Global investigation and meta-analysis of the C9orf72 (G4C2)n repeat in Parkinson disease

Optical genome mapping of structural variants in Parkinson's disease-related induced pluripotent stem cells

BACKGROUND

Certain structural variants (SVs) including large-scale genetic copy number variants, as well as copy number-neutral inversions and translocations may not all be resolved by chromosome karyotype studies. The identification of genetic risk factors for Parkinson's disease (PD) has been primarily focused on the gene-disruptive single nucleotide variants. In contrast, larger SVs, which may significantly influence human phenotypes, have been largely underexplored. Optical genomic mapping (OGM) represents a novel approach that offers greater sensitivity and resolution for detecting SVs. In this study, we used induced pluripotent stem cell (iPSC) lines of patients with PD-linked SNCA and PRKN variants as a proof of concept to (i) show the detection of pathogenic SVs in PD with OGM and (ii) provide a comprehensive screening of genetic abnormalities in iPSCs.

RESULTS

OGM detected SNCA gene triplication and duplication in patient-derived iPSC lines, which were not identified by long-read sequencing. Additionally, various exon deletions were confirmed by OGM in the PRKN gene of iPSCs, of which exon 3-5 and exon 2 deletions were unable to phase with conventional multiplex-ligation-dependent probe amplification. In terms of chromosomal abnormalities in iPSCs, no gene fusions, no aneuploidy but two balanced inter-chromosomal translocations were detected in one line that were absent in the parental fibroblasts and not identified by routine single nucleotide variant karyotyping.

CONCLUSIONS

In summary, OGM can detect pathogenic SVs in PD-linked genes as well as reveal genomic abnormalities for iPSCs that were not identified by other techniques, which is supportive for OGM's future use in gene discovery and iPSC line screening.

Distribution of the C9orf72 hexanucleotide repeat expansion in healthy subjects: a multicenter study promoted by the Italian IRCCS network of neuroscience and neurorehabilitation

Introduction

High repeat expansion (HRE) alleles in C9orf72 have been linked to both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD); ranges for intermediate allelic expansions have not been defined yet, and clinical interpretation of molecular data lacks a defined genotype-phenotype association. In this study, we provide results from a large multicenter epidemiological study reporting the distribution of C9orf72 repeats in healthy elderly from the Italian population.

Methods

A total of 967 samples were collected from neurologically evaluated healthy individuals over 70 years of age in the 13 institutes participating in the RIN (IRCCS Network of Neuroscience and Neurorehabilitation) based in Italy. All samples were genotyped using the AmplideXPCR/CE C9orf72 Kit (Asuragen, Inc.), using standardized protocols that have been validated through blind proficiency testing.

Results

All samples carried hexanucleotide G4C2 expansion alleles in the normal range. All samples were characterized by alleles with less than 25 repeats. In particular, 93.7% of samples showed a number of repeats ≤10, 99.9% ≤20 repeats, and 100% ≤25 repeats.

Conclusion

This study describes the distribution of hexanucleotide G4C2 expansion alleles in an Italian healthy population, providing a definition of alleles associated with the neurological healthy phenotype. Moreover, this study provides an effective model of federation between institutes, highlighting the importance of sharing genomic data and standardizing analysis techniques, promoting translational research. Data derived from the study may improve genetic counseling and future studies on ALS/FTD.

Differential Expression of Proteins Associated with Bipolar Disorder as Identified Using the PeptideShaker Software

The prevalence of bipolar disorder (BD) in modern society is growing rapidly, but due to the lack of paraclinical criteria, its differential diagnosis with other mental disorders is somewhat challenging. In this regard, the relevance of proteomic studies is increasing due to the development of methods for processing large data arrays; this contributes to the discovery of protein patterns of pathological processes and the creation of new methods of diagnosis and treatment. It seems promising to search for proteins involved in the pathogenesis of BD in an easily accessible material-blood serum. Sera from BD patients and healthy individuals were purified via affinity chromatography to isolate 14 major proteins and separated using 1D SDS-PAGE. After trypsinolysis, the proteins in the samples were identified via HPLC/mass spectrometry. Mass spectrometric data were processed using the OMSSA and X!Tandem search algorithms using the UniProtKB database, and the results were analyzed using PeptideShaker. Differences in proteomes were assessed via an unlabeled NSAF-based analysis using a two-tailed Bonferroni-adjusted t-test. When comparing the blood serum proteomes of BD patients and healthy individuals, 10 proteins showed significant differences in NSAF values. Of these, four proteins were predominantly present in BD patients with the maximum NSAF value: 14-3-3 protein zeta/delta; ectonucleoside triphosphate diphosphohydrolase 7; transforming growth factor-beta-induced protein ig-h3; and B-cell CLL/lymphoma 9 protein. Further exploration of the role of these proteins in BD is warranted; conducting such studies will help develop new paraclinical criteria and discover new targets for BD drug therapy.

Young Onset Alzheimer's Disease Associated with C9ORF72 Hexanucleotide Expansion: Further Evidence for a Still Unsolved Association

Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are recognized as part of a disease continuum (FTD-ALS spectrum), in which the most common genetic cause is chromosome 9 open reading frame 72 (C9ORF72) gene hexanucleotide repeat expansion. The clinical phenotype of patients carrying this expansion varies widely and includes diseases beyond the FTD-ALS spectrum. Although a few cases of patients with C9ORF72 expansion and a clinical or biomarker-supported diagnosis of Alzheimer's disease (AD) have been described, they have been considered too sparse to establish a definite association between the C9ORF72 expansion and AD pathology. Here, we describe a C9ORF72 family with pleomorphic phenotypical expressions: a 54-year-old woman showing cognitive impairment and behavioral disturbances with both neuroimaging and cerebrospinal fluid (CSF) biomarkers consistent with AD pathology, her 49-year-old brother with typical FTD-ALS, and their 63-year-old mother with the behavioral variant of FTD and CSF biomarkers suggestive of AD pathology. The young onset of disease in all three family members and their different phenotypes and biomarker profiles make the simple co-occurrence of different diseases an extremely unlikely explanation. Our report adds to previous findings and may contribute to further expanding the spectrum of diseases associated with C9ORF72 expansion.

Motor, cognitive and behavioural profiles of C9orf72 expansion-related amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) individuals carrying the hexanucleotide repeat expansion (HRE) in the C9orf72 gene (C9Pos) have been described as presenting distinct features compared to the general ALS population (C9Neg). We aim to identify the phenotypic traits more closely associated with the HRE and analyse the role of the repeat length as a modifier factor.

METHODS

We studied a cohort of 960 ALS patients (101 familial and 859 sporadic cases). Motor phenotype was determined using the MRC scale, the lower motor neuron score (LMNS) and the Penn upper motor neuron score (PUMNS). Neuropsychological profile was studied using the Italian version of the Edinburgh Cognitive and Behavioral ALS Screen (ECAS), the Frontal Behavioral Inventory (FBI), the Beck Depression Inventory-II (BDI-II) and the State-Trait Anxiety Inventory (STAI). A two-step PCR protocol and Southern blotting were performed to determine the presence and the size of C9orf72 HRE, respectively.

RESULTS

C9orf72 HRE was detected in 55/960 ALS patients. C9Pos patients showed a younger onset, higher odds of bulbar onset, increased burden of UMN signs, reduced survival and higher frequency of concurrent dementia. We found an inverse correlation between the HRE length and the performance at ECAS ALS-specific tasks (P = 0.031). Patients also showed higher burden of behavioural disinhibition (P = 1.6 × 10^-4), lower degrees of depression (P = 0.015) and anxiety (P = 0.008) compared to C9Neg cases.

CONCLUSIONS

Our study provides an extensive characterization of motor, cognitive and behavioural features of C9orf72-related ALS, indicating that the C9orf72 HRE size may represent a modifier of the cognitive phenotype.

Expanding the spectrum of C9ORF72-related neurodegenerative disorders in the Greek population

The C9ORF72 hexanucleotide repeat expansion is an established cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) and has also been associated with Huntington disease (HD)-like syndromes and rarely with Parkinson's disease (PD) and Alzheimer's disease (AD). In the present study we aimed to investigate the genotypic and phenotypic profile of C9ORF72-related disorders in Greece. For this reason, 957 patients (467 with ALS, 53 with HD-like syndromes, 247 with dementia, 175 with PD and 15 with hereditary spastic paraplegia, HSP) and 321 controls were tested for the C9ORF72 repeat expansion. Forty-nine patients with ALS (10.5%), 2 with HD-like syndromes (3.8%), 13 with FTD (11.5%), 1 with AD (1.6%), and 2 with PD (1.1%) were expansion-positive. The expansion was not detected in the HSP or control groups. The results of this study provide an update on the spectrum of C9ORF72-related neurodegenerative diseases, emphasizing the importance of C9ORF72 genetic testing in Greek patients with familial and sporadic ALS and/or FTD and HD-like syndromes.

Differences in Motor Features of C9orf72, MAPT, or GRN Variant Carriers With Familial Frontotemporal Lobar Degeneration

BACKGROUND AND OBJECTIVES

Familial frontotemporal lobar degeneration (f-FTLD) is a phenotypically heterogeneous spectrum of neurodegenerative disorders most often caused by variants within chromosome 9 open reading frame 72 (C9orf72), microtubule-associated protein tau (MAPT), or granulin (GRN). The phenotypic association with each of these genes is incompletely understood. We hypothesized that the frequency of specific clinical features would correspond with different genes.

METHODS

We screened the Advancing Research and Treatment in Frontotemporal Lobar Degeneration (ARTFL)/Longitudinal Evaluation of Familial Frontotemporal Dementia Subjects (LEFFTDS)/ARTFL LEFFTDS Longitudinal Frontotemporal Lobar Degeneration Consortium for symptomatic carriers of pathogenic variants in C9orf72, MAPT, or GRN. We assessed for clinical differences among these 3 groups based on data recorded as part of a detailed neurologic examination, the Progressive Supranuclear Palsy Rating Scale, Progressive Supranuclear Palsy-Quality of Life Rating Scale, Unified Parkinson's Disease Rating Scale Part III (motor items), and the Amyotrophic Lateral Sclerosis Functional Rating Scale, revised version. Data were analyzed using Kruskal-Wallis and Wilcoxon rank-sum tests and Fisher exact test.

RESULTS

We identified 184 symptomatic participants who had a single pathogenic variant in C9orf72 (n = 88), MAPT (n = 53), or GRN (n = 43). Motor symptom age at onset was earliest in the MAPT participants followed by C9orf72, whereas the GRN pathogenic variant carriers developed symptoms later. C9orf72 participants more often had fasciculations, muscle atrophy, and weakness, whereas parkinsonism was less frequent. Vertical oculomotor abnormalities were more common in the MAPT cohort, whereas apraxia and focal limb dystonia occurred more often in participants with GRN variants.

DISCUSSION

We present a large comparative study of motor features in C9orf72, MAPT, and GRN pathogenic variant carriers with symptomatic f-FTLD. Our findings demonstrate characteristic phenotypic differences corresponding with specific gene variants that increase our understanding of the genotype-phenotype relationship in this complex spectrum of neurodegenerative disorders.

TRIAL REGISTRATION INFORMATION

NCT02365922, NCT02372773, and NCT04363684.

C9orf72-G4C2 Intermediate Repeats and Parkinson's Disease; A Data-Driven Hypothesis

Pathogenic C9orf72-G₄C₂ repeat expansions are associated with ALS/FTD, but not with Parkinson’s disease (PD); yet the possible link between intermediate repeat lengths and PD remains inconclusive. We aim to study the potential involvement of these repeats in PD. The number of C9orf72-repeats were determined by flanking and repeat-primed PCR assays, and the risk-haplotype was determined by SNP-array. Their association with PD was assessed in a stratified manner: in PD-patients-carriers of mutations in LRRK2, GBA, or SMPD1 genes (n = 388), and in PD-non-carriers (NC, n = 718). Allelic distribution was significantly different only in PD-NC compared to 600 controls when looking both at the allele with higher repeat’s size (p = 0.034) and at the combined number of repeats from both alleles (p = 0.023). Intermediate repeats (20–60 repeats) were associated with PD in PD-NC patients (p = 0.041; OR = 3.684 (CI 1.05–13.0)) but not in PD-carriers (p = 0.684). The C9orf72 risk-haplotype, determined in a subgroup of 588 PDs and 126 controls, was observed in higher frequency in PD-NC (dominant model, OR = 1.71, CI 1.04–2.81, p = 0.0356). All 19 alleles within the risk-haplotype were associated with higher C9orf72 RNA levels according to the GTEx database. Based on our data, we suggest a model in which intermediate repeats are a risk factor for PD in non-carriers, driven not only by the number of repeats but also by the variants’ genotypes within the risk-haplotype. Further studies are needed to elucidate this possible role of C9orf72 in PD pathogenesis.

C9orf72 Intermediate Repeats Confer Genetic Risk for Severe COVID-19 Pneumonia Independently of Age

A cytokine storm, autoimmune features and dysfunctions of myeloid cells significantly contribute to severe coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Genetic background of the host seems to be partly responsible for severe phenotype and genes related to innate immune response seem critical host determinants. The C9orf72 gene has a role in vesicular trafficking, autophagy regulation and lysosome functions, is highly expressed in myeloid cells and is involved in immune functions, regulating the lysosomal degradation of mediators of innate immunity. A large non-coding hexanucleotide repeat expansion (HRE) in this gene is the main genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), both characterized by neuroinflammation and high systemic levels of proinflammatory cytokines, while HREs of intermediate length, although rare, are more frequent in autoimmune disorders. C9orf72 full mutation results in haploinsufficiency and intermediate HREs seem to modulate gene expression as well and impair autophagy. Herein, we sought to explore whether intermediate HREs in C9orf72 may be a risk factor for severe COVID-19. Although we found intermediate HREs in only a small portion of 240 patients with severe COVID-19 pneumonia, the magnitude of risk for requiring non-invasive or mechanical ventilation conferred by harboring intermediate repeats >10 units in at least one C9orf72 allele was more than twice respect to having shorter expansions, when adjusted for age (odds ratio (OR) 2.36; 95% confidence interval (CI) 1.04-5.37, p = 0.040). The association between intermediate repeats >10 units and more severe clinical outcome (p = 0.025) was also validated in an independent cohort of 201 SARS-CoV-2 infected patients. These data suggest that C9orf72 HREs >10 units may influence the pathogenic process driving more severe COVID-19 phenotypes.

Unravelling the clinical spectrum and the role of repeat length in C9ORF72 repeat expansions

Since the discovery of the C9orf72 repeat expansion as the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis, it has increasingly been associated with a wider spectrum of phenotypes, including other types of dementia, movement disorders, psychiatric symptoms and slowly progressive FTD. Prompt recognition of patients with C9orf72-associated diseases is essential in light of upcoming clinical trials. The striking clinical heterogeneity associated with C9orf72 repeat expansions remains largely unexplained. In contrast to other repeat expansion disorders, evidence for an effect of repeat length on phenotype is inconclusive. Patients with C9orf72-associated diseases typically have very long repeat expansions, containing hundreds to thousands of GGGGCC-repeats, but smaller expansions might also have clinical significance. The exact threshold at which repeat expansions lead to neurodegeneration is unknown, and discordant cut-offs between laboratories pose a challenge for genetic counselling. Accurate and large-scale measurement of repeat expansions has been severely hindered by technical difficulties in sizing long expansions and by variable repeat lengths across and within tissues. Novel long-read sequencing approaches have produced promising results and open up avenues to further investigate this enthralling repeat expansion, elucidating whether its length, purity, and methylation pattern might modulate clinical features of C9orf72-related diseases.

Clinical Update on C9orf72: Frontotemporal Dementia, Amyotrophic Lateral Sclerosis, and Beyond

The identification of C9orf72 gene has led to important scientific progresses and has considerably changed our clinical practice. However, a decade after C9orf72 discovery, some important clinical questions remain unsolved. The reliable cutoff for the pathogenic repeat number and the implication of intermediate alleles in frontotemporal dementia, amyotrophic lateral sclerosis, or in other diseases are still uncertain. The occurrence of an anticipation phenomenon - at the clinical and molecular levels - in C9orf72 kindreds is still debated as well, and the factors driving age at onset and phenotype variability are largely unknown. All these questions have a significant impact not only in clinical practice for diagnosis and genetic counseling but also in a research context for the initiation of therapeutic trials. In this chapter, we will address all those issues and summarize the recent updates about clinical aspects of C9orf72 disease, focusing on both the common and the less typical phenotypes.

Correlation between C9ORF72 mutation and neurodegenerative diseases: A comprehensive review of the literature

Chromosome 9 open reading frame 72 (C9ORF72) encodes a 54-kDa protein with unknown function that is expressed at high levels in the central nervous system. The C9ORF72 hexanucleotide amplification is one of the most recently discovered repetitive amplification diseases related to neurodegeneration. Its association with amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) spectrum diseases has been fully established, although a causative role for C9ORF72 in Alzheimer's disease (AD) and Parkinson's disease (PD) remains to be established. Therefore, in this article, we will review the evidence for C9ORF72 as a causative factor in neurodegenerative diseases, the underlying mechanisms, and the potential for targeting C9ORF72 as a strategy to alleviate neurodegenerative disease progression.

Carriership of two copies of C9orf72 hexanucleotide repeat intermediate-length alleles is a risk factor for ALS in the Finnish population

The hexanucleotide repeat expansion in intron 1 of the C9orf72 gene causes amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. In addition to the effects of the pathogenic expansion, a role of intermediate-length alleles has been suggested in ALS, corticobasal degeneration and Parkinson’s disease. Due to the rarity of intermediate-length alleles with over 20 repeats and the geographical variability in their frequency, large studies that account for population stratification are needed to elucidate their effects. To this aim, we used repeat-primed PCR and confirmatory PCR assays to determine the C9orf72 repeat allele lengths in 705 ALS patients and 3958 controls from Finland. After exclusion of expansion carriers (25.5% of the ALS patients and 0.2% of the controls), we compared the frequency of intermediate-length allele carriers of 525 ALS cases and 3950 controls using several intermediate-length allele thresholds (7–45, 17–45, 21–45, 24–45 and 24–30). The carriership of an intermediate-length allele did not associate with ALS (Fisher’s test, all p ≥ 0.15) nor was there any association with survival (p ≥ 0.33), when we divided our control group into three age groups (18–65, 66–84 and 85–105 years). Carriership of two intermediate-length alleles was associated with ALS, when the longer allele was ≥ 17 repeats (p = 0.002, OR 5.32 95% CI 2.02–14.05) or ≥ 21 repeats (p = 0.00016, OR 15.21 95% CI 3.79–61.0). Our results show that intermediate-length alleles are a risk factor of ALS when present in both alleles, whereas carrying just one intermediate-length allele was not associated with ALS or survival.

Isolated parkinsonism is an atypical presentation of GRN and C9orf72 gene mutations

INTRODUCTION

A phenotype of isolated parkinsonism mimicking Idiopathic Parkinson's Disease (IPD) is a rare clinical presentation of GRN and C9orf72 mutations, the major genetic causes of frontotemporal dementia (FTD). It still remains controversial if this association is fortuitous or not, and which clinical clues could reliably suggest a genetic FTD etiology in IPD patients. This study aims to describe the clinical characteristics of FTD mutation carriers presenting with IPD phenotype, provide neuropathological evidence of the mutation's causality, and specifically address their "red flags" according to current IPD criteria.

METHODS

Seven GRN and C9orf72 carriers with isolated parkinsonism at onset, and three patients from the literature were included in this study. To allow better delineation of their phenotype, the presence of supportive, exclusion and "red flag" features from MDS criteria were analyzed for each case.

RESULTS

Amongst the ten patients (5 GRN, 5 C9orf72), seven fulfilled probable IPD criteria during all the disease course, while behavioral/language or motoneuron dysfunctions occurred later in three. Disease duration was longer and dopa-responsiveness was more sustained in C9orf72 than in GRN carriers. Subtle motor features, cognitive/behavioral changes, family history of dementia/ALS were suggestive clues for a genetic diagnosis. Importantly, neuropathological examination in one patient revealed typical TDP-43-inclusions without alpha-synucleinopathy, thus demonstrating the causal link between FTD mutations, TDP-43-pathology and PD phenotype.

CONCLUSION

We showed that, altogether, family history of early-onset dementia/ALS, the presence of cognitive/behavioral dysfunction and subtle motor characteristics are atypical features frequently present in the parkinsonian presentations of GRN and C9orf72 mutations.

RAB39B's role in membrane traffic, autophagy, and associated neuropathology

Neuropathological disorders are increasingly associated with dysfunctions in neuronal membrane traffic and autophagy, with defects among members of the Rab family of small GTPases implicated. Mutations in the human Xq28 localized gene RAB39B have been associated with X-linked neurodevelopmental defects including macrocephaly, intellectual disability, autism spectrum disorder (ASD), as well as rare cases of early-onset Parkinson's disease (PD). Despite the finding that RAB39B regulates GluA2 trafficking and could thus influence synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit composition, reasons for the wide-ranging neuropathological consequences associated with RAB39B defects have been unclear. Recent studies have now unraveled possible mechanisms underlying the neuropathological roles of this brain-enriched small GTPase. Studies in RAB39B knockout mice showed that RAB39B interacts with components of Class I phosphatidylinositol-3-kinase (PI3K) signaling. In its absence, the PI3K-AKT-mechanistic target of rapamycin signaling pathway in neural progenitor cells (NPCs) is hyperactivated, which promotes NPC proliferation, leading to macrocephaly and ASD. Pertaining to early-onset PD, a complex of C9orf72, Smith-Magenis syndrome chromosome region candidate 8 and WD repeat domain 41 that functions in autophagy has been identified as a guanine nucleotide exchange factor of RAB39B. Here, recent findings that have shed light on our mechanistic understanding of RAB39B's role in neurodevelopmental and neurodegenerative pathologies are reviewed. Caveats and unanswered questions are also discussed, and future perspectives outlined.

Organochlorine pesticide levels in Greek patients with Parkinson's disease

Background

Parkinson’s disease (PD) is a neurodegenerative disease, mostly presenting with characteristic motor symptoms. Organochlorines (OC) are a class of widely-used pesticides that have been included among the list of environmental factors incriminated in PD pathogenesis. However, most studies reporting this association are based on questionnaires, and few have reported exposure data.

Aim

To examine the relationship between OC blood concentrations and PD risk.

Methods

In the present study, we studied the concentrations of 8 OC compounds (hexachlorobenzene, heptachlor, hepachlor epoxide, c-chlordane, a-chlordane, p,p’-DDE, DDD, DDT) in 104 Greek PD patients and 110 healthy controls.

Results

All substances studied were present in at least one sample. The most frequently detected (above the level of quantification) pesticides were p,p’-DDE (n = 214, 100 % of both groups) and hexachlorobenzene, HCB (n = 189, cases 46.5 %, controls 53.5 %). Higher levels of DDE were detected among PD patients in comparison to controls by using logistic regression analysis to control for confounders [Odds Ratio, OR (95 % confidence interval, C.I.)]: 2.592,(1.29–5.21)], whilst lower levels of HCB were detect among PD patients [OR,95 %CI:0.176(0.09−0.35)].

Conclusions

Our data suggest that exposure to specific OCs is related to the risk of PD. Further studies, using real exposure data, are needed in order to confirm and extend these findings.

The Beneficial Effects of Computer-Based Cognitive Training in Parkinson’s Disease: A Systematic Review

Background

Cognitive dysfunction is one of the most prevalent non-motor aspects of Parkinson’s disease (PD). The present review focuses on published studies investigating the effect of computer-based cognitive training (CT) on neuropsychological performance in PD.

Methods

A systematic search of the PubMed database and Google Scholar was carried out. Randomized controlled studies published before September 2019, investigating the effect of computer-based CT (regardless of the comparator, active or placebo) on PD patients were included. Literature search, data extraction, and Risk of Bias (RoB) evaluation (based on the RoB Cochrane tool for Randomized Trials) were performed by two authors (A.N. and M.M), independently.

Results

Among 30 full-texts assessed for eligibility, seven articles fulfilled the inclusion criteria and were involved in the qualitative analysis. The main outcomes of the retrieved studies (all studies used similar cognitive rehabilitation methodologies) were indicative of cognitive improvement in most cognitive domains, particularly memory, executive function, processing speed, and attention, that is, the domains primarily impaired in the disease.

Conclusion

Multidomain CT, which is exclusively based on computer software, leads to measurable improvements in most cognitive domains affected in patients with PD. The present review is the first to include studies assessing the effect of computer-based CT techniques without deploying CT with paper-pencil techniques. Limitations originate mainly due to the heterogeneity among included studies (differences in CT softwares, PD stages, number, and duration of training sessions.

Prevalence of C9ORF72 Expansion in a Large Series of Patients with Idiopathic Normal-Pressure Hydrocephalus

BACKGROUND/AIMS

The C9ORF72 expansion is known to cause frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). We aim to identify the prevalence of the C9ORF72 expansion in idiopathic normal pressure hydrocephalus (iNPH).

METHODS

We analysed the C9ORF72 expansion in a large cohort of patients with possible iNPH (n = 487) and cognitively intact elderly controls (n = 432; age > 65 years).

RESULTS

While the C9ORF72 expansion was detected in 1.6% (n = 8/487) of cases with possible iNPH, no control subject was found to carry the mutation. The mean age at onset of symptoms of C9ORF72 expansion carriers was 59 years (range: 52-67 years), 11 years less than non-carriers (p = 0.0002). The most frequent initial/main symptom pertained to gait difficulties. Despite identified mutation, only 3 of the patients fulfilled the criteria for the FTLD-ALS spectrum. Clinically significant shunt response was detected in 6 out of 7 shunted C9ORF72 expansion carriers.

CONCLUSION

This is the first study cohort identifying the underlying C9ORF72 expansion in patients with iNPH providing evidence for the potential comorbidity between iNPH and the FTLD-ALS spectrum. Analysis of the C9ORF72 expansion should be considered for patients with probable iNPH presenting with frontal atrophy and personality changes or other severe psychiatric symptoms.

Parkinsonism in frontotemporal dementias

Frontotemporal dementia is a clinically and pathologically heterogeneous group of neurodegenerative disorders, with progressive impairment of behavior and language. They can be closely related to amyotrophic lateral sclerosis, clinically and through shared genetics and similar pathology. Approximately 40% of people with frontotemporal dementia report a family history of dementia, motor neuron disease or parkinsonism, and half of these familial cases are attributed to mutations in three genes (C9orf72, MAPT and PGRN). Akinetic-rigidity is a common feature in several types of frontotemporal dementia, particularly the behavioral variant and the non-fluent agrammatic variant of primary progressive aphasia, and the familial dementias. The majority of patients develop a degree of parkinsonism during the course of the illness, and signs may be present at the time of initial diagnosis. However, the parkinsonism of frontotemporal dementia is very different from that observed in idiopathic Parkinson's disease: it may be symmetric, axial, and poorly responsive to levodopa. Tremor is uncommon, and may be postural, action or occasionally rest tremor. The emergence of parkinsonism is often part of an evolving phenotype, in which frontotemporal dementia comes to resemble corticobasal syndrome or progressive supranuclear palsy. This chapter describes the prevalence and phenomenology of parkinsonism in each of the major syndromes, and according to the common genetic forms of frontotemporal dementia. We discuss the changing nosology and terminology surrounding the diagnoses, and the significance of parkinsonism as a core feature of frontotemporal dementia, relevant to clinical management and the design of future clinical trials.

C9orf72 intermediate repeats are associated with corticobasal degeneration, increased C9orf72 expression and disruption of autophagy

Microsatellite repeat expansion disease loci can exhibit pleiotropic clinical and biological effects depending on repeat length. Large expansions in C9orf72 (100s-1000s of units) are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration (FTD). However, whether intermediate expansions also contribute to neurodegenerative disease is not well understood. Several studies have identified intermediate repeats in Parkinson's disease patients, but the association was not found in autopsy-confirmed cases. We hypothesized that intermediate C9orf72 repeats are a genetic risk factor for corticobasal degeneration (CBD), a neurodegenerative disease that can be clinically similar to Parkinson's but has distinct tau protein pathology. Indeed, intermediate C9orf72 repeats were significantly enriched in autopsy-proven CBD (n = 354 cases, odds ratio = 3.59, p = 0.00024). While large C9orf72 repeat expansions are known to decrease C9orf72 expression, intermediate C9orf72 repeats result in increased C9orf72 expression in human brain tissue and CRISPR/cas9 knockin iPSC-derived neural progenitor cells. In contrast to cases of FTD/ALS with large C9orf72 expansions, CBD with intermediate C9orf72 repeats was not associated with pathologic RNA foci or dipeptide repeat protein aggregates. Knock-in cells with intermediate repeats exhibit numerous changes in gene expression pathways relating to vesicle trafficking and autophagy. Additionally, overexpression of C9orf72 without the repeat expansion leads to defects in autophagy under nutrient starvation conditions. These results raise the possibility that therapeutic strategies to reduce C9orf72 expression may be beneficial for the treatment of CBD.

Genotype-phenotype links in frontotemporal lobar degeneration

Frontotemporal lobar degeneration (FTLD) represents a group of neurodegenerative brain diseases with highly heterogeneous clinical, neuropathological and genetic characteristics. This high degree of heterogeneity results from the presence of several different underlying molecular disease processes; consequently, it is unlikely that all patients with FTLD will benefit from a single therapy. Therapeutic strategies for FTLD are currently being explored, and tools are urgently needed that enable the selection of patients who are the most likely to benefit from a particular therapy. Definition of the phenotypic characteristics in patients with different FTLD subtypes that share the same underlying disease processes would assist in the stratification of patients into homogeneous groups. The most common subtype of FTLD is characterized by TAR DNA-binding protein 43 (TDP43) pathology (FTLD-TDP). In this group, pathogenic mutations have been identified in four genes: C9orf72, GRN, TBK1 and VCP. Here, we provide a comprehensive overview of the phenotypic characteristics of patients with FTLD-TDP, highlighting shared features and differences among groups of patients who have a pathogenic mutation in one of these four genes.

ERCC6L2 rs591486 polymorphism and risk for amyotrophic lateral sclerosis in Greek population

BACKGROUND

Α number of genetic variants have been associated with amyotrophic lateral sclerosis (ALS). A recent study supports that rs591486 across the ERCC6L2 gene and exposure to pesticides seem to have a joint effect on the development of Parkinson's disease, a disease which shares a few common characteristics with ALS.

OBJECTIVE

To detect a possible contribution of rs591486 ERCC6L2 to ALS.

METHODS

A total of 155 patients with ALS and 155 healthy controls were included in the study and genotyped for rs591486. Using logistic regression analyses (crude and adjusted for age and sex), rs591486 was tested for association with ALS risk. Subgroup analysis based on ALS site of onset was also performed. Cox regression analysis was applied in order for the effect of ERCC6L2 rs591486 on ALS age of onset to be tested.

RESULTS

Adjusted analysis showed that ERCC6L2 rs591486 was associated with an increased risk of ALS development, in dominant [odds ratio, OR (95% confidence interval, CI) 2.15 (1.04-4.46), p = 0.037] and over-dominant [OR (95%CI) = 1.91 (1.01-3.60), p = 0.043], modes. Subgroup analysis based on ALS site of onset revealed an association between ERCC6L2 rs591486 and ALS with limb onset. Results for Cox regression analysis indicated that G/A carriers had a lower age of ALS limb onset when compared to G/G carriers.

CONCLUSIONS

The current study provides preliminary indication for an implication of ERCC6L2 rs591486 in ALS development, as a possible genetic risk factor. These results possibly suggest that oxidative stress may be the main contributor in the pathophysiology of ALS.

C9orf72 hexanucleotide repeat length in older population: normal variation and effects on cognition

The hexanucleotide repeat expansion in C9orf72 is a common cause of amyotrophic lateral sclerosis/frontotemporal dementia and also rarely found in other psychiatric and neurodegenerative conditions. Alleles with >30 repeats are often considered an expansion, but the pathogenic repeat length threshold is still unclear. It is also unclear whether intermediate repeat length alleles (often defined either as 7-30 or 20-30 repeats) have clinically significant effects. We determined the C9orf72 repeat length distribution in 3142 older Finns (aged 60-104 years). The longest nonexpanded allele was 45 repeats. We found 7-45 repeats in 1036/3142 (33%) individuals, 20-45 repeats in 56/3142 (1.8%), 30-45 repeats in 12/3142 (0.38%), and expansion (>45 repeats) in 6/3142 (0.19%). There was no apparent clustering of neurodegenerative or psychiatric diseases in individuals with 30-45 repeats indicating that 30-45 repeats are not pathogenic. None of the 6 expansion carriers had a diagnosis of amyotrophic lateral sclerosis/frontotemporal dementia but 4 had a diagnosis of a neurodegenerative or psychiatric disease. Intermediate length alleles (categorized as 7-45 and 20-45 repeats) did not associate with Alzheimer's disease or cognitive impairment.

Lack of Association of the rs11655081 ARSG Gene with Blepharospasm

Blepharospasm (BSP) is a sub-phenotype of focal dystonia. A few genetic risk factors are considered to be implicated in the risk of developing BSP. There is recent evidence, based on results from GWAS and meta-analyses, to suggest that arylsulfatase G (ARSG), and more specifically rs11655081, is implicated in focal dystonia. The aim of the present study was to evaluate the effect of rs11655081 ARSG on BSP. A Greek cohort, which consisted of 206 BSP patients and an equal number of healthy controls, was genotyped for rs11655081. Only a marginal trend for the association between rs11655081 and the risk of BSP was found in the over-dominant model of inheritance [odds ratio, OR (95% confidence interval, CI): 0.64 (0.38-1.07), p = 0.088]. It is rather unlikely that rs11655081 across ARSG is a major genetic risk contributor for BSP.

Risk Factor Genes in Patients with Dystonia: A Comprehensive Review

Background

Dystonia is a movement disorder with high heterogeneity regarding phenotypic appearance and etiology that occurs in both sporadic and familial forms. The etiology of the disease remains unknown. However, there is increasing evidence suggesting that a small number of gene alterations may lead to dystonia. Although pathogenic variants to the familial type of dystonia have been extensively reviewed and discussed, relatively little is known about the contribution of single-nucleotide polymorphisms (SNPs) to dystonia. This review focuses on the potential role of SNPs and other variants in dystonia susceptibility.

Methods

We searched the PubMed database for peer-reviewed articles published in English, from its inception through January 2018, that concerned human studies of dystonia and genetic variants. The following search terms were included: “dystonia” in combination with the following terms: 1) “polymorphisms” and 2) “SNPs” as free words.

Results

A total of 43 published studies regarding TOR1A, BDNF, DRD5, APOE, ARSG, NALC, OR4X2, COL4A1, TH, DDC, DBH, MAO, COMT, DAT, GCH1, PRKRA, MR-1, SGCE, ATP1A3, TAF1, THAP1, GNAL, DRD2, HLA-DRB, CBS, MTHFR, and MS genes, were included in the current review.

Discussion

To date, a few variants, which are possibly involved in several molecular pathways, have been related to dystonia. Large cohort studies are needed to determine robust associations between variants and dystonia with adjustment for other potential cofounders, in order to elucidate the pathogenic mechanisms of dystonia and the net effect of the genes.

Comprehensive genotyping of the C9orf72 hexanucleotide repeat region in 2095 ALS samples from the NINDS collection using a two-mode, long-read PCR assay

OBJECTIVE

Expansion of the G₄C₂ repeat tract in the C9orf72 gene is linked to frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Here, we provide comprehensive genotyping of the C9orf72 repeat region for the National Institute of Neurological Disorders and Stroke (NINDS) ALS collection (n = 2095), using a novel bimodal PCR assay capable of amplifying nearly 100% GC-rich sequences.

METHODS

A single-tube 3-primer PCR assay mode, resolved using capillary electrophoresis, was used for sizing up to 145 repeats with single-repeat accuracy, for detecting expansions irrespective of their overall size, and for flagging confounding 3' sequence variations (SVs). A modified two-primer PCR mode, resolved via agarose gel electrophoresis, provided further size information for hyper-expanded samples (>145 repeats) up to ∼5.8 kb amplicons (∼950 G₄C₂ repeats).

RESULTS

Within the evaluated cohort, 177 (8.4%) samples were expanded, with 175 (99%) samples being hyper-expanded. 3'-SVs were identified in 64 (3.1%) samples, and were most common in expanded alleles. Genotypes of all 606 (29%) homozygous samples were confirmed using an orthogonal PCR assay.

CONCLUSION

This study and PCR method may improve and standardize molecular characterization of the C9orf72 locus, and have the potential to inform phenotype-genotype correlations and therapeutic development in ALS/FTD.

The Role of MicroRNAs in Patients with Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a serious neurodegenerative disease that affects motor neurons and leads to death within 2 to 3 years after the first symptoms manifest. MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression in fundamental cellular processes and, post-transcriptionally, the translation levels of target mRNA transcripts. We searched PubMed for studies that examined miRNAs in ALS patients and attempted to group the results in order to find the strongest miRNA candidate for servings as an ALS biomarker. The studies on humans so far have been diverse, yielding considerably heterogeneous results, as they were performed on a wide variety of tissues and subjects. Among the miRNAs that were found consistently deregulated are miR-206, miR-133, miR-149, and miR-338-3p. Additively, the deregulation of some specific miRNAs seems to compose a miRNA expression profile that is specific for ALS. More research is required in order for the scientific community to reach a consensus.

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.

Targeted exome sequencing reveals homozygous TREM2 R47C mutation presenting with behavioral variant frontotemporal dementia without bone involvement

To identify genes associated with frontotemporal dementia (FTD) in South-East Asia, targeted exome sequencing and C9orf72 genotyping was performed in 198 subjects (52 patients with FTD and 146 healthy controls) who were screened for mutations in 12 FTD-associated genes. We detected a homozygous TREM2 R47C mutation in a patient with behavioral variant FTD without bone cysts or bone-associated phenotype. Two novel nonsense GRN mutations in 3 FTD patients from the Philippines were detected, but no known pathogenic mutations in other FTD-associated genes were found. In 45 subjects screened for C9orf72 repeat expansions, no pathogenic expansion (≥30 repeats) was identified, but there was a higher proportion of intermediate length (≥10-29 repeats) alleles in patients compared with controls (8/90 alleles, 8.9% vs. 9/164 alleles, 5.5%). Overall, we detected a mutation rate of 7.7% (4/52 patients) in our cohort. Given recent findings of enrichment of rare TREM2 variants (including R47C) in Alzheimer's disease, it is notable that we detected a homozygous TREM2 R47C carrier presenting with an FTD rather than an Alzheimer's disease phenotype.

The Genetics of C9orf72 Expansions

Repeat expansions in the promoter region of C9orf72 are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and related disorders of the ALS/frontotemporal lobar degeneration (FTLD) spectrum. Remarkable clinical heterogeneity among patients with a repeat expansion has been observed, and genetic anticipation over different generations has been suggested. Genetic factors modifying the clinical phenotype have been proposed, including genetic variation in other known disease genes, the genomic context of the C9orf72 repeat, and expanded repeat size, which has been estimated between 45 and several thousand units. The role of variability in normal and expanded repeat sizes for disease risk and clinical phenotype is under debate. Different pathogenic mechanisms have been proposed, including loss of function, RNA toxicity, and dipeptide repeat (DPR) protein toxicity resulting from abnormal translation of the expanded repeat, but the major mechanism is yet unclear.

Sleep disorders and Parkinson disease; lessons from genetics

Parkinson disease is a common, age-related neurodegenerative disorder, projected to afflict millions of individuals in the near future. Understanding its etiology and identifying clinical, genetic or biological markers for Parkinson disease onset and progression is therefore of major importance. Various sleep-related disorders are the most common group of non-motor symptoms in advanced Parkinson disease, but they can also occur during its prodromal phase. However, with the exception of REM sleep behavior disorder, it is unclear whether they are part of the early pathological process of Parkinson disease, or if they develop as Parkinson disease advances because of treatments and neurodegeneration progression. The advancements in genetic studies in the past two decades have generated a wealth of information, and recent genetic studies offer new insight on the association of sleep-related disorders with Parkinson disease. More specifically, comparing genetic data between Parkinson disease and sleep-related disorders can clarify their association, which may assist in determining whether they can serve as clinical markers for Parkinson disease risk or progression. In this review, we discuss the current knowledge on the genetics of sleep-related disorders in Parkinson disease context, and the potential implications on research, diagnosis, counseling and treatment.

Pipeline to gene discovery - Analysing familial Parkinsonism in the Queensland Parkinson's Project

INTRODUCTION

Family based study designs provide an informative resource to identify disease-causing mutations. The Queensland Parkinson's Project (QPP) has been involved in numerous genetic screening studies; however, details of the families enrolled into the register have not been comprehensively reported. This article characterises the families enrolled in the QPP and summarises monogenic forms of hereditary Parkinsonism found in the register.

METHOD

The presence of pathogenic point mutations and copy number variations (CNVs) were, generally, screened in a sample of over 1000 PD patients from the total of 1725. Whole exome sequencing (WES) was performed on eighteen probands from multiplex families.

RESULTS

The QPP contains seventeen incidences of confirmed monogenic forms of PD, including LRRK2 p.G2019S, VPS35 p.D620N, SNCA duplications and PARK2 p.G430D (hom) & exon 4 deletion (hom). Of these seventeen, five belong to multi-incident families, while another eight have a family history of at least one other case of PD. In additional families, WES did not identify known forms of monogenic Parkinsonism; however, three heterozygous mutations in PARK2, p.R275W, p.Q34fs, and a 40bp deletion in exon 3 were identified. Of these three mutations, only the 40bp deletion segregated with disease in a dominant inheritance pattern.

CONCLUSION

Eighteen probands have screened negative for known CNVs and mutations that cause clear monogenic forms of PD. Each family is a candidate for further genetic analysis to identify genetic variants segregating with disease. The families enrolled in the QPP provide a useful resource to aid in identifying novel forms of monogenic PD.

Frontotemporal dementia

Frontotemporal dementia (FTD) is a neurodegenerative disorder characterized by progressive changes in behavior, personality, and language with involvement of the frontal and temporal regions of the brain. About 40% of FTD cases have a positive family history, and about 10% of these cases are inherited in an autosomal-dominant pattern. These gene defects present with distinct clinical phenotypes. As the diagnosis of FTD becomes more recognizable, it will become increasingly important to keep these gene mutations in mind. In this chapter, we review the genes with known associations to FTD. We discuss protein functions, mutation frequencies, clinical phenotypes, imaging characteristics, and pathology associated with these genes.

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.

Relationship between C9orf72 repeat size and clinical phenotype

Patient carriers of a C9orf72 repeat expansion exhibit remarkable heterogeneous clinical and pathological characteristics suggesting the presence of modifying factors. In accordance with other repeat expansion diseases, repeat length is the prime candidate as a genetic modifier. Observations of earlier onset ages in younger generations of large families suggested a mechanism of disease anticipation. Yet, studies of repeat size and onset age have led to conflicting results. Also, the correlation between repeat size and diagnosis is poorly understood. We review what has been published regarding C9orf72 repeat size as modifier for phenotypic characteristics. Conclusive evidence is lacking, partly due to the difficulties in accurately defining the exact repeat size and the presence of repeat variability due to somatic mosaicism.

The genetic background of Parkinson's disease: current progress and future prospects

Almost two decades of genetic research in Parkinson's disease (PD) have remarkably increased our knowledge regarding the genetic basis of PD with numerous genes and genetic loci having been found to cause familial PD or affect the risk for PD. Approximately 5-10% of PD patients have monogenic forms of the disease, exhibiting a classical Mendelian type of inheritance, however, the majority PD cases are sporadic, probably caused by a combination of genetic and environmental risk factors. Nowadays, six genes, alpha synuclein, LRRK2, VPS35, Parkin, PINK1 and DJ-1, have definitely been associated with an autosomal dominant or recessive PD mode of inheritance. The advent of genome-wide association studies (GWAS) and the implementation of new technologies, like next generation sequencing (NGS) and exome sequencing has undoubtedly greatly aided the identification on novel risk variants for sporadic PD. In this review, we will summarize the current progress and future prospects in the field of PD genetics.

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.

Distinct neurological disorders with C9orf72 mutations: genetics, pathogenesis, and therapy

The G4C2 repeat expansion within C9orf72 has been recently identified as the most common genetic cause of frontotemporal dementia and amyotrophic lateral sclerosis. This mutation has also been detected in a variety of other neurological diseases with distinct clinical manifestations. The exact mechanisms of how this mutation leads to the wide spectrum of clinical syndromes remain unknown. A series of molecular changes together with some potential modifiers may play a key role. Nucleolar stress, nucleocytoplasmic transport defect, oxidative damage, inhibited stress granules assembly, activated endoplasmic reticulum stress, and inhibited proteasome activity are mechanisms that contribute to the pathogenesis of these diseases. Additional mutations, epigenetic modifiers, and repeat size are potential modifiers that modulate specific phenotypes on the basis of the molecular changes. Here, we summarize distinct C9orf72-related neurological disorders and their corresponding neuropathological changes. Then, we elucidate the existing molecular knowledge and the potential modifiers. Finally, we detail the main target of treatment aiming at controlling expanded RNA transcripts.

Characterization of Movement Disorder Phenomenology in Genetically Proven, Familial Frontotemporal Lobar Degeneration: A Systematic Review and Meta-Analysis

Background

Mutations in granulin (PGRN) and tau (MAPT), and hexanucleotide repeat expansions near the C9orf72 genes are the most prevalent genetic causes of frontotemporal lobar degeneration. Although behavior, language and movement presentations are common, the relationship between genetic subgroup and movement disorder phenomenology is unclear.

Objective

We conducted a systematic review and meta-analysis of the literature characterizing the spectrum and prevalence of movement disorders in genetic frontotemporal lobar degeneration.

Methods

Electronic databases were searched using terms related to frontotemporal lobar degeneration and movement disorders. Articles were included when cases had a proven genetic cause. Study-specific prevalence estimates for clinical features were transformed using Freeman-Tukey arcsine transformation, allowing for pooled estimates of prevalence to be generated using random-effects models.

Results

The mean age at onset was earlier in those with MAPT mutations compared to PGRN (p<0.001) and C9orf72 (p = 0.024). 66.5% of subjects had an initial non-movement presentation that was most likely a behavioral syndrome (35.7%). At any point during the disease, parkinsonism was the most common movement syndrome reported in 79.8% followed by progressive supranuclear palsy (PSPS) and corticobasal (CBS) syndromes in 12.2% and 10.7%, respectively. The prevalence of movement disorder as initial presentation was higher in MAPT subjects (35.8%) compared to PGRN subjects (10.1). In those with a non-movement presentation, language disorder was more common in PGRN subjects (18.7%) compared to MAPT subjects (5.4%).

Summary

This represents the first systematic review and meta-analysis of the occurrence of movement disorder phenomenology in genetic frontotemporal lobar degeneration. Standardized prospective collection of clinical information in conjunction with genetic characterization will be crucial for accurate clinico-genetic correlation.

Atypical parkinsonism in C9orf72 expansions: a case report and systematic review of 45 cases from the literature

While C9orf72 repeat expansions usually present with frontotemporal dementia (FTD) and/or amyotrophic lateral sclerosis (ALS), an increasing number of reports suggests that the primary phenotype of C9orf72 patients may also include movement disorders. We here provide the first systematic clinical characterisation of C9orf72-associated parkinsonism. We report a C9orf72 expansion carrier presenting with a clinical syndrome of progressive supranuclear palsy (PSP), pronounced mesencephalic atrophy on MRI and PSP-characteristic electrooculography findings. Moreover, we systematically review all previous reports on C9orf72 patients with parkinsonian features. Review of 28 reports revealed 45 C9orf72-positive patients with hypokinesia, rigidity and/or resting tremor. C9orf72-associated parkinsonism predominantly consisted in a hypokinetic-rigid syndrome without resting tremor (61%), with both asymmetric (59%) and symmetric (41%) distributions. Additional features included upper motor neuron signs (60%), lower motor neuron signs (36%), cognitive dysfunction (85%), behaviour and/or personality change (55%) and psychiatric symptoms (29%). Vertical supranuclear gaze palsy was reported in three further cases and cerebellar dysfunction in four cases. Family history frequently yielded evidence of ALS (31%) and FTD (21%). Atypical parkinsonism is a recurrent phenotypic manifestation of C9orf72 expansions. It occurs as part of a broad spectrum of C9orf72-related multi-system neurodegeneration, which can include basal ganglia, mesencephalic and cerebellar dysfunction. C9orf72 genotyping should be considered in those patients with atypical parkinsonism who present with a family history of ALS or FTD, upper or lower motor neuron signs and/or cognitive dysfunction with pronounced frontotemporal impairment.