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1.  The Type 2 Diabetes associated rs7903146 T allele within TCF7L2 is significantly under-represented in Hereditary Multiple Exostoses: insights into pathogenesis 
Bone  2014;72:123-127.
Hereditary Multiple Exostoses (HME) is an autosomal-dominant disorder characterized by benign cartilage tumors (exostoses) forming near the growth plates, leading to severe health problems. EXT1 and EXT2 are the two genes known to harbor heterozygous loss-of-function mutations that account for the vast majority of the primary genetic component of HME. However, patients present with wide clinical heterogeneity, suggesting that modifier genes play a role in determining severity. Our previous work has pointed to an imbalance of β-catenin signaling being involved in the pathogenesis of osteochondroma formation. TCF7L2 is one of the key ‘gate-keeper’ TCF family members for Wnt/β-catenin signaling pathway, and TCF7L2 and EXT2 are among the earliest associated loci reported in genome wide appraisals of type 2 diabetes (T2D). Thus we investigated if the key T allele of single nucleotide polymorphism (SNP) rs7903146 within the TCF7L2 locus, which is strongly over-represented among T2D cases, was also associated with HME. We leveraged genotype data available from ongoing GWAS efforts from genomics and orthopaedic centers in the US, Canada and Italy. Collectively 213 cases and 1,890 controls were analyzed and, surprisingly, the T allele was in fact significantly under-represented in the HME patient group [P=0.009; odds ratio=0.737 (95% C.I. 0.587 - 0.926)]; in addition, the direction of effect was consistent within each individual cohort. Immunohistochemical analyses revealed that TCF7L2 is differentially expressed and distributed in normal human growth plate zones, and exhibits substantial variability in human exostoses in terms of staining intensity and distribution. In summary, the data indicate that there is a putative genetic connection between TCF7L2 and EXT in the context of HME. Given this observation, we suggest that these loci could possibly modulate shared pathways, in particular with respect to β-catenin, and their respective variants interplay to influence HME pathogenesis as well as T2D.
PMCID: PMC4300120  PMID: 25498973
Transcription factor 7 like 2 (TCF7L2); Hereditary Multiple Exostoses (HME); osteochondroma; Exostosin (EXT); type 2 diabetes (T2D)
2.  Transcriptome Profiling of Human Ulcerative Colitis Mucosa Reveals Altered Expression of Pathways Enriched in Genetic Susceptibility Loci 
PLoS ONE  2014;9(5):e96153.
Human colonic mucosa altered by inflammation due to ulcerative colitis (UC) displays a drastically altered pattern of gene expression compared with healthy tissue. We aimed to understand the underlying molecular pathways influencing these differences by analyzing three publically-available, independently-generated microarray datasets of gene expression from endoscopic biopsies of the colon. Gene set enrichment analysis (GSEA) revealed that all three datasets share 87 gene sets upregulated in UC lesions and 8 gene sets downregulated (false discovery rate <0.05). The upregulated pathways were dominated by gene sets involved in immune function and signaling, as well as the control of mitosis. We applied pathway analysis to genotype data derived from genome-wide association studies (GWAS) of UC, consisting of 5,584 cases and 11,587 controls assembled from eight European-ancestry cohorts. The upregulated pathways derived from the gene expression data showed a highly significant overlap with pathways derived from the genotype data (33 of 56 gene sets, hypergeometric P = 1.49×10–19). This study supports the hypothesis that heritable variation in gene expression as measured by GWAS signals can influence key pathways in the development of disease, and that comparison of genetic susceptibility loci with gene expression signatures can differentiate key drivers of inflammation from secondary effects on gene expression of the inflammatory process.
PMCID: PMC4006814  PMID: 24788701
3.  A genome wide association study of plasma uric acid levels in obese cases and never-overweight controls 
Obesity (Silver Spring, Md.)  2013;21(9):E490-E494.
To identify plasma uric acid related genes in extremely obese and normal weight individuals using genome wide association studies (GWAS).
Design and Methods
Using genotypes from a GWAS focusing on obesity and thinness, we performed quantitative trait association analyses (PLINK) for plasma uric acid levels in 1,060 extremely obese individuals [body mass index (BMI) >35 kg/m2] and normal-weight controls (BMI<25kg/m2). In 961 samples with uric acid data, 924 were females.
Significant associations were found in SLC2A9 gene SNPs and plasma uric acid levels (rs6449213, P=3.15×10−12). DIP2C gene SNP rs877282 also reached genome wide significance(P=4,56×10−8). Weaker associations (P<1×10−5) were found in F5, PXDNL, FRAS1, LCORL, and MICAL2genes. Besides SLC2A9, 3 previously identified uric acid related genes ABCG2 (rs2622605, P=0.0026), SLC17A1 (rs3799344, P=0.0017), and RREB1 (rs1615495, P =0.00055) received marginal support in our study.
Two genes/chromosome regions reached genome wide association significance (P< 1× 10−7, 550K SNPs) in our GWAS : SLC2A9, the chromosome 2 60.1 Mb region (rs6723995), and the DIP2C gene region. Five other genes (F5, PXDNL, FRAS1, LCORL, and MICAL2) yielded P<1× 10−5. Four previous reported associations were replicated in our study, including SLC2A9, ABCG2, RREB, and SLC17A1.
PMCID: PMC3762924  PMID: 23703922
uric acid; genome wide association study; obesity
4.  The Genetics of Pediatric Obesity 
Obesity among children and adults has notably escalated over recent decades and represents a global major health problem. We now know that both genetics and environmental factors contribute to its complex etiology. Genome-wide association studies (GWAS) have revealed compelling genetic signals influencing obesity risk in adults. Recent reports for childhood obesity revealed that many adult loci also play a role in the pediatric setting. Childhood GWAS have uncovered novel loci below the detection range in adult studies, suggesting that obesity genes may be more easily uncovered in the pediatric setting. Shedding light on the genetic architecture of childhood obesity will facilitate prevention and treatment of pediatric cases and will have fundamental implications for diseases that present later in life.
PMCID: PMC4673034  PMID: 26439977
5.  The missense variation landscape of FTO, MC4R and TMEM18 in obese children of African ancestry 
Obesity (Silver Spring, Md.)  2013;21(1):159-163.
Common variation at the loci harboring FTO, MC4R and TMEM18 is consistently reported as being statistically the most strongly associated with obesity. We investigated if these loci also harbor rarer missense variants that confer substantially higher risk of common childhood obesity in African American (AA) children. We sequenced the exons of FTO, MC4R and TMEM18 in an initial subset of our cohort i.e. 200 obese (BMI≥95th percentile) and 200 lean AA children (BMI≤5th percentile). Any missense exonic variants that were uncovered went on to be further genotyped in a further 768 obese and 768 lean (BMI≤50th percentile) children of the same ethnicity. A number of exonic variants were observed from our sequencing effort: seven in FTO, of which four were non-synonymous (A163T, G182A, M400V and A405V), thirteen in MC4R, of which six were non-synonymous (V103I, N123S, S136A, F202L, N240S and I251L) and four in TMEM18, of which two were non-synonymous (P2S and V113L). Follow-up genotyping of these missense variants revealed only one significant difference in allele frequency between cases and controls, namely with N240S in MC4R(Fisher's Exact P = 0.0001). In summary, moderately rare missense variants within the FTO, MC4R and TMEM18 genes observed in our study did not confer risk of common childhood obesity in African Americans except for a degree of evidence for one known loss-of-function variant in MC4R.
PMCID: PMC3605748  PMID: 23505181
Obesity; Pediatrics; Genomics
6.  New loci associated with birth weight identify genetic links between intrauterine growth and adult height and metabolism 
Horikoshi, Momoko | Yaghootkar, Hanieh | Mook-Kanamori, Dennis O. | Sovio, Ulla | Taal, H. Rob | Hennig, Branwen J. | Bradfield, Jonathan P. | St. Pourcain, Beate | Evans, David M. | Charoen, Pimphen | Kaakinen, Marika | Cousminer, Diana L. | Lehtimäki, Terho | Kreiner-Møller, Eskil | Warrington, Nicole M. | Bustamante, Mariona | Feenstra, Bjarke | Berry, Diane J. | Thiering, Elisabeth | Pfab, Thiemo | Barton, Sheila J. | Shields, Beverley M. | Kerkhof, Marjan | van Leeuwen, Elisabeth M. | Fulford, Anthony J. | Kutalik, Zoltán | Zhao, Jing Hua | den Hoed, Marcel | Mahajan, Anubha | Lindi, Virpi | Goh, Liang-Kee | Hottenga, Jouke-Jan | Wu, Ying | Raitakari, Olli T. | Harder, Marie N. | Meirhaeghe, Aline | Ntalla, Ioanna | Salem, Rany M. | Jameson, Karen A. | Zhou, Kaixin | Monies, Dorota M. | Lagou, Vasiliki | Kirin, Mirna | Heikkinen, Jani | Adair, Linda S. | Alkuraya, Fowzan S. | Al-Odaib, Ali | Amouyel, Philippe | Andersson, Ehm Astrid | Bennett, Amanda J. | Blakemore, Alexandra I.F. | Buxton, Jessica L. | Dallongeville, Jean | Das, Shikta | de Geus, Eco J. C. | Estivill, Xavier | Flexeder, Claudia | Froguel, Philippe | Geller, Frank | Godfrey, Keith M. | Gottrand, Frédéric | Groves, Christopher J. | Hansen, Torben | Hirschhorn, Joel N. | Hofman, Albert | Hollegaard, Mads V. | Hougaard, David M. | Hyppönen, Elina | Inskip, Hazel M. | Isaacs, Aaron | Jørgensen, Torben | Kanaka-Gantenbein, Christina | Kemp, John P. | Kiess, Wieland | Kilpeläinen, Tuomas O. | Klopp, Norman | Knight, Bridget A. | Kuzawa, Christopher W. | McMahon, George | Newnham, John P. | Niinikoski, Harri | Oostra, Ben A. | Pedersen, Louise | Postma, Dirkje S. | Ring, Susan M. | Rivadeneira, Fernando | Robertson, Neil R. | Sebert, Sylvain | Simell, Olli | Slowinski, Torsten | Tiesler, Carla M.T. | Tönjes, Anke | Vaag, Allan | Viikari, Jorma S. | Vink, Jacqueline M. | Vissing, Nadja Hawwa | Wareham, Nicholas J. | Willemsen, Gonneke | Witte, Daniel R. | Zhang, Haitao | Zhao, Jianhua | Wilson, James F. | Stumvoll, Michael | Prentice, Andrew M. | Meyer, Brian F. | Pearson, Ewan R. | Boreham, Colin A.G. | Cooper, Cyrus | Gillman, Matthew W. | Dedoussis, George V. | Moreno, Luis A | Pedersen, Oluf | Saarinen, Maiju | Mohlke, Karen L. | Boomsma, Dorret I. | Saw, Seang-Mei | Lakka, Timo A. | Körner, Antje | Loos, Ruth J.F. | Ong, Ken K. | Vollenweider, Peter | van Duijn, Cornelia M. | Koppelman, Gerard H. | Hattersley, Andrew T. | Holloway, John W. | Hocher, Berthold | Heinrich, Joachim | Power, Chris | Melbye, Mads | Guxens, Mònica | Pennell, Craig E. | Bønnelykke, Klaus | Bisgaard, Hans | Eriksson, Johan G. | Widén, Elisabeth | Hakonarson, Hakon | Uitterlinden, André G. | Pouta, Anneli | Lawlor, Debbie A. | Smith, George Davey | Frayling, Timothy M. | McCarthy, Mark I. | Grant, Struan F.A. | Jaddoe, Vincent W.V. | Jarvelin, Marjo-Riitta | Timpson, Nicholas J. | Prokopenko, Inga | Freathy, Rachel M.
Nature genetics  2012;45(1):76-82.
Birth weight within the normal range is associated with a variety of adult-onset diseases, but the mechanisms behind these associations are poorly understood1. Previous genome-wide association studies identified a variant in the ADCY5 gene associated both with birth weight and type 2 diabetes, and a second variant, near CCNL1, with no obvious link to adult traits2. In an expanded genome-wide association meta-analysis and follow-up study (up to 69,308 individuals of European descent from 43 studies), we have now extended the number of genome-wide significant loci to seven, accounting for a similar proportion of variance to maternal smoking. Five of the loci are known to be associated with other phenotypes: ADCY5 and CDKAL1 with type 2 diabetes; ADRB1 with adult blood pressure; and HMGA2 and LCORL with adult height. Our findings highlight genetic links between fetal growth and postnatal growth and metabolism.
PMCID: PMC3605762  PMID: 23202124
7.  Copy Number Variations in Alternative Splicing Gene Networks Impact Lifespan 
PLoS ONE  2013;8(1):e53846.
Longevity has a strong genetic component evidenced by family-based studies. Lipoprotein metabolism, FOXO proteins, and insulin/IGF-1 signaling pathways in model systems have shown polygenic variations predisposing to shorter lifespan. To test the hypothesis that rare variants could influence lifespan, we compared the rates of CNVs in healthy children (0–18 years of age) with individuals 67 years or older. CNVs at a significantly higher frequency in the pediatric cohort were considered risk variants impacting lifespan, while those enriched in the geriatric cohort were considered longevity protective variants. We performed a whole-genome CNV analysis on 7,313 children and 2,701 adults of European ancestry genotyped with 302,108 SNP probes. Positive findings were evaluated in an independent cohort of 2,079 pediatric and 4,692 geriatric subjects. We detected 8 deletions and 10 duplications that were enriched in the pediatric group (P = 3.33×10−8–1.6×10−2 unadjusted), while only one duplication was enriched in the geriatric cohort (P = 6.3×10−4). Population stratification correction resulted in 5 deletions and 3 duplications remaining significant (P = 5.16×10−5–4.26×10−2) in the replication cohort. Three deletions and four duplications were significant combined (combined P = 3.7×10−4−3.9×10−2). All associated loci were experimentally validated using qPCR. Evaluation of these genes for pathway enrichment demonstrated ∼50% are involved in alternative splicing (P = 0.0077 Benjamini and Hochberg corrected). We conclude that genetic variations disrupting RNA splicing could have long-term biological effects impacting lifespan.
PMCID: PMC3559729  PMID: 23382853
8.  Examination of All Type 2 Diabetes GWAS Loci Reveals HHEX-IDE as a Locus Influencing Pediatric BMI 
Diabetes  2009;59(3):751-755.
A number of studies have found that BMI in early life influences the risk of developing type 2 diabetes later in life. Our goal was to investigate if any type 2 diabetes variants uncovered through genome-wide association studies (GWAS) impact BMI in childhood.
Using data from an ongoing GWAS of pediatric BMI in our cohort, we investigated the association of pediatric BMI with 20 single nucleotide polymorphisms at 18 type 2 diabetes loci uncovered through GWAS, consisting of ADAMTS9, CDC123-CAMK1D, CDKAL1, CDKN2A/B, EXT2, FTO, HHEX-IDE, IGF2BP2, the intragenic region on 11p12, JAZF1, KCNQ1, LOC387761, MTNR1B, NOTCH2, SLC30A8, TCF7L2, THADA, and TSPAN8-LGR5. We randomly partitioned our cohort exactly in half in order to have a discovery cohort (n = 3,592) and a replication cohort (n = 3,592).
Our data show that the major type 2 diabetes risk–conferring G allele of rs7923837 at the HHEX-IDE locus was associated with higher pediatric BMI in both the discovery (P = 0.0013 and survived correction for 20 tests) and replication (P = 0.023) sets (combined P = 1.01 × 10−4). Association was not detected with any other known type 2 diabetes loci uncovered to date through GWAS except for the well-established FTO.
Our data show that the same genetic HHEX-IDE variant, which is associated with type 2 diabetes from previous studies, also influences pediatric BMI.
PMCID: PMC2828649  PMID: 19933996
9.  Examination of Type 2 Diabetes Loci Implicates CDKAL1 as a Birth Weight Gene 
Diabetes  2009;58(10):2414-2418.
A number of studies have found that reduced birth weight is associated with type 2 diabetes later in life; however, the underlying mechanism for this correlation remains unresolved. Recently, association has been demonstrated between low birth weight and single nucleotide polymorphisms (SNPs) at the CDKAL1 and HHEX-IDE loci, regions that were previously implicated in the pathogenesis of type 2 diabetes. In order to investigate whether type 2 diabetes risk–conferring alleles associate with low birth weight in our Caucasian childhood cohort, we examined the effects of 20 such loci on this trait.
Using data from an ongoing genome-wide association study in our cohort of 5,465 Caucasian children with recorded birth weights, we investigated the association of the previously reported type 2 diabetes–associated variation at 20 loci including TCF7L2, HHEX-IDE, PPARG, KCNJ11, SLC30A8, IGF2BP2, CDKAL1, CDKN2A/2B, and JAZF1 with birth weight.
Our data show that the minor allele of rs7756992 (P = 8 × 10−5) at the CDKAL1 locus is strongly associated with lower birth weight, whereas a perfect surrogate for variation previously implicated for the trait at the same locus only yielded nominally significant association (P = 0.01; r2 rs7756992 = 0.677). However, association was not detected with any of the other type 2 diabetes loci studied.
We observe association between lower birth weight and type 2 diabetes risk–conferring alleles at the CDKAL1 locus. Our data show that the same genetic locus that has been identified as a marker for type 2 diabetes in previous studies also influences birth weight.
PMCID: PMC2750235  PMID: 19592620
10.  Genetic evidence for causal relationships between maternal obesity-related traits and birth weight 
JAMA  2016;315(11):1129-1140.
Structured abstract
Neonates born to overweight/obese women are larger and at higher risk of birth complications. Many maternal obesity-related traits are observationally associated with birth weight, but the causal nature of these associations is uncertain.
To test for genetic evidence of causal associations of maternal body mass index (BMI) and related traits with birth weight.
Design, Setting and Participants
We used Mendelian randomization to test whether maternal BMI and obesity-related traits are causally related to offspring birth weight. Mendelian randomization makes use of the fact that genotypes are randomly determined at conception and are thus not confounded by non-genetic factors. Data were analysed on 30,487 women from 18 studies. Participants were of European ancestry from population- or community-based studies located in Europe, North America or Australia and participating in the Early Growth Genetics (EGG) Consortium. Live, term, singleton offspring born between 1929 and 2013 were included. We tested associations between a genetic score of 30 BMI-associated single nucleotide polymorphisms (SNPs) and (i) maternal BMI and (ii) birth weight, to estimate the causal relationship between BMI and birth weight. Analyses were repeated for other obesity-related traits.
Genetic scores for BMI, fasting glucose level, type 2 diabetes, systolic blood pressure (SBP), triglyceride level, HDL-cholesterol level, vitamin D status and adiponectin level.
Main Outcome(s) and Measure(s)
Offspring birth weight measured by trained study personnel (n=2 studies), from medical records (n= 10 studies) or from maternal report (n=6 studies).
Among the 30,487 newborns the mean birth weight in the various cohorts ranged from 3325 g to 3679 g. The genetic score for BMI was associated with a 2g (95%CI: 0, 3g) higher offspring birth weight per maternal BMI-raising allele (P=0.008). The maternal genetic scores for fasting glucose and SBP were also associated with birth weight with effect sizes of 8g (95%CI: 6, 10g) per glucose-raising allele (P=7×10−14) and −4g (95%CI: −6, −2g) per SBP-raising allele (P=1×10−5), respectively. A 1 standard deviation (1 SD ≈ 4kg/m2) genetically higher maternal BMI was associated with a 55g (95% CI: 17, 93g) higher birth weight. A 1-SD genetically higher maternal fasting glucose (≈ 0.4mmol/L) or SBP (10mmHg) were associated with a 114g (95%CI: 80, 147g) higher or −208g (95% CI: −394, −21g) lower birth weight, respectively. For BMI and fasting glucose these genetic associations were consistent with the observational associations, but for SBP, the genetic and observational associations were in opposite directions.
Conclusions and Relevance
In this Mendelian randomization study of more than 30,000 women with singleton offspring from 18 studies, genetically elevated maternal BMI and blood glucose levels were potentially causally associated with higher offspring birth weight, whereas genetically elevated maternal systolic blood pressure was shown to be potentially causally related to lower birth weight. If replicated, these findings may have implications for counseling and managing pregnancies to avoid adverse weight-related birth outcomes.
PMCID: PMC4811305  PMID: 26978208
11.  A trans-ethnic genome-wide association study identifies gender-specific loci influencing pediatric aBMD and BMC at the distal radius 
Human Molecular Genetics  2015;24(17):5053-5059.
Childhood fractures are common, with the forearm being the most common site. Genome-wide association studies (GWAS) have identified more than 60 loci associated with bone mineral density (BMD) in adults but less is known about genetic influences specific to bone in childhood. To identify novel genetic factors that influence pediatric bone strength at a common site for childhood fractures, we performed a sex-stratified trans-ethnic genome-wide association study of areal BMD (aBMD) and bone mineral content (BMC) Z-scores measured by dual energy X-ray absorptiometry at the one-third distal radius, in a cohort of 1399 children without clinical abnormalities in bone health. We tested signals with P < 5 × 10−6 for replication in an independent, same-age cohort of 486 Caucasian children. Two loci yielded a genome-wide significant combined P-value: rs7797976 within CPED1 in females [P = 2.4 × 10−11, β =− 0.30 standard deviations (SD) per T allele; aBMD-Z] and rs7035284 at 9p21.3 in males (P = 1.2 × 10−8, β = 0.28 SD per G allele; BMC-Z). Signals at the CPED1-WNT16-FAM3C locus have been previously associated with BMD at other skeletal sites in adults and children. Our result at the distal radius underscores the importance of this locus at multiple skeletal sites. The 9p21.3 locus is within a gene desert, with the nearest gene flanking each side being MIR31HG and MTAP, neither of which has been implicated in BMD or BMC previously. These findings suggest that genetic determinants of childhood bone accretion at the radius, a skeletal site that is primarily cortical bone, exist and also differ by sex.
PMCID: PMC4527490  PMID: 26041818
12.  SNP genotyping on a genome-wide amplified DOP-PCR template 
Nucleic Acids Research  2002;30(22):e125.
With the increasing demand for higher throughput single nucleotide polymorphism (SNP) genotyping, the quantity of genomic DNA often falls short of the number of assays required. We investigated the use of degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) to generate a template for our SNP genotyping methodology of fluorescence polarization template-directed dye-terminator incorporation detection. DOP-PCR employs a degenerate primer (5′-CCGACTCGAGNNNNNNATGTGG-3′) to produce non-specific uniform amplification of DNA. This approach has been successfully applied to microsatellite genotyping. We compared genotyping of DOP-PCR-amplified genomic DNA to genomic DNA as a template. Results were analyzed with respect to feasibility, allele loss of alleles, genotyping accuracy and storage conditions in a high-throughput genotyping environment. DOP-PCR yielded overall satisfactory results, with a certain loss in accuracy and quality of the genotype assignments. Accuracy and quality of genotypes generated from the DOP-PCR template also depended on storage conditions. Adding carrier DNA to a final concentration of 10 ng/µl improved results. In conclusion, we have successfully used DOP-PCR to amplify our genomic DNA collection for subsequent SNP genotyping as a standard process.
PMCID: PMC137182  PMID: 12434007
13.  Investigating the Causal Relationship of C-Reactive Protein with 32 Complex Somatic and Psychiatric Outcomes: A Large-Scale Cross-Consortium Mendelian Randomization Study 
PLoS Medicine  2016;13(6):e1001976.
C-reactive protein (CRP) is associated with immune, cardiometabolic, and psychiatric traits and diseases. Yet it is inconclusive whether these associations are causal.
Methods and Findings
We performed Mendelian randomization (MR) analyses using two genetic risk scores (GRSs) as instrumental variables (IVs). The first GRS consisted of four single nucleotide polymorphisms (SNPs) in the CRP gene (GRSCRP), and the second consisted of 18 SNPs that were significantly associated with CRP levels in the largest genome-wide association study (GWAS) to date (GRSGWAS). To optimize power, we used summary statistics from GWAS consortia and tested the association of these two GRSs with 32 complex somatic and psychiatric outcomes, with up to 123,865 participants per outcome from populations of European ancestry. We performed heterogeneity tests to disentangle the pleiotropic effect of IVs. A Bonferroni-corrected significance level of less than 0.0016 was considered statistically significant. An observed p-value equal to or less than 0.05 was considered nominally significant evidence for a potential causal association, yet to be confirmed.
The strengths (F-statistics) of the IVs were 31.92–3,761.29 and 82.32–9,403.21 for GRSCRP and GRSGWAS, respectively. CRP GRSGWAS showed a statistically significant protective relationship of a 10% genetically elevated CRP level with the risk of schizophrenia (odds ratio [OR] 0.86 [95% CI 0.79–0.94]; p < 0.001). We validated this finding with individual-level genotype data from the schizophrenia GWAS (OR 0.96 [95% CI 0.94–0.98]; p < 1.72 × 10−6). Further, we found that a standardized CRP polygenic risk score (CRPPRS) at p-value thresholds of 1 × 10−4, 0.001, 0.01, 0.05, and 0.1 using individual-level data also showed a protective effect (OR < 1.00) against schizophrenia; the first CRPPRS (built of SNPs with p < 1 × 10−4) showed a statistically significant (p < 2.45 × 10−4) protective effect with an OR of 0.97 (95% CI 0.95–0.99). The CRP GRSGWAS showed that a 10% increase in genetically determined CRP level was significantly associated with coronary artery disease (OR 0.88 [95% CI 0.84–0.94]; p < 2.4 × 10−5) and was nominally associated with the risk of inflammatory bowel disease (OR 0.85 [95% CI 0.74–0.98]; p < 0.03), Crohn disease (OR 0.81 [95% CI 0.70–0.94]; p < 0.005), psoriatic arthritis (OR 1.36 [95% CI 1.00–1.84]; p < 0.049), knee osteoarthritis (OR 1.17 [95% CI 1.01–1.36]; p < 0.04), and bipolar disorder (OR 1.21 [95% CI 1.05–1.40]; p < 0.007) and with an increase of 0.72 (95% CI 0.11–1.34; p < 0.02) mm Hg in systolic blood pressure, 0.45 (95% CI 0.06–0.84; p < 0.02) mm Hg in diastolic blood pressure, 0.01 ml/min/1.73 m2 (95% CI 0.003–0.02; p < 0.005) in estimated glomerular filtration rate from serum creatinine, 0.01 g/dl (95% CI 0.0004–0.02; p < 0.04) in serum albumin level, and 0.03 g/dl (95% CI 0.008–0.05; p < 0.009) in serum protein level. However, after adjustment for heterogeneity, neither GRS showed a significant effect of CRP level (at p < 0.0016) on any of these outcomes, including coronary artery disease, nor on the other 20 complex outcomes studied. Our study has two potential limitations: the limited variance explained by our genetic instruments modeling CRP levels in blood and the unobserved bias introduced by the use of summary statistics in our MR analyses.
Genetically elevated CRP levels showed a significant potentially protective causal relationship with risk of schizophrenia. We observed nominal evidence at an observed p < 0.05 using either GRSCRP or GRSGWAS—with persistence after correction for heterogeneity—for a causal relationship of elevated CRP levels with psoriatic osteoarthritis, rheumatoid arthritis, knee osteoarthritis, systolic blood pressure, diastolic blood pressure, serum albumin, and bipolar disorder. These associations remain yet to be confirmed. We cannot verify any causal effect of CRP level on any of the other common somatic and neuropsychiatric outcomes investigated in the present study. This implies that interventions that lower CRP level are unlikely to result in decreased risk for the majority of common complex outcomes.
Using genetic instruments, Behrooz Z. Alizadeh and colleagues examine the hypothesis that increased CRP levels play a causal role in common somatic and psychiatric conditions.
Editors' Summary
Inflammation is an important part of the human immune response, the network of cells and molecules that protects the body from attack by pathogens (infectious organisms) and from harmful substances and foreign particles (for example, splinters). When human cells are attacked by pathogens or injured by trauma or chemicals, molecules called inflammatory mediators induce fluid leakage from the blood vessels into the damaged tissue and attract “phagocytes” (a type of immune cell) to the site of infection or injury to “eat” the germs and dead or damaged cells. The end result is inflammation, which is characterized by swelling, redness, heat, and pain. The inflammatory response, although unpleasant, limits the damage caused by foreign invaders or chemicals by preventing further contact with body tissues. Sometimes, however, inflammation can be harmful. Persistent dysregulation of the inflammatory response is implicated in numerous somatic disorders (diseases that affect the body, such as cardiovascular disease) and neuropsychiatric disorders (mental disorders attributable to diseases of the nervous system, such as schizophrenia).
Why Was This Study Done?
Observational studies suggest that increased blood levels of C-reactive protein (CRP, an inflammatory protein) are associated with certain somatic and neuropsychiatric disorders. But observational studies cannot prove that changes in CRP levels actually cause any of these disorders. It could be that the individuals who develop a specific disease and who have a high CRP level also share another unknown characteristic that is actually responsible for disease development (confounding). Alternatively, it could be that the disease itself increases CRP levels (reverse causation). It is important to know whether CRP is causally involved in the development of specific diseases because it might then be possible to prevent or treat these diseases using drugs that control CRP levels. Here, the researchers undertake a Mendelian randomization study to determine whether CRP has a causal relationship with 32 common complex somatic and neuropsychiatric outcomes. Because gene variants are inherited randomly, they are not prone to confounding and are free from reverse causation. So, if CRP levels actually cause a specific somatic or neuropsychiatric disease, genetic variants that affect CRP levels should be associated with an altered risk for that disease.
What Did the Researchers Do and Find?
The researchers used data collected by several consortia involved in large genome-wide association studies (studies that ask whether specific genetic changes across the whole human genome, or blueprint, are associated with specific diseases) to look for associations between 32 somatic and neuropsychiatric outcomes and two genetic risk scores (GRSs) for CRP level. GRSCRP consisted of four single nucleotide polymorphisms (SNPs; a type of genetic variant) in the gene encoding CRP; GRSGWAS consisted of 18 SNPs that were associated with CRP level in a genome-wide association study. The researchers report that a genetically increased CRP level was significantly associated with a reduced risk of schizophrenia (a significant association is one unlikely to have arisen by chance). In addition, they found a nominally significant association (an association that needs to be confirmed) between genetically increased CRP levels and an increased risk of knee osteoarthritis, raised diastolic and systolic blood pressure, and bipolar disorder. Notably, there was no evidence for an effect of genetically increased CRP levels on any of the other 27 outcomes studied.
What Do These Findings Mean?
These findings suggest that genetically raised levels of CRP are causally associated with protection against schizophrenia, an unexpected finding given other recent studies that suggest that raised CRP levels and brain inflammation predispose individuals to schizophrenia. The findings also provide preliminary evidence that genetically raised levels of CRP may be causally associated with an increased risk of raised blood pressure, knee arthritis, and bipolar disorder. The lack of any association between genetically raised levels of CRP and the other outcomes studied suggests, however, that many previously identified disease-associated rises in CRP levels might be a response to the disease process rather than a cause of these diseases. Like all Mendelian randomization studies, the reliability of these findings depends on the validity of several assumptions made by the researchers and on the ability of the GRSs used in the study to explain variations in CRP level. Importantly, however, these findings suggest that interventions designed to lower CRP level are unlikely to decrease the risk of people developing the majority of common complex somatic and neuropsychiatric outcomes.
Additional Information
This list of resources contains links that can be accessed when viewing the PDF on a device or via the online version of the article at
Wikipedia has pages on inflammation, C-reactive protein, and Mendelian randomization (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
The MedlinePlus encyclopedia has a page on C-reactive protein (in English and Spanish)
The American Heart Association provides a short article on inflammation and heart disease
A UK National Health Service “Behind the Headlines” article explains a recent study that found an association between immune activity in the brain and schizophrenia
PMCID: PMC4915710  PMID: 27327646
14.  Contribution of common non-synonymous variants in PCSK1 to body mass index variation and risk of obesity: a systematic review and meta-analysis with evidence from up to 331 175 individuals 
Human Molecular Genetics  2015;24(12):3582-3594.
Polymorphisms rs6232 and rs6234/rs6235 in PCSK1 have been associated with extreme obesity [e.g. body mass index (BMI) ≥ 40 kg/m2], but their contribution to common obesity (BMI ≥ 30 kg/m2) and BMI variation in a multi-ethnic context is unclear. To fill this gap, we collected phenotypic and genetic data in up to 331 175 individuals from diverse ethnic groups. This process involved a systematic review of the literature in PubMed, Web of Science, Embase and the NIH GWAS catalog complemented by data extraction from pre-existing GWAS or custom-arrays in consortia and single studies. We employed recently developed global meta-analytic random-effects methods to calculate summary odds ratios (OR) and 95% confidence intervals (CIs) or beta estimates and standard errors (SE) for the obesity status and BMI analyses, respectively. Significant associations were found with binary obesity status for rs6232 (OR = 1.15, 95% CI 1.06–1.24, P = 6.08 × 10−6) and rs6234/rs6235 (OR = 1.07, 95% CI 1.04–1.10, P = 3.00 × 10−7). Similarly, significant associations were found with continuous BMI for rs6232 (β = 0.03, 95% CI 0.00–0.07; P = 0.047) and rs6234/rs6235 (β = 0.02, 95% CI 0.00–0.03; P = 5.57 × 10−4). Ethnicity, age and study ascertainment significantly modulated the association of PCSK1 polymorphisms with obesity. In summary, we demonstrate evidence that common gene variation in PCSK1 contributes to BMI variation and susceptibility to common obesity in the largest known meta-analysis published to date in genetic epidemiology.
PMCID: PMC4498155  PMID: 25784503
15.  Meta-analysis of shared genetic architecture across ten pediatric autoimmune diseases 
Nature medicine  2015;21(9):1018-1027.
Genome-wide association studies (GWASs) have identified hundreds of susceptibility genes, including shared associations across clinically distinct autoimmune diseases. We performed an inverse χ2 meta-analysis across ten pediatric-age-of-onset autoimmune diseases (pAIDs) in a case-control study including more than 6,035 cases and 10,718 shared population-based controls. We identified 27 genome-wide significant loci associated with one or more pAIDs, mapping to in silico–replicated autoimmune-associated genes (including IL2RA) and new candidate loci with established immunoregulatory functions such as ADGRL2, TENM3, ANKRD30A, ADCY7 and CD40LG. The pAID-associated single-nucleotide polymorphisms (SNPs) were functionally enriched for deoxyribonuclease (DNase)-hypersensitivity sites, expression quantitative trait loci (eQTLs), microRNA (miRNA)-binding sites and coding variants. We also identified biologically correlated, pAID-associated candidate gene sets on the basis of immune cell expression profiling and found evidence of genetic sharing. Network and protein-interaction analyses demonstrated converging roles for the signaling pathways of type 1, 2 and 17 helper T cells (TH1, TH2 and TH17), JAK-STAT, interferon and interleukin in multiple autoimmune diseases.
PMCID: PMC4863040  PMID: 26301688
16.  Directional dominance on stature and cognition in diverse human populations 
Joshi, Peter K. | Esko, Tonu | Mattsson, Hannele | Eklund, Niina | Gandin, Ilaria | Nutile, Teresa | Jackson, Anne U. | Schurmann, Claudia | Smith, Albert V. | Zhang, Weihua | Okada, Yukinori | Stančáková, Alena | Faul, Jessica D. | Zhao, Wei | Bartz, Traci M. | Concas, Maria Pina | Franceschini, Nora | Enroth, Stefan | Vitart, Veronique | Trompet, Stella | Guo, Xiuqing | Chasman, Daniel I. | O’Connel, Jeffery R. | Corre, Tanguy | Nongmaithem, Suraj S. | Chen, Yuning | Mangino, Massimo | Ruggiero, Daniela | Traglia, Michela | Farmaki, Aliki-Eleni | Kacprowski, Tim | Bjonnes, Andrew | van der Spek, Ashley | Wu, Ying | Giri, Anil K. | Yanek, Lisa R. | Wang, Lihua | Hofer, Edith | Rietveld, Cornelius A. | McLeod, Olga | Cornelis, Marilyn C. | Pattaro, Cristian | Verweij, Niek | Baumbach, Clemens | Abdellaoui, Abdel | Warren, Helen R. | Vuckovic, Dragana | Mei, Hao | Bouchard, Claude | Perry, John R.B. | Cappellani, Stefania | Mirza, Saira S. | Benton, Miles C. | Broeckel, Ulrich | Medland, Sarah E. | Lind, Penelope A. | Malerba, Giovanni | Drong, Alexander | Yengo, Loic | Bielak, Lawrence F. | Zhi, Degui | van der Most, Peter J. | Shriner, Daniel | Mägi, Reedik | Hemani, Gibran | Karaderi, Tugce | Wang, Zhaoming | Liu, Tian | Demuth, Ilja | Zhao, Jing Hua | Meng, Weihua | Lataniotis, Lazaros | van der Laan, Sander W. | Bradfield, Jonathan P. | Wood, Andrew R. | Bonnefond, Amelie | Ahluwalia, Tarunveer S. | Hall, Leanne M. | Salvi, Erika | Yazar, Seyhan | Carstensen, Lisbeth | de Haan, Hugoline G. | Abney, Mark | Afzal, Uzma | Allison, Matthew A. | Amin, Najaf | Asselbergs, Folkert W. | Bakker, Stephan J.L. | Barr, R. Graham | Baumeister, Sebastian E. | Benjamin, Daniel J. | Bergmann, Sven | Boerwinkle, Eric | Bottinger, Erwin P. | Campbell, Archie | Chakravarti, Aravinda | Chan, Yingleong | Chanock, Stephen J. | Chen, Constance | Chen, Y.-D. Ida | Collins, Francis S. | Connell, John | Correa, Adolfo | Cupples, L. Adrienne | Smith, George Davey | Davies, Gail | Dörr, Marcus | Ehret, Georg | Ellis, Stephen B. | Feenstra, Bjarke | Feitosa, Mary F. | Ford, Ian | Fox, Caroline S. | Frayling, Timothy M. | Friedrich, Nele | Geller, Frank | Scotland, Generation | Gillham-Nasenya, Irina | Gottesman, Omri | Graff, Misa | Grodstein, Francine | Gu, Charles | Haley, Chris | Hammond, Christopher J. | Harris, Sarah E. | Harris, Tamara B. | Hastie, Nicholas D. | Heard-Costa, Nancy L. | Heikkilä, Kauko | Hocking, Lynne J. | Homuth, Georg | Hottenga, Jouke-Jan | Huang, Jinyan | Huffman, Jennifer E. | Hysi, Pirro G. | Ikram, M. Arfan | Ingelsson, Erik | Joensuu, Anni | Johansson, Åsa | Jousilahti, Pekka | Jukema, J. Wouter | Kähönen, Mika | Kamatani, Yoichiro | Kanoni, Stavroula | Kerr, Shona M. | Khan, Nazir M. | Koellinger, Philipp | Koistinen, Heikki A. | Kooner, Manraj K. | Kubo, Michiaki | Kuusisto, Johanna | Lahti, Jari | Launer, Lenore J. | Lea, Rodney A. | Lehne, Benjamin | Lehtimäki, Terho | Liewald, David C.M. | Lind, Lars | Loh, Marie | Lokki, Marja-Liisa | London, Stephanie J. | Loomis, Stephanie J. | Loukola, Anu | Lu, Yingchang | Lumley, Thomas | Lundqvist, Annamari | Männistö, Satu | Marques-Vidal, Pedro | Masciullo, Corrado | Matchan, Angela | Mathias, Rasika A. | Matsuda, Koichi | Meigs, James B. | Meisinger, Christa | Meitinger, Thomas | Menni, Cristina | Mentch, Frank D. | Mihailov, Evelin | Milani, Lili | Montasser, May E. | Montgomery, Grant W. | Morrison, Alanna | Myers, Richard H. | Nadukuru, Rajiv | Navarro, Pau | Nelis, Mari | Nieminen, Markku S. | Nolte, Ilja M. | O’Connor, George T. | Ogunniyi, Adesola | Padmanabhan, Sandosh | Palmas, Walter R. | Pankow, James S. | Patarcic, Inga | Pavani, Francesca | Peyser, Patricia A. | Pietilainen, Kirsi | Poulter, Neil | Prokopenko, Inga | Ralhan, Sarju | Redmond, Paul | Rich, Stephen S. | Rissanen, Harri | Robino, Antonietta | Rose, Lynda M. | Rose, Richard | Sala, Cinzia | Salako, Babatunde | Salomaa, Veikko | Sarin, Antti-Pekka | Saxena, Richa | Schmidt, Helena | Scott, Laura J. | Scott, William R. | Sennblad, Bengt | Seshadri, Sudha | Sever, Peter | Shrestha, Smeeta | Smith, Blair H. | Smith, Jennifer A. | Soranzo, Nicole | Sotoodehnia, Nona | Southam, Lorraine | Stanton, Alice V. | Stathopoulou, Maria G. | Strauch, Konstantin | Strawbridge, Rona J. | Suderman, Matthew J. | Tandon, Nikhil | Tang, Sian-Tsun | Taylor, Kent D. | Tayo, Bamidele O. | Töglhofer, Anna Maria | Tomaszewski, Maciej | Tšernikova, Natalia | Tuomilehto, Jaakko | Uitterlinden, Andre G. | Vaidya, Dhananjay | van Hylckama Vlieg, Astrid | van Setten, Jessica | Vasankari, Tuula | Vedantam, Sailaja | Vlachopoulou, Efthymia | Vozzi, Diego | Vuoksimaa, Eero | Waldenberger, Melanie | Ware, Erin B. | Wentworth-Shields, William | Whitfield, John B. | Wild, Sarah | Willemsen, Gonneke | Yajnik, Chittaranjan S. | Yao, Jie | Zaza, Gianluigi | Zhu, Xiaofeng | Project, The BioBank Japan | Salem, Rany M. | Melbye, Mads | Bisgaard, Hans | Samani, Nilesh J. | Cusi, Daniele | Mackey, David A. | Cooper, Richard S. | Froguel, Philippe | Pasterkamp, Gerard | Grant, Struan F.A. | Hakonarson, Hakon | Ferrucci, Luigi | Scott, Robert A. | Morris, Andrew D. | Palmer, Colin N.A. | Dedoussis, George | Deloukas, Panos | Bertram, Lars | Lindenberger, Ulman | Berndt, Sonja I. | Lindgren, Cecilia M. | Timpson, Nicholas J. | Tönjes, Anke | Munroe, Patricia B. | Sørensen, Thorkild I.A. | Rotimi, Charles N. | Arnett, Donna K. | Oldehinkel, Albertine J. | Kardia, Sharon L.R. | Balkau, Beverley | Gambaro, Giovanni | Morris, Andrew P. | Eriksson, Johan G. | Wright, Margie J. | Martin, Nicholas G. | Hunt, Steven C. | Starr, John M. | Deary, Ian J. | Griffiths, Lyn R. | Tiemeier, Henning | Pirastu, Nicola | Kaprio, Jaakko | Wareham, Nicholas J. | Pérusse, Louis | Wilson, James G. | Girotto, Giorgia | Caulfield, Mark J. | Raitakari, Olli | Boomsma, Dorret I. | Gieger, Christian | van der Harst, Pim | Hicks, Andrew A. | Kraft, Peter | Sinisalo, Juha | Knekt, Paul | Johannesson, Magnus | Magnusson, Patrik K.E. | Hamsten, Anders | Schmidt, Reinhold | Borecki, Ingrid B. | Vartiainen, Erkki | Becker, Diane M. | Bharadwaj, Dwaipayan | Mohlke, Karen L. | Boehnke, Michael | van Duijn, Cornelia M. | Sanghera, Dharambir K. | Teumer, Alexander | Zeggini, Eleftheria | Metspalu, Andres | Gasparini, Paolo | Ulivi, Sheila | Ober, Carole | Toniolo, Daniela | Rudan, Igor | Porteous, David J. | Ciullo, Marina | Spector, Tim D. | Hayward, Caroline | Dupuis, Josée | Loos, Ruth J.F. | Wright, Alan F. | Chandak, Giriraj R. | Vollenweider, Peter | Shuldiner, Alan | Ridker, Paul M. | Rotter, Jerome I. | Sattar, Naveed | Gyllensten, Ulf | North, Kari E. | Pirastu, Mario | Psaty, Bruce M. | Weir, David R. | Laakso, Markku | Gudnason, Vilmundur | Takahashi, Atsushi | Chambers, John C. | Kooner, Jaspal S. | Strachan, David P. | Campbell, Harry | Hirschhorn, Joel N. | Perola, Markus | Polašek, Ozren | Wilson, James F.
Nature  2015;523(7561):459-462.
Homozygosity has long been associated with rare, often devastating, Mendelian disorders1 and Darwin was one of the first to recognise that inbreeding reduces evolutionary fitness2. However, the effect of the more distant parental relatedness common in modern human populations is less well understood. Genomic data now allow us to investigate the effects of homozygosity on traits of public health importance by observing contiguous homozygous segments (runs of homozygosity, ROH), which are inferred to be homozygous along their complete length. Given the low levels of genome-wide homozygosity prevalent in most human populations, information is required on very large numbers of people to provide sufficient power3,4. Here we use ROH to study 16 health-related quantitative traits in 354,224 individuals from 102 cohorts and find statistically significant associations between summed runs of homozygosity (SROH) and four complex traits: height, forced expiratory lung volume in 1 second (FEV1), general cognitive ability (g) and educational attainment (nominal p<1 × 10−300, 2.1 × 10−6, 2.5 × 10−10, 1.8 × 10−10). In each case increased homozygosity was associated with decreased trait value, equivalent to the offspring of first cousins being 1.2 cm shorter and having 10 months less education. Similar effect sizes were found across four continental groups and populations with different degrees of genome-wide homozygosity, providing convincing evidence for the first time that homozygosity, rather than confounding, directly contributes to phenotypic variance. Contrary to earlier reports in substantially smaller samples5,6, no evidence was seen of an influence of genome-wide homozygosity on blood pressure and low density lipoprotein (LDL) cholesterol, or ten other cardio-metabolic traits. Since directional dominance is predicted for traits under directional evolutionary selection7, this study provides evidence that increased stature and cognitive function have been positively selected in human evolution, whereas many important risk factors for late-onset complex diseases may not have been.
PMCID: PMC4516141  PMID: 26131930
17.  Genetic sharing and heritability of paediatric age of onset autoimmune diseases 
Nature Communications  2015;6:8442.
Autoimmune diseases (AIDs) are polygenic diseases affecting 7–10% of the population in the Western Hemisphere with few effective therapies. Here, we quantify the heritability of paediatric AIDs (pAIDs), including JIA, SLE, CEL, T1D, UC, CD, PS, SPA and CVID, attributable to common genomic variations (SNP-h2). SNP-h2 estimates are most significant for T1D (0.863±s.e. 0.07) and JIA (0.727±s.e. 0.037), more modest for UC (0.386±s.e. 0.04) and CD (0.454±0.025), largely consistent with population estimates and are generally greater than that previously reported by adult GWAS. On pairwise analysis, we observed that the diseases UC-CD (0.69±s.e. 0.07) and JIA-CVID (0.343±s.e. 0.13) are the most strongly correlated. Variations across the MHC strongly contribute to SNP-h2 in T1D and JIA, but does not significantly contribute to the pairwise rG. Together, our results partition contributions of shared versus disease-specific genomic variations to pAID heritability, identifying pAIDs with unexpected risk sharing, while recapitulating known associations between autoimmune diseases previously reported in adult cohorts.
Autoimmune diseases are genetically complex disorders that affect up to 10% of the Western population. Here Li et al. quantify the heritability of a range of autoimmune diseases in the largest paediatric cohort examined to date, illustrating that genetic and non-genetic components variably contribute to the susceptibility of each disease.
PMCID: PMC4633631  PMID: 26450413
18.  Pathway-Based Genome-Wide Association Studies for Plasma Triglycerides in Obese Females and Normal-Weight Controls 
PLoS ONE  2015;10(8):e0134923.
Pathway-based analysis as an alternative approach can provide complementary information to single-marker genome-wide association studies (GWASs), which always ignore the epistasis and does not have sufficient power to find rare variants. In this study, using genotypes from a genome-wide association study (GWAS), pathway-based association studies were carried out by a modified Gene Set Enrichment Algorithm (GSEA) method (GenGen) for triglyceride in 1028 unrelated European-American extremely obese females (BMI≥35kg/m2) and normal-weight controls (BMI<25kg/m2), and another pathway association analysis (ICSNPathway) was also used to verify the GenGen result in the same data. The GO0009110 pathway (vitamin anabolism) was among the strongest associations with triglyceride (empirical P<0.001); the result remained significant after FDR correction (P = 0.022). MMAB, an obesity-related locus, included in this pathway. The ABCG1 and BCL6 gene was found in several triglyceride-related pathways (empirical P<0.05), which were also replicated by ICSNPathway (empirical P<0.05, FDR<0.05). We also performed single-marked GWAS using PLINK for TG levels (log-transformed). Significant associations were found between ASTN2 gene SNPs and plasma triglyceride levels (rs7035794, P = 2.24×10−10). Our study suggested that vitamin anabolism pathway, BCL6 gene pathways and ASTN2 gene may contribute to the genetic variation of plasma triglyceride concentrations.
PMCID: PMC4550433  PMID: 26308950
19.  Pathway-Based Genome-wide Association Studies Reveal That the Rac1 Pathway Is Associated with Plasma Adiponectin Levels 
Scientific Reports  2015;5:13422.
Pathway-based analysis as an alternative and effective approach to identify disease-related genes or loci has been verified. To decipher the genetic background of plasma adiponectin levels, we performed genome wide pathway-based association studies in extremely obese individuals and normal-weight controls. The modified Gene Set Enrichment Algorithm (GSEA) was used to perform the pathway-based analyses (the GenGen Program) in 746 European American females, which were collected from our previous GWAS in extremely obese (BMI > 35 kg/m2) and never-overweight (BMI<25 kg/m2) controls. Rac1 cell motility signaling pathway was associated with plasma adiponectin after false-discovery rate (FDR) correction (empirical P < 0.001, FDR = 0.008, family-wise error rate = 0.008). Other several Rac1-centered pathways, such as cdc42racPathway (empirical P < 0.001), hsa00603 (empirical P = 0.003) were among the top associations. The RAC1 pathway association was replicated by the ICSNPathway method, yielded a FDR = 0.002. Quantitative pathway analyses yielded similar results (empirical P = 0.001) for the Rac1 pathway, although it failed to pass the multiple test correction (FDR = 0.11). We further replicated our pathway associations in the ADIPOGen Consortium data by the GSA-SNP method. Our results suggest that Rac1 and related cell motility pathways might be associated with plasma adiponectin levels and biological functions of adiponectin.
PMCID: PMC4642532  PMID: 26299439
20.  BMD Loci Contribute to Ethnic and Developmental Differences in Skeletal Fragility across Populations: Assessment of Evolutionary Selection Pressures 
Molecular Biology and Evolution  2015;32(11):2961-2972.
Bone mineral density (BMD) is a highly heritable trait used both for the diagnosis of osteoporosis in adults and to assess bone health in children. Ethnic differences in BMD have been documented, with markedly higher levels in individuals of African descent, which partially explain disparity in osteoporosis risk across populations. To date, 63 independent genetic variants have been associated with BMD in adults of Northern-European ancestry. Here, we demonstrate that at least 61 of these variants are predictive of BMD early in life by studying their compound effect within two multiethnic pediatric cohorts. Furthermore, we show that within these cohorts and across populations worldwide the frequency of those alleles associated with increased BMD is systematically elevated in individuals of Sub-Saharan African ancestry. The amount of differentiation in the BMD genetic scores among Sub-Saharan and non-Sub-Saharan populations together with neutrality tests, suggest that these allelic differences are compatible with the hypothesis of selective pressures acting on the genetic determinants of BMD. These findings constitute an explorative contribution to the role of selection on ethnic BMD differences and likely a new example of polygenic adaptation acting on a human trait.
PMCID: PMC4651235  PMID: 26226985
genome-wide association studies; bone mineral density; polygenic; adaptation; ethnic differences; selective pressures
21.  Genome-wide copy number variation study associates metabotropic glutamate receptor gene networks with attention deficit hyperactivity disorder 
Nature genetics  2011;44(1):78-84.
Attention deficit hyperactivity disorder (ADHD) is a common, heritable neuropsychiatric disorder of unknown etiology. We performed a whole-genome copy number variation (CNV) study on 1,013 cases with ADHD and 4,105 healthy children of European ancestry using 550,000 SNPs. We evaluated statistically significant findings in multiple independent cohorts, with a total of 2,493 cases with ADHD and 9,222 controls of European ancestry, using matched platforms. CNVs affecting metabotropic glutamate receptor genes were enriched across all cohorts (P = 2.1 × 10−9). We saw GRM5 (encoding glutamate receptor, metabotropic 5) deletions in ten cases and one control (P = 1.36 × 10−6). We saw GRM7 deletions in six cases, and we saw GRM8 deletions in eight cases and no controls. GRM1 was duplicated in eight cases. We experimentally validated the observed variants using quantitative RT-PCR. A gene network analysis showed that genes interacting with the genes in the GRM family are enriched for CNVs in ~10% of the cases (P = 4.38 × 10−10) after correction for occurrence in the controls. We identified rare recurrent CNVs affecting glutamatergic neurotransmission genes that were overrepresented in multiple ADHD cohorts.
PMCID: PMC4310555  PMID: 22138692
22.  Association of variants of the interleukin-23 receptor (IL23R) gene with susceptibility to pediatric Crohn’s disease 
Background & Aims
Recently an association was demonstrated between the single nucleotide polymorphism (SNP), rs11209026, within the interleukin-23 receptor (IL23R) locus and Crohn’s disease (CD) as a consequence of a genome wide association study of this disease in adults. We examined the effects of this and other previously reported SNPs at this locus with respect to CD in children.
Utilizing data from our ongoing genome-wide association study in our cohort of 142 pediatric CD cases and 281 matched controls, we investigated the association of the previously reported SNPs at the IL23R locus with the childhood form of this disease.
Using a Fisher’s exact test, the minor allele frequency (MAF) of rs1120902 in the cases was 1.75% while it was 6.61% in controls, yielding a protective odds ratio (OR) of 0.25 (95% CI 0.10 – 0.65; one-sided P = 9.2×10−4). Furthermore, of all the SNPs previously reported, rs11209026 was the most strongly associated. A subsequent family-based association test (which is more resistant to population stratification) with 65 sets of trios derived from our initial patient cohort yielded significant association with rs11209026 in a transmission disequilibrium test (one-sided P=0.0017). In contrast, no association was detected to the CARD15 gene for the IBD phenotype.
The OR of the IL23R variant in our pediatric study is highly comparable with that reported previously in a non-Jewish adult IBD case-control cohort (OR=0.26). As such, variants in IL23R gene confer a similar magnitude of risk of CD to children as for their adult counterparts.
PMCID: PMC4287202  PMID: 17618837
IL23R; gene; association; Crohn’s Disease
23.  DNA binding by FOXP3 domain-swapped dimer suggests mechanisms of long-range chromosomal interactions 
Nucleic Acids Research  2015;43(2):1268-1282.
FOXP3 is a lineage-specific transcription factor that is required for regulatory T cell development and function. In this study, we determined the crystal structure of the FOXP3 forkhead domain bound to DNA. The structure reveals that FOXP3 can form a stable domain-swapped dimer to bridge DNA in the absence of cofactors, suggesting that FOXP3 may play a role in long-range gene interactions. To test this hypothesis, we used circular chromosome conformation capture coupled with high throughput sequencing (4C-seq) to analyze FOXP3-dependent genomic contacts around a known FOXP3-bound locus, Ptpn22. Our studies reveal that FOXP3 induces significant changes in the chromatin contacts between the Ptpn22 locus and other Foxp3-regulated genes, reflecting a mechanism by which FOXP3 reorganizes the genome architecture to coordinate the expression of its target genes. Our results suggest that FOXP3 mediates long-range chromatin interactions as part of its mechanisms to regulate specific gene expression in regulatory T cells.
PMCID: PMC4333414  PMID: 25567984
24.  Two novel type 2 diabetes loci revealed through integration of TCF7L2 DNA occupancy and SNP association data 
The transcription factor 7-like 2 (TCF7L2) locus is strongly implicated in the pathogenesis of type 2 diabetes (T2D). We previously mapped the genomic regions bound by TCF7L2 using ChIP (chromatin immunoprecipitation)-seq in the colorectal carcinoma cell line, HCT116, revealing an unexpected highly significant over-representation of genome-wide association studies (GWAS) loci associated primarily with endocrine (in particular T2D) and cardiovascular traits.
In order to further explore if this observed phenomenon occurs in other cell lines, we carried out ChIP-seq in HepG2 cells and leveraged ENCODE data for five additional cell lines. Given that only a minority of the predicted genetic component to most complex traits has been identified to date, plus our GWAS-related observations with respect to TCF7L2 occupancy, we investigated if restricting association analyses to the genes yielded from this approach, in order to reduce the constraints of multiple testing, could reveal novel T2D loci.
We found strong evidence for the continued enrichment of endocrine and cardiovascular GWAS categories, with additional support for cancer. When investigating all the known GWAS loci bound by TCF7L2 in the shortest gene list, derived from HCT116, the coronary artery disease-associated variant, rs46522 at the UBE2Z-GIP-ATP5G1-SNF8 locus, yielded significant association with T2D within DIAGRAM. Furthermore, when we analyzed tag-SNPs (single nucleotide polymorphisms) in genes not previously implicated by GWAS but bound by TCF7L2 within 5 kb, we observed a significant association of rs4780476 within CPPED1 in DIAGRAM.
ChIP-seq data generated with this GWAS-implicated transcription factor provided a biologically plausible method to limit multiple testing in the assessment of genome-wide genotyping data to uncover two novel T2D-associated loci.
PMCID: PMC4250976  PMID: 25469308
Genetic Association; Type 2; Transcription Factor; Gene
25.  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.
PMCID: PMC4447786  PMID: 25281659

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