PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-25 (50)
 

Clipboard (0)
None

Select a Filter Below

Journals
more »
Year of Publication
3.  A pathway-based analysis provides additional support for an immune-related genetic susceptibility to Parkinson's disease 
Holmans, Peter | Moskvina, Valentina | Jones, Lesley | Sharma, Manu | Vedernikov, Alexey | Buchel, Finja | Sadd, Mohamad | Bras, Jose M. | Bettella, Francesco | Nicolaou, Nayia | Simón-Sánchez, Javier | Mittag, Florian | Gibbs, J. Raphael | Schulte, Claudia | Durr, Alexandra | Guerreiro, Rita | Hernandez, Dena | Brice, Alexis | Stefánsson, Hreinn | Majamaa, Kari | Gasser, Thomas | Heutink, Peter | Wood, Nicholas W. | Martinez, Maria | Singleton, Andrew B. | Nalls, Michael A. | Hardy, John | Morris, Huw R. | Williams, Nigel M. | Arepalli, Sampath | Barker, Roger | Barrett, Jeffrey | Ben-Shlomo, Yoav | Berendse, Henk W. | Berg, Daniela | Bhatia, Kailash | de Bie, Rob M.A. | Biffi, Alessandro | Bloem, Bas | Brice, Alexis | Bochdanovits, Zoltan | Bonin, Michael | Bras, Jose M. | Brockmann, Kathrin | Brooks, Janet | Burn, David J. | Charlesworth, Gavin | Chen, Honglei | Chinnery, Patrick F. | Chong, Sean | Clarke, Carl E. | Cookson, Mark R. | Cooper, Jonathan M. | Corvol, Jen-Christophe | Counsell, Carl | Damier, Philippe | Dartigues, Jean Francois | Deloukas, Panagiotis | Deuschl, Günther | Dexter, David T. | van Dijk, Karin D. | Dillman, Allissa | Durif, Frank | Durr, Alexandra | Edkins, Sarah | Evans, Jonathan R. | Foltynie, Thomas | Gao, Jianjun | Gardner, Michelle | Gasser, Thomas | Gibbs, J. Raphael | Goate, Alison | Gray, Emma | Guerreiro, Rita | Gústafsson, Ómar | Hardy, John | Harris, Clare | Hernandez, Dena G. | Heutink, Peter | van Hilten, Jacobus J. | Hofman, Albert | Hollenbeck, Albert | Holmans, Peter | Holton, Janice | Hu, Michele | Huber, Heiko | Hudson, Gavin | Hunt, Sarah E. | Huttenlocher, Johanna | Illig, Thomas | Langford, Cordelia | Lees, Andrew | Lesage, Suzanne | Lichtner, Peter | Limousin, Patricia | Lopez, Grisel | Lorenz, Delia | Martinez, Maria | McNeill, Alisdair | Moorby, Catriona | Moore, Matthew | Morris, Huw | Morrison, Karen E. | Moskvina, Valentina | Mudanohwo, Ese | Nalls, Michael A. | Pearson, Justin | Perlmutter, Joel S. | Pétursson, Hjörvar | Plagnol, Vincent | Pollak, Pierre | Post, Bart | Potter, Simon | Ravina, Bernard | Revesz, Tamas | Riess, Olaf | Rivadeneira, Fernando | Rizzu, Patrizia | Ryten, Mina | Saad, Mohamad | Sawcer, Stephen | Schapira, Anthony | Scheffer, Hans | Sharma, Manu | Shaw, Karen | Sheerin, Una-Marie | Shoulson, Ira | Schulte, Claudia | Sidransky, Ellen | Simón-Sánchez, Javier | Singleton, Andrew B. | Smith, Colin | Stefánsson, Hreinn | Stefánsson, Kári | Steinberg, Stacy | Stockton, Joanna D. | Sveinbjornsdottir, Sigurlaug | Talbot, Kevin | Tanner, Carlie M. | Tashakkori-Ghanbaria, Avazeh | Tison, François | Trabzuni, Daniah | Traynor, Bryan J. | Uitterlinden, André G. | Velseboer, Daan | Vidailhet, Marie | Walker, Robert | van de Warrenburg, Bart | Wickremaratchi, Mirdhu | Williams, Nigel | Williams-Gray, Caroline H. | Winder-Rhodes, Sophie | Wood, Nicholas
Human Molecular Genetics  2012;22(5):1039-1049.
Parkinson's disease (PD) is the second most common neurodegenerative disease affecting 1–2% in people >60 and 3–4% in people >80. Genome-wide association (GWA) studies have now implicated significant evidence for association in at least 18 genomic regions. We have studied a large PD-meta analysis and identified a significant excess of SNPs (P < 1 × 10−16) that are associated with PD but fall short of the genome-wide significance threshold. This result was independent of variants at the 18 previously implicated regions and implies the presence of additional polygenic risk alleles. To understand how these loci increase risk of PD, we applied a pathway-based analysis, testing for biological functions that were significantly enriched for genes containing variants associated with PD. Analysing two independent GWA studies, we identified that both had a significant excess in the number of functional categories enriched for PD-associated genes (minimum P = 0.014 and P = 0.006, respectively). Moreover, 58 categories were significantly enriched for associated genes in both GWA studies (P < 0.001), implicating genes involved in the ‘regulation of leucocyte/lymphocyte activity’ and also ‘cytokine-mediated signalling’ as conferring an increased susceptibility to PD. These results were unaltered by the exclusion of all 178 genes that were present at the 18 genomic regions previously reported to be strongly associated with PD (including the HLA locus). Our findings, therefore, provide independent support to the strong association signal at the HLA locus and imply that the immune-related genetic susceptibility to PD is likely to be more widespread in the genome than previously appreciated.
doi:10.1093/hmg/dds492
PMCID: PMC3561909  PMID: 23223016
5.  Resequencing Three Candidate Genes for Major Depressive Disorder in a Dutch Cohort 
PLoS ONE  2013;8(11):e79921.
Major depressive disorder (MDD) is a psychiatric disorder, characterized by periods of low mood of more than two weeks, loss of interest in normally enjoyable activities and behavioral changes. MDD is a complex disorder and does not have a single genetic cause. In 2009 a genome wide association study (GWAS) was performed on the Dutch GAIN-MDD cohort. Many of the top signals of this GWAS mapped to a region spanning the gene PCLO, and the non-synonymous coding single nucleotide polymorphism (SNP) rs2522833 in the PCLO gene became genome wide significant after post-hoc analysis. We performed resequencing of PCLO, GRM7, and SLC6A4 in 50 control samples from the GAIN-MDD cohort, to detect new genomic variants. Subsequently, we genotyped these variants in the entire GAIN-MDD cohort and performed association analysis to investigate if rs2522833 is the causal variant or simply in linkage disequilibrium with a more associated variant. GRM7 and SLC6A4 are both candidate genes for MDD from literature. We aimed to gather more evidence that rs2522833 is indeed the causal variant in the GAIN-MDD cohort or to find a previously undetected common variant in either PCLO, GRM7, or SLC6A4 with a higher association in this cohort. After next generation sequencing and association analysis we excluded the possibility of an undetected common variant to be more associated. For neither PCLO nor GRM7 we found a more associated variant. For SLC6A4, we found a new SNP that showed a lower P-value (P = 0.07) than in the GAIN-MDD GWAS (P = 0.09). However, no evidence for genome-wide significance was found. Although we did not take into account rare variants, we conclude that our results provide further support for the hypothesis that the non-synonymous coding SNP rs2522833 in the PCLO gene is indeed likely to be the causal variant in the GAIN-MDD cohort.
doi:10.1371/journal.pone.0079921
PMCID: PMC3836783  PMID: 24278217
6.  Using genome-wide complex trait analysis to quantify ‘missing heritability’ in Parkinson's disease 
Human Molecular Genetics  2012;21(22):4996-5009.
Genome-wide association studies (GWASs) have been successful at identifying single-nucleotide polymorphisms (SNPs) highly associated with common traits; however, a great deal of the heritable variation associated with common traits remains unaccounted for within the genome. Genome-wide complex trait analysis (GCTA) is a statistical method that applies a linear mixed model to estimate phenotypic variance of complex traits explained by genome-wide SNPs, including those not associated with the trait in a GWAS. We applied GCTA to 8 cohorts containing 7096 case and 19 455 control individuals of European ancestry in order to examine the missing heritability present in Parkinson's disease (PD). We meta-analyzed our initial results to produce robust heritability estimates for PD types across cohorts. Our results identify 27% (95% CI 17–38, P = 8.08E − 08) phenotypic variance associated with all types of PD, 15% (95% CI −0.2 to 33, P = 0.09) phenotypic variance associated with early-onset PD and 31% (95% CI 17–44, P = 1.34E − 05) phenotypic variance associated with late-onset PD. This is a substantial increase from the genetic variance identified by top GWAS hits alone (between 3 and 5%) and indicates there are substantially more risk loci to be identified. Our results suggest that although GWASs are a useful tool in identifying the most common variants associated with complex disease, a great deal of common variants of small effect remain to be discovered.
doi:10.1093/hmg/dds335
PMCID: PMC3576713  PMID: 22892372
7.  Dissecting the genetic make-up of North-East Sardinia using a large set of haploid and autosomal markers 
Sardinia has been used for genetic studies because of its historical isolation, genetic homogeneity and increased prevalence of certain rare diseases. Controversy remains concerning the genetic substructure and the extent of genetic homogeneity, which has implications for the design of genome-wide association studies (GWAS). We revisited this issue by examining the genetic make-up of a sample from North-East Sardinia using a dense set of autosomal, Y chromosome and mitochondrial markers to assess the potential of the sample for GWAS and fine mapping studies. We genotyped individuals for 500K single-nucleotide polymorphisms, Y chromosome markers and sequenced the mitochondrial hypervariable (HVI–HVII) regions. We identified major haplogroups and compared these with other populations. We estimated linkage disequilibrium (LD) and haplotype diversity across autosomal markers, and compared these with other populations. Our results show that within Sardinia there is no major population substructure and thus it can be considered a genetically homogenous population. We did not find substantial differences in the extent of LD in Sardinians compared with other populations. However, we showed that at least 9% of genomic regions in Sardinians differed in LD structure, which is helpful for identifying functional variants using fine mapping. We concluded that Sardinia is a powerful setting for genetic studies including GWAS and other mapping approaches.
doi:10.1038/ejhg.2012.22
PMCID: PMC3421114  PMID: 22378280
Sardinia; POPRES; HAPMAP; population genetics
8.  Fine-Mapping, Gene Expression and Splicing Analysis of the Disease Associated LRRK2 Locus 
PLoS ONE  2013;8(8):e70724.
Association studies have identified several signals at the LRRK2 locus for Parkinson's disease (PD), Crohn's disease (CD) and leprosy. However, little is known about the molecular mechanisms mediating these effects. To further characterize this locus, we fine-mapped the risk association in 5,802 PD and 5,556 controls using a dense genotyping array (ImmunoChip). Using samples from 134 post-mortem control adult human brains (UK Human Brain Expression Consortium), where up to ten brain regions were available per individual, we studied the regional variation, splicing and regulation of LRRK2. We found convincing evidence for a common variant PD association located outside of the LRRK2 protein coding region (rs117762348, A>G, P = 2.56×10−8, case/control MAF 0.083/0.074, odds ratio 0.86 for the minor allele with 95% confidence interval [0.80–0.91]). We show that mRNA expression levels are highest in cortical regions and lowest in cerebellum. We find an exon quantitative trait locus (QTL) in brain samples that localizes to exons 32–33 and investigate the molecular basis of this eQTL using RNA-Seq data in n = 8 brain samples. The genotype underlying this eQTL is in strong linkage disequilibrium with the CD associated non-synonymous SNP rs3761863 (M2397T). We found two additional QTLs in liver and monocyte samples but none of these explained the common variant PD association at rs117762348. Our results characterize the LRRK2 locus, and highlight the importance and difficulties of fine-mapping and integration of multiple datasets to delineate pathogenic variants and thus develop an understanding of disease mechanisms.
doi:10.1371/journal.pone.0070724
PMCID: PMC3742662  PMID: 23967090
9.  FADS2 Genetic Variance in Combination with Fatty Acid Intake Might Alter Composition of the Fatty Acids in Brain 
PLoS ONE  2013;8(6):e68000.
Multiple lines of evidence suggest that fatty acids (FA) play an important role in cognitive function. However, little is known about the functional genetic pathways involved in cognition. The main goals of this study were to replicate previously reported interaction effects between breast feeding (BF) and FA desaturase (FADS) genetic variation on IQ and to investigate the possible mechanisms by which these variants might moderate BF effect, focusing on brain expression. Using a sample of 534 twins, we observed a trend in the moderation of BF effects on IQ by FADS2 variation. In addition, we made use of publicly available gene expression databases from both humans (193) and mice (93) and showed that FADS2 variants also correlate with FADS1 brain expression (P-value<1.1E-03). Our results provide novel clues for the understanding of the genetic mechanisms regulating FA brain expression and improve the current knowledge of the FADS moderation effect on cognition.
doi:10.1371/journal.pone.0068000
PMCID: PMC3694926  PMID: 23826354
10.  The chromosome 9 ALS and FTD locus is probably derived from a single founder 
Neurobiology of Aging  2011;33(1):209.e3-209.e8.
We and others have recently reported an association between ALS and single nucleotide polymorphisms on chromosome 9p21 in several populations. Here we show that the associated haplotype is the same in all populations and that several families previously shown to have genetic linkage to this region also share this haplotype. The most parsimonious explanation of these data is that there is a single founder for this form of disease.
doi:10.1016/j.neurobiolaging.2011.08.005
PMCID: PMC3312749  PMID: 21925771
Genetics; amyotrophic lateral sclerosis; frontotemporal dementia; Finland
11.  Genome-wide association study confirms extant PD risk loci among the Dutch 
In view of the population-specific heterogeneity in reported genetic risk factors for Parkinson's disease (PD), we conducted a genome-wide association study (GWAS) in a large sample of PD cases and controls from the Netherlands. After quality control (QC), a total of 514 799 SNPs genotyped in 772 PD cases and 2024 controls were included in our analyses. Direct replication of SNPs within SNCA and BST1 confirmed these two genes to be associated with PD in the Netherlands (SNCA, rs2736990: P=1.63 × 10−5, OR=1.325 and BST1, rs12502586: P=1.63 × 10−3, OR=1.337). Within SNCA, two independent signals in two different linkage disequilibrium (LD) blocks in the 3′ and 5′ ends of the gene were detected. Besides, post-hoc analysis confirmed GAK/DGKQ, HLA and MAPT as PD risk loci among the Dutch (GAK/DGKQ, rs2242235: P=1.22 × 10−4, OR=1.51; HLA, rs4248166: P=4.39 × 10−5, OR=1.36; and MAPT, rs3785880: P=1.9 × 10−3, OR=1.19).
doi:10.1038/ejhg.2010.254
PMCID: PMC3110043  PMID: 21248740
SNCA; BST1; GAK/DGKQ; HLA; MAPT; PD
12.  Somatic retrotransposition alters the genetic landscape of the human brain 
Nature  2011;479(7374):534-537.
Retrotransposons are mobile genetic elements that employ a germ line “copy-and-paste” mechanism to spread throughout metazoan genomes1. At least 50% of the human genome is derived from retrotransposons, with three active families (L1, Alu and SVA) associated with insertional mutagenesis and disease2-3. Epigenetic and post-transcriptional suppression block retrotransposition in somatic cells4-5, excluding early embryo development and some malignancies6-7. Recent reports of L1 expression8-9 and copy number variation10-11 (CNV) in the human brain suggest L1 mobilization may also occur during later development. However, the corresponding integration sites have not been mapped. Here we apply a high-throughput method to identify numerous L1, Alu and SVA germ line mutations, as well as 7,743 putative somatic L1 insertions in the hippocampus and caudate nucleus of three individuals. Surprisingly, we also found 13,692 and 1,350 somatic Alu and SVA insertions, respectively. Our results demonstrate that retrotransposons mobilize to protein-coding genes differentially expressed and active in the brain. Thus, somatic genome mosaicism driven by retrotransposition may reshape the genetic circuitry that underpins normal and abnormal neurobiological processes.
doi:10.1038/nature10531
PMCID: PMC3224101  PMID: 22037309
13.  A Fine-Mapping Study of 7 Top Scoring Genes from a GWAS for Major Depressive Disorder 
PLoS ONE  2012;7(5):e37384.
Major depressive disorder (MDD) is a psychiatric disorder that is characterized -amongst others- by persistent depressed mood, loss of interest and pleasure and psychomotor retardation. Environmental circumstances have proven to influence the aetiology of the disease, but MDD also has an estimated 40% heritability, probably with a polygenic background. In 2009, a genome wide association study (GWAS) was performed on the Dutch GAIN-MDD cohort. A non-synonymous coding single nucleotide polymorphism (SNP) rs2522833 in the PCLO gene became only nominally significant after post-hoc analysis with an Australian cohort which used similar ascertainment. The absence of genome-wide significance may be caused by low SNP coverage of genes. To increase SNP coverage to 100% for common variants (m.a.f.>0.1, r2>0.8), we selected seven genes from the GAIN-MDD GWAS: PCLO, GZMK, ANPEP, AFAP1L1, ST3GAL6, FGF14 and PTK2B. We genotyped 349 SNPs and obtained the lowest P-value for rs2715147 in PCLO at P = 6.8E−7. We imputed, filling in missing genotypes, after which rs2715147 and rs2715148 showed the lowest P-value at P = 1.2E−6. When we created a haplotype of these SNPs together with the non-synonymous coding SNP rs2522833, the P-value decreased to P = 9.9E−7 but was not genome wide significant. Although our study did not identify a more strongly associated variant, the results for PCLO suggest that the causal variant is in high LD with rs2715147, rs2715148 and rs2522833.
doi:10.1371/journal.pone.0037384
PMCID: PMC3359349  PMID: 22649524
14.  Genetic and Clinical Features of Progranulin-Associated Frontotemporal Lobar Degeneration 
Archives of neurology  2011;68(4):488-497.
Objective
To assess the relative frequency of unique mutations and their associated characteristics in 97 individuals with mutations in progranulin (GRN), an important cause of frontotemporal lobar degeneration (FTLD).
Participants and Design
A 46-site International Frontotemporal Lobar Degeneration Collaboration was formed to collect cases of FTLD with TAR DNA-binding protein of 43-kDa (TDP-43)–positive inclusions (FTLD-TDP). We identified 97 individuals with FTLD-TDP with pathogenic GRN mutations (GRN+ FTLD-TDP), assessed their genetic and clinical characteristics, and compared them with 453 patients with FTLD-TDP in which GRN mutations were excluded (GRN− FTLD-TDP). No patients were known to be related. Neuropathologic characteristics were confirmed as FTLD-TDP in 79 of the 97 GRN+ FTLDTDP cases and all of the GRN− FTLD-TDP cases.
Results
Age at onset of FTLD was younger in patients with GRN+ FTLD-TDP vs GRN− FTLD-TDP (median, 58.0 vs 61.0 years; P<.001), as was age at death (median, 65.5 vs 69.0 years; P<.001). Concomitant motor neuron disease was much less common in GRN+ FTLDTDP vs GRN− FTLD-TDP (5.4% vs 26.3%; P<.001). Fifty different GRN mutations were observed, including 2 novel mutations: c.139delG (p.D47TfsX7) and c.378C>A (p.C126X). The 2 most common GRN mutations were c.1477C>T (p.R493X, found in 18 patients, representing 18.6% of GRN cases) and c.26C>A (p.A9D, found in 6 patients, representing 6.2% of cases). Patients with the c.1477C>T mutation shared a haplotype on chromosome 17; clinically, they resembled patients with other GRN mutations. Patients with the c.26C>A mutation appeared to have a younger age at onset of FTLD and at death and more parkinsonian features than those with other GRN mutations.
Conclusion
GRN+ FTLD-TDP differs in key features from GRN− FTLD-TDP.
doi:10.1001/archneurol.2011.53
PMCID: PMC3160280  PMID: 21482928
15.  Comprehensive Research Synopsis and Systematic Meta-Analyses in Parkinson's Disease Genetics: The PDGene Database 
PLoS Genetics  2012;8(3):e1002548.
More than 800 published genetic association studies have implicated dozens of potential risk loci in Parkinson's disease (PD). To facilitate the interpretation of these findings, we have created a dedicated online resource, PDGene, that comprehensively collects and meta-analyzes all published studies in the field. A systematic literature screen of ∼27,000 articles yielded 828 eligible articles from which relevant data were extracted. In addition, individual-level data from three publicly available genome-wide association studies (GWAS) were obtained and subjected to genotype imputation and analysis. Overall, we performed meta-analyses on more than seven million polymorphisms originating either from GWAS datasets and/or from smaller scale PD association studies. Meta-analyses on 147 SNPs were supplemented by unpublished GWAS data from up to 16,452 PD cases and 48,810 controls. Eleven loci showed genome-wide significant (P<5×10−8) association with disease risk: BST1, CCDC62/HIP1R, DGKQ/GAK, GBA, LRRK2, MAPT, MCCC1/LAMP3, PARK16, SNCA, STK39, and SYT11/RAB25. In addition, we identified novel evidence for genome-wide significant association with a polymorphism in ITGA8 (rs7077361, OR 0.88, P = 1.3×10−8). All meta-analysis results are freely available on a dedicated online database (www.pdgene.org), which is cross-linked with a customized track on the UCSC Genome Browser. Our study provides an exhaustive and up-to-date summary of the status of PD genetics research that can be readily scaled to include the results of future large-scale genetics projects, including next-generation sequencing studies.
Author Summary
The genetic basis of Parkinson's disease is complex, i.e. it is determined by a number of different disease-causing and disease-predisposing genes. Especially the latter have proven difficult to find, evidenced by more than 800 published genetic association studies, typically showing discrepant results. To facilitate the interpretation of this large and continuously increasing body of data, we have created a freely available online database (“PDGene”: http://www.pdgene.org) which provides an exhaustive account of all published genetic association studies in PD. One particularly useful feature is the calculation and display of up-to-date summary statistics of published data for overlapping DNA sequence variants (polymorphisms). These meta-analyses revealed eleven gene loci that showed a statistically very significant (P<5×10−8; a.k.a. genome-wide significance) association with risk for PD: BST1, CCDC62/HIP1R, DGKQ/GAK, GBA, LRRK2, MAPT, MCCC1/LAMP3, PARK16, SNCA, STK39, SYT11/RAB25. In addition and purely by data-mining, we identified one novel PD susceptibility locus in a gene called ITGA8 (rs7077361, P = 1.3×10−8). We note that our continuously updated database represents the most comprehensive research synopsis of genetic association studies in PD to date. In addition to vastly facilitating the work of other PD geneticists, our approach may serve as a valuable example for other complex diseases.
doi:10.1371/journal.pgen.1002548
PMCID: PMC3305333  PMID: 22438815
16.  Cooperative Genome-Wide Analysis Shows Increased Homozygosity in Early Onset Parkinson's Disease 
PLoS ONE  2012;7(3):e28787.
Parkinson's disease (PD) occurs in both familial and sporadic forms, and both monogenic and complex genetic factors have been identified. Early onset PD (EOPD) is particularly associated with autosomal recessive (AR) mutations, and three genes, PARK2, PARK7 and PINK1, have been found to carry mutations leading to AR disease. Since mutations in these genes account for less than 10% of EOPD patients, we hypothesized that further recessive genetic factors are involved in this disorder, which may appear in extended runs of homozygosity.
We carried out genome wide SNP genotyping to look for extended runs of homozygosity (ROHs) in 1,445 EOPD cases and 6,987 controls. Logistic regression analyses showed an increased level of genomic homozygosity in EOPD cases compared to controls. These differences are larger for ROH of 9 Mb and above, where there is a more than three-fold increase in the proportion of cases carrying a ROH. These differences are not explained by occult recessive mutations at existing loci. Controlling for genome wide homozygosity in logistic regression analyses increased the differences between cases and controls, indicating that in EOPD cases ROHs do not simply relate to genome wide measures of inbreeding. Homozygosity at a locus on chromosome19p13.3 was identified as being more common in EOPD cases as compared to controls. Sequencing analysis of genes and predicted transcripts within this locus failed to identify a novel mutation causing EOPD in our cohort.
There is an increased rate of genome wide homozygosity in EOPD, as measured by an increase in ROHs. These ROHs are a signature of inbreeding and do not necessarily harbour disease-causing genetic variants. Although there might be other regions of interest apart from chromosome 19p13.3, we lack the power to detect them with this analysis.
doi:10.1371/journal.pone.0028787
PMCID: PMC3299635  PMID: 22427796
17.  High Content Screening in Neurodegenerative Diseases 
The functional annotation of genomes, construction of molecular networks and novel drug target identification, are important challenges that need to be addressed as a matter of great urgency1-4. Multiple complementary 'omics' approaches have provided clues as to the genetic risk factors and pathogenic mechanisms underlying numerous neurodegenerative diseases, but most findings still require functional validation5. For example, a recent genome wide association study for Parkinson's Disease (PD), identified many new loci as risk factors for the disease, but the underlying causative variant(s) or pathogenic mechanism is not known6, 7. As each associated region can contain several genes, the functional evaluation of each of the genes on phenotypes associated with the disease, using traditional cell biology techniques would take too long.
There is also a need to understand the molecular networks that link genetic mutations to the phenotypes they cause. It is expected that disease phenotypes are the result of multiple interactions that have been disrupted. Reconstruction of these networks using traditional molecular methods would be time consuming. Moreover, network predictions from independent studies of individual components, the reductionism approach, will probably underestimate the network complexity8. This underestimation could, in part, explain the low success rate of drug approval due to undesirable or toxic side effects. Gaining a network perspective of disease related pathways using HT/HC cellular screening approaches, and identifying key nodes within these pathways, could lead to the identification of targets that are more suited for therapeutic intervention.
High-throughput screening (HTS) is an ideal methodology to address these issues9-12. but traditional methods were one dimensional whole-well cell assays, that used simplistic readouts for complex biological processes. They were unable to simultaneously quantify the many phenotypes observed in neurodegenerative diseases such as axonal transport deficits or alterations in morphology properties13, 14. This approach could not be used to investigate the dynamic nature of cellular processes or pathogenic events that occur in a subset of cells. To quantify such features one has to move to multi-dimensional phenotypes termed high-content screening (HCS)4, 15-17. HCS is the cell-based quantification of several processes simultaneously, which provides a more detailed representation of the cellular response to various perturbations compared to HTS.
HCS has many advantages over HTS18, 19, but conducting a high-throughput (HT)-high-content (HC) screen in neuronal models is problematic due to high cost, environmental variation and human error. In order to detect cellular responses on a 'phenomics' scale using HC imaging one has to reduce variation and error, while increasing sensitivity and reproducibility.
Herein we describe a method to accurately and reliably conduct shRNA screens using automated cell culturing20 and HC imaging in neuronal cellular models. We describe how we have used this methodology to identify modulators for one particular protein, DJ1, which when mutated causes autosomal recessive parkinsonism21.
Combining the versatility of HC imaging with HT methods, it is possible to accurately quantify a plethora of phenotypes. This could subsequently be utilized to advance our understanding of the genome, the pathways involved in disease pathogenesis as well as identify potential therapeutic targets.
doi:10.3791/3452
PMCID: PMC3369774  PMID: 22257990
Medicine;  Issue 59;  High-throughput screening;  high-content screening;  neurodegeneration;  automated cell culturing;  Parkinson’s disease
18.  Identification of common variants influencing risk of the tauopathy Progressive Supranuclear Palsy 
Nature genetics  2011;43(7):699-705.
Progressive supranuclear palsy (PSP) is a movement disorder with prominent tau neuropathology. Brain diseases with abnormal tau deposits are called tauopathies, the most common being Alzheimer’s disease. Environmental causes of tauopathies include repetitive head trauma associated with some sports. To identify common genetic variation contributing to risk for tauopathies, we carried out a genome-wide association study of 1,114 PSP cases and 3,247 controls (Stage 1) followed up by a second stage where 1,051 cases and 3,560 controls were genotyped for Stage 1 SNPs that yielded P ≤ 10−3. We found significant novel signals (P < 5 × 10−8) associated with PSP risk at STX6, EIF2AK3, and MOBP. We confirmed two independent variants in MAPT affecting risk for PSP, one of which influences MAPT brain expression. The genes implicated encode proteins for vesicle-membrane fusion at the Golgi-endosomal interface, for the endoplasmic reticulum unfolded protein response, and for a myelin structural component.
doi:10.1038/ng.859
PMCID: PMC3125476  PMID: 21685912
19.  The chromosome 9 ALS and FTD locus is probably derived from a single founder 
Neurobiology of Aging  2012;33(1):209.e3-209.e8.
We and others have recently reported an association between amyotrophic lateral sclerosis (ALS) and single nucleotide polymorphisms on chromosome 9p21 in several populations. Here we show that the associated haplotype is the same in all populations and that several families previously shown to have genetic linkage to this region also share this haplotype. The most parsimonious explanation of these data are that there is a single founder for this form of disease.
doi:10.1016/j.neurobiolaging.2011.08.005
PMCID: PMC3312749  PMID: 21925771
Genetics; Amyotrophic lateral sclerosis; Frontotemporal dementia; Finland
21.  Parkinsonian phenotype in Machado-Joseph disease (MJD/SCA3): a two-case report 
BMC Neurology  2011;11:131.
Background
Machado-Joseph disease (MJD), or spinocerebellar ataxia type 3 (SCA3), is an autosomal dominant neurodegenerative disorder of late onset, which is caused by a CAG repeat expansion in the coding region of the ATXN3 gene. This disease presents clinical heterogeneity, which cannot be completely explained by the size of the repeat tract. MJD presents extrapyramidal motor signs, namely Parkinsonism, more frequently than the other subtypes of autosomal dominant cerebellar ataxias. Although Parkinsonism seems to segregate within MJD families, only a few MJD patients develop parkinsonian features and, therefore, the clinical and genetic aspects of these rare presentations remain poorly investigated. The main goal of this work was to describe two MJD patients displaying the parkinsonian triad (tremor, bradykinesia and rigidity), namely on what concerns genetic variation in Parkinson's disease (PD) associated loci (PARK2, LRRK2, PINK1, DJ-1, SNCA, MAPT, APOE, and mtDNA tRNAGln T4336C).
Case presentation
Patient 1 is a 40 year-old female (onset at 30 years of age), initially with a pure parkinsonian phenotype (similar to the phenotype previously reported for her mother). Patient 2 is a 38 year-old male (onset at 33 years of age), presenting an ataxic phenotype with parkinsonian features (not seen either in other affected siblings or in his father). Both patients presented an expanded ATXN3 allele with 72 CAG repeats. No PD mutations were found in the analyzed loci. However, allelic variants previously associated with PD were observed in DJ-1 and APOE genes, for both patients.
Conclusions
The present report adds clinical and genetic information on this particular and rare MJD presentation, and raises the hypothesis that DJ-1 and APOE polymorphisms may confer susceptibility to the parkinsonian phenotype in MJD.
doi:10.1186/1471-2377-11-131
PMCID: PMC3217914  PMID: 22023810
22.  Performance of Genotype Imputation for Rare Variants Identified in Exons and Flanking Regions of Genes 
PLoS ONE  2011;6(9):e24945.
Genotype imputation has the potential to assess human genetic variation at a lower cost than assaying the variants using laboratory techniques. The performance of imputation for rare variants has not been comprehensively studied. We utilized 8865 human samples with high depth resequencing data for the exons and flanking regions of 202 genes and Genome-Wide Association Study (GWAS) data to characterize the performance of genotype imputation for rare variants. We evaluated reference sets ranging from 100 to 3713 subjects for imputing into samples typed for the Affymetrix (500K and 6.0) and Illumina 550K GWAS panels. The proportion of variants that could be well imputed (true r2>0.7) with a reference panel of 3713 individuals was: 31% (Illumina 550K) or 25% (Affymetrix 500K) with MAF (Minor Allele Frequency) less than or equal 0.001, 48% or 35% with 0.0010.05. The performance for common SNPs (MAF>0.05) within exons and flanking regions is comparable to imputation of more uniformly distributed SNPs. The performance for rare SNPs (0.01
doi:10.1371/journal.pone.0024945
PMCID: PMC3176314  PMID: 21949800
PLoS ONE  2011;6(8):e23450.
In recent years, DISC1 has emerged as one of the most credible and best supported candidate genes for schizophrenia and related neuropsychiatric disorders. Furthermore, increasing evidence – both genetic and functional – indicates that many of its protein interaction partners are also involved in the development of these diseases. In this study, we applied a pooled sample 454 sequencing strategy, to explore the contribution of genetic variation in DISC1 and 10 of its interaction partners (ATF5, Grb2, FEZ1, LIS-1, PDE4B, NDE1, NDEL1, TRAF3IP1, YWHAE, and ZNF365) to schizophrenia susceptibility in an isolated northern Swedish population. Mutation burden analysis of the identified variants in a population of 486 SZ patients and 514 control individuals, revealed that non-synonymous rare variants with a MAF<0.01 were significantly more present in patients compared to controls (8.64% versus 4.7%, P = 0.018), providing further evidence for the involvement of DISC1 and some of its interaction partners in psychiatric disorders. This increased burden of rare missense variants was even more striking in a subgroup of early onset patients (12.9% versus 4.7%, P = 0.0004), highlighting the importance of studying subgroups of patients and identifying endophenotypes. Upon investigation of the potential functional effects associated with the identified missense variants, we found that ∼90% of these variants reside in intrinsically disordered protein regions. The observed increase in mutation burden in patients provides further support for the role of the DISC1 pathway in schizophrenia. Furthermore, this study presents the first evidence supporting the involvement of mutations within intrinsically disordered protein regions in the pathogenesis of psychiatric disorders. As many important biological functions depend directly on the disordered state, alteration of this disorder in key pathways may represent an intriguing new disease mechanism for schizophrenia and related neuropsychiatric diseases. Further research into this unexplored domain will be required to elucidate the role of the identified variants in schizophrenia etiology.
doi:10.1371/journal.pone.0023450
PMCID: PMC3154939  PMID: 21853134
A female patient with a partial trisomy 16q was described previously. Her clinical characteristics included obesity, severe anisomastia, moderate to severe mental retardation, attention deficit hyperactivity disorder, dysmorphic facies, and contractions of the small joints. In this paper, we describe a more detailed analysis of the genetic anomaly in this patient. We were particularly interested in the involvement of the fat mass and obesity associated gene (FTO) in her duplication. Single nucleotide polymorphisms in FTO have recently been associated with obesity. The breakpoints of the duplication were precisely mapped using high resolution oligonucleotide array comparative genomic hybridization (CGH). We found that the duplication spans 11.45 Mb on 16q11.2 to 16q13 and it includes FTO. The increased copy number of FTO was confirmed with a qPCR on genomic DNA of the patient. We investigated the influence of the increased FTO copy number on FTO gene expression in immortalized lymphocytes from the patient using qPCR. No evidence of increased FTO expression was detected in the patient’s lymphocytes. We discuss these findings and shared phenotypic features of patients with overlapping 16q duplications, as well as candidate genes for some of the clinical manifestations.
doi:10.1002/ajmg.a.33229
PMCID: PMC3031344  PMID: 20186806
16q duplication; obesity; FTO; CGH; qPCR; maternal imprinting; SLC6A2; ADHD; BBS2
PLoS ONE  2010;5(11):e13857.
Technology advances have promoted gene-based sequencing studies with the aim of identifying rare mutations responsible for complex diseases. A complication in these types of association studies is that the vast majority of non-synonymous mutations are believed to be neutral to phenotypes. It is thus critical to distinguish potential causative variants from neutral variation before performing association tests. In this study, we used existing predicting algorithms to predict functional amino acid substitutions, and incorporated that information into association tests. Using simulations, we comprehensively studied the effects of several influential factors, including the sensitivity and specificity of functional variant predictions, number of variants, and proportion of causative variants, on the performance of association tests. Our results showed that incorporating information regarding functional variants obtained from existing prediction algorithms improves statistical power under certain conditions, particularly when the proportion of causative variants is moderate. The application of the proposed tests to a real sequencing study confirms our conclusions. Our work may help investigators who are planning to pursue gene-based sequencing studies.
doi:10.1371/journal.pone.0013857
PMCID: PMC2975623  PMID: 21079782

Results 1-25 (50)