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1.  Bayesian refinement of association signals for 14 loci in 3 common diseases 
Nature genetics  2012;44(12):1294-1301.
To further investigate susceptibility loci identified by genome-wide association studies, we genotyped 5,500 SNPs across 14 associated regions in 8,000 samples from a control group and 3 diseases: type 2 diabetes (T2D), coronary artery disease (CAD) and Graves’ disease. We defined, using Bayes theorem, credible sets of SNPs that were 95% likely, based on posterior probability, to contain the causal disease-associated SNPs. In 3 of the 14 regions, TCF7L2 (T2D), CTLA4 (Graves’ disease) and CDKN2A-CDKN2B (T2D), much of the posterior probability rested on a single SNP, and, in 4 other regions (CDKN2A-CDKN2B (CAD) and CDKAL1, FTO and HHEX (T2D)), the 95% sets were small, thereby excluding most SNPs as potentially causal. Very few SNPs in our credible sets had annotated functions, illustrating the limitations in understanding the mechanisms underlying susceptibility to common diseases. Our results also show the value of more detailed mapping to target sequences for functional studies.
doi:10.1038/ng.2435
PMCID: PMC3791416  PMID: 23104008
2.  Participant identification in genetic association studies: improved methods and practical implications 
Background In a recent paper by Homer et al. (Resolving individuals contributing trace amounts of DNA to highly complex mixtures using high-density SNP genotyping microarrays. PLoS Genet 2008;4:e1000167), a method for detecting whether a given individual is a contributor to a particular genomic mixture was proposed. This prompted grave concern about the public dissemination of aggregate statistics from genome-wide association studies. It is of clear scientific importance that such data be shared widely, but the confidentiality of study participants must not be compromised. The issue of what summary genomic data can safely be posted on the web is only addressed satisfactorily when the theoretical underpinnings of the proposed method are clarified and its performance evaluated in terms of dependence on underlying assumptions.
Methods The original method raised a number of concerns and several alternatives have since been proposed, including a simple linear regression approach. In our proposed generalized estimating equation approach, we maintain the simplicity of the linear regression model but obtain inferences that are more robust to approximation of the variance/covariance structure and can accommodate linkage disequilibrium.
Results We affirm that, in principle, it is possible to determine that a ‘candidate’ individual has participated in a study, given a subset of aggregate statistics from that study. However, the methods depend critically on a number of key factors including: the ancestry of participants in the study; the absolute and relative numbers of cases and controls; and the number of single nucleotide polymorphisms.
Conclusions Simple guidelines for publication that are based on a single criterion are therefore unlikely to suffice. In particular, ‘directed’ summary statistics should not be posted openly on the web but could be protected by an internet-based access check as proposed by the P3G_Consortium et al. (Public access to genome-wide data: five views on balancing research with privacy and protection. PLoS Genet 2009;5:e1000665).
doi:10.1093/ije/dyr149
PMCID: PMC3235023  PMID: 22158671
Identification; linear regression; generalized estimating equations; linkage disequilibrium; case–control genetic association studies
3.  Is rigorous retrospective harmonization possible? Application of the DataSHaPER approach across 53 large studies 
Background Proper understanding of the roles of, and interactions between genetic, lifestyle, environmental and psycho-social factors in determining the risk of development and/or progression of chronic diseases requires access to very large high-quality databases. Because of the financial, technical and time burdens related to developing and maintaining very large studies, the scientific community is increasingly synthesizing data from multiple studies to construct large databases. However, the data items collected by individual studies must be inferentially equivalent to be meaningfully synthesized. The DataSchema and Harmonization Platform for Epidemiological Research (DataSHaPER; http://www.datashaper.org) was developed to enable the rigorous assessment of the inferential equivalence, i.e. the potential for harmonization, of selected information from individual studies.
Methods This article examines the value of using the DataSHaPER for retrospective harmonization of established studies. Using the DataSHaPER approach, the potential to generate 148 harmonized variables from the questionnaires and physical measures collected in 53 large population-based studies (6.9 million participants) was assessed. Variable and study characteristics that might influence the potential for data synthesis were also explored.
Results Out of all assessment items evaluated (148 variables for each of the 53 studies), 38% could be harmonized. Certain characteristics of variables (i.e. relative importance, individual targeted, reference period) and of studies (i.e. observational units, data collection start date and mode of questionnaire administration) were associated with the potential for harmonization. For example, for variables deemed to be essential, 62% of assessment items paired could be harmonized.
Conclusion The current article shows that the DataSHaPER provides an effective and flexible approach for the retrospective harmonization of information across studies. To implement data synthesis, some additional scientific, ethico-legal and technical considerations must be addressed. The success of the DataSHaPER as a harmonization approach will depend on its continuing development and on the rigour and extent of its use. The DataSHaPER has the potential to take us closer to a truly collaborative epidemiology and offers the promise of enhanced research potential generated through synthesized databases.
doi:10.1093/ije/dyr106
PMCID: PMC3204208  PMID: 21804097
Data synthesis; data quality; data pooling; harmonization; meta-analysis; DataSHaPER; retrospective harmonization
4.  Effect of Five Genetic Variants Associated with Lung Function on the Risk of Chronic Obstructive Lung Disease, and Their Joint Effects on Lung Function 
Rationale: Genomic loci are associated with FEV1 or the ratio of FEV1 to FVC in population samples, but their association with chronic obstructive pulmonary disease (COPD) has not yet been proven, nor have their combined effects on lung function and COPD been studied.
Objectives: To test association with COPD of variants at five loci (TNS1, GSTCD, HTR4, AGER, and THSD4) and to evaluate joint effects on lung function and COPD of these single-nucleotide polymorphisms (SNPs), and variants at the previously reported locus near HHIP.
Methods: By sampling from 12 population-based studies (n = 31,422), we obtained genotype data on 3,284 COPD case subjects and 17,538 control subjects for sentinel SNPs in TNS1, GSTCD, HTR4, AGER, and THSD4. In 24,648 individuals (including 2,890 COPD case subjects and 13,862 control subjects), we additionally obtained genotypes for rs12504628 near HHIP. Each allele associated with lung function decline at these six SNPs contributed to a risk score. We studied the association of the risk score to lung function and COPD.
Measurements and Main Results: Association with COPD was significant for three loci (TNS1, GSTCD, and HTR4) and the previously reported HHIP locus, and suggestive and directionally consistent for AGER and TSHD4. Compared with the baseline group (7 risk alleles), carrying 10–12 risk alleles was associated with a reduction in FEV1 (β = –72.21 ml, P = 3.90 × 10−4) and FEV1/FVC (β = –1.53%, P = 6.35 × 10−6), and with COPD (odds ratio = 1.63, P = 1.46 × 10−5).
Conclusions: Variants in TNS1, GSTCD, and HTR4 are associated with COPD. Our highest risk score category was associated with a 1.6-fold higher COPD risk than the population average score.
doi:10.1164/rccm.201102-0192OC
PMCID: PMC3398416  PMID: 21965014
FEV1; FVC; genome-wide association study; modeling risk
5.  Identification of seven loci affecting mean telomere length and their association with disease 
Codd, Veryan | Nelson, Christopher P. | Albrecht, Eva | Mangino, Massimo | Deelen, Joris | Buxton, Jessica L. | Jan Hottenga, Jouke | Fischer, Krista | Esko, Tõnu | Surakka, Ida | Broer, Linda | Nyholt, Dale R. | Mateo Leach, Irene | Salo, Perttu | Hägg, Sara | Matthews, Mary K. | Palmen, Jutta | Norata, Giuseppe D. | O’Reilly, Paul F. | Saleheen, Danish | Amin, Najaf | Balmforth, Anthony J. | Beekman, Marian | de Boer, Rudolf A. | Böhringer, Stefan | Braund, Peter S. | Burton, Paul R. | de Craen, Anton J. M. | Denniff, Matthew | Dong, Yanbin | Douroudis, Konstantinos | Dubinina, Elena | Eriksson, Johan G. | Garlaschelli, Katia | Guo, Dehuang | Hartikainen, Anna-Liisa | Henders, Anjali K. | Houwing-Duistermaat, Jeanine J. | Kananen, Laura | Karssen, Lennart C. | Kettunen, Johannes | Klopp, Norman | Lagou, Vasiliki | van Leeuwen, Elisabeth M. | Madden, Pamela A. | Mägi, Reedik | Magnusson, Patrik K.E. | Männistö, Satu | McCarthy, Mark I. | Medland, Sarah E. | Mihailov, Evelin | Montgomery, Grant W. | Oostra, Ben A. | Palotie, Aarno | Peters, Annette | Pollard, Helen | Pouta, Anneli | Prokopenko, Inga | Ripatti, Samuli | Salomaa, Veikko | Suchiman, H. Eka D. | Valdes, Ana M. | Verweij, Niek | Viñuela, Ana | Wang, Xiaoling | Wichmann, H.-Erich | Widen, Elisabeth | Willemsen, Gonneke | Wright, Margaret J. | Xia, Kai | Xiao, Xiangjun | van Veldhuisen, Dirk J. | Catapano, Alberico L. | Tobin, Martin D. | Hall, Alistair S. | Blakemore, Alexandra I.F. | van Gilst, Wiek H. | Zhu, Haidong | Erdmann, Jeanette | Reilly, Muredach P. | Kathiresan, Sekar | Schunkert, Heribert | Talmud, Philippa J. | Pedersen, Nancy L. | Perola, Markus | Ouwehand, Willem | Kaprio, Jaakko | Martin, Nicholas G. | van Duijn, Cornelia M. | Hovatta, Iiris | Gieger, Christian | Metspalu, Andres | Boomsma, Dorret I. | Jarvelin, Marjo-Riitta | Slagboom, P. Eline | Thompson, John R. | Spector, Tim D. | van der Harst, Pim | Samani, Nilesh J.
Nature genetics  2013;45(4):422-427e2.
Inter-individual variation in mean leukocyte telomere length (LTL) is associated with cancer and several age-associated diseases. Here, in a genome-wide meta-analysis of 37,684 individuals with replication of selected variants in a further 10,739 individuals, we identified seven loci, including five novel loci, associated with mean LTL (P<5x10−8). Five of the loci contain genes (TERC, TERT, NAF1, OBFC1, RTEL1) that are known to be involved in telomere biology. Lead SNPs at two loci (TERC and TERT) associate with several cancers and other diseases, including idiopathic pulmonary fibrosis. Moreover, a genetic risk score analysis combining lead variants at all seven loci in 22,233 coronary artery disease cases and 64,762 controls showed an association of the alleles associated with shorter LTL with increased risk of CAD (21% (95% CI: 5–35%) per standard deviation in LTL, p=0.014). Our findings support a causal role of telomere length variation in some age-related diseases.
doi:10.1038/ng.2528
PMCID: PMC4006270  PMID: 23535734
6.  GENETIC ARCHITECTURE OF AMBULATORY BLOOD PRESSURE IN THE GENERAL POPULATION – INSIGHTS FROM CARDIOVASCULAR GENE-CENTRIC ARRAY 
Hypertension  2010;56(6):1069-1076.
Genetic determinants of blood pressure are poorly defined. We undertook a large-scale gene-centric analysis to identify loci and pathways associated with ambulatory systolic and diastolic blood pressure.
We measured 24-hour ambulatory BP in 2020 individuals from 520 white European nuclear families (the GRAPHIC Study) and genotyped their DNA using the Illumina HumanCVD BeadChip array which contains approximately 50000 single nucleotide polymorphisms in >2000 cardiovascular candidate loci. We found a strong association between rs13306560 polymorphism in the promoter region of MTHFR and CLCN6 and mean 24-hour diastolic blood pressure - each minor allele copy of rs13306560 was associated with 2.6 mmHg lower mean 24-hour diastolic blood pressure (P=1.2×10−8). rs13306560 was also associated with clinic diastolic blood pressure in a combined analysis of 8129 subjects from the GRAPHIC Study, the CoLaus Study and the Silesian Cardiovascular Study (P=5.4×10−6). Additional analysis of associations between variants in Gene Ontology-defined pathways and mean 24-hour blood pressure in the GRAPHIC Study showed that cell survival control signalling cascades could play a role in blood pressure regulation. There was also a significant over-representation of rare variants (minor allele frequency <0.05) amongst polymorphisms showing at least nominal association with mean 24-hour blood pressure indicating that a considerable proportion of its heritability may be explained by uncommon alleles.
Through a large scale gene-centric analysis of ambulatory blood pressure, we identified an association of a novel variant at the MTHFR/CLNC6 locus with diastolic blood pressure and provided new insights into the genetic architecture of blood pressure.
doi:10.1161/HYPERTENSIONAHA.110.155721
PMCID: PMC3035934  PMID: 21060006
gene; genetics; blood pressure; single nucleotide polymorphism; association; heritability
7.  Realizing the promise of population biobanks: a new model for translation 
Human Genetics  2011;130(3):333-345.
The promise of science lies in expectations of its benefits to societies and is matched by expectations of the realisation of the significant public investment in that science. In this paper, we undertake a methodological analysis of the science of biobanking and a sociological analysis of translational research in relation to biobanking. Part of global and local endeavours to translate raw biomedical evidence into practice, biobanks aim to provide a platform for generating new scientific knowledge to inform development of new policies, systems and interventions to enhance the public’s health. Effectively translating scientific knowledge into routine practice, however, involves more than good science. Although biobanks undoubtedly provide a fundamental resource for both clinical and public health practice, their potentiating ontology—that their outputs are perpetually a promise of scientific knowledge generation—renders translation rather less straightforward than drug discovery and treatment implementation. Biobanking science, therefore, provides a perfect counterpoint against which to test the bounds of translational research. We argue that translational research is a contextual and cumulative process: one that is necessarily dynamic and interactive and involves multiple actors. We propose a new multidimensional model of translational research which enables us to imagine a new paradigm: one that takes us from bench to bedside to backyard and beyond, that is, attentive to the social and political context of translational science, and is cognisant of all the players in that process be they researchers, health professionals, policy makers, industry representatives, members of the public or research participants, amongst others.
doi:10.1007/s00439-011-1036-3
PMCID: PMC3155676  PMID: 21706184
8.  A Comprehensive Evaluation of Potential Lung Function Associated Genes in the SpiroMeta General Population Sample 
PLoS ONE  2011;6(5):e19382.
Rationale
Lung function measures are heritable traits that predict population morbidity and mortality and are essential for the diagnosis of chronic obstructive pulmonary disease (COPD). Variations in many genes have been reported to affect these traits, but attempts at replication have provided conflicting results. Recently, we undertook a meta-analysis of Genome Wide Association Study (GWAS) results for lung function measures in 20,288 individuals from the general population (the SpiroMeta consortium).
Objectives
To comprehensively analyse previously reported genetic associations with lung function measures, and to investigate whether single nucleotide polymorphisms (SNPs) in these genomic regions are associated with lung function in a large population sample.
Methods
We analysed association for SNPs tagging 130 genes and 48 intergenic regions (+/−10 kb), after conducting a systematic review of the literature in the PubMed database for genetic association studies reporting lung function associations.
Results
The analysis included 16,936 genotyped and imputed SNPs. No loci showed overall significant association for FEV1 or FEV1/FVC traits using a carefully defined significance threshold of 1.3×10−5. The most significant loci associated with FEV1 include SNPs tagging MACROD2 (P = 6.81×10−5), CNTN5 (P = 4.37×10−4), and TRPV4 (P = 1.58×10−3). Among ever-smokers, SERPINA1 showed the most significant association with FEV1 (P = 8.41×10−5), followed by PDE4D (P = 1.22×10−4). The strongest association with FEV1/FVC ratio was observed with ABCC1 (P = 4.38×10−4), and ESR1 (P = 5.42×10−4) among ever-smokers.
Conclusions
Polymorphisms spanning previously associated lung function genes did not show strong evidence for association with lung function measures in the SpiroMeta consortium population. Common SERPINA1 polymorphisms may affect FEV1 among smokers in the general population.
doi:10.1371/journal.pone.0019382
PMCID: PMC3098839  PMID: 21625484
9.  Quality, quantity and harmony: the DataSHaPER approach to integrating data across bioclinical studies 
Background Vast sample sizes are often essential in the quest to disentangle the complex interplay of the genetic, lifestyle, environmental and social factors that determine the aetiology and progression of chronic diseases. The pooling of information between studies is therefore of central importance to contemporary bioscience. However, there are many technical, ethico-legal and scientific challenges to be overcome if an effective, valid, pooled analysis is to be achieved. Perhaps most critically, any data that are to be analysed in this way must be adequately ‘harmonized’. This implies that the collection and recording of information and data must be done in a manner that is sufficiently similar in the different studies to allow valid synthesis to take place.
Methods This conceptual article describes the origins, purpose and scientific foundations of the DataSHaPER (DataSchema and Harmonization Platform for Epidemiological Research; http://www.datashaper.org), which has been created by a multidisciplinary consortium of experts that was pulled together and coordinated by three international organizations: P3G (Public Population Project in Genomics), PHOEBE (Promoting Harmonization of Epidemiological Biobanks in Europe) and CPT (Canadian Partnership for Tomorrow Project).
Results The DataSHaPER provides a flexible, structured approach to the harmonization and pooling of information between studies. Its two primary components, the ‘DataSchema’ and ‘Harmonization Platforms’, together support the preparation of effective data-collection protocols and provide a central reference to facilitate harmonization. The DataSHaPER supports both ‘prospective’ and ‘retrospective’ harmonization.
Conclusion It is hoped that this article will encourage readers to investigate the project further: the more the research groups and studies are actively involved, the more effective the DataSHaPER programme will ultimately be.
doi:10.1093/ije/dyq139
PMCID: PMC2972444  PMID: 20813861
Data synthesis; data quality; data pooling; harmonization; meta-analysis; DataSHaPER; prospective harmonization; retrospective harmonization
10.  DataSHIELD: resolving a conflict in contemporary bioscience—performing a pooled analysis of individual-level data without sharing the data 
Background Contemporary bioscience sometimes demands vast sample sizes and there is often then no choice but to synthesize data across several studies and to undertake an appropriate pooled analysis. This same need is also faced in health-services and socio-economic research. When a pooled analysis is required, analytic efficiency and flexibility are often best served by combining the individual-level data from all sources and analysing them as a single large data set. But ethico-legal constraints, including the wording of consent forms and privacy legislation, often prohibit or discourage the sharing of individual-level data, particularly across national or other jurisdictional boundaries. This leads to a fundamental conflict in competing public goods: individual-level analysis is desirable from a scientific perspective, but is prevented by ethico-legal considerations that are entirely valid.
Methods Data aggregation through anonymous summary-statistics from harmonized individual-level databases (DataSHIELD), provides a simple approach to analysing pooled data that circumvents this conflict. This is achieved via parallelized analysis and modern distributed computing and, in one key setting, takes advantage of the properties of the updating algorithm for generalized linear models (GLMs).
Results The conceptual use of DataSHIELD is illustrated in two different settings.
Conclusions As the study of the aetiological architecture of chronic diseases advances to encompass more complex causal pathways—e.g. to include the joint effects of genes, lifestyle and environment—sample size requirements will increase further and the analysis of pooled individual-level data will become ever more important. An aim of this conceptual article is to encourage others to address the challenges and opportunities that DataSHIELD presents, and to explore potential extensions, for example to its use when different data sources hold different data on the same individuals.
doi:10.1093/ije/dyq111
PMCID: PMC2972441  PMID: 20630989
Pooling; analysis; meta-analysis; individual-level; study-level; generalized linear model; GLM; ethico-legal; ELSI; identification; disclosure; distributed computing; bioinformatics; information technology; IT
11.  Genome-wide association study identifies five loci associated with lung function 
Repapi, Emmanouela | Sayers, Ian | Wain, Louise V | Burton, Paul R | Johnson, Toby | Obeidat, Ma’en | Zhao, Jing Hua | Ramasamy, Adaikalavan | Zhai, Guangju | Vitart, Veronique | Huffman, Jennifer E | Igl, Wilmar | Albrecht, Eva | Deloukas, Panos | Henderson, John | Granell, Raquel | McArdle, Wendy L | Rudnicka, Alicja R | Barroso, Inês | Loos, Ruth J F | Wareham, Nicholas J | Mustelin, Linda | Rantanen, Taina | Surakka, Ida | Imboden, Medea | Wichmann, H Erich | Grkovic, Ivica | Jankovic, Stipan | Zgaga, Lina | Hartikainen, Anna-Liisa | Peltonen, Leena | Gyllensten, Ulf | Johansson, Åsa | Zaboli, Ghazal | Campbell, Harry | Wild, Sarah H | Wilson, James F | Gläser, Sven | Homuth, Georg | Völzke, Henry | Mangino, Massimo | Soranzo, Nicole | Spector, Tim D | Polašek, Ozren | Rudan, Igor | Wright, Alan F | Heliövaara, Markku | Ripatti, Samuli | Pouta, Anneli | Naluai, Åsa Torinsson | Olin, Anna-Carin | Torén, Kjell | Cooper, Matthew N | James, Alan L | Palmer, Lyle J | Hingorani, Aroon D | Wannamethee, S Goya | Whincup, Peter H | Smith, George Davey | Ebrahim, Shah | McKeever, Tricia M | Pavord, Ian D | MacLeod, Andrew K | Morris, Andrew D | Porteous, David J | Cooper, Cyrus | Dennison, Elaine | Shaheen, Seif | Karrasch, Stefan | Schnabel, Eva | Schulz, Holger | Grallert, Harald | Bouatia-Naji, Nabila | Delplanque, Jérôme | Froguel, Philippe | Blakey, John D | Britton, John R | Morris, Richard W | Holloway, John W | Lawlor, Debbie A | Hui, Jennie | Nyberg, Fredrik | Jarvelin, Marjo-Riitta | Jackson, Cathy | Kähönen, Mika | Kaprio, Jaakko | Probst-Hensch, Nicole M | Koch, Beate | Hayward, Caroline | Evans, David M | Elliott, Paul | Strachan, David P | Hall, Ian P | Tobin, Martin D
Nature genetics  2009;42(1):36-44.
Pulmonary function measures are heritable traits that predict morbidity and mortality and define chronic obstructive pulmonary disease (COPD). We tested genome-wide association with forced expiratory volume in 1 s (FEV1) and the ratio of FEV1 to forced vital capacity (FVC) in the SpiroMeta consortium (n = 20,288 individuals of European ancestry). We conducted a meta-analysis of top signals with data from direct genotyping (n ≤ 32,184 additional individuals) and in silico summary association data from the CHARGE Consortium (n = 21,209) and the Health 2000 survey (n ≤ 883). We confirmed the reported locus at 4q31 and identified associations with FEV1 or FEV1/FVC and common variants at five additional loci: 2q35 in TNS1 (P = 1.11 × 10−12), 4q24 in GSTCD (2.18 × 10−23), 5q33 in HTR4 (P = 4.29 × 10−9), 6p21 in AGER (P = 3.07 × 10−15) and 15q23 in THSD4 (P = 7.24 × 10−15). mRNA analyses showed expression of TNS1, GSTCD, AGER, HTR4 and THSD4 in human lung tissue. These associations offer mechanistic insight into pulmonary function regulation and indicate potential targets for interventions to alleviate respiratory disease.
doi:10.1038/ng.501
PMCID: PMC2862965  PMID: 20010834
12.  Genome-Wide Association Studies, Field Synopses, and the Development of the Knowledge Base on Genetic Variation and Human Diseases 
American Journal of Epidemiology  2009;170(3):269-279.
Genome-wide association studies (GWAS) have led to a rapid increase in available data on common genetic variants and phenotypes and numerous discoveries of new loci associated with susceptibility to common complex diseases. Integrating the evidence from GWAS and candidate gene studies depends on concerted efforts in data production, online publication, database development, and continuously updated data synthesis. Here the authors summarize current experience and challenges on these fronts, which were discussed at a 2008 multidisciplinary workshop sponsored by the Human Genome Epidemiology Network. Comprehensive field synopses that integrate many reported gene-disease associations have been systematically developed for several fields, including Alzheimer's disease, schizophrenia, bladder cancer, coronary heart disease, preterm birth, and DNA repair genes in various cancers. The authors summarize insights from these field synopses and discuss remaining unresolved issues—especially in the light of evidence from GWAS, for which they summarize empirical P-value and effect-size data on 223 discovered associations for binary outcomes (142 with P < 10−7). They also present a vision of collaboration that builds reliable cumulative evidence for genetic associations with common complex diseases and a transparent, distributed, authoritative knowledge base on genetic variation and human health. As a next step in the evolution of Human Genome Epidemiology reviews, the authors invite investigators to submit field synopses for possible publication in the American Journal of Epidemiology.
doi:10.1093/aje/kwp119
PMCID: PMC2714948  PMID: 19498075
association; database; encyclopedias; epidemiologic methods; genome, human; genome-wide association study; genomics; meta-analysis
13.  Size matters: just how big is BIG? 
Background Despite earlier doubts, a string of recent successes indicates that if sample sizes are large enough, it is possible—both in theory and in practice—to identify and replicate genetic associations with common complex diseases. But human genome epidemiology is expensive and, from a strategic perspective, it is still unclear what ‘large enough’ really means. This question has critical implications for governments, funding agencies, bioscientists and the tax-paying public. Difficult strategic decisions with imposing price tags and important opportunity costs must be taken.
Methods Conventional power calculations for case–control studies disregard many basic elements of analytic complexity—e.g. errors in clinical assessment, and the impact of unmeasured aetiological determinants—and can seriously underestimate true sample size requirements. This article describes, and applies, a rigorous simulation-based approach to power calculation that deals more comprehensively with analytic complexity and has been implemented on the web as ESPRESSO: (www.p3gobservatory.org/powercalculator.htm).
Results Using this approach, the article explores the realistic power profile of stand-alone and nested case–control studies in a variety of settings and provides a robust quantitative foundation for determining the required sample size both of individual biobanks and of large disease-based consortia. Despite universal acknowledgment of the importance of large sample sizes, our results suggest that contemporary initiatives are still, at best, at the lower end of the range of desirable sample size. Insufficient power remains particularly problematic for studies exploring gene–gene or gene–environment interactions.
Discussion Sample size calculation must be both accurate and realistic, and we must continue to strengthen national and international cooperation in the design, conduct, harmonization and integration of studies in human genome epidemiology.
doi:10.1093/ije/dyn147
PMCID: PMC2639365  PMID: 18676414
Human genome epidemiology; biobank; sample size; statistical power; simulation studies; measurement error; reliability; aetiological heterogeneity
14.  Mendelian Randomisation and Causal Inference in Observational Epidemiology 
PLoS Medicine  2008;5(8):e177.
Nuala Sheehan and colleagues describe how Mendelian randomization provides an alternative way of dealing with the problems of observational studies, especially confounding.
doi:10.1371/journal.pmed.0050177
PMCID: PMC2522255  PMID: 18752343
15.  Genome-wide linkage analysis of longitudinal phenotypes using σ2A random effects (SSARs) fitted by Gibbs sampling 
BMC Genetics  2003;4(Suppl 1):S12.
The study of change in intermediate phenotypes over time is important in genetics. In this paper we explore a new approach to phenotype definition in the genetic analysis of longitudinal phenotypes. We utilized data from the longitudinal Framingham Heart Study Family Cohort to investigate the familial aggregation and evidence for linkage to change in systolic blood pressure (SBP) over time. We used Gibbs sampling to derive sigma-squared-A-random-effects (SSARs) for the longitudinal phenotype, and then used these as a new phenotype in subsequent genome-wide linkage analyses.
Additive genetic effects (σ2A.time) were estimated to account for ~9.2% of the variance in the rate of change of SBP with age, while additive genetic effects (σ2A) were estimated to account for ~43.9% of the variance in SBP at the mean age. The linkage results suggested that one or more major loci regulating change in SBP over time may localize to chromosomes 2, 3, 4, 6, 10, 11, 17, and 19. The results also suggested that one or more major loci regulating level of SBP may localize to chromosomes 3, 8, and 14.
Our results support a genetic component to both SBP and change in SBP with age, and are consistent with a complex, multifactorial susceptibility to the development of hypertension. The use of SSARs derived from quantitative traits as input to a conventional linkage analysis appears to be valuable in the linkage analysis of genetically complex traits. We have now demonstrated in this paper the use of SSARs in the context of longitudinal family data.
doi:10.1186/1471-2156-4-S1-S12
PMCID: PMC1866446  PMID: 14975080
16.  Longitudinal variance components models for systolic blood pressure, fitted using Gibbs sampling 
BMC Genetics  2003;4(Suppl 1):S25.
This paper describes an analysis of systolic blood pressure (SBP) in the Genetic Analysis Workshop 13 (GAW13) simulated data. The main aim was to assess evidence for both general and specific genetic effects on the baseline blood pressure and on the rate of change (slope) of blood pressure with time. Generalized linear mixed models were fitted using Gibbs sampling in WinBUGS, and the additive polygenic random effects estimated using these models were then used as continuous phenotypes in a variance components linkage analysis. The first-stage analysis provided evidence for general genetic effects on both the baseline and slope of blood pressure, and the linkage analysis found evidence of several genes, again for both baseline and slope.
doi:10.1186/1471-2156-4-S1-S25
PMCID: PMC1866460  PMID: 14975093
17.  Intrapartum risk factors for newborn encephalopathy: the Western Australian case-control study 
BMJ : British Medical Journal  1998;317(7172):1554-1558.
Objective
To identify intrapartum predictors of newborn encephalopathy in term infants.
Design
Population based, unmatched case-control study.
Setting
Metropolitan area of Western Australia, June 1993 to September 1995.
Subjects
All 164 term infants with moderate or severe newborn encephalopathy; 400 randomly selected controls.
Main outcome measures
Adjusted odds ratio estimates.
Results
The birth prevalence of moderate or severe newborn encephalopathy was 3.8/1000 term live births. The neonatal fatality was 9.1%. Maternal pyrexia (odds ratio 3.82), a persistent occipitoposterior position (4.29), and an acute intrapartum event (4.44) were all risk factors for newborn encephalopathy. More case infants than control infants were induced (41.5% and 30.5%, respectively) and fewer case infants were delivered by caesarean section without labour (3.7% and 14.5%, respectively). Operative vaginal delivery (2.34) and emergency caesarean section (2.17) were both associated with an increased risk. There was an inverse relation between elective caesarean section (0.17) and newborn encephalopathy. After application of a set of consensus criteria for elective caesarean section only three (7%) eligible case mothers compared with 33 (65%) eligible control mothers were sectioned electively. Of all the case infants, 113 (69%) had only antepartum risk factors for newborn encephalopathy identified; 39 (24%) had antepartum and intrapartum factors; eight (5%) had only intrapartum factors; and four (2%) had no recognised antepartum or intrapartum factors.
Conclusions
The causes of newborn encephalopathy are heterogeneous and many relate to the antepartum period. Elective caesarean section has an inverse association with newborn encephalopathy. Intrapartum hypoxia alone accounts for only a small proportion of newborn encephalopathy. These results question the view that most risk factors for newborn encephalopathy lie in the intrapartum period.
Key messagesIntrapartum risk factors for newborn encephalopathy include maternal pyrexia, persistent occipitoposterior position, and acute intrapartum eventsOperative vaginal delivery and emergency caesarean section were both associated with an increased risk whereas there was an inverse relation with elective caesarean sectionThere was no evidence of intrapartum hypoxia in over 70% of cases of newborn encephalopathyThe causes of newborn encephalopathy are heterogeneous and many relate to the antepartum periodThese findings bring into question the view that most risk factors for newborn encephalopathy lie in the intrapartum period
PMCID: PMC28733  PMID: 9836653
18.  Antepartum risk factors for newborn encephalopathy: the Western Australian case-control study 
BMJ : British Medical Journal  1998;317(7172):1549-1553.
Objective
To ascertain antepartum predictors of newborn encephalopathy in term infants.
Design
Population based, unmatched case-control study.
Setting
Metropolitan area of Western Australia, June 1993 to September 1995.
Subjects
All 164 term infants with moderate or severe newborn encephalopathy; 400 randomly selected controls.
Main outcome measures
Adjusted odds ratio estimates.
Results
The birth prevalence of moderate or severe newborn encephalopathy was 3.8/1000 term live births. The neonatal fatality was 9.1%. The risk of newborn encephalopathy increased with increasing maternal age and decreased with increasing parity. There was an increased risk associated with having a mother who was unemployed (odds ratio 3.60), an unskilled manual worker (3.84), or a housewife (2.48). Other risk factors from before conception were not having private health insurance (3.46), a family history of seizures (2.55), a family history of neurological disease (2.73), and infertility treatment (4.43). Risk factors during pregnancy were maternal thyroid disease (9.7), severe pre-eclampsia (6.30), moderate or severe bleeding (3.57), a clinically diagnosed viral illness (2.97), not having drunk alcohol (2.91); and placenta described at delivery as abnormal (2.07). Factors related to the baby were birth weight adjusted for gestational age between the third and ninth centile (4.37) or below the third centile (38.23). The risk relation with gestational age was J shaped with 38 and 39 weeks having the lowest risk.
Conclusions
The causes of newborn encephalopathy are heterogeneous and many of the causal pathways start before birth.
Key messagesThe birth prevalence of moderate or severe newborn encephalopathy was 3.8 per 1000 term live births and the neonatal case fatality was 9.1%Independent risk factors before conception and in the antepartum period for newborn encephalopathy include socioeconomic status, family history of seizures or other neurological disease, conception after infertility treatment, maternal thyroid disease, severe pre-eclampsia, bleeding in pregnancy, viral illness, having an abnormal placenta, intrauterine growth restriction, and postmaturityThe causes of newborn encephalopathy are heterogeneous and many causal pathways start in the antepartum period
PMCID: PMC28732  PMID: 9836652
19.  Isolation and Characterization of Two Cell Types of Coxiella burneti Phase I 
Journal of Bacteriology  1972;110(1):368-377.
Two morphologically distinct cell types of Coxiella burneti phase I have been separated on the basis of unique buoyant densities. When centrifuged to equilibrium in cesium chloride or density gradients of sucrose or Renografin, the cells band in two zones. Electron micrographs of ultrathin sections of the two cesium chloride-separated cell types indicate a considerable number of morphological differences. The lower-density cells are small, compact, and rodshaped and have very dense nucleoids. The cell type of highest density is larger, rounded, and more pleomorphic, and the nucleoid filaments are more dispersed. The two cell types are nearly identical in sedimentation rates, and both infect chick yolk sac cells and are lethal to chick embryos. They convert to a mixture of cell types when cultured separately. Treatment with Formalin induces all cells to band at the same position when centrifuged to equilibrium in cesium chloride. The cell type variance was found to be independent of the antigenic phase phenomenon of C. burneti.
Images
PMCID: PMC247420  PMID: 5018025
21.  FINE STRUCTURE AND REPLICATION OF THE KINETOPLAST OF TRYPANOSOMA LEWISI 
The Journal of Cell Biology  1968;39(2):318-331.
The kinetoplastic DNA of Trypanosoma lewisi is described as a filamentous body lying within a mitochondrion, with the filaments oriented parallel to the long axis of the cell. The manner of fixation, the replicative state, and perhaps the physiological state of the cell, may result in slight morphological differences among such bodies. The kinetoplastic DNA replicates to form "left" and "right" rather than "upper" and "lower" members, and both the kinetoplast and nucleus incorporate radiothymidine as shown by radioautography. Radioautographic analyses suggest a random incorporation of radiothymidine by kinetoplasts. Silver grains were occasionally observed over centriolar elements. Finally, the observations are discussed with respect to the sequential replication of the aforementioned organelles by T. lewisi.
PMCID: PMC2107538  PMID: 5677967
22.  Variants near TERC are associated with mean telomere length. 
Nature genetics  2010;42(3):197-199.
We conducted genome-wide association analyses of mean leukocyte telomere length in 2,917 subjects and follow-up replication analyses in 9,492 and identified a locus on 3q26 encompassing the telomerase RNA component TERC, with compelling evidence for association (rs12696304, combined P value 3.72×10−14). Each copy of the minor allele of rs12696304 was associated with ≈75 base pairs shorter mean telomere length equivalent to ≈3.6 years of age-related attrition of mean telomere length.
doi:10.1038/ng.532
PMCID: PMC3773906  PMID: 20139977
23.  Large-Scale Candidate Gene Analysis of HDL Particle Features 
PLoS ONE  2011;6(1):e14529.
Background
HDL cholesterol (HDL-C) is an established marker of cardiovascular risk with significant genetic determination. However, HDL particles are not homogenous, and refined HDL phenotyping may improve insight into regulation of HDL metabolism. We therefore assessed HDL particles by NMR spectroscopy and conducted a large-scale candidate gene association analysis.
Methodology/Principal Findings
We measured plasma HDL-C and determined mean HDL particle size and particle number by NMR spectroscopy in 2024 individuals from 512 British Caucasian families. Genotypes were 49,094 SNPs in >2,100 cardiometabolic candidate genes/loci as represented on the HumanCVD BeadChip version 2. False discovery rates (FDR) were calculated to account for multiple testing. Analyses on classical HDL-C revealed significant associations (FDR<0.05) only for CETP (cholesteryl ester transfer protein; lead SNP rs3764261: p = 5.6*10−15) and SGCD (sarcoglycan delta; rs6877118: p = 8.6*10−6). In contrast, analysis with HDL mean particle size yielded additional associations in LIPC (hepatic lipase; rs261332: p = 6.1*10−9), PLTP (phospholipid transfer protein, rs4810479: p = 1.7*10−8) and FBLN5 (fibulin-5; rs2246416: p = 6.2*10−6). The associations of SGCD and Fibulin-5 with HDL particle size could not be replicated in PROCARDIS (n = 3,078) and/or the Women's Genome Health Study (n = 23,170).
Conclusions
We show that refined HDL phenotyping by NMR spectroscopy can detect known genes of HDL metabolism better than analyses on HDL-C.
doi:10.1371/journal.pone.0014529
PMCID: PMC3024972  PMID: 21283740
24.  Eight blood pressure loci identified by genome-wide association study of 34,433 people of European ancestry 
Newton-Cheh, Christopher | Johnson, Toby | Gateva, Vesela | Tobin, Martin D | Bochud, Murielle | Coin, Lachlan | Najjar, Samer S | Zhao, Jing Hua | Heath, Simon C | Eyheramendy, Susana | Papadakis, Konstantinos | Voight, Benjamin F | Scott, Laura J | Zhang, Feng | Farrall, Martin | Tanaka, Toshiko | Wallace, Chris | Chambers, John C | Khaw, Kay-Tee | Nilsson, Peter | van der Harst, Pim | Polidoro, Silvia | Grobbee, Diederick E | Onland-Moret, N Charlotte | Bots, Michiel L | Wain, Louise V | Elliott, Katherine S | Teumer, Alexander | Luan, Jian’an | Lucas, Gavin | Kuusisto, Johanna | Burton, Paul R | Hadley, David | McArdle, Wendy L | Brown, Morris | Dominiczak, Anna | Newhouse, Stephen J | Samani, Nilesh J | Webster, John | Zeggini, Eleftheria | Beckmann, Jacques S | Bergmann, Sven | Lim, Noha | Song, Kijoung | Vollenweider, Peter | Waeber, Gerard | Waterworth, Dawn M | Yuan, Xin | Groop, Leif | Orho-Melander, Marju | Allione, Alessandra | Di Gregorio, Alessandra | Guarrera, Simonetta | Panico, Salvatore | Ricceri, Fulvio | Romanazzi, Valeria | Sacerdote, Carlotta | Vineis, Paolo | Barroso, Inês | Sandhu, Manjinder S | Luben, Robert N | Crawford, Gabriel J. | Jousilahti, Pekka | Perola, Markus | Boehnke, Michael | Bonnycastle, Lori L | Collins, Francis S | Jackson, Anne U | Mohlke, Karen L | Stringham, Heather M | Valle, Timo T | Willer, Cristen J | Bergman, Richard N | Morken, Mario A | Döring, Angela | Gieger, Christian | Illig, Thomas | Meitinger, Thomas | Org, Elin | Pfeufer, Arne | Wichmann, H Erich | Kathiresan, Sekar | Marrugat, Jaume | O’Donnell, Christopher J | Schwartz, Stephen M | Siscovick, David S | Subirana, Isaac | Freimer, Nelson B | Hartikainen, Anna-Liisa | McCarthy, Mark I | O’Reilly, Paul F | Peltonen, Leena | Pouta, Anneli | de Jong, Paul E | Snieder, Harold | van Gilst, Wiek H | Clarke, Robert | Goel, Anuj | Hamsten, Anders | Peden, John F | Seedorf, Udo | Syvänen, Ann-Christine | Tognoni, Giovanni | Lakatta, Edward G | Sanna, Serena | Scheet, Paul | Schlessinger, David | Scuteri, Angelo | Dörr, Marcus | Ernst, Florian | Felix, Stephan B | Homuth, Georg | Lorbeer, Roberto | Reffelmann, Thorsten | Rettig, Rainer | Völker, Uwe | Galan, Pilar | Gut, Ivo G | Hercberg, Serge | Lathrop, G Mark | Zeleneka, Diana | Deloukas, Panos | Soranzo, Nicole | Williams, Frances M | Zhai, Guangju | Salomaa, Veikko | Laakso, Markku | Elosua, Roberto | Forouhi, Nita G | Völzke, Henry | Uiterwaal, Cuno S | van der Schouw, Yvonne T | Numans, Mattijs E | Matullo, Giuseppe | Navis, Gerjan | Berglund, Göran | Bingham, Sheila A | Kooner, Jaspal S | Paterson, Andrew D | Connell, John M | Bandinelli, Stefania | Ferrucci, Luigi | Watkins, Hugh | Spector, Tim D | Tuomilehto, Jaakko | Altshuler, David | Strachan, David P | Laan, Maris | Meneton, Pierre | Wareham, Nicholas J | Uda, Manuela | Jarvelin, Marjo-Riitta | Mooser, Vincent | Melander, Olle | Loos, Ruth JF | Elliott, Paul | Abecasis, Goncalo R | Caulfield, Mark | Munroe, Patricia B
Nature genetics  2009;41(6):666-676.
Elevated blood pressure is a common, heritable cause of cardiovascular disease worldwide. To date, identification of common genetic variants influencing blood pressure has proven challenging. We tested 2.5m genotyped and imputed SNPs for association with systolic and diastolic blood pressure in 34,433 subjects of European ancestry from the Global BPgen consortium and followed up findings with direct genotyping (N≤71,225 European ancestry, N=12,889 Indian Asian ancestry) and in silico comparison (CHARGE consortium, N=29,136). We identified association between systolic or diastolic blood pressure and common variants in 8 regions near the CYP17A1 (P=7×10−24), CYP1A2 (P=1×10−23), FGF5 (P=1×10−21), SH2B3 (P=3×10−18), MTHFR (P=2×10−13), c10orf107 (P=1×10−9), ZNF652 (P=5×10−9) and PLCD3 (P=1×10−8) genes. All variants associated with continuous blood pressure were associated with dichotomous hypertension. These associations between common variants and blood pressure and hypertension offer mechanistic insights into the regulation of blood pressure and may point to novel targets for interventions to prevent cardiovascular disease.
doi:10.1038/ng.361
PMCID: PMC2891673  PMID: 19430483

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