dataset (AUC = 0.70, 95% CI: 0.56-0.82).

CONCLUSIONS

Overall, our results show that the DNA methylation differences in AD are largely distinct between males and females. Our best-performing sex-specific methylation-based prediction model in females performed better than that for males and additionally included estimated cell-type proportions. The significant discriminatory classification of AD samples with our methylation-based prediction models demonstrates that sex-specific DNA methylation could be a predictive biomarker for AD. As sex is a strong factor underlying phenotypic variability in AD, the results of our study are particularly relevant for a better understanding of the epigenetic architecture that underlie AD and for promoting precision medicine in AD.

Genetic study of young-onset dementia using targeted gene panel sequencing in Taiwan

Recent genetic progress allows the molecular diagnosis of young-onset dementia, including Alzheimer's disease (AD) and frontotemporal dementia (FTD). We aimed to identify the mutational and clinical spectra of causal genes in a Taiwanese cohort of young-onset dementia. Ninety-one patients with young-onset dementia and 22 age/gender-matched controls were recruited. Genetic causes were identified by a targeted panel containing 90 causative genes for AD, FTD, and related neurodegenerative disorders. Plasma biomarkers, including total tau, Aβ42, and Aβ40, were assayed. Molecular amyloid and tau PET scans were performed in some patients carrying mutations. Nine of 52 patients (17.3%) with young-onset AD had mutations: 2 (22.2%), 4 (44.5%), 2 (22.2%), and 1 (11.1%) in APP, PSEN1, PSEN2, and TREM2, respectively. Two of 33 patients (6.1%) with young-onset FTD had mutations in MAPT and LRRK2. Three of the 6 patients (50.0%) with possible FTD combined with other neurodegenerative disorders had individual mutations in APP, PSEN2, or MAPT. Patients with PSEN1 mutations had earlier onset of disease than those without mutations (p = .02). Plasma level of total tau was increased and Aβ42 and Aβ40 levels decreased in all groups of dementia patients compared to controls. Our findings provide a genetic spectrum of young-onset dementia in our population.

Sex differences in Alzheimer disease - the gateway to precision medicine

Alzheimer disease (AD) is characterized by wide heterogeneity in cognitive and behavioural syndromes, risk factors and pathophysiological mechanisms. Addressing this phenotypic variation will be crucial for the development of precise and effective therapeutics in AD. Sex-related differences in neural anatomy and function are starting to emerge, and sex might constitute an important factor for AD patient stratification and personalized treatment. Although the effects of sex on AD epidemiology are currently the subject of intense investigation, the notion of sex-specific clinicopathological AD phenotypes is largely unexplored. In this Review, we critically discuss the evidence for sex-related differences in AD symptomatology, progression, biomarkers, risk factor profiles and treatment. The cumulative evidence reviewed indicates sex-specific patterns of disease manifestation as well as sex differences in the rates of cognitive decline and brain atrophy, suggesting that sex is a crucial variable in disease heterogeneity. We discuss critical challenges and knowledge gaps in our current understanding. Elucidating sex differences in disease phenotypes will be instrumental in the development of a 'precision medicine' approach in AD, encompassing individual, multimodal, biomarker-driven and sex-sensitive strategies for prevention, detection, drug development and treatment.

A clinical and genetic study of early-onset and familial parkinsonism in taiwan: An integrated approach combining gene dosage analysis and next-generation sequencing

Background

Recent genetic progress has allowed for the molecular diagnosis of Parkinson's disease. However, genetic causes of PD vary widely in different ethnicities. Mutational frequencies and clinical phenotypes of genes associated with PD in Asian populations are largely unknown. The objective of this study was to identify the mutational frequencies and clinical spectrums of multiple PD‐causative genes in a Taiwanese PD cohort.

Methods

A total of 571 participants including 324 patients with early‐onset parkinsonism (onset age, <50 years) and 247 parkinsonism pedigrees were recruited at a tertiary referral center in Taiwan from 2002 to 2017. Genetic causes were identified by an integrated approach including gene dosage analysis, a targeted next‐generation sequencing panel containing 40 known PD‐causative genes, repeat‐primed polymerase chain reaction, and whole‐exome sequencing analysis.

Results

Thirty of the 324 patients with early‐onset parkinsonism (9.3%) were found to carry mutations in Parkin, PINK1, or PLA2G6 or had increased trinucleotide repeats in SCA8. Twenty‐nine of 109 probands with autosomal‐recessive inheritance of parkinsonism (26.6%) were found to carry mutations in Parkin, PINK1, GBA, or HTRA2. The genetic causes for the 138 probands with an autosomal‐dominant inheritance pattern of parkinsonism were more heterogeneous. Seventeen probands (12.3%) carried pathogenic mutations in LRRK2, VPS35, MAPT, GBA, DNAJC13, C9orf72, SCA3, or SCA17. A novel missense mutation in the UQCRC1 gene was found in a family with autosomal‐dominant inheritance parkinsonism via whole‐exome sequencing analysis.

Conclusions

Our findings provide a better understanding of the genetic architecture of PD in eastern Asia and broaden the clinical spectrum of PD‐causing mutations. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

C9orf72 and its Relevance in Parkinsonism and Movement Disorders: A Comprehensive Review of the Literature

Background

The C9orf72 hexanucleotide expansion is one of the latest discovered repeat expansion disorders related to neurodegeneration. Its association with the FTD/ALS spectrum disorders is well established, and it is considered to be one of the leading related genes. It has also been reported as a possible cause of several other phenotypes, including parkinsonism and other movement disorders. Its significance, though outside the FTD/ALS spectrum, is not well defined.

Methods

A comprehensive search of the literature was performed. All relevant papers, including reviews and case series/reports on movement disorder phenotypes reported with the C9orf72 repeat expansion, were reviewed. Data on frequency, natural history, phenotype, genetics, and possible underlying mechanisms were assessed.

Results and Discussion

In a number of studies, C9orf72 accounts for a small fraction of typical PD. Atypical parkinsonian syndromes, including CBS, PSP, and MSA have also been reported. Features that increase the probability of positive testing include early cognitive and/or behavioral symptoms, positive family history of ALS or FTD, and the presence of UMN and LMN signs. Furthermore, several studies conclude that C9orf72 is the most common cause of HD-phenocopies. Interestingly, many cases with the parkinsonian phenotype that bear an intermediate range of repeats are also reported, questioning the direct causal role of C9orf72 and suggesting the possibility of being a susceptibility factor, while the presence of the expansion in normal controls questions its clinical significance. Finally, studies on pathology reveal a distinctive broad range of C9orf72-related neurodegeneration that could explain the wide phenotypic variation.

Sex Differences in Cognitive Decline in Subjects with High Likelihood of Mild Cognitive Impairment due to Alzheimer's disease

Sex differences in Alzheimer’s disease (AD) biology and progression are not yet fully characterized. The goal of this study is to examine the effect of sex on cognitive progression in subjects with high likelihood of mild cognitive impairment (MCI) due to Alzheimer’s and followed up to 10 years in the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Cerebrospinal fluid total-tau and amyloid-beta (Aβ42) ratio values were used to sub-classify 559 MCI subjects (216 females, 343 males) as having “high” or “low” likelihood for MCI due to Alzheimer’s. Data were analyzed using mixed-effects models incorporating all follow-ups. The worsening from baseline in Alzheimer’s Disease Assessment Scale-Cognitive score (mean, SD) (9 ± 12) in subjects with high likelihood of MCI due to Alzheimer’s was markedly greater than that in subjects with low likelihood (1 ± 6, p < 0.0001). Among MCI due to AD subjects, the mean worsening in cognitive score was significantly greater in females (11.58 ± 14) than in males (6.87 ± 11, p = 0.006). Our findings highlight the need to further investigate these findings in other populations and develop sex specific timelines for Alzheimer’s disease progression.

Intrafamilial phenotypic heterogeneity in a Taiwanese family with a MAPT p.R5H mutation: a case report and literature review

Background

Frontotemporal degeneration (FTD) is a clinically and genetically heterogeneous neurodegenerative disorder characterized by deficits in executive function that frequently overlaps with parkinsonism and motor neuron disorders. Several genes have been identified to cause autosomal dominant forms of FTD, including the gene coding for the protein associated with microtubule tau (MAPT). While most reported pathogenic mutations in MAPT occur in exons 9–13, few families have been reported with mutations outside of this region. Herein, we report a first Taiwanese family having the exon 1 p.Arg5His mutation in MAPT with intrafamilial phenotype heterogeneity.

Case presentation

A 63-year-old man presented with progressive non-fluent speech and impaired memory for 3 years. He then developed apraxia, myoclonus and parkinsonism feature at his right hand. Extensive neurologic and neurocognitive examination lead to a diagnosis of FTD mixed with corticobasal syndrome. Magnetic resonance imaging revealed asymmetric atrophy in the left frontal and temporal lobes and single-photon emission computed tomography indicated decreased metabolism in the same areas as well as the left basal ganglia. The patient’s mother had been diagnosed with amyotrophic lateral sclerosis (ALS) at the age of 60 and was deceased 10 years later due to respiratory failure. The patient’s younger sister had persistent depressive disorder in her early forties and did not have any prominent cognitive or motor dysfunctions. We performed genetic analysis applying a targeted next generation sequencing (NGS) panel covering MAPT, GRN, VCP, FUS, CHMP2B, and TARDBP on the proband, followed by Sanger sequencing of candidate genes in eight family members. Hexanucleotide repeat expansion of C9Orf72 was determined by repeat-primed PCR. We identified a missense mutation in exon 1 of MAPT gene, c.14G > A (p.R5H), which was previously reported in only two Japanese patients in a literature review. This substitution co-segregated with the disease phenotypes in the family.

Conclusions

This is the first report of the occurrence of the MAPT p.R5H mutation in the Taiwanese population. Our findings extend the current knowledge of phenotypic heterogeneity among family members carrying the MAPT p.R5H mutation.

Intermediate C9orf72 alleles in neurological disorders: does size really matter?

C9orf72 repeat expansions is a major cause of familial frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) worldwide. Sizes of <20 hexanucleotide repeats are observed in controls, while up to thousands associate with disease. Intermediate C9orf72 repeat lengths, however, remain uncertain. We systematically reviewed the role of intermediate C9orf72 alleles in C9orf72-related neurological disorders. We identified 49 studies with adequate available data on normal or intermediate C9orf72 repeat length, involving subjects with FTD, ALS, Parkinson’s disease (PD), atypical parkinsonism, Alzheimer’s disease (AD) and other aetiologies. We found that, overall, normal or intermediate C9orf72 repeat lengths are not associated with higher disease risk across these disorders, but intermediate allele sizes appear to associate more frequently with neuropsychiatric phenotypes. Intermediate sizes were detected in subjects with personal or family history of FTD and/or psychiatric illness, parkinsonism complicated by psychosis and rarely in psychiatric cohorts. Length of the hexanucleotide repeat may be influenced by ethnicity (with Asian controls displaying shorter normal repeat lengths compared with Caucasians) and underlying haplotype, with more patients and controls carrying the ‘risk’ haplotype rs3849942 displaying intermediate alleles. There is some evidence that intermediate alleles display increased methylation levels and affect normal transcriptional activity of the C9orf72 promoter, but the ‘critical’ repeat size required for initiation of neurodegeneration remains unknown and requires further study. In common neurological diseases, intermediate C9orf72 repeats do not influence disease risk but may associate with higher frequency of neuropsychiatric symptoms. This has important clinical relevance as intermediate carriers pose a challenge for genetic counselling.

C9ORF72 repeat expansions in Chinese patients with Parkinson's disease and multiple system atrophy

The hexanucleotide repeat expansions in the C9ORF72 gene has been found in some patients with atypical Parkinsonism. A number of hexanucleotide repeats were examined in a Chinese population, including 619 patients with Parkinson's disease (PD), 381 patients with multiple system atrophy (MSA), and 632 healthy controls. We did not identify any pathogenic repeat expansions in either patients or controls, and any associations between repeats number and disease risk. C9ORF72 expansions are not involved the wider spectrum of Parkinsonism.

The Association between C9orf72 Repeats and Risk of Alzheimer's Disease and Amyotrophic Lateral Sclerosis: A Meta-Analysis

C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) in Caucasian populations. However, the relationship between C9orf72 repeats and Alzheimer's disease (AD) was not clear. Additionally, there were few articles assessing C9orf72 in other ethnicities with ALS. In this meta-analysis, we aimed to investigate the relationship between C9orf72 repeat expansions (≥30 repeats) and intermediate repeat copies (20–29 repeats) and AD or ALS. The results suggested positive correlations between C9orf72 repeat expansions and the risk of Alzheimer's disease (OR = 6.36, 95% CI = 3.13–12.92, and p < 0.00001), while intermediate repeat copies of C9orf72 gene were not associated with the risk of the disease. C9orf72 repeat expansions were positively correlated with the risk of familial and sporadic ALS (OR = 293.25, 95% CI = 148.17–580.38, and p < 0.00001; OR = 35.57, 95% CI = 19.61–64.51, and p < 0.00001). There was a positive correlation between the gene variations and ALS risk among Caucasians and Asians (OR = 57.56, 95% CI = 36.73–90.22, and p < 0.00001; OR = 6.35, 95% CI = 1.39–29.02, and p = 0.02).

Mutational analysis of angiogenin gene in Parkinson's disease

Mutations in the angiogenic factor, angiogenin (ANG), have been identified in patients with both familial and sporadic amyotrophic lateral sclerosis (ALS) and are thought to have a neuroprotective function. Parkinsonism has been noted in kindreds with ANG mutations and variants in the ANG gene have been found to associate with PD in two Caucasian populations. We therefore hypothesized that mutations in ANG may also contribute to idiopathic Parkinson's disease (PD). We sequenced ANG gene in a total of 1498 participants comprising 750 PD patients and 748 age/gender matched controls from Taiwan. We identified one novel synonymous substitution, c.C100T (p.L10L), in a single heterozygous state in one PD patient, which was not observed in controls. The clinical phenotypes and [^99mTc]-TORDAT-SPECT images of the p.L10L carrier were similar to that seen in idiopathic PD. In addition, we also identified one common variant, c.T330G (p.G110G, rs11701), which was previously reported to associate with PD risk in Caucasians. However, the frequency of TG/GG genotype was comparable between PD cases and controls (odds ratio: 0.85, 95% confidence interval: 0.29–2.55, P = 0.78). Our results did not support that ANG rs11701 variant is a genetic risk factor for PD in our population. We conclude that mutations in ANG are not a common cause for idiopathic PD.