Search

While the central common feature of the neurodegenerative diseases (NDs) is the accumulation of misfolded proteins, they share other pathogenic mechanisms. However, we miss an explanation for the onset of the NDs. The mechanisms through which genetic mutations, present from conception are expressed only after several decades of life are unknown. We aim to find clues on the complexity of the disease onset trigger of the different NDs expressed in the number of steps of factors related to a disease. We collected brain autopsies on diseased patients with NDs, and found a dynamic increase of the ND multimorbidity with the advance of age. Together with the observation that the NDs accumulate multiple misfolded proteins, and the same misfolded proteins are involved in more than one ND, motivated us to propose a model for a genealogical tree of the NDs. To collect the dynamic data needed to build the tree, we used a Big-data approach that searched automatically epidemiological datasets for age-stratified incidence of NDs. Based on meta-analysis of over 400 datasets, we developed an algorithm that checks whether a ND follows a multistep model, finds the number of steps necessary for the onset of each ND, finds the number of common steps with other NDs and the number of specific steps of each ND, and builds with these findings a parsimony tree of the genealogy of the NDs. The tree discloses three types of NDs: the stem NDs with less than 3 steps; the trunk NDs with 5 to 6 steps; and the crown NDs with more than 7 steps. The tree provides a comprehensive understanding of the relationship across the different NDs, as well as a mathematical framework for dynamic adjustment of the genealogical tree of the NDs with the appearance of new epidemiological studies and the addition of new NDs to the model, thus setting the basis for the search for the identity and order of these steps. Understanding the complexity, or number of steps, of factors related to disease onset trigger is important prior deciding to study single factors for a multiple steps disease.

Background: Loss-of-function mutations in GRN cause frontotemporal lobar degeneration (FTLD). Patients with GRN mutations present with a uniform subtype of TAR DNA-binding protein 43 (TDP-43) pathology at autopsy (FTLD-TDP type A); however, age at onset and clinical presentation are variable, even within families. We aimed to identify potential genetic modifiers of disease onset and disease risk in GRN mutation carriers., Methods: The study was done in three stages: a discovery stage, a replication stage, and a meta-analysis of the discovery and replication data. In the discovery stage, genome-wide logistic and linear regression analyses were done to test the association of genetic variants with disease risk (case or control status) and age at onset in patients with a GRN mutation and controls free of neurodegenerative disorders. Suggestive loci (p<1 × 10 -5 ) were genotyped in a replication cohort of patients and controls, followed by a meta-analysis. The effect of genome-wide significant variants at the GFRA2 locus on expression of GFRA2 was assessed using mRNA expression studies in cerebellar tissue samples from the Mayo Clinic brain bank. The effect of the GFRA2 locus on progranulin concentrations was studied using previously generated ELISA-based expression data. Co-immunoprecipitation experiments in HEK293T cells were done to test for a direct interaction between GFRA2 and progranulin., Findings: Individuals were enrolled in the current study between Sept 16, 2014, and Oct 5, 2017. After quality control measures, statistical analyses in the discovery stage included 382 unrelated symptomatic GRN mutation carriers and 1146 controls free of neurodegenerative disorders collected from 34 research centres located in the USA, Canada, Australia, and Europe. In the replication stage, 210 patients (67 symptomatic GRN mutation carriers and 143 patients with FTLD without GRN mutations pathologically confirmed as FTLD-TDP type A) and 1798 controls free of neurodegenerative diseases were recruited from 26 sites, 20 of which overlapped with the discovery stage. No genome-wide significant association with age at onset was identified in the discovery or replication stages, or in the meta-analysis. However, in the case-control analysis, we replicated the previously reported TMEM106B association (rs1990622 meta-analysis odds ratio [OR] 0·54, 95% CI 0·46-0·63; p=3·54 × 10 -16 ), and identified a novel genome-wide significant locus at GFRA2 on chromosome 8p21.3 associated with disease risk (rs36196656 meta-analysis OR 1·49, 95% CI 1·30-1·71; p=1·58 × 10 -8 ). Expression analyses showed that the risk-associated allele at rs36196656 decreased GFRA2 mRNA concentrations in cerebellar tissue (p=0·04). No effect of rs36196656 on plasma and CSF progranulin concentrations was detected by ELISA; however, co-immunoprecipitation experiments in HEK293T cells did suggest a direct binding of progranulin and GFRA2., Interpretation: TMEM106B-related and GFRA2-related pathways might be future targets for treatments for FTLD, but the biological interaction between progranulin and these potential disease modifiers requires further study. TMEM106B and GFRA2 might also provide opportunities to select and stratify patients for future clinical trials and, when more is known about their potential effects, to inform genetic counselling, especially for asymptomatic individuals., Funding: National Institute on Aging, National Institute of Neurological Disorders and Stroke, Canadian Institutes of Health Research, Italian Ministry of Health, UK National Institute for Health Research, National Health and Medical Research Council of Australia, and the French National Research Agency., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Parkinson's disease (PD) is the second most common neurodegenerative disorder, affecting millions of people. Genome-wide association studies (GWAS) have found >25 genetic risk factors and at least 15 loci directly associated with PD. Recent advances in new next-generation DNA sequencing technologies, such as the semiconductor-based Ion Torrent platform, make multigene sequencing cheaper, faster, and more reliable., Objectives: Our objective was to test the power of this next-generation sequencing technology to analyze large samples by screening the majority of the most relevant PD-related genes known for single and compound mutations., Methods: To archive a rapid, robust, and cost-effective genetic analysis of a PD cohort, we designed a multiplex, polymerase chain reaction (PCR)-based primer panel to amplify and sequence coding exons of 15 PD-associated genes (SNCA, LRRK2, PARK2, PINK1, PARK7, GIGYF2, ATP13A2, UCHL1, PLA2G6, FBXO7, EIF4G1, VPS35, ACMSD, APOE, and GBA). We conducted parallel sequencing using the Ion Torrent Personal Genome Machine(®) system to detect mutations in 92 blood DNA samples from PD patients., Results: After bioinformatics analysis and filtering, 95.13 % coverage of the targeted region was obtained at >40-fold mean coverage. The results revealed 44 previously documented variants in these 15 genes, with five revealed as pathogenic. We also discovered six novel variants, five of which had an in silico prediction of being pathogenic., Conclusions: Benchtop next-generation sequencing is a powerful method for genetic screening for PD. Our results indicated that it yielded a high frequency of discovery (66 %; n = 92) of variants in carriers from an enriched Spanish PD sample.

Objective: Describe the incidence of cancer in a large cohort of patients with myotonic dystrophy type 1 (DM1) and to unravel the underlying molecular mechanisms., Methods: Standardized incidence ratios (SIRs) were calculated in the Gipuzkoa DM1 cohort (1985-2013), dividing observed numbers by expected numbers for all cancers combined and stratified by sex. An estimation of the expected incidence was achieved by multiplying the age- and sex-specific incidence rates from the Basque population cancer registry by the person-years observed in the study cohort. Large-scale gene expression of peripheral blood mononuclear cell samples derived from 10 individuals with DM1 (5 men, 5 women) and 10 healthy matched controls was analyzed by the Human Gene 1.0 ST Affymetrix microarray., Results: During 18,796 person-years of follow-up, corresponding to 424 patients with DM1, we observed 70 cancers in 62 patients giving a 1.81-fold risk (95% confidence interval [CI] 1.37-2.36), which was stronger in women than in men. Ovary (SIR 8.33, 95% CI 1.72-24.31) and endometrium (SIR 6.86, 95% CI 2.23-16.02) in women and thyroid (SIR 23.33, 95% CI 9.38-48.08) and brain (SIR 9.80, 95% CI 3.18-22.88) in both sexes were tumor sites with significantly higher risks in DM1. There were differences in gene expression between healthy controls and patients with DM1 and between men and women with DM1; all patients with DM1 combined and female patients with DM1 displayed significant downregulation of the microRNA (miRNA)-200c/141 tumor suppressor family., Conclusions: Oncologic risk is increased in DM1, especially in women and for gynecologic, brain, and thyroid cancer. Expression of the miRNA-200/miRNA-141 tumor suppressor family is decreased in women with DM1., (© 2016 American Academy of Neurology.)

Background: The objective of this study was to study motor and nonmotor symptoms and striatal dopaminergic denervation, as well as the relationship between them, in a cohort of asymptomatic relatives of patients with Parkinson's disease (PD) with the R1441G-leucine-rich repeat kinase 2 mutation., Methods: Asymptomatic relatives of patients with PD and this mutation were tested for the presence of the mutation and evaluated for striatal, putamenal, and caudate dopaminergic transporters using (123)I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane single-photon emission computed tomography binding ratios. Clinical and neuropsychological evaluations including timed motor tests, a smell identification test, and global cognition, attention, executive, visuospatial, and memory functions as well as depression, constipation, and rapid eye movement sleep behavior disorder were also assessed., Results: Twenty-seven carriers and 19 noncarriers were studied. Compared with noncarriers, mutation carriers had significantly lower (123)I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropan mean striatal (P = 0.03), mean putamenal (P = 0.01), and lowest putamenal (P = 0.01) binding ratios. Multiple linear regression analysis showed that the carrier status and the execution of timed tests significantly predicted striatal (123)I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane binding. The proportion of variation accounted for by the regression model of these variables was 69% for the putamen and 53% for the caudate nucleus., Conclusions: Asymptomatic carriers of the R1441G-leucine-rich repeat kinase 2 mutation have evidence of dopaminergic nigrostriatal denervation, mainly in the putamen, which is associated with a decline in the execution of complex motor tests. These tests could be early indicators of the ongoing dopaminergic deficit in this group at risk of PD., (© 2015 International Parkinson and Movement Disorder Society.)

The MAPT H1 haplotype has been linked to several disorders, but its relationship with Alzheimer's disease (AD) remains controversial. A rare variant in MAPT (p.A152T) has been linked with frontotemporal dementia (FTD) and AD. We genotyped H1/H2 and p.A152T MAPT in 11,572 subjects from Spain (4,327 AD, 563 FTD, 648 Parkinson's disease (PD), 84 progressive supranuclear palsy (PSP), and 5,950 healthy controls). Additionally, we included 101 individuals from 21 families with genetic FTD. MAPT p.A152T was borderline significantly associated with FTD [odds ratio (OR) = 2.03; p = 0.063], but not with AD. MAPT H1 haplotype was associated with AD risk (OR = 1.12; p = 0.0005). Stratification analysis showed that this association was mainly driven by APOE ɛ4 noncarriers (OR = 1.14; p = 0.0025). MAPT H1 was also associated with risk for PD (OR = 1.30; p = 0.0003) and PSP (OR = 3.18; p = 8.59 × 10-8) but not FTD. Our results suggest that the MAPT H1 haplotype increases the risk of PD, PSP, and non-APOE ɛ4 AD.

A hexanucleotide repeat expansion in chromosome 9 open reading frame 72 (C9orf72) can cause amyotrophic lateral sclerosis (ALS) and/or frontotemporal dementia (FTD). We assessed its frequency in 781 sporadic ALS (sALS) and 155 familial ALS (fALS) cases, and in 248 Spanish controls. We tested the presence of the reported founder haplotype among mutation carriers and in 171 Ceph Europeans from Utah (CEU), 170 Yoruba Africans, 81 Han Chinese, and 85 Japanese subjects. The C9orf72 expansion was present in 27.1% of fALS and 3.2% of sALS. Mutation carriers showed lower age at onset (P = 0.04), shorter survival (P = 0.02), greater co-occurrence of FTD (P = 8.2 × 10(-5)), and more family history of ALS (P = 1.4 × 10(-20)), than noncarriers. No association between alleles within the normal range and the risk of ALS was found (P = 0.12). All 61 of the mutation carriers were tested and a patient carrying 28 hexanucleotide repeats presented with the founder haplotype. This haplotype was found in 5.6% Yoruba Africans, 8.9% CEU, 3.9% Japanese, and 1.6% Han Chinese chromosomes., (© 2012 Wiley Periodicals, Inc.)

Mutations in the progranulin (PGRN) gene have been identified as a cause of frontotemporal dementia (FTD). However, little is known about the neuropsychological abilities of asymptomatic carriers of these mutations. The aim of the study was to assess cognitive functioning in asymptomatic c.709-1G>A PGRN mutation carriers. We hypothesized that poorer neuropsychological performance could be present before the development of clinically significant FTD symptoms. Thirty-two asymptomatic first-degree relatives of FTD patients carrying the c.709-1G>A mutation served as study participants, including 13 PGRN mutation carriers (A-PGRN+) and 19 non-carriers (PGRN-). A neuropsychological battery was administered. We found that the A-PGRN+ participants obtained significantly poorer scores than PGRN- individuals on tests of attention (Trail-Making Test Part A), mental flexibility (Trail-Making Test Part B), and language (Boston Naming Test). Poorer performance on these tests in asymptomatic PGRN mutation carriers may reflect a prodromal phase preceding the onset of clinically significant symptoms of FTD.

It has been proposed that olfactory tests and metaiodobenzylguanidine cardiac scintigraphy may help diagnose idiopathic Parkinson's disease in the premotor phase. However, it is not clear what value these tests have in all patients with Parkinson's disease and, particularly, in those who carry mutations in LRRK2. The objective was to analyze olfactory dysfunction and the changes in cardiac I-metaiodobenzylguanidine uptake in patients with Parkinson's disease carrying the R1441G and G2019S mutations in LRRK2, and in patients with Parkinson's disease with no known mutations. Patients with Parkinson's disease were screened for R1441G and G2019S LRRK2 gene mutations and classified as LRRK2 mutation carriers or noncarriers. A total of 190 patients with Parkinson's disease (44 LRRK2 mutation carriers) were tested for olfactory dysfunction using the Brief Smell Identification Test. Cardiac (123) I-metaiodobenzylguanidine scintigraphy was performed on 90 patients with Parkinson's disease (27 LRRK2 mutation carriers). Thirty-six percent of patients with LRRK2 mutations have hyposmia, compared to 75% of noncarrier patients with Parkinson's disease (P < .001). Sixty-six percent of LRRK2 mutation carriers have low early metaiodobenzylguanidine uptake, compared to 86% of noncarriers (P = .048). Similarly, the heart/mediastinum ratio in delayed metaiodobenzylguanidine images appeared to differ between these groups of patients with Parkinson's disease, although these results did not reach statistical significance. The data obtained indicate that olfactory and cardiac impairment is less prevalent when Parkinson's disease is associated with mutations in LRRK2, although the underlying mechanisms for this difference remain unclear. Thus, such screening would be less useful to detect the premotor phase in asymptomatic relatives who carry mutations in LRRK2 than in cases not associated with LRRK2., (Copyright © 2011 Movement Disorder Society.)

Frontotemporal lobar degeneration because of mutations in the progranulin (PGRN) gene presents a high variability both in the clinical phenotype and age of onset of disease. Factors that influence this variability remain largely unknown. The aim of our study was to determine whether selected genetic variables modify age at onset of disease in our series of 21 patients with a single splicing mutation (c.709-1G>A) in the PGRN gene, all of whom were of Basque descent. In our analysis, we included the following genetic variables: PGRN rs5848 and rs9897526 polymorphisms, APOE and microtubule-associated protein tau genotypes, and PRNP codon 129 polymorphism. We found no association between PGRN polymorphisms, APOE and microtubule-associated protein tau genotypes, and age at onset of the disease; whereas we report evidence for an association between PRNP codon 129 polymorphism and age at onset of disease in frontotemporal dementia-PGRN(+) patients. MM homozygous carriers presented onset of disease on average 8.5 years earlier than patients who carried at least 1 valine on their PRNP codon 129 (MV or VV). The biological justification for this association remains speculative., (Copyright © 2011 by Lippincott Williams & Wilkins)

We report the clinical, histological and genetic findings in 10 families (19 patients) presenting mutations in the valosin-containing protein (VCP). The mean age at onset was 42 years. The clinical pattern was characterized by an early involvement of the proximal upper limbs with scapular winging. Axial and lower limb muscles were often affected, whereas facial, oculobulbar muscles were spared. Ten patients were wheelchair bound after a mean disease course of 9 years and six patients required canes for walking. Two patients required mechanically assisted ventilation and seven patients had reduced vital capacity. There was no cardiac involvement. Paget's disease of bone was observed in eight patients and cognitive impairment in nine patients. Seven patients died as a consequence of weakness and respiratory distress. Muscle biopsy showed rimmed vacuolar myopathy. Genetic analysis revealed missense heterozygous mutations mostly located in exon 5 of the VCP gene, four of which were not previously reported. We observed intrafamilial and interfamilial variability in terms of severity, distribution of weakness and presence or not of Paget's disease or cognitive impairment.

Background: There is an increasing interest in the clinico-pathological correlation of mutations in progranulin (PGRN) and frontotemporal lobar degeneration (FTLD) complex diseases. We aim to study the PGRN expression variability in patients with different clinical features for a better understanding of its roles in FTLD disease., Methods: We sequenced the PGRN gene in 72 patients suffering from FTLD (25 familial and 47 sporadic cases) and in 24 asymptomatic at-risk relatives. We also analyzed PGRN expression in blood by quantitative real-time polymerase chain reaction from 37 patients, 8 asymptomatic mutation carriers, and 10 control subjects as well as in brain tissue from 16 patients and 9 control subjects., Results: Four novel mutations were associated with familial and sporadic FTLD and familial dementia associated with amyotrophic lateral sclerosis. We identified a close association between the IVS6-1G>A mutation in PGRN and corticobasal syndrome. Brain tissue was available for carriers of two of the four mutations (IVS6-1 G>A and P357HfsX3). Immunohistochemical analysis revealed ubiquitin- and TDP-43positive and tau/alpha-synuclein negative immunoreactive neuronal intranuclear inclusions. The relative expression of PGRN in the clinical sample was significantly lower in carriers of the IVS6-1 G>A than in control subjects., Conclusions: Progranulopathies are a major cause of the main phenotypes included in the FTLD complex. According to our results, the level of expression of PGRN in blood could be a useful marker both for diagnostics of part of the spectrum of FTLD conditions and for monitoring future treatments that might boost the level of PGRN in this disorder.

Limb-girdle muscular dystrophy type 2A (LGMD2A) is caused by any of over 150 mutations in the calpain-3 (CAPN3) gene. Of those, 2362AG --> TCATCT is particularly prevalent in Basque patients, and this mutation was hypothesized to have arisen in the Basque Country. To explore the natural history of this mutation, we genotyped 65 Basque and non-Basque patients with LGMD2A who carry the 2362AG --> TCATCT mutation for four microsatellites within or flanking the gene. A particular haplotype was found in three-fourths of the patients and was assumed to be ancestral. From the average number of recombinations and mutations accumulated from this ancestral haplotype, the age of the 2362AG ----> TCATCT mutation was estimated to be 50 generations (i.e., 1,250 years), which is more recent than the Paleolithic Basque heritage. The subsequent spread of the 2362AG --> TCATCT mutation can be related to gene flow out of the Basque Country, even across a cultural border.