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2.  Genetic risk for autism spectrum disorders and neuropsychiatric variation in the general population 
Nature genetics  2016;48(5):552-555.
Almost all genetic risk factors for autism spectrum disorders (ASDs) can be found in the general population, but the effects of that risk are unclear in people not ascertained for neuropsychiatric symptoms. Using several large ASD consortia and population based resources (total n>38,000), we find genomewide genetic links between ASDs and typical variation in social behavior and adaptive functioning. This finding is evidenced through both LD score correlation and de novo variant analysis, indicating that multiple types of genetic risk for ASDs influence a continuum of behavioral and developmental traits, the severe tail of which can result in an ASD or other neuropsychiatric disorder diagnosis. A continuum model should inform the design and interpretation of studies of neuropsychiatric disease biology.
doi:10.1038/ng.3529
PMCID: PMC4986048  PMID: 26998691
3.  Genome-wide association study of blood lead shows multiple associations near ALAD 
Human Molecular Genetics  2015;24(13):3871-3879.
Exposure to high levels of environmental lead, or biomarker evidence of high body lead content, is associated with anaemia, developmental and neurological deficits in children, and increased mortality in adults. Adverse effects of lead still occur despite substantial reduction in environmental exposure. There is genetic variation between individuals in blood lead concentration but the polymorphisms contributing to this have not been defined. We measured blood or erythrocyte lead content, and carried out genome-wide association analysis, on population-based cohorts of adult volunteers from Australia and UK (N = 5433). Samples from Australia were collected in two studies, in 1993–1996 and 2002–2005 and from UK in 1991–1992. One locus, at ALAD on chromosome 9, showed consistent association with blood lead across countries and evidence for multiple independent allelic effects. The most significant single nucleotide polymorphism (SNP), rs1805313 (P = 3.91 × 10−14 for lead concentration in a meta-analysis of all data), is known to have effects on ALAD expression in blood cells but other SNPs affecting ALAD expression did not affect blood lead. Variants at 12 other loci, including ABO, showed suggestive associations (5 × 10−6 > P > 5 × 10−8). Identification of genetic polymorphisms affecting blood lead reinforces the view that genetic factors, as well as environmental ones, are important in determining blood lead levels. The ways in which ALAD variation affects lead uptake or distribution are still to be determined.
doi:10.1093/hmg/ddv112
PMCID: PMC4459389  PMID: 25820613
4.  Meta-analysis of genome-wide association studies identifies 10 loci influencing allergic sensitization 
Nature genetics  2013;45(8):902-906.
Allergen-specific IgE (allergic sensitization) plays a central role in the pathogenesis of allergic disease. We performed the first large-scale genome wide association study (GWAS) of allergic sensitization in 5,789 affected individuals and 10,056 controls and followed up the top SNP from 26 loci in 6,114 affected individuals and 9,920 controls. We increased the number of susceptibility loci with genome-wide significant association to allergic sensitization from three to 10, including SNPs in or near TLR6, C11orf30, STAT6, SLC25A46, HLA-DQB1, IL1RL1, LPP, MYC, IL2 and HLA-B. All the top-SNPs were associated with allergic symptoms in an independent study. Risk variants at these 10 loci were estimated to account for at least 25% of allergic sensitization and allergic rhinitis. Understanding the molecular mechanisms underlying these associations may provide novel insight into the etiology of allergic disease.
doi:10.1038/ng.2694
PMCID: PMC4922420  PMID: 23817571
5.  Meta-analysis of gene–environment-wide association scans accounting for education level identifies additional loci for refractive error 
Fan, Qiao | Verhoeven, Virginie J. M. | Wojciechowski, Robert | Barathi, Veluchamy A. | Hysi, Pirro G. | Guggenheim, Jeremy A. | Höhn, René | Vitart, Veronique | Khawaja, Anthony P. | Yamashiro, Kenji | Hosseini, S Mohsen | Lehtimäki, Terho | Lu, Yi | Haller, Toomas | Xie, Jing | Delcourt, Cécile | Pirastu, Mario | Wedenoja, Juho | Gharahkhani, Puya | Venturini, Cristina | Miyake, Masahiro | Hewitt, Alex W. | Guo, Xiaobo | Mazur, Johanna | Huffman, Jenifer E. | Williams, Katie M. | Polasek, Ozren | Campbell, Harry | Rudan, Igor | Vatavuk, Zoran | Wilson, James F. | Joshi, Peter K. | McMahon, George | St Pourcain, Beate | Evans, David M. | Simpson, Claire L. | Schwantes-An, Tae-Hwi | Igo, Robert P. | Mirshahi, Alireza | Cougnard-Gregoire, Audrey | Bellenguez, Céline | Blettner, Maria | Raitakari, Olli | Kähönen, Mika | Seppala, Ilkka | Zeller, Tanja | Meitinger, Thomas | Ried, Janina S. | Gieger, Christian | Portas, Laura | van Leeuwen, Elisabeth M. | Amin, Najaf | Uitterlinden, André G. | Rivadeneira, Fernando | Hofman, Albert | Vingerling, Johannes R. | Wang, Ya Xing | Wang, Xu | Tai-Hui Boh, Eileen | Ikram, M. Kamran | Sabanayagam, Charumathi | Gupta, Preeti | Tan, Vincent | Zhou, Lei | Ho, Candice E. H. | Lim, Wan'e | Beuerman, Roger W. | Siantar, Rosalynn | Tai, E-Shyong | Vithana, Eranga | Mihailov, Evelin | Khor, Chiea-Chuen | Hayward, Caroline | Luben, Robert N. | Foster, Paul J. | Klein, Barbara E. K. | Klein, Ronald | Wong, Hoi-Suen | Mitchell, Paul | Metspalu, Andres | Aung, Tin | Young, Terri L. | He, Mingguang | Pärssinen, Olavi | van Duijn, Cornelia M. | Jin Wang, Jie | Williams, Cathy | Jonas, Jost B. | Teo, Yik-Ying | Mackey, David A. | Oexle, Konrad | Yoshimura, Nagahisa | Paterson, Andrew D. | Pfeiffer, Norbert | Wong, Tien-Yin | Baird, Paul N. | Stambolian, Dwight | Wilson, Joan E. Bailey | Cheng, Ching-Yu | Hammond, Christopher J. | Klaver, Caroline C. W. | Saw, Seang-Mei | Rahi, Jugnoo S. | Korobelnik, Jean-François | Kemp, John P. | Timpson, Nicholas J. | Smith, George Davey | Craig, Jamie E. | Burdon, Kathryn P. | Fogarty, Rhys D. | Iyengar, Sudha K. | Chew, Emily | Janmahasatian, Sarayut | Martin, Nicholas G. | MacGregor, Stuart | Xu, Liang | Schache, Maria | Nangia, Vinay | Panda-Jonas, Songhomitra | Wright, Alan F. | Fondran, Jeremy R. | Lass, Jonathan H. | Feng, Sheng | Zhao, Jing Hua | Khaw, Kay-Tee | Wareham, Nick J. | Rantanen, Taina | Kaprio, Jaakko | Pang, Chi Pui | Chen, Li Jia | Tam, Pancy O. | Jhanji, Vishal | Young, Alvin L. | Döring, Angela | Raffel, Leslie J. | Cotch, Mary-Frances | Li, Xiaohui | Yip, Shea Ping | Yap, Maurice K.H. | Biino, Ginevra | Vaccargiu, Simona | Fossarello, Maurizio | Fleck, Brian | Yazar, Seyhan | Tideman, Jan Willem L. | Tedja, Milly | Deangelis, Margaret M. | Morrison, Margaux | Farrer, Lindsay | Zhou, Xiangtian | Chen, Wei | Mizuki, Nobuhisa | Meguro, Akira | Mäkelä, Kari Matti
Nature Communications  2016;7:11008.
Myopia is the most common human eye disorder and it results from complex genetic and environmental causes. The rapidly increasing prevalence of myopia poses a major public health challenge. Here, the CREAM consortium performs a joint meta-analysis to test single-nucleotide polymorphism (SNP) main effects and SNP × education interaction effects on refractive error in 40,036 adults from 25 studies of European ancestry and 10,315 adults from 9 studies of Asian ancestry. In European ancestry individuals, we identify six novel loci (FAM150B-ACP1, LINC00340, FBN1, DIS3L-MAP2K1, ARID2-SNAT1 and SLC14A2) associated with refractive error. In Asian populations, three genome-wide significant loci AREG, GABRR1 and PDE10A also exhibit strong interactions with education (P<8.5 × 10−5), whereas the interactions are less evident in Europeans. The discovery of these loci represents an important advance in understanding how gene and environment interactions contribute to the heterogeneity of myopia.
This report by the Consortium for Refractive Error and Myopia uses gene-environment-wide interaction study (GEWIS) to identify genetic loci that affect environmental influence in myopia development, and identifies ethnic specific genetic loci that attribute to eye refractive errors.
doi:10.1038/ncomms11008
PMCID: PMC4820539  PMID: 27020472
6.  Meta-analysis of Genome-Wide Association Studies for Extraversion: Findings from the Genetics of Personality Consortium 
van den Berg, Stéphanie M. | de Moor, Marleen H. M. | Verweij, Karin J. H. | Krueger, Robert F. | Luciano, Michelle | Arias Vasquez, Alejandro | Matteson, Lindsay K. | Derringer, Jaime | Esko, Tõnu | Amin, Najaf | Gordon, Scott D. | Hansell, Narelle K. | Hart, Amy B. | Seppälä, Ilkka | Huffman, Jennifer E. | Konte, Bettina | Lahti, Jari | Lee, Minyoung | Miller, Mike | Nutile, Teresa | Tanaka, Toshiko | Teumer, Alexander | Viktorin, Alexander | Wedenoja, Juho | Abdellaoui, Abdel | Abecasis, Goncalo R. | Adkins, Daniel E. | Agrawal, Arpana | Allik, Jüri | Appel, Katja | Bigdeli, Timothy B. | Busonero, Fabio | Campbell, Harry | Costa, Paul T. | Smith, George Davey | Davies, Gail | de Wit, Harriet | Ding, Jun | Engelhardt, Barbara E. | Eriksson, Johan G. | Fedko, Iryna O. | Ferrucci, Luigi | Franke, Barbara | Giegling, Ina | Grucza, Richard | Hartmann, Annette M. | Heath, Andrew C. | Heinonen, Kati | Henders, Anjali K. | Homuth, Georg | Hottenga, Jouke-Jan | Iacono, William G. | Janzing, Joost | Jokela, Markus | Karlsson, Robert | Kemp, John P. | Kirkpatrick, Matthew G. | Latvala, Antti | Lehtimäki, Terho | Liewald, David C. | Madden, Pamela A. F. | Magri, Chiara | Magnusson, Patrik K. E. | Marten, Jonathan | Maschio, Andrea | Mbarek, Hamdi | Medland, Sarah E. | Mihailov, Evelin | Milaneschi, Yuri | Montgomery, Grant W. | Nauck, Matthias | Nivard, Michel G. | Ouwens, Klaasjan G. | Palotie, Aarno | Pettersson, Erik | Polasek, Ozren | Qian, Yong | Pulkki-Råback, Laura | Raitakari, Olli T. | Realo, Anu | Rose, Richard J. | Ruggiero, Daniela | Schmidt, Carsten O. | Slutske, Wendy S. | Sorice, Rossella | Starr, John M. | St Pourcain, Beate | Sutin, Angelina R. | Timpson, Nicholas J. | Trochet, Holly | Vermeulen, Sita | Vuoksimaa, Eero | Widen, Elisabeth | Wouda, Jasper | Wright, Margaret J. | Zgaga, Lina | Porteous, David | Minelli, Alessandra | Palmer, Abraham A. | Rujescu, Dan | Ciullo, Marina | Hayward, Caroline | Rudan, Igor | Metspalu, Andres | Kaprio, Jaakko | Deary, Ian J. | Räikkönen, Katri | Wilson, James F. | Keltikangas-Järvinen, Liisa | Bierut, Laura J. | Hettema, John M. | Grabe, Hans J. | Penninx, Brenda W. J. H. | van Duijn, Cornelia M. | Evans, David M. | Schlessinger, David | Pedersen, Nancy L. | Terracciano, Antonio | McGue, Matt | Martin, Nicholas G. | Boomsma, Dorret I.
Behavior Genetics  2015;46:170-182.
Extraversion is a relatively stable and heritable personality trait associated with numerous psychosocial, lifestyle and health outcomes. Despite its substantial heritability, no genetic variants have been detected in previous genome-wide association (GWA) studies, which may be due to relatively small sample sizes of those studies. Here, we report on a large meta-analysis of GWA studies for extraversion in 63,030 subjects in 29 cohorts. Extraversion item data from multiple personality inventories were harmonized across inventories and cohorts. No genome-wide significant associations were found at the single nucleotide polymorphism (SNP) level but there was one significant hit at the gene level for a long non-coding RNA site (LOC101928162). Genome-wide complex trait analysis in two large cohorts showed that the additive variance explained by common SNPs was not significantly different from zero, but polygenic risk scores, weighted using linkage information, significantly predicted extraversion scores in an independent cohort. These results show that extraversion is a highly polygenic personality trait, with an architecture possibly different from other complex human traits, including other personality traits. Future studies are required to further determine which genetic variants, by what modes of gene action, constitute the heritable nature of extraversion.
Electronic supplementary material
The online version of this article (doi:10.1007/s10519-015-9735-5) contains supplementary material, which is available to authorized users.
doi:10.1007/s10519-015-9735-5
PMCID: PMC4751159  PMID: 26362575
Personality; Phenotype harmonization; Common genetic variants; Imputation; Polygenic risk
7.  Fractional exhaled nitric oxide in childhood is associated with 17q11.2-q12 and 17q12-q21 variants 
Background
The fractional concentration of nitric oxide in exhaled air (FeNO) is a biomarker of eosinophilic airway inflammation and associated with childhood asthma. Identification of common genetic variants associated with childhood FeNO may help to define biological mechanisms related to specific asthma phenotypes.
Objective
To identify genetic variants associated with childhood FeNO, and their relation with asthma.
Methods
FeNO was measured in children aged 5 to 15 years. In 14 genome-wide association (GWA) studies (N = 8,858), we examined the associations of ~2.5 million single nucleotide polymorphisms (SNPs) with FeNO. Subsequently, we assessed whether significant SNPs were expression quantitative trait loci (eQTLs) in genome-wide expression datasets of lymphoblastoid cell lines (N = 1,830), and were related with asthma in a previously published GWA dataset (cases: n=10,365; controls: n=16,110).
Results
We identified 3 SNPs associated with FeNO: rs3751972 in LYR motif containing 9 (LYRM9) (P = 1.97×10−10) and rs944722 in inducible nitric oxide synthase 2 (NOS2) (P = 1.28×10−9) both located at 17q11.2-q12, and rs8069176 near gasdermin B (GSDMB) (P = 1.88×10−8) at 17q12-q21. We found a cis eQTL for the transcript soluble galactoside-binding lectin 9 (LGALS9) that is in linkage disequilibrium with rs944722. Rs8069176 was associated with GSDMB and ORM1-like 3 (ORMDL3) expression. Rs8069176 at 17q12-q21, and not rs3751972 and rs944722 at 17q11.2-q12, were associated with physician-diagnosed asthma.
Conclusion
This study identified 3 variants associated with FeNO, explaining 0.95% of the variance. Identification of functional SNPs and haplotypes in these regions might provide novel insight in the regulation of FeNO. This study highlights that both shared and distinct genetic factors affect FeNO and childhood asthma.
doi:10.1016/j.jaci.2013.08.053
PMCID: PMC4334587  PMID: 24315451
airway inflammation; asthma phenotypes; biomarker; genetics; genome-wide association study
8.  Does Vitamin D Mediate the Protective Effects of Time Outdoors On Myopia? Findings From a Prospective Birth Cohort 
Purpose.
More time outdoors is associated with a lesser risk of myopia, but the underlying mechanism is unclear. We tested the hypothesis that 25-hydroxyvitamin D (vitamin D) mediates the protective effects of time outdoors against myopia.
Methods.
We analyzed data for children participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) population-based birth cohort: noncycloplegic autorefraction at age 7 to 15 years; maternal report of time outdoors at age 8 years and serum vitamin D2 and D3 at age 10 years. A survival analysis hazard ratio (HR) for incident myopia was calculated for children spending a high- versus low-time outdoors, before and after controlling for vitamin D level (N = 3677).
Results.
Total vitamin D and D3, but not D2, levels were higher in children who spent more time outdoors (mean [95% confidence interval (CI)] vitamin D in nmol/L: Total, 60.0 [59.4–60.6] vs. 56.9 [55.0–58.8], P = 0.001; D3, 55.4 [54.9–56.0] vs. 53.0 [51.3–54.9], P = 0.014; D2, 5.7 [5.5–5.8] vs. 5.4 [5.1–5.8], P = 0.23). In models including both time outdoors and sunlight-exposure–related vitamin D, there was no independent association between vitamin D and incident myopia (Total, HR = 0.83 [0.66–1.04], P = 0.11; D3, HR = 0.89 [0.72–1.10], P = 0.30), while time outdoors retained the same strong negative association with incident myopia as in unadjusted models (HR = 0.69 [0.55–0.86], P = 0.001).
Conclusions.
Total vitamin D and D3 were biomarkers for time spent outdoors, however there was no evidence they were independently associated with future myopia.
In a birth cohort with longitudinal refractive error covering ages 7 to 15 years, the evidence did not support the hypothesis that vitamin D mediated the protective effects of time spent outdoors against incident myopia. This suggests an alternative mechanism underlies time outdoors' protective effects.
doi:10.1167/iovs.14-15839
PMCID: PMC4280087  PMID: 25406278
myopia; refractive error; epidemiology; vitamin D; light levels
9.  Examination of the relationship between variation at 17q21 and childhood wheeze phenotypes 
Background
Genome-wide association studies have identified associations of genetic variants at 17q21 near ORMDL3 with childhood asthma.
Objectives
To find out whether associations in this region are specific to particular asthma phenotypes and specific to ORMDL3.
Methods
We examined associations between 244 independent single nucleotide polymorphisms (SNPs) plus 13 previously identified asthma-related SNPs in the region between 34 and 36 Mb on chromosome 17 and early wheezing phenotypes, doctor-diagnosed asthma and atopy at 7½ years, bronchial hyper-responsiveness and lung function at 8½ years in 7,045 children from the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort study. With this, cis expression quantitative trait loci (eQTL) signals for the same SNPs were assessed in 875 samples across genes in the same region.
Results
The strongest evidence for phenotypic association was seen for persistent wheezing (rs8076131 near ORMDL3, relative risk ratio (RRR) 1.60 (95% CI 1.40, 1.84), p=1.4×10−11, rs2305480 near GSDML 1.60; 1.39-1.83, p=1.5×10−11 and rs9303277 near IKZF3 1.57; 1.37-1.79, p=4.4×10−11). Similar, but less precisely estimated effects were seen for intermediate-onset wheeze, but there was little evidence of associations with other wheezing phenotypes. There was some evidence of associations with bronchial hyper responsiveness. SNPs across the whole region show strong evidence of association with differential levels of expression at GSDML, IKZF3 and MED24, as well as ORMDL3.
Conclusions
Associations of SNPs in the 17q21 locus are specific to asthma and to specific wheezing phenotypes, and are not explained by associations with intermediate phenotypes, such as atopy or lung function.
doi:10.1016/j.jaci.2012.09.021
PMCID: PMC4427593  PMID: 23154084
ALSPAC; wheezing phenotypes; chromosome 17; ORMDL3; gene expression
10.  Shared Genetic Influences Between Attention-Deficit/Hyperactivity Disorder (ADHD) Traits in Children and Clinical ADHD 
Objective
Twin studies and genome-wide complex trait analysis (GCTA) are not in agreement regarding heritability estimates for behavioral traits in children from the general population. This has sparked a debate on the possible difference in genetic architecture between behavioral traits and psychiatric disorders. In this study, we test whether polygenic risk scores associated with variation in attention-deficit/hyperactivity disorder (ADHD) trait levels in children from the general population predict ADHD diagnostic status and severity in an independent clinical sample.
Method
Single nucleotide polymorphisms (SNPs) with p < .5 from a genome-wide association study of ADHD traits in 4,546 children (mean age, 7 years 7 months) from the Avon Longitudinal Study of Parents and Children (ALSPAC; general population sample) were selected to calculate polygenic risk scores in 508 children with an ADHD diagnosis (independent clinical sample) and 5,081 control participants. Polygenic scores were tested for association with case-control status and severity of disorder in the clinical sample.
Results
Increased polygenic score for ADHD traits predicted ADHD case-control status (odds ratio = 1.17 [95% CI = 1.08–1.28], p = .0003), higher ADHD symptom severity (β = 0.29 [95% CI = 0.04–0.54], p = 0.02), and symptom domain severity in the clinical sample.
Conclusion
This study highlights the relevance of additive genetic variance in ADHD, and provides evidence that shared genetic factors contribute to both behavioral traits in the general population and psychiatric disorders at least in the case of ADHD.
doi:10.1016/j.jaac.2015.01.010
PMCID: PMC4382052  PMID: 25791149
attention-deficit/hyperactivity disorder (ADHD); polygenic risk scores; Avon Longitudinal Study of Parents and Children (ALSPAC); common variants; genetics
11.  Common variation near ROBO2 is associated with expressive vocabulary in infancy 
Nature communications  2014;5:4831.
Twin studies suggest that expressive vocabulary at ~24 months is modestly heritable. However, the genes influencing this early linguistic phenotype are unknown. Here we conduct a genome-wide screen and follow-up study of expressive vocabulary in toddlers of European descent from up to four studies of the EArly Genetics and Lifecourse Epidemiology (EAGLE) consortium, analysing an early (15-18 months, ‘one-word stage’, NTotal=8,889) and a later (24-30 months, ‘two-word stage’, NTotal=10,819) phase of language acquisition. For the early phase, one SNP (rs7642482) at 3p12.3 near ROBO2, encoding a conserved axon binding receptor, reaches the genome-wide significance level (p=1.3×10−8) in the combined sample. This association links language-related common genetic variation in the general population to a potential autism susceptibility locus and a linkage region for dyslexia, speech-sound disorder and reading. The contribution of common genetic influences is, although modest, supported by Genome-wide Complex Trait Analysis (meta-GCTA h215-18-months=0.13, meta-GCTA h224-30-months=0.14) and in concordance with additional twin analysis (5,733 pairs of European descent, h224-months=0.20).
doi:10.1038/ncomms5831
PMCID: PMC4175587  PMID: 25226531
12.  Assumption-free estimation of the genetic contribution to refractive error across childhood 
Molecular Vision  2015;21:621-632.
Purpose
Studies in relatives have generally yielded high heritability estimates for refractive error: twins 75–90%, families 15–70%. However, because related individuals often share a common environment, these estimates are inflated (via misallocation of unique/common environment variance). We calculated a lower-bound heritability estimate for refractive error free from such bias.
Methods
Between the ages 7 and 15 years, participants in the Avon Longitudinal Study of Parents and Children (ALSPAC) underwent non-cycloplegic autorefraction at regular research clinics. At each age, an estimate of the variance in refractive error explained by single nucleotide polymorphism (SNP) genetic variants was calculated using genome-wide complex trait analysis (GCTA) using high-density genome-wide SNP genotype information (minimum N at each age=3,404).
Results
The variance in refractive error explained by the SNPs (“SNP heritability”) was stable over childhood: Across age 7–15 years, SNP heritability averaged 0.28 (SE=0.08, p<0.001). The genetic correlation for refractive error between visits varied from 0.77 to 1.00 (all p<0.001) demonstrating that a common set of SNPs was responsible for the genetic contribution to refractive error across this period of childhood. Simulations suggested lack of cycloplegia during autorefraction led to a small underestimation of SNP heritability (adjusted SNP heritability=0.35; SE=0.09). To put these results in context, the variance in refractive error explained (or predicted) by the time participants spent outdoors was <0.005 and by the time spent reading was <0.01, based on a parental questionnaire completed when the child was aged 8–9 years old.
Conclusions
Genetic variation captured by common SNPs explained approximately 35% of the variation in refractive error between unrelated subjects. This value sets an upper limit for predicting refractive error using existing SNP genotyping arrays, although higher-density genotyping in larger samples and inclusion of interaction effects is expected to raise this figure toward twin- and family-based heritability estimates. The same SNPs influenced refractive error across much of childhood. Notwithstanding the strong evidence of association between time outdoors and myopia, and time reading and myopia, less than 1% of the variance in myopia at age 15 was explained by crude measures of these two risk factors, indicating that their effects may be limited, at least when averaged over the whole population.
PMCID: PMC4445077  PMID: 26019481
13.  Heritability and genome-wide analyses of problematic peer relationships during childhood and adolescence 
Human Genetics  2014;134(6):539-551.
Peer behaviour plays an important role in the development of social adjustment, though little is known about its genetic architecture. We conducted a twin study combined with a genome-wide complex trait analysis (GCTA) and a genome-wide screen to characterise genetic influences on problematic peer behaviour during childhood and adolescence. This included a series of longitudinal measures (parent-reported Strengths-and-Difficulties Questionnaire) from a UK population-based birth-cohort (ALSPAC, 4–17 years), and a UK twin sample (TEDS, 4–11 years). Longitudinal twin analysis (TEDS; N ≤ 7,366 twin pairs) showed that peer problems in childhood are heritable (4–11 years, 0.60 < twin-h2 ≤ 0.71) but genetically heterogeneous from age to age (4–11 years, twin-rg = 0.30). GCTA (ALSPAC: N ≤ 5,608, TEDS: N ≤ 2,691) provided furthermore little support for the contribution of measured common genetic variants during childhood (4–12 years, 0.02 < GCTA-h2(Meta) ≤ 0.11) though these influences become stronger in adolescence (13–17 years, 0.14 < GCTA-h2(ALSPAC) ≤ 0.27). A subsequent cross-sectional genome-wide screen in ALSPAC (N ≤ 6,000) focussed on peer problems with the highest GCTA-heritability (10, 13 and 17 years, 0.0002 < GCTA-P ≤ 0.03). Single variant signals (P ≤ 10−5) were followed up in TEDS (N ≤ 2835, 9 and 11 years) and, in search for autism quantitative trait loci, explored within two autism samples (AGRE: NPedigrees = 793; ACC: NCases = 1,453/NControls = 7,070). There was, however, no evidence for association in TEDS and little evidence for an overlap with the autistic continuum. In summary, our findings suggest that problematic peer relationships are heritable but genetically complex and heterogeneous from age to age, with an increase in common measurable genetic variation during adolescence.
doi:10.1007/s00439-014-1514-5
PMCID: PMC4424375  PMID: 25515860
14.  A novel common variant in DCST2 is associated with length in early life and height in adulthood 
van der Valk, Ralf J.P. | Kreiner-Møller, Eskil | Kooijman, Marjolein N. | Guxens, Mònica | Stergiakouli, Evangelia | Sääf, Annika | Bradfield, Jonathan P. | Geller, Frank | Hayes, M. Geoffrey | Cousminer, Diana L. | Körner, Antje | Thiering, Elisabeth | Curtin, John A. | Myhre, Ronny | Huikari, Ville | Joro, Raimo | Kerkhof, Marjan | Warrington, Nicole M. | Pitkänen, Niina | Ntalla, Ioanna | Horikoshi, Momoko | Veijola, Riitta | Freathy, Rachel M. | Teo, Yik-Ying | Barton, Sheila J. | Evans, David M. | Kemp, John P. | St Pourcain, Beate | Ring, Susan M. | Davey Smith, George | Bergström, Anna | Kull, Inger | Hakonarson, Hakon | Mentch, Frank D. | Bisgaard, Hans | Chawes, Bo | Stokholm, Jakob | Waage, Johannes | Eriksen, Patrick | Sevelsted, Astrid | Melbye, Mads | van Duijn, Cornelia M. | Medina-Gomez, Carolina | Hofman, Albert | de Jongste, Johan C. | Taal, H. Rob | Uitterlinden, André G. | Armstrong, Loren L. | Eriksson, Johan | Palotie, Aarno | Bustamante, Mariona | Estivill, Xavier | Gonzalez, Juan R. | Llop, Sabrina | Kiess, Wieland | Mahajan, Anubha | Flexeder, Claudia | Tiesler, Carla M.T. | Murray, Clare S. | Simpson, Angela | Magnus, Per | Sengpiel, Verena | Hartikainen, Anna-Liisa | Keinanen-Kiukaanniemi, Sirkka | Lewin, Alexandra | Da Silva Couto Alves, Alexessander | Blakemore, Alexandra I. | Buxton, Jessica L. | Kaakinen, Marika | Rodriguez, Alina | Sebert, Sylvain | Vaarasmaki, Marja | Lakka, Timo | Lindi, Virpi | Gehring, Ulrike | Postma, Dirkje S. | Ang, Wei | Newnham, John P. | Lyytikäinen, Leo-Pekka | Pahkala, Katja | Raitakari, Olli T. | Panoutsopoulou, Kalliope | Zeggini, Eleftheria | Boomsma, Dorret I. | Groen-Blokhuis, Maria | Ilonen, Jorma | Franke, Lude | Hirschhorn, Joel N. | Pers, Tune H. | Liang, Liming | Huang, Jinyan | Hocher, Berthold | Knip, Mikael | Saw, Seang-Mei | Holloway, John W. | Melén, Erik | Grant, Struan F.A. | Feenstra, Bjarke | Lowe, William L. | Widén, Elisabeth | Sergeyev, Elena | Grallert, Harald | Custovic, Adnan | Jacobsson, Bo | Jarvelin, Marjo-Riitta | Atalay, Mustafa | Koppelman, Gerard H. | Pennell, Craig E. | Niinikoski, Harri | Dedoussis, George V. | Mccarthy, Mark I. | Frayling, Timothy M. | Sunyer, Jordi | Timpson, Nicholas J. | Rivadeneira, Fernando | Bønnelykke, Klaus | Jaddoe, Vincent W.V.
Human Molecular Genetics  2014;24(4):1155-1168.
Common genetic variants have been identified for adult height, but not much is known about the genetics of skeletal growth in early life. To identify common genetic variants that influence fetal skeletal growth, we meta-analyzed 22 genome-wide association studies (Stage 1; N = 28 459). We identified seven independent top single nucleotide polymorphisms (SNPs) (P < 1 × 10−6) for birth length, of which three were novel and four were in or near loci known to be associated with adult height (LCORL, PTCH1, GPR126 and HMGA2). The three novel SNPs were followed-up in nine replication studies (Stage 2; N = 11 995), with rs905938 in DC-STAMP domain containing 2 (DCST2) genome-wide significantly associated with birth length in a joint analysis (Stages 1 + 2; β = 0.046, SE = 0.008, P = 2.46 × 10−8, explained variance = 0.05%). Rs905938 was also associated with infant length (N = 28 228; P = 5.54 × 10−4) and adult height (N = 127 513; P = 1.45 × 10−5). DCST2 is a DC-STAMP-like protein family member and DC-STAMP is an osteoclast cell-fusion regulator. Polygenic scores based on 180 SNPs previously associated with human adult stature explained 0.13% of variance in birth length. The same SNPs explained 2.95% of the variance of infant length. Of the 180 known adult height loci, 11 were genome-wide significantly associated with infant length (SF3B4, LCORL, SPAG17, C6orf173, PTCH1, GDF5, ZNFX1, HHIP, ACAN, HLA locus and HMGA2). This study highlights that common variation in DCST2 influences variation in early growth and adult height.
doi:10.1093/hmg/ddu510
PMCID: PMC4447786  PMID: 25281659
15.  Genome-wide association study identifies loci affecting blood copper, selenium and zinc 
Human Molecular Genetics  2013;22(19):3998-4006.
Genetic variation affecting absorption, distribution or excretion of essential trace elements may lead to health effects related to sub-clinical deficiency. We have tested for allelic effects of single-nucleotide polymorphisms (SNPs) on blood copper, selenium and zinc in a genome-wide association study using two adult cohorts from Australia and the UK. Participants were recruited in Australia from twins and their families and in the UK from pregnant women. We measured erythrocyte Cu, Se and Zn (Australian samples) or whole blood Se (UK samples) using inductively coupled plasma mass spectrometry. Genotyping was performed with Illumina chips and >2.5 m SNPs were imputed from HapMap data. Genome-wide significant associations were found for each element. For Cu, there were two loci on chromosome 1 (most significant SNPs rs1175550, P = 5.03 × 10−10, and rs2769264, P = 2.63 × 10−20); for Se, a locus on chromosome 5 was significant in both cohorts (combined P = 9.40 × 10−28 at rs921943); and for Zn three loci on chromosomes 8, 15 and X showed significant results (rs1532423, P = 6.40 × 10−12; rs2120019, P = 1.55 × 10−18; and rs4826508, P = 1.40 × 10−12, respectively). The Se locus covers three genes involved in metabolism of sulphur-containing amino acids and potentially of the analogous Se compounds; the chromosome 8 locus for Zn contains multiple genes for the Zn-containing enzyme carbonic anhydrase. Where potentially relevant genes were identified, they relate to metabolism of the element (Se) or to the presence at high concentration of a metal-containing protein (Cu).
doi:10.1093/hmg/ddt239
PMCID: PMC3766178  PMID: 23720494
16.  Common variation near ROBO2 is associated with expressive vocabulary in infancy 
Nature Communications  2014;5:4831.
Twin studies suggest that expressive vocabulary at ~24 months is modestly heritable. However, the genes influencing this early linguistic phenotype are unknown. Here we conduct a genome-wide screen and follow-up study of expressive vocabulary in toddlers of European descent from up to four studies of the EArly Genetics and Lifecourse Epidemiology consortium, analysing an early (15–18 months, ‘one-word stage’, NTotal=8,889) and a later (24–30 months, ‘two-word stage’, NTotal=10,819) phase of language acquisition. For the early phase, one single-nucleotide polymorphism (rs7642482) at 3p12.3 near ROBO2, encoding a conserved axon-binding receptor, reaches the genome-wide significance level (P=1.3 × 10−8) in the combined sample. This association links language-related common genetic variation in the general population to a potential autism susceptibility locus and a linkage region for dyslexia, speech-sound disorder and reading. The contribution of common genetic influences is, although modest, supported by genome-wide complex trait analysis (meta-GCTA h215–18-months=0.13, meta-GCTA h224–30-months=0.14) and in concordance with additional twin analysis (5,733 pairs of European descent, h224-months=0.20).
The genetic basis of expressive vocabulary in children around 2 years old is poorly understood. Here, the authors show that a genetic variant near the ROBO2 gene is associated with early language acquisition in the general population and highlight a potential genetic link between language-related common genetic variation and a linkage region for dyslexia, speech-sound disorder and reading.
doi:10.1038/ncomms5831
PMCID: PMC4175587  PMID: 25226531
17.  Does Bone Resorption Stimulate Periosteal Expansion? A Cross‐Sectional Analysis of β‐C‐telopeptides of Type I Collagen (CTX), Genetic Markers of the RANKL Pathway, and Periosteal Circumference as Measured by pQCT 
Journal of Bone and Mineral Research  2014;29(4):1015-1024.
ABSTRACT
We hypothesized that bone resorption acts to increase bone strength through stimulation of periosteal expansion. Hence, we examined whether bone resorption, as reflected by serum β‐C‐telopeptides of type I collagen (CTX), is positively associated with periosteal circumference (PC), in contrast to inverse associations with parameters related to bone remodeling such as cortical bone mineral density (BMDC). CTX and mid‐tibial peripheral quantitative computed tomography (pQCT) scans were available in 1130 adolescents (mean age 15.5 years) from the Avon Longitudinal Study of Parents and Children (ALSPAC). Analyses were adjusted for age, gender, time of sampling, tanner stage, lean mass, fat mass, and height. CTX was positively related to PC (β = 0.19 [0.13, 0.24]) (coefficient = SD change per SD increase in CTX, 95% confidence interval)] but inversely associated with BMDC (β = –0.46 [–0.52,–0.40]) and cortical thickness [β = –0.11 (–0.18, –0.03)]. CTX was positively related to bone strength as reflected by the strength‐strain index (SSI) (β = 0.09 [0.03, 0.14]). To examine the causal nature of this relationship, we then analyzed whether single‐nucleotide polymorphisms (SNPs) within key osteoclast regulatory genes, known to reduce areal/cortical BMD, conversely increase PC. Fifteen such genetic variants within or proximal to genes encoding receptor activator of NF‐κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) were identified by literature search. Six of the 15 alleles that were inversely related to BMD were positively related to CTX (p < 0.05 cut‐off) (n = 2379). Subsequently, we performed a meta‐analysis of associations between these SNPs and PC in ALSPAC (n = 3382), Gothenburg Osteoporosis and Obesity Determinants (GOOD) (n = 938), and the Young Finns Study (YFS) (n = 1558). Five of the 15 alleles that were inversely related to BMD were positively related to PC (p < 0.05 cut‐off). We conclude that despite having lower BMD, individuals with a genetic predisposition to higher bone resorption have greater bone size, suggesting that higher bone resorption is permissive for greater periosteal expansion. © 2014 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
doi:10.1002/jbmr.2093
PMCID: PMC4138988  PMID: 24014423
CTX; BONE RESORPTION; PERIOSTEAL EXPANSION; pQCT
18.  Genetic Variation Associated with Differential Educational Attainment in Adults Has Anticipated Associations with School Performance in Children 
PLoS ONE  2014;9(7):e100248.
Genome-wide association study results have yielded evidence for the association of common genetic variants with crude measures of completed educational attainment in adults. Whilst informative, these results do not inform as to the mechanism of these effects or their presence at earlier ages and where educational performance is more routinely and more precisely assessed. Single nucleotide polymorphisms exhibiting genome-wide significant associations with adult educational attainment were combined to derive an unweighted allele score in 5,979 and 6,145 young participants from the Avon Longitudinal Study of Parents and Children with key stage 3 national curriculum test results (SATS results) available at age 13 to 14 years in English and mathematics respectively. Standardised (z-scored) results for English and mathematics showed an expected relationship with sex, with girls exhibiting an advantage over boys in English (0.433 SD (95%CI 0.395, 0.470), p<10−10) with more similar results (though in the opposite direction) in mathematics (0.042 SD (95%CI 0.004, 0.080), p = 0.030). Each additional adult educational attainment increasing allele was associated with 0.041 SD (95%CI 0.020, 0.063), p = 1.79×10−04 and 0.028 SD (95%CI 0.007, 0.050), p = 0.01 increases in standardised SATS score for English and mathematics respectively. Educational attainment is a complex multifactorial behavioural trait which has not had heritable contributions to it fully characterised. We were able to apply the results from a large study of adult educational attainment to a study of child exam performance marking events in the process of learning rather than realised adult end product. Our results support evidence for common, small genetic contributions to educational attainment, but also emphasise the likely lifecourse nature of this genetic effect. Results here also, by an alternative route, suggest that existing methods for child examination are able to recognise early life variation likely to be related to ultimate educational attainment.
doi:10.1371/journal.pone.0100248
PMCID: PMC4102483  PMID: 25032841
19.  Genome Wide Association Identifies Common Variants at the SERPINA6/SERPINA1 Locus Influencing Plasma Cortisol and Corticosteroid Binding Globulin 
PLoS Genetics  2014;10(7):e1004474.
Variation in plasma levels of cortisol, an essential hormone in the stress response, is associated in population-based studies with cardio-metabolic, inflammatory and neuro-cognitive traits and diseases. Heritability of plasma cortisol is estimated at 30–60% but no common genetic contribution has been identified. The CORtisol NETwork (CORNET) consortium undertook genome wide association meta-analysis for plasma cortisol in 12,597 Caucasian participants, replicated in 2,795 participants. The results indicate that <1% of variance in plasma cortisol is accounted for by genetic variation in a single region of chromosome 14. This locus spans SERPINA6, encoding corticosteroid binding globulin (CBG, the major cortisol-binding protein in plasma), and SERPINA1, encoding α1-antitrypsin (which inhibits cleavage of the reactive centre loop that releases cortisol from CBG). Three partially independent signals were identified within the region, represented by common SNPs; detailed biochemical investigation in a nested sub-cohort showed all these SNPs were associated with variation in total cortisol binding activity in plasma, but some variants influenced total CBG concentrations while the top hit (rs12589136) influenced the immunoreactivity of the reactive centre loop of CBG. Exome chip and 1000 Genomes imputation analysis of this locus in the CROATIA-Korcula cohort identified missense mutations in SERPINA6 and SERPINA1 that did not account for the effects of common variants. These findings reveal a novel common genetic source of variation in binding of cortisol by CBG, and reinforce the key role of CBG in determining plasma cortisol levels. In turn this genetic variation may contribute to cortisol-associated degenerative diseases.
Author Summary
Cortisol is a steroid hormone from the adrenal glands that is essential in the response to stress. Most cortisol in blood is bound to corticosteroid binding globulin (CBG). Diseases causing cortisol deficiency (Addison's disease) or excess (Cushing's syndrome) are life-threatening. Variations in plasma cortisol have been associated with cardiovascular and psychiatric diseases and their risk factors. To dissect the genetic contribution to variation in plasma cortisol, we formed the CORtisol NETwork (CORNET) consortium and recruited collaborators with suitable samples from more than 15,000 people. The results reveal that the major genetic influence on plasma cortisol is mediated by variations in the binding capacity of CBG. This is determined by differences in the circulating concentrations of CBG and also in the immunoreactivity of its ‘reactive centre loop’, potentially influencing not only binding affinity for cortisol but also the stability of CBG and hence the tissue delivery of cortisol. These findings provide the first evidence for a common genetic effect on levels of this clinically important hormone, suggest that differences in CBG between individuals are biologically important, and pave the way for further research to dissect causality in the associations of plasma cortisol with common diseases.
doi:10.1371/journal.pgen.1004474
PMCID: PMC4091794  PMID: 25010111
20.  Genome-wide association and longitudinal analyses reveal genetic loci linking pubertal height growth, pubertal timing and childhood adiposity 
Human Molecular Genetics  2013;22(13):2735-2747.
The pubertal height growth spurt is a distinctive feature of childhood growth reflecting both the central onset of puberty and local growth factors. Although little is known about the underlying genetics, growth variability during puberty correlates with adult risks for hormone-dependent cancer and adverse cardiometabolic health. The only gene so far associated with pubertal height growth, LIN28B, pleiotropically influences childhood growth, puberty and cancer progression, pointing to shared underlying mechanisms. To discover genetic loci influencing pubertal height and growth and to place them in context of overall growth and maturation, we performed genome-wide association meta-analyses in 18 737 European samples utilizing longitudinally collected height measurements. We found significant associations (P < 1.67 × 10−8) at 10 loci, including LIN28B. Five loci associated with pubertal timing, all impacting multiple aspects of growth. In particular, a novel variant correlated with expression of MAPK3, and associated both with increased prepubertal growth and earlier menarche. Another variant near ADCY3-POMC associated with increased body mass index, reduced pubertal growth and earlier puberty. Whereas epidemiological correlations suggest that early puberty marks a pathway from rapid prepubertal growth to reduced final height and adult obesity, our study shows that individual loci associating with pubertal growth have variable longitudinal growth patterns that may differ from epidemiological observations. Overall, this study uncovers part of the complex genetic architecture linking pubertal height growth, the timing of puberty and childhood obesity and provides new information to pinpoint processes linking these traits.
doi:10.1093/hmg/ddt104
PMCID: PMC3674797  PMID: 23449627
21.  Phenotypic Dissection of Bone Mineral Density Reveals Skeletal Site Specificity and Facilitates the Identification of Novel Loci in the Genetic Regulation of Bone Mass Attainment 
PLoS Genetics  2014;10(6):e1004423.
Heritability of bone mineral density (BMD) varies across skeletal sites, reflecting different relative contributions of genetic and environmental influences. To quantify the degree to which common genetic variants tag and environmental factors influence BMD, at different sites, we estimated the genetic (rg) and residual (re) correlations between BMD measured at the upper limbs (UL-BMD), lower limbs (LL-BMD) and skull (SK-BMD), using total-body DXA scans of ∼4,890 participants recruited by the Avon Longitudinal Study of Parents and their Children (ALSPAC). Point estimates of rg indicated that appendicular sites have a greater proportion of shared genetic architecture (LL-/UL-BMD rg = 0.78) between them, than with the skull (UL-/SK-BMD rg = 0.58 and LL-/SK-BMD rg = 0.43). Likewise, the residual correlation between BMD at appendicular sites (re = 0.55) was higher than the residual correlation between SK-BMD and BMD at appendicular sites (re = 0.20–0.24). To explore the basis for the observed differences in rg and re, genome-wide association meta-analyses were performed (n∼9,395), combining data from ALSPAC and the Generation R Study identifying 15 independent signals from 13 loci associated at genome-wide significant level across different skeletal regions. Results suggested that previously identified BMD-associated variants may exert site-specific effects (i.e. differ in the strength of their association and magnitude of effect across different skeletal sites). In particular, variants at CPED1 exerted a larger influence on SK-BMD and UL-BMD when compared to LL-BMD (P = 2.01×10−37), whilst variants at WNT16 influenced UL-BMD to a greater degree when compared to SK- and LL-BMD (P = 2.31×10−14). In addition, we report a novel association between RIN3 (previously associated with Paget's disease) and LL-BMD (rs754388: β = 0.13, SE = 0.02, P = 1.4×10−10). Our results suggest that BMD at different skeletal sites is under a mixture of shared and specific genetic and environmental influences. Allowing for these differences by performing genome-wide association at different skeletal sites may help uncover new genetic influences on BMD.
Author Summary
The heritability of bone mineral density (BMD) varies across skeletal sites, reflecting different relative contributions of genetic and environmental influences. To investigate whether the genes underlying bone acquisition act in a site-specific manner, we quantified the shared genetic influences across axial and appendicular skeletal sites by estimating the genetic and residual correlation of BMD at the upper limb, lower limb and the skull. Our results suggest that different skeletal sites as measured by total-body Dual-Energy X-Ray Absorptiometry are to a certain extent under distinct genetic and environmental influences. To further explore the basis for these differences, genome-wide association meta-analyses were performed to identify genetic loci that are preferentially associated with one or more skeletal regions. Variants at 13 loci (including RIN3, a novel BMD associated locus) reached genome-wide significance and several displayed evidence of differential association with BMD across the different skeletal sites in particular CPED1 and WNT16. Our results suggest that it may be advantageous to decompose the total-body BMD measures and perform GWAS at separate skeletal regions. By allowing for site-specific differences, new genetic variants affecting BMD and future risk of osteoporosis may be uncovered.
doi:10.1371/journal.pgen.1004423
PMCID: PMC4063697  PMID: 24945404
22.  META-ANALYSIS OF GENOME-WIDE STUDIES IDENTIFIES WNT16 AND ESR1 SNPS ASSOCIATED WITH BONE MINERAL DENSITY IN PREMENOPAUSAL WOMEN 
Previous genome-wide association studies (GWAS) have identified common variants in genes associated with variation in bone mineral density (BMD), although most have been carried out in combined samples of older women and men. Meta-analyses of these results have identified numerous SNPs of modest effect at genome-wide significance levels in genes involved in both bone formation and resorption, as well as other pathways. We performed a meta-analysis restricted to premenopausal white women from four cohorts (n= 4,061 women, ages 20 to 45) to identify genes influencing peak bone mass at the lumbar spine and femoral neck. Following imputation, age- and weight-adjusted BMD values were tested for association with each SNP. Association of a SNP in the WNT16 gene (rs3801387; p=1.7 × 10−9) and multiple SNPs in the ESR1/C6orf97 (rs4870044; p=1.3 × 10−8) achieved genome-wide significance levels for lumbar spine BMD. These SNPs, along with others demonstrating suggestive evidence of association, were then tested for association in seven Replication cohorts that included premenopausal women of European, Hispanic-American, and African-American descent (combined n=5,597 for femoral neck; 4,744 for lumbar spine). When the data from the Discovery and Replication cohorts were analyzed jointly, the evidence was more significant (WNT16 joint p=1.3 × 10−11; ESR1/C6orf97 joint p= 1.4 × 10−10). Multiple independent association signals were observed with spine BMD at the ESR1 region after conditioning on the primary signal. Analyses of femoral neck BMD also supported association with SNPs in WNT16 and ESR1/C6orf97 (p< 1 × 10−5). Our results confirm that several of the genes contributing to BMD variation across a broad age range in both sexes have effects of similar magnitude on BMD of the spine in premenopausal women. These data support the hypothesis that variants in these genes of known skeletal function also affect BMD during the premenopausal period.
doi:10.1002/jbmr.1796
PMCID: PMC3691010  PMID: 23074152
Bone mineral density; GWAS; premenopausal; meta-analysis; genetics
23.  Variability in the common genetic architecture of social-communication spectrum phenotypes during childhood and adolescence 
Molecular Autism  2014;5:18.
Background
Social-communication abilities are heritable traits, and their impairments overlap with the autism continuum. To characterise the genetic architecture of social-communication difficulties developmentally and identify genetic links with the autistic dimension, we conducted a genome-wide screen of social-communication problems at multiple time-points during childhood and adolescence.
Methods
Social-communication difficulties were ascertained at ages 8, 11, 14 and 17 years in a UK population-based birth cohort (Avon Longitudinal Study of Parents and Children; N ≤ 5,628) using mother-reported Social Communication Disorder Checklist scores. Genome-wide Complex Trait Analysis (GCTA) was conducted for all phenotypes. The time-points with the highest GCTA heritability were subsequently analysed for single SNP association genome-wide. Type I error in the presence of measurement relatedness and the likelihood of observing SNP signals near known autism susceptibility loci (co-location) were assessed via large-scale, genome-wide permutations. Association signals (P ≤ 10−5) were also followed up in Autism Genetic Resource Exchange pedigrees (N = 793) and the Autism Case Control cohort (Ncases/Ncontrols = 1,204/6,491).
Results
GCTA heritability was strongest in childhood (h2(8 years) = 0.24) and especially in later adolescence (h2(17 years) = 0.45), with a marked drop during early to middle adolescence (h2(11 years) = 0.16 and h2(14 years) = 0.08). Genome-wide screens at ages 8 and 17 years identified for the latter time-point evidence for association at 3p22.2 near SCN11A (rs4453791, P = 9.3 × 10−9; genome-wide empirical P = 0.011) and suggestive evidence at 20p12.3 at PLCB1 (rs3761168, P = 7.9 × 10−8; genome-wide empirical P = 0.085). None of these signals contributed to risk for autism. However, the co-location of population-based signals and autism susceptibility loci harbouring rare mutations, such as PLCB1, is unlikely to be due to chance (genome-wide empirical Pco-location = 0.007).
Conclusions
Our findings suggest that measurable common genetic effects for social-communication difficulties vary developmentally and that these changes may affect detectable overlaps with the autism spectrum.
doi:10.1186/2040-2392-5-18
PMCID: PMC3940728  PMID: 24564958
ALSPAC; ASD; Autism; GCTA heritability; GWAS; Social communication
25.  Mining the Human Phenome Using Allelic Scores That Index Biological Intermediates 
PLoS Genetics  2013;9(10):e1003919.
It is common practice in genome-wide association studies (GWAS) to focus on the relationship between disease risk and genetic variants one marker at a time. When relevant genes are identified it is often possible to implicate biological intermediates and pathways likely to be involved in disease aetiology. However, single genetic variants typically explain small amounts of disease risk. Our idea is to construct allelic scores that explain greater proportions of the variance in biological intermediates, and subsequently use these scores to data mine GWAS. To investigate the approach's properties, we indexed three biological intermediates where the results of large GWAS meta-analyses were available: body mass index, C-reactive protein and low density lipoprotein levels. We generated allelic scores in the Avon Longitudinal Study of Parents and Children, and in publicly available data from the first Wellcome Trust Case Control Consortium. We compared the explanatory ability of allelic scores in terms of their capacity to proxy for the intermediate of interest, and the extent to which they associated with disease. We found that allelic scores derived from known variants and allelic scores derived from hundreds of thousands of genetic markers explained significant portions of the variance in biological intermediates of interest, and many of these scores showed expected correlations with disease. Genome-wide allelic scores however tended to lack specificity suggesting that they should be used with caution and perhaps only to proxy biological intermediates for which there are no known individual variants. Power calculations confirm the feasibility of extending our strategy to the analysis of tens of thousands of molecular phenotypes in large genome-wide meta-analyses. We conclude that our method represents a simple way in which potentially tens of thousands of molecular phenotypes could be screened for causal relationships with disease without having to expensively measure these variables in individual disease collections.
Author Summary
The standard approach in genome-wide association studies is to analyse the relationship between genetic variants and disease one marker at a time. Significant associations between markers and disease are then used as evidence to implicate biological intermediates and pathways likely to be involved in disease aetiology. However, single genetic variants typically only explain small amounts of disease risk. Our idea is to construct allelic scores that explain greater proportions of the variance in biological intermediates than single markers, and then use these scores to data mine genome-wide association studies. We show how allelic scores derived from known variants as well as allelic scores derived from hundreds of thousands of genetic markers across the genome explain significant portions of the variance in body mass index, levels of C-reactive protein, and LDLc cholesterol, and many of these scores show expected correlations with disease. Power calculations confirm the feasibility of scaling our strategy to the analysis of tens of thousands of molecular phenotypes in large genome-wide meta-analyses. Our method represents a simple way in which tens of thousands of molecular phenotypes could be screened for potential causal relationships with disease.
doi:10.1371/journal.pgen.1003919
PMCID: PMC3814299  PMID: 24204319

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