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1.  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
4.  Single-Cell Expression Profiling of Dopaminergic Neurons Combined with Association Analysis Identifies Pyridoxal Kinase as Parkinson’s Disease Gene 
Annals of neurology  2009;66(6):792-798.
Objective
The etiology of Parkinson disease (PD) is complex and multifactorial, with hereditary and environmental factors contributing. Monogenic forms have provided molecular clues to disease mechanisms but genetic modifiers of idiopathic PD are still to be determined.
Methods
We carried out whole-genome expression profiling of isolated human substantia nigra (SN) neurons from patients with PD vs. controls followed by association analysis of tagging single-nucleotide polymorphisms (SNPs) in differentially regulated genes. Association was investigated in a German PD sample and confirmed in Italian and British cohorts.
Results
We identified four differentially expressed genes located in PD candidate pathways, ie, MTND2 (mitochondrial, p = 7.14 × 10−7), PDXK (vitamin B6/dopamine metabolism, p = 3.27 × 10−6), SRGAP3 (axon guidance, p = 5.65 × 10−6), and TRAPPC4 (vesicle transport, p = 5.81 × 10−6). We identified a DNA variant (rs2010795) in PDXK associated with an increased risk of PD in the German cohort (p = 0.00032). This association was confirmed in the British (p = 0.028) and Italian (p = 0.0025) cohorts individually and reached a combined value of p = 1.2 × 10−7 (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.18–1.44).
Interpretation
We provide an example of how microgenomic genome-wide expression studies in combination with association analysis can aid to identify genetic modifiers in neurodegenerative disorders. The detection of a genetic variant in PDXK, together with evidence accumulating from clinical studies, emphasize the impact of vitamin B6 status and metabolism on disease risk and therapy in PD.
doi:10.1002/ana.21780
PMCID: PMC4034432  PMID: 20035503
6.  Comparable Autoantibody Serum Levels against Amyloid- and Inflammation-Associated Proteins in Parkinson’s Disease Patients and Controls 
PLoS ONE  2014;9(2):e88604.
Naturally occurring autoantibodies (NAbs) against a number of potentially disease-associated cellular proteins, including Amyloid-beta1–42 (Abeta1–42), Alpha-synuclein (Asyn), myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG), and S100 calcium binding protein B (S100B) have been suggested to be associated with neurodegenerative disorders, in particular Alzheimer’s (AD) and Parkinson’s disease (PD). Whereas the (reduced) occurrence of specific NAbs in AD is widely accepted, previous literature examining the relation of these NAb titres between PD patients and controls, as well as comparing these levels with demographic and clinical parameters in PD patients have produced inconsistent findings. We therefore aimed, in a cross-sectional approach, to determine serum titres of the above NAbs in a cohort of 93 PD patients (31 of them demented) and 194 controls. Levels were correlated with demographic and clinical variables, cerebrospinal fluid Abeta1–42, total tau and phospho-tau levels, as well as with single nucleotide polymorphisms (SNPs) of genes which either have been reported to influence the immune system, the amyloid cascade or the occurrence of PD (ApoE, GSK3B, HLA-DRA, HSPA5, SNCA, and STK39). The investigated NAb titres were neither significantly associated with the occurrence of PD, nor with demographic and clinical parameters, neurodegenerative markers or genetic variables. These results argue against a major potential of blood-borne parameters of the adaptive immune system to serve as trait or state markers in PD.
doi:10.1371/journal.pone.0088604
PMCID: PMC3931625  PMID: 24586351
7.  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
8.  Large-scale replication and heterogeneity in Parkinson disease genetic loci 
Sharma, Manu | Ioannidis, John P.A. | Aasly, Jan O. | Annesi, Grazia | Brice, Alexis | Van Broeckhoven, Christine | Bertram, Lars | Bozi, Maria | Crosiers, David | Clarke, Carl | Facheris, Maurizio | Farrer, Matthew | Garraux, Gaetan | Gispert, Suzana | Auburger, Georg | Vilariño-Güell, Carles | Hadjigeorgiou, Georgios M. | Hicks, Andrew A. | Hattori, Nobutaka | Jeon, Beom | Lesage, Suzanne | Lill, Christina M. | Lin, Juei-Jueng | Lynch, Timothy | Lichtner, Peter | Lang, Anthony E. | Mok, Vincent | Jasinska-Myga, Barbara | Mellick, George D. | Morrison, Karen E. | Opala, Grzegorz | Pramstaller, Peter P. | Pichler, Irene | Park, Sung Sup | Quattrone, Aldo | Rogaeva, Ekaterina | Ross, Owen A. | Stefanis, Leonidas | Stockton, Joanne D. | Satake, Wataru | Silburn, Peter A. | Theuns, Jessie | Tan, Eng-King | Toda, Tatsushi | Tomiyama, Hiroyuki | Uitti, Ryan J. | Wirdefeldt, Karin | Wszolek, Zbigniew | Xiromerisiou, Georgia | Yueh, Kuo-Chu | Zhao, Yi | Gasser, Thomas | Maraganore, Demetrius | Krüger, Rejko | Boyle, R.S | Sellbach, A | O'Sullivan, J.D. | Sutherland, G.T. | Siebert, G.A | Dissanayaka, N.N.W | Van Broeckhoven, Christine | Theuns, Jessie | Crosiers, David | Pickut, Barbara | Engelborghs, Sebastiaan | Meeus, Bram | De Deyn, Peter P. | Cras, Patrick | Rogaeva, Ekaterina | Lang, Anthony E | Agid, Y | Anheim, M | Bonnet, A-M | Borg, M | Brice, A | Broussolle, E | Corvol, JC | Damier, P | Destée, A | Dürr, A | Durif, F | Lesage, S | Lohmann, E | Pollak, P | Rascol, O | Tison, F | Tranchant, C | Viallet, F | Vidailhet, M | Tzourio, Christophe | Amouyel, Philippe | Loriot, Marie-Anne | Mutez, Eugénie | Duflot, Aurélie | Legendre, Jean-Philippe | Waucquier, Nawal | Gasser, Thomas | Riess, Olaf | Berg, Daniela | Schulte, Claudia | Klein, Christine | Djarmati, Ana | Hagenah, Johann | Lohmann, Katja | Auburger, Georg | Hilker, Rüdiger | van de Loo, Simone | Dardiotis, Efthimios | Tsimourtou, Vaia | Ralli, Styliani | Kountra, Persa | Patramani, Gianna | Vogiatzi, Cristina | Hattori, Nobutaka | Tomiyama, Hiroyuki | Funayama, Manabu | Yoshino, Hiroyo | Li, Yuanzhe | Imamichi, Yoko | Toda, Tatsushi | Satake, Wataru | Lynch, Tim | Gibson, J. Mark | Valente, Enza Maria | Ferraris, Alessandro | Dallapiccola, Bruno | Ialongo, Tamara | Brighina, Laura | Corradi, Barbara | Piolti, Roberto | Tarantino, Patrizia | Annesi, Ferdinanda | Jeon, Beom S. | Park, Sung-Sup | Aasly, J | Opala, Grzegorz | Jasinska-Myga, Barbara | Klodowska-Duda, Gabriela | Boczarska-Jedynak, Magdalena | Tan, Eng King | Belin, Andrea Carmine | Olson, Lars | Galter, Dagmar | Westerlund, Marie | Sydow, Olof | Nilsson, Christer | Puschmann, Andreas | Lin, JJ | Maraganore, Demetrius M. | Ahlskog, J, Eric | de Andrade, Mariza | Lesnick, Timothy G. | Rocca, Walter A. | Checkoway, Harvey | Ross, Owen A | Wszolek, Zbigniew K. | Uitti, Ryan J.
Neurology  2012;79(7):659-667.
Objective:
Eleven genetic loci have reached genome-wide significance in a recent meta-analysis of genome-wide association studies in Parkinson disease (PD) based on populations of Caucasian descent. The extent to which these genetic effects are consistent across different populations is unknown.
Methods:
Investigators from the Genetic Epidemiology of Parkinson's Disease Consortium were invited to participate in the study. A total of 11 SNPs were genotyped in 8,750 cases and 8,955 controls. Fixed as well as random effects models were used to provide the summary risk estimates for these variants. We evaluated between-study heterogeneity and heterogeneity between populations of different ancestry.
Results:
In the overall analysis, single nucleotide polymorphisms (SNPs) in 9 loci showed significant associations with protective per-allele odds ratios of 0.78–0.87 (LAMP3, BST1, and MAPT) and susceptibility per-allele odds ratios of 1.14–1.43 (STK39, GAK, SNCA, LRRK2, SYT11, and HIP1R). For 5 of the 9 replicated SNPs there was nominally significant between-site heterogeneity in the effect sizes (I2 estimates ranged from 39% to 48%). Subgroup analysis by ethnicity showed significantly stronger effects for the BST1 (rs11724635) in Asian vs Caucasian populations and similar effects for SNCA, LRRK2, LAMP3, HIP1R, and STK39 in Asian and Caucasian populations, while MAPT rs2942168 and SYT11 rs34372695 were monomorphic in the Asian population, highlighting the role of population-specific heterogeneity in PD.
Conclusion:
Our study allows insight to understand the distribution of newly identified genetic factors contributing to PD and shows that large-scale evaluation in diverse populations is important to understand the role of population-specific heterogeneity. Neurology® 2012;79:659–667
doi:10.1212/WNL.0b013e318264e353
PMCID: PMC3414661  PMID: 22786590
9.  SNCA Variants Are Associated with Increased Risk for Multiple System Atrophy 
Annals of neurology  2009;65(5):610-614.
To test whether the synucleinopathies Parkinson’s disease and multiple system atrophy (MSA) share a common genetic etiology, we performed a candidate single nucleotide polymorphism (SNP) association study of the 384 most associated SNPs in a genome-wide association study of Parkinson’s disease in 413 MSA cases and 3,974 control subjects. The 10 most significant SNPs were then replicated in additional 108 MSA cases and 537 controls. SNPs at the SNCA locus were significantly associated with risk for increased risk for the development of MSA (combined p = 5.5 × 1012; odds ratio 6.2).
doi:10.1002/ana.21685
PMCID: PMC3520128  PMID: 19475667
10.  S100B is increased in Parkinson’s disease and ablation protects against MPTP-induced toxicity through the RAGE and TNF-α pathway 
Brain  2012;135(11):3336-3347.
Parkinson’s disease is a neurodegenerative disorder that can, at least partly, be mimicked by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. S100B is a calcium-binding protein expressed in, and secreted by, astrocytes. There is increasing evidence that S100B acts as a cytokine or damage-associated molecular pattern protein not only in inflammatory but also in neurodegenerative diseases. In this study, we show that S100B protein levels were higher in post-mortem substantia nigra of patients with Parkinson’s disease compared with control tissue, and cerebrospinal fluid S100B levels were higher in a large cohort of patients with Parkinson’s disease compared with controls. Correspondingly, mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine showed upregulated S100B messenger RNA and protein levels. In turn, ablation of S100B resulted in neuroprotection, reduced microgliosis and reduced expression of both the receptor for advanced glycation endproducts and tumour necrosis factor-α. Our results demonstrate a role of S100B in the pathophysiology of Parkinson’s disease. Targeting S100B may emerge as a potential treatment strategy in this disorder.
doi:10.1093/brain/aws250
PMCID: PMC3501971  PMID: 23169921
calcium-binding protein; MPTP; Parkinson’s disease; S100B
11.  Serum and Cerebrospinal Fluid Levels of Transthyretin in Lewy Body Disorders with and without Dementia 
PLoS ONE  2012;7(10):e48042.
Parkinson’s disease (PD) without (non-demented, PDND) and with dementia (PDD), and dementia with Lewy bodies (DLB) are subsumed under the umbrella term Lewy body disorders (LBD). The main component of the underlying pathologic substrate, i.e. Lewy bodies and Lewy neurites, is misfolded alpha-synuclein (Asyn), and - in particular in demented LBD patients - co-occurring misfolded amyloid-beta (Abeta). Lowered blood and cerebrospinal fluid (CSF) levels of transthyretin (TTR) - a clearance protein mainly produced in the liver and, autonomously, in the choroid plexus - are associated with Abeta accumulation in Alzheimer’s disease. In addition, a recent study suggests that TTR is involved in Asyn clearance. We measured TTR protein levels in serum and cerebrospinal fluid of 131 LBD patients (77 PDND, 26 PDD, and 28 DLB) and 72 controls, and compared TTR levels with demographic and clinical data as well as neurodegenerative markers in the CSF. Five single nucleotide polymorphisms of the TTR gene which are considered to influence the ability of the protein to carry its ligands were also analyzed. CSF TTR levels were significantly higher in LBD patients compared to controls. Post-hoc analysis demonstrated that this effect was driven by PDND patients. In addition, CSF TTR levels correlated negatively with CSF Abeta1–42, total tau and phospho-tau levels. Serum TTR levels did not significantly differ among the studied groups. There were no relevant associations between TTR levels and genetic, demographic and clinical data, respectively. These results suggest an involvement of the clearance protein TTR in LBD pathophysiology, and should motivate to elucidate TTR-related mechanisms in LBD in more detail.
doi:10.1371/journal.pone.0048042
PMCID: PMC3485000  PMID: 23133543
12.  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
13.  Dissecting the role of the mitochondrial chaperone mortalin in Parkinson's disease: functional impact of disease-related variants on mitochondrial homeostasis 
Human Molecular Genetics  2010;19(22):4437-4452.
The mitochondrial chaperone mortalin has been linked to neurodegeneration in Parkinson's disease (PD) based on reduced protein levels in affected brain regions of PD patients and its interaction with the PD-associated protein DJ-1. Recently, two amino acid exchanges in the ATPase domain (R126W) and the substrate-binding domain (P509S) of mortalin were identified in Spanish PD patients. Here, we identified a separate and novel variant (A476T) in the substrate-binding domain of mortalin in German PD patients. To define a potential role as a susceptibility factor in PD, we characterized the functions of all three variants in different cellular models. In vitro import assays revealed normal targeting of all mortalin variants. In neuronal and non-neuronal human cell lines, the disease-associated variants caused a mitochondrial phenotype of increased reactive oxygen species and reduced mitochondrial membrane potential, which were exacerbated upon proteolytic stress. These functional impairments correspond with characteristic alterations of the mitochondrial network in cells overexpressing mutant mortalin compared with wild-type (wt), which were confirmed in fibroblasts from a carrier of the A476T variant. In line with a loss of function hypothesis, knockdown of mortalin in human cells caused impaired mitochondrial function that was rescued by wt mortalin, but not by the variants. Our genetic and functional studies of novel disease-associated variants in the mortalin gene define a loss of mortalin function, which causes impaired mitochondrial function and dynamics. Our results support the role of this mitochondrial chaperone in neurodegeneration and underscore the concept of impaired mitochondrial protein quality control in PD.
doi:10.1093/hmg/ddq370
PMCID: PMC3298849  PMID: 20817635
14.  Genetic basis of Parkinson’s disease: inheritance, penetrance, and expression 
Parkinson’s disease can be caused by rare familial genetic mutations, but in most cases it is likely to result from an interaction between multiple genetic and environmental risk factors. Over recent years, many variants in a growing number of genes involved in the pathogenesis of Parkinson’s disease have been identified. Mutations in several genes have been shown to cause familial parkinsonism. In this review, we discuss 12 of them (SNCA, LRRK2, Parkin, PINK1, DJ1, ATP13A2, PLA2G6, FBXO7, UCHL1, GIGYF2, HTRA2, and EIF4G1). Additionally, six genes have been shown conclusively to be risk factors for sporadic Parkinson’s disease, and are also discussed (GBA, MAPT, BST1, PARK16, GAK, and HLA). Many more genes and genetic loci have been suggested, but need confirmation. There is evidence that pathways involved in the rare familial forms also play a role in the sporadic form, and that the respective genes might also be risk factors for sporadic Parkinson’s disease. The identification of genes involved in the development of Parkinson’s disease will improve our understanding of the underlying molecular mechanisms, and will hopefully lead to new drug targets and treatment strategies.
doi:10.2147/TACG.S11639
PMCID: PMC3681179  PMID: 23776368
Parkinson’s disease; genetics; SNCA; LRRK2; GBA; MAPT
15.  ARHGEF7 (BETA-PIX) Acts as Guanine Nucleotide Exchange Factor for Leucine-Rich Repeat Kinase 2 
PLoS ONE  2010;5(10):e13762.
Background
Mutations within the leucine-rich repeat kinase 2 (LRRK2) gene are a common cause of familial and sporadic Parkinson's disease. The multidomain protein LRRK2 exhibits overall low GTPase and kinase activity in vitro.
Methodology/Principal Findings
Here, we show that the rho guanine nucleotide exchange factor ARHGEF7 and the small GTPase CDC42 are interacting with LRRK2 in vitro and in vivo. GTPase activity of full-length LRRK2 increases in the presence of recombinant ARHGEF7. Interestingly, LRRK2 phosphorylates ARHGEF7 in vitro at previously unknown phosphorylation sites. We provide evidence that ARHGEF7 might act as a guanine nucleotide exchange factor for LRRK2 and that R1441C mutant LRRK2 with reduced GTP hydrolysis activity also shows reduced binding to ARHGEF7.
Conclusions/Significance
Downstream effects of phosphorylation of ARHGEF7 through LRRK2 could be (i) a feedback control mechanism for LRRK2 activity as well as (ii) an impact of LRRK2 on actin cytoskeleton regulation. A newly identified familial mutation N1437S, localized within the GTPase domain of LRRK2, further underlines the importance of the GTPase domain of LRRK2 in Parkinson's disease pathogenesis.
doi:10.1371/journal.pone.0013762
PMCID: PMC2966438  PMID: 21048939
16.  Genome-Wide Association Study reveals genetic risk underlying Parkinson’s disease 
Nature genetics  2009;41(12):1308-1312.
We performed a genome-wide association study (GWAS) in 1,713 Caucasian patients with Parkinson’s disease (PD) and 3,978 controls. After replication in 3,361 cases and 4,573 controls, two strong association signals were observed: in the α-synuclein gene(SNCA) (rs2736990, OR=1.23, p=2.24×10−16) and at the MAPT locus (rs393152, OR=0.77, p=1.95×10−16). We exchanged data with colleagues performing a GWAS in Asian PD cases. Association at SNCA was replicated in the Asian GWAS1, confirming this as a major risk locus across populations. We were able to replicate the effect of a novel locus detected in the Asian cohort (PARK16, rs823128, OR=0.66, p=7.29×10−8) and provide evidence supporting the role of common variability around LRRK2 in modulating risk for PD (rs1491923, OR=1.14, p=1.55×10−5). These data demonstrate an unequivocal role for common genetic variability in the etiology of typical PD and suggest population specific genetic heterogeneity in this disease.
doi:10.1038/ng.487
PMCID: PMC2787725  PMID: 19915575
17.  Multi-center analysis of glucocerebrosidase mutations in Parkinson disease 
The New England journal of medicine  2009;361(17):1651-1661.
Background
Recent studies indicate an increased frequency of mutations in the gene for Gaucher disease, glucocerebrosidase (GBA), among patients with Parkinson disease. An international collaborative study was conducted to ascertain the frequency of GBA mutations in ethnically diverse patients with Parkinson disease.
Methods
Sixteen centers participated, including five from the Americas, six from Europe, two from Israel and three from Asia. Each received a standard DNA panel to compare genotyping results. Genotypes and phenotypic data from patients and controls were analyzed using multivariate logistic regression models and the Mantel Haenszel procedure to estimate odds ratios (ORs) across studies. The sample included 5691 patients (780 Ashkenazi Jews) and 4898 controls (387 Ashkenazi Jews).
Results
All 16 centers could detect GBA mutations, L444P and N370S, and the two were found in 15.3% of Ashkenazi patients with Parkinson disease (ORs = 4.95 for L444P and 5.62 for N370S), and in 3.2% of non-Ashkenazi patients (ORs = 9.68 for L444P and 3.30 for N370S). GBA was sequenced in 1642 non-Ashkenazi subjects, yielding a frequency of 6.9% for all mutations, demonstrate that limited mutation screens miss half the mutant alleles. The presence of any GBA mutation was associated with an OR of 5.43 across studies. Clinically, although phenotypes varied, subjects with a GBA mutation presented earlier, and were more likely to have affected relatives and atypical manifestations.
Conclusion
Data collected from sixteen centers demonstrate that there is a strong association between GBA mutations and Parkinson disease.
doi:10.1056/NEJMoa0901281
PMCID: PMC2856322  PMID: 19846850

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