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1.  GAD2 on Chromosome 10p12 Is a Candidate Gene for Human Obesity 
PLoS Biology  2003;1(3):e68.
The gene GAD2 encoding the glutamic acid decarboxylase enzyme (GAD65) is a positional candidate gene for obesity on Chromosome 10p11–12, a susceptibility locus for morbid obesity in four independent ethnic populations. GAD65 catalyzes the formation of γ-aminobutyric acid (GABA), which interacts with neuropeptide Y in the paraventricular nucleus to contribute to stimulate food intake. A case-control study (575 morbidly obese and 646 control subjects) analyzing GAD2 variants identified both a protective haplotype, including the most frequent alleles of single nucleotide polymorphisms (SNPs) +61450 C>A and +83897 T>A (OR = 0.81, 95% CI [0.681–0.972], p = 0.0049) and an at-risk SNP (−243 A>G) for morbid obesity (OR = 1.3, 95% CI [1.053–1.585], p = 0.014). Furthermore, familial-based analyses confirmed the association with the obesity of SNP +61450 C>A and +83897 T>A haplotype (χ2 = 7.637, p = 0.02). In the murine insulinoma cell line βTC3, the G at-risk allele of SNP −243 A>G increased six times GAD2 promoter activity (p < 0.0001) and induced a 6-fold higher affinity for nuclear extracts. The −243 A>G SNP was associated with higher hunger scores (p = 0.007) and disinhibition scores (p = 0.028), as assessed by the Stunkard Three-Factor Eating Questionnaire. As GAD2 is highly expressed in pancreatic β cells, we analyzed GAD65 antibody level as a marker of β-cell activity and of insulin secretion. In the control group, −243 A>G, +61450 C>A, and +83897 T>A SNPs were associated with lower GAD65 autoantibody levels (p values of 0.003, 0.047, and 0.006, respectively). SNP +83897 T>A was associated with lower fasting insulin and insulin secretion, as assessed by the HOMA-B% homeostasis model of β-cell function (p = 0.009 and 0.01, respectively). These data support the hypothesis of the orexigenic effect of GABA in humans and of a contribution of genes involved in GABA metabolism in the modulation of food intake and in the development of morbid obesity.
A large case-control study, family-based genetic analyses, and functional data suggest that variation in the GAD2 gene affects eating behavior and insulin metabolism
PMCID: PMC270019  PMID: 14691540
2.  Prospective Analysis of Genetic Polymorphisms and Risk of Recurrence in Renal Cell Cancer 
The lancet oncology  2012;14(1):81-87.
Germline genetic polymorphisms may affect the risk of recurrence in patients with localized renal cell carcinoma (RCC). Our aim was to investigate the association of genetic polymorphisms with RCC recurrence.
Patients and Methods
We analyzed germline DNA samples extracted from 554 (discovery cohort of 403 and an independent validation cohort of 151) patients with localized RCC treated at Dana-Farber/Harvard Cancer Center (DF/HCC) and of European-American ancestry (Caucasians). The discovery cohort was selected from a prospective database at Dana-Farber/Harvard Cancer Center and the validation cohort was identified from the Brigham and Women’s Hospital surgery and pathology department records. Single nucleotide polymorphims (SNPs) residing in 70 genes involved in RCC pathogenesis including the VHL/HIF/VEGF, PI3K/AKT/mTOR pathways, and genes involved in immune regulation and metabolism were genotyped for the discovery cohort (total 285 SNPs successfully genotyped and assessable for analysis). The analyses of genotype associations with recurrence free survival (RFS) were assessed using Cox proportional hazards model, Kaplan-Meier method and logrank test. False discovery rate (FDR) q-value was used to adjust for multiple comparisons in selecting potential SNPs with RFS association. The finding from the discovery cohort was validated in an external independent cohort.
We report the significant association between genotype variants of SNP rs11762213 (c.144G>A; p.Ala48Ala, located in exon two c-MET) and primary analysis endpoint of RFS using both univariate and multivariable analysis. Specifically, patients carrying one or two copies of the minor (risk) allele had an increased risk of recurrence or death (hazard ratio (HR) =1·86, 95% confidence interval (CI), 1·17,2·95; p=0·0084) in the multivariate analysis adjusted for clinical and pathological factors. The median RFS for carriers of the risk allele was 19 months (95%CI: 9,*) compared to 50 months (95%CI: 37,75) for homozygotes of the non-risk allele. The significant association was validated using data from the validation cohort with a HR of 2·45 (95%CI: 1·01,5·95; p=0·048), although of borderline significance. The rs11762213 results in a synonymous aminoacid change in cMET gene. * unable to estimate due to small sample.
Patients with localized RCC and c-MET polymorphism (rs11762213) may have an increased risk of recurrence after nephrectomy. If these results are further validated, it may be incorporated in future prognostic tools, potentially aiding in the design of adjuvant clinical trials with c-MET inhibitors, and clinical management.
This project is funded by the Conquer Cancer Foundation and ASCO under a Career Development Award (CDA) for Dr. Choueiri, The Trust Family Research for Kidney cancer for Dr. Choueiri and the NIH/NCI Kidney cancer SPORE.
PMCID: PMC3769687  PMID: 23219378
localized renal cell cancer; nephrectomy; recurrence free interval; genetic polymorphisms; single nucleotide polymorphisms; MET; VEGF
3.  Association Study of 182 Candidate Genes in Anorexia Nervosa 
We performed association studies with 5,151 SNPs that were judged as likely candidate genetic variations conferring susceptibility to anorexia nervosa (AN) based on location under reported linkage peaks, previous results in the literature (182 candidate genes), brain expression, biological plausibility, and estrogen responsivity. We employed a case–control design that tested each SNP individually as well as haplotypes derived from these SNPs in 1,085 case individuals with AN diagnoses and 677 control individuals. We also performed separate association analyses using three increasingly restrictive case definitions for AN: all individuals with any subtype of AN (All AN: n = 1,085); individuals with AN with no binge eating behavior (AN with No Binge Eating: n = 687); and individuals with the restricting subtype of AN (Restricting AN: n = 421). After accounting for multiple comparisons, there were no statistically significant associations for any individual SNP or haplotype block with any definition of illness. These results underscore the importance of large samples to yield appropriate power to detect genotypic differences in individuals with AN and also motivate complementary approaches involving Genome-Wide Association (GWA) studies, Copy Number Variation (CNV) analyses, sequencing-based rare variant discovery assays, and pathway-based analysis in order to make up for deficiencies in traditional candidate gene approaches to AN.
PMCID: PMC2963154  PMID: 20468064
single nucleotide polymorphisms; probands; anorexia nervosa; bulimia nervosa
4.  Polymorphisms in the SUFU gene are Associated with Organ Injury Protection and Sepsis Severity in Patients with Enterobacteriacea Bacteremia 
Organ injury including acute kidney injury (AKI) and acute lung Injury (ALI) are major contributors to mortality and morbidity in the setting of sepsis. Hedgehog pathway has been recognized as an important mediator in repair of organ injury. There are some clinical predictors associated with the development of organ injury in sepsis; however few host genetic risk factors have been identified and candidate genes for organ injury susceptibility and severity are largely unknown.
A prospective cohort study in a tertiary care hospital included 250 adult hospitalized patients with Enterobacteriacea bacteremia. We selected a panel of 69 tagging SNPs for genes in the Hedgehog signaling pathway using the TagSNP functionality of the SNPInfo web server and designed a panel on the GoldenGate Veracode genotyping assay (Illumina). We confirmed Illumina data using Taqman allelic discrimination assays. We assessed SNPs in combination with clinical variables for associations with outcomes and organ injury.
Significant associations were identified using logistic regression models, controlling for age, race and gender. From the 69 tagging SNPs, 5 SNPs were associated with renal function and 2 with APACHEII score after false discovery rate correction. After multivariate analysis SNPs rs10786691 (p=0.03), rs12414407 (p=0.026), rs10748825 (p=0.01), and rs7078511 (p=0.006), all in the suppressor of fused homolog (SUFU) gene, correlated with renal function. Likewise, SUFU SNPs rs7907760 (p=0.009) and rs10748825 (p=0.029) were associated with APACHEII score. SNPs rs12414407 and rs1078825 are in linkage disequilibrium (LD) with rs2296590, a SNP in the 5′-UTR region that is within a predicted transcription factor bind site for CCAAT-enhancer-binding proteins. In multivariate analyses functional SNP rs2296590 was correlated with renal function (p=0.004) and APACHEII score (p=0.049).
Host susceptibility factors play an important role in sepsis development and sepsis related organ injury. Polymorphisms in the SUFU gene (encoding for a negative regulator of the hedgehog signaling pathway) are associated with protection from Enterobacteriacea bacteremia related organ injury and sepsis severity.
PMCID: PMC3669235  PMID: 23538333
Gram negative sepsis; organ injury; polymorphism; SUFU
5.  Associations of glutamate decarboxylase genes with initial sensitivity and age-at-onset of alcohol dependence in the Irish Affected Sib Pair Study of Alcohol Dependence 
Drug and alcohol dependence  2008;101(1-2):80-87.
The relation of γ-aminobutyric acid (GABA) to alcohol dependence (AD) has been widely studied. Several previous studies suggest that GABA may be involved in alcohol withdrawal, tolerance, and the symptoms that form an AD diagnosis. The genes coding for glutamate decarboxylase (GAD), the rate-limiting enzyme in GABA synthesis, are of potential interest for their association to ethanol consumption and AD. There are two isoforms of GAD, GAD1 and GAD2, which were reported to be associated with AD in males of Han Taiwanese (GAD1) and Russian (GAD2) ancestry. The present study examined the association of the two GAD isoforms with AD and relevant alcohol-related traits in the Irish Affected Sib Pair Study of Alcohol Dependence [Prescott, C.A., Sullivan, P.F., Myers, J.M., Patterson, D.G., Devitt, M., Halberstadt, L.J., Walsh, D., Kendler, K.S., 2005. The Irish Affected Sib Pair Study of Alcohol Dependence: study methodology and validation of diagnosis by interview and family history. Alcohol.-Clin. Exp. Res. 29 (3) 417–429].
Participants were recruited in Ireland, including 575 independent cases who met DSM-IV AD criteria and 530 controls, screened for heavy drinking. We first conducted case-control analyses of the GAD genes with AD and, within the cases, examined associations with age at onset of AD, withdrawal symptoms, and two quantitative measures: initial sensitivity and tolerance (based on scales from the Self-Rating of the Effects of Ethanol) [Schuckit, M.A., Smith, T.L., Tipp, J.E., 1997. The self-rating of the effects of alcohol (SRE) form as a retrospective measure of the risk for alcoholism. Addiction 92, 979–988]. A total of 29 SNPs were genotyped for GAD1 and GAD2 using the Illumina GoldenGate protocols. Statistical procedures were implemented to control for false discovery rates (FDR).
Nine of 29 markers with minor allele frequencies less than 0.01 were removed from standard analysis; the remaining 20 markers were all in Hardy-Weinberg equilibrium. Three markers in the intronic regions of GAD1 were associated with initial sensitivity to alcohol (P = 0.002); the associations remained significant after a FDR based correction for multiple testing. In addition, one marker located 3 kb upstream of GAD1 exhibited association with age at onset of AD (P = 0.0001). Gender specific effects were observed in results of both single marker and haplotype analyses.
We found no evidence for the association of GAD genes with AD but significant association of GAD1 with initial sensitivity and age at onset of AD. Our findings suggest that the underlying pathophysiology regulated by genes like GAD1 may be more directly related to the component processes that form AD than to the clinical disorder.
PMCID: PMC2844896  PMID: 19111404
GABA; Initial sensitivity; Response to ethanol; Withdrawal; Gender difference
6.  Identification of KIF3A as a Novel Candidate Gene for Childhood Asthma Using RNA Expression and Population Allelic Frequencies Differences 
PLoS ONE  2011;6(8):e23714.
Asthma is a chronic inflammatory disease with a strong genetic predisposition. A major challenge for candidate gene association studies in asthma is the selection of biologically relevant genes.
Methodology/Principal Findings
Using epithelial RNA expression arrays, HapMap allele frequency variation, and the literature, we identified six possible candidate susceptibility genes for childhood asthma including ADCY2, DNAH5, KIF3A, PDE4B, PLAU, SPRR2B. To evaluate these genes, we compared the genotypes of 194 predominantly tagging SNPs in 790 asthmatic, allergic and non-allergic children. We found that SNPs in all six genes were nominally associated with asthma (p<0.05) in our discovery cohort and in three independent cohorts at either the SNP or gene level (p<0.05). Further, we determined that our selection approach was superior to random selection of genes either differentially expressed in asthmatics compared to controls (p = 0.0049) or selected based on the literature alone (p = 0.0049), substantiating the validity of our gene selection approach. Importantly, we observed that 7 of 9 SNPs in the KIF3A gene more than doubled the odds of asthma (OR = 2.3, p<0.0001) and increased the odds of allergic disease (OR = 1.8, p<0.008). Our data indicate that KIF3A rs7737031 (T-allele) has an asthma population attributable risk of 18.5%. The association between KIF3A rs7737031 and asthma was validated in 3 independent populations, further substantiating the validity of our gene selection approach.
Our study demonstrates that KIF3A, a member of the kinesin superfamily of microtubule associated motors that are important in the transport of protein complexes within cilia, is a novel candidate gene for childhood asthma. Polymorphisms in KIF3A may in part be responsible for poor mucus and/or allergen clearance from the airways. Furthermore, our study provides a promising framework for the identification and evaluation of novel candidate susceptibility genes.
PMCID: PMC3166061  PMID: 21912604
7.  Genetic Polymorphisms in Host Antiviral Genes: Associations with Humoral and Cellular Immunity to Measles Vaccine 
Vaccine  2011;29(48):8988-8997.
Host antiviral genes are important regulators of antiviral immunity and plausible genetic determinants of immune response heterogeneity after vaccination. We genotyped and analyzed 307 common candidate tagSNPs from 12 antiviral genes in a cohort of 745 schoolchildren immunized with two doses of measles-mumps-rubella vaccine. Associations between SNPs/haplotypes and measles virus-specific immune outcomes were assessed using linear regression methodologies in Caucasians and African-Americans.
Genetic variants within the DDX58/RIG-I gene, including a coding polymorphism (rs3205166/Val800Val), were associated as single-SNPs (p≤0.017; although these SNPs did not remain significant after correction for false discovery rate/FDR) and in haplotype-level analysis, with measles-specific antibody variations in Caucasians (haplotype allele p-value=0.021; haplotype global p-value=0.076). Four DDX58 polymorphisms, in high LD, demonstrated also associations (after correction for FDR) with variations in both measles-specific IFN-γ and IL-2 secretion in Caucasians (p≤0.001, q=0.193). Two intronic OAS1 polymorphisms, including the functional OAS1 SNP rs10774671 (p=0.003), demonstrated evidence of association with a significant allele-dose-related increase in neutralizing antibody levels in African-Americans. Genotype and haplotype-level associations demonstrated the role of ADAR genetic variants, including a non-synonymous SNP (rs2229857/Arg384Lys; p=0.01), in regulating measles virus-specific IFN-γ Elispot responses in Caucasians (haplotype global p-value=0.017). After correction FDR, 15 single-SNP associations (11 SNPs in Caucasians and 4 SNPs in African-Americans) still remained significant at the q-value<0.20.
In conclusion, our findings strongly point to genetic variants/genes, involved in antiviral sensing and antiviral control, as critical determinants, differentially modulating the adaptive immune responses to live attenuated measles vaccine in Caucasians and African-Americans.
PMCID: PMC3941984  PMID: 21939710
Single Nucleotide Polymorphisms; Haplotypes; Antiviral genes; Measles vaccine; Immunity
8.  Germline Predictors of Androgen Deprivation Therapy Response in Advanced Prostate Cancer 
Mayo Clinic Proceedings  2012;87(3):240-246.
To evaluate whether germline variations in genes involved in sex steroid biosynthesis and metabolic pathways predict time to treatment failure for patients with advanced prostate cancer undergoing androgen deprivation therapy (ADT), because there are few known clinical predictors of response.
Patients and Methods
In a cohort of 304 patients with advanced prostate cancer undergoing ADT, we genotyped 746 single-nucleotide polymorphisms (SNPs) from 72 genes from germline DNA (680 tagSNPs from 58 genes and 66 candidate SNPs from 20 genes [6 genes common in both]). Association with the primary end point of time to ADT failure was assessed using proportional hazards regression models at the gene level (for genes with tagging SNPs) and at the SNP level. False discovery rates (FDRs) of 0.10 or less were considered noteworthy to account for multiple testing.
At the gene level, TRMT11 showed the strongest association with time to ADT failure (P<.001; FDR=0.008). Two of 4 TRMT11 tagSNPs were associated with time to ADT failure. Median time to ADT failure for rs1268121 (A>G) was 3.05 years for the AA, 4.27 years for the AG, and 6.22 years for the GG genotypes (P=.002), and for rs6900796 (G>A), it was 2.42 years for the GG, 3.52 years for the AG, and 4.18 years for the AA genotypes (P<.001). No other gene level or SNP level tests had an FDR of 0.10 or less.
Genetic variation in TRMT11 was associated with time to ADT failure. Confirmation of these preliminary findings in an independent cohort is needed.
PMCID: PMC3538410  PMID: 22386179
9.  Whole Genome Sequencing versus Traditional Genotyping for Investigation of a Mycobacterium tuberculosis Outbreak: A Longitudinal Molecular Epidemiological Study 
PLoS Medicine  2013;10(2):e1001387.
In an outbreak investigation of Mycobacterium tuberculosis comparing whole genome sequencing (WGS) with traditional genotyping, Stefan Niemann and colleagues found that classical genotyping falsely clustered some strains, and WGS better reflected contact tracing.
Understanding Mycobacterium tuberculosis (Mtb) transmission is essential to guide efficient tuberculosis control strategies. Traditional strain typing lacks sufficient discriminatory power to resolve large outbreaks. Here, we tested the potential of using next generation genome sequencing for identification of outbreak-related transmission chains.
Methods and Findings
During long-term (1997 to 2010) prospective population-based molecular epidemiological surveillance comprising a total of 2,301 patients, we identified a large outbreak caused by an Mtb strain of the Haarlem lineage. The main performance outcome measure of whole genome sequencing (WGS) analyses was the degree of correlation of the WGS analyses with contact tracing data and the spatio-temporal distribution of the outbreak cases. WGS analyses of the 86 isolates revealed 85 single nucleotide polymorphisms (SNPs), subdividing the outbreak into seven genome clusters (two to 24 isolates each), plus 36 unique SNP profiles. WGS results showed that the first outbreak isolates detected in 1997 were falsely clustered by classical genotyping. In 1998, one clone (termed “Hamburg clone”) started expanding, apparently independently from differences in the social environment of early cases. Genome-based clustering patterns were in better accordance with contact tracing data and the geographical distribution of the cases than clustering patterns based on classical genotyping. A maximum of three SNPs were identified in eight confirmed human-to-human transmission chains, involving 31 patients. We estimated the Mtb genome evolutionary rate at 0.4 mutations per genome per year. This rate suggests that Mtb grows in its natural host with a doubling time of approximately 22 h (400 generations per year). Based on the genome variation discovered, emergence of the Hamburg clone was dated back to a period between 1993 and 1997, hence shortly before the discovery of the outbreak through epidemiological surveillance.
Our findings suggest that WGS is superior to conventional genotyping for Mtb pathogen tracing and investigating micro-epidemics. WGS provides a measure of Mtb genome evolution over time in its natural host context.
Please see later in the article for the Editors' Summary
Editors' Summary
Tuberculosis—a contagious bacterial disease that usually infects the lungs—is a major public health problem, particularly in low- and middle-income countries. In 2011, an estimated 8.7 million people developed tuberculosis globally, and 1.4 million people died from the disease. Tuberculosis is second only to HIV/AIDS in terms of global deaths from a single infectious agent. Mycobacterium tuberculosis, the bacterium that causes tuberculosis, is readily spread in airborne droplets when people with active disease cough or sneeze. The characteristic symptoms of tuberculosis include persistent cough, weight loss, fever, and night sweats. Diagnostic tests for the disease include sputum smear analysis (examination of mucus coughed up from the lungs for the presence of M. tuberculosis), mycobacterial culture (growth of M. tuberculosis from sputum), and chest X-rays. Tuberculosis can be cured by taking several antibiotics daily for at least six months, although the recent emergence of multidrug-resistant M. tuberculosis is making tuberculosis harder to treat.
Why Was This Study Done?
Although efforts to reduce the global burden of tuberculosis are showing some improvements, the annual decline in the number of people developing tuberculosis continues to be slow. To develop optimized control strategies, experts need to be able to accurately track M. tuberculosis transmission within human populations. Because M. tuberculosis, like all bacteria, accumulates genetic changes over time, there are many different strains (genetic variants) of M. tuberculosis. Genotyping methods have been developed that identify different bacterial strains by examining specific regions of the bacterial genome (blueprint), but because these methods examine only a small part of the genome, they may not distinguish between related transmission chains. That is, traditional strain genotyping methods may not be able to determine accurately where a tuberculosis outbreak started or how it spread through a population. In this longitudinal cohort study, the researchers compare the ability of whole genome sequencing (WGS), which is rapidly becoming widely available, and traditional genotyping to provide information about a recent German tuberculosis outbreak. In a longitudinal cohort study, a population is followed over time to analyze the occurrence of a specific disease.
What Did the Researchers Do and Find?
During long-term (1997–2010) population-based molecular epidemiological surveillance (disease surveillance that uses molecular techniques rather than reports of illness) in Hamburg and Schleswig-Holstein, the researchers identified a large tuberculosis outbreak caused by M. tuberculosis isolates of the Haarlem lineage using classical strain typing. The researchers examined each of the 86 isolates from this outbreak using WGS and classical genotyping and asked whether the results of these two approaches correlated with contact tracing data (information is routinely collected about the people a patient with tuberculosis has recently met so that these contacts can be tested for tuberculosis and treated if necessary) and with the spatio-temporal distribution of outbreak cases. WGS of the isolates identified 85 single nucleotide polymorphisms (SNPs; genomic sequence variants in which single building blocks, or nucleotides, are altered) that subdivided the outbreak into seven clusters of isolates and 36 unique isolates. The WGS results showed that the first isolates of the outbreak were incorrectly clustered by classical genotyping and that one strain—the “Hamburg clone”—started expanding in 1998. Notably, the genome-based clustering patterns were in better accordance with contact tracing data and with the geographical distribution of cases than clustering patterns based on classical genotyping, and they identified eight confirmed human-to-human transmission chains that involved 31 patients and a maximum of three SNPs. Finally, the researchers used their WGS results to estimate that the Hamburg clone emerged between 1993 and 1997, shortly before the discovery of the tuberculosis outbreak through epidemiological surveillance.
What Do These Findings Mean?
These findings show that WGS can be used to identify specific strains within large tuberculosis outbreaks more accurately than classical genotyping. They also provide new information about the evolution of M. tuberculosis during outbreaks and indicate how WGS data should be interpreted in future genome-based molecular epidemiology studies. WGS has the potential to improve the molecular epidemiological surveillance and control of tuberculosis and of other infectious diseases. Importantly, note the researchers, ongoing reductions in the cost of WGS, the increased availability of “bench top” genome sequencers, and bioinformatics developments should all accelerate the implementation of WGS as a standard method for the identification of transmission chains in infectious disease outbreaks.
Additional Information
Please access these websites via the online version of this summary at
The World Health Organization provides information (in several languages) on all aspects of tuberculosis, including the Global Tuberculosis Report 2012
The Stop TB Partnership is working towards tuberculosis elimination; patient stories about tuberculosis are available (in English and Spanish)
The US Centers for Disease Control and Prevention has information about tuberculosis, including information on tuberculosis genotyping (some information in English and Spanish)
The US National Institute of Allergy and Infectious Diseases also has detailed information on all aspects of tuberculosis
The Tuberculosis Survival Project, which aims to raise awareness of tuberculosis and provide support for people with tuberculosis, provides personal stories about treatment for tuberculosis; the Tuberculosis Vaccine Initiative also provides personal stories about dealing with tuberculosis
MedlinePlus has links to further information about tuberculosis (in English and Spanish)
Wikipedia has a page on whole-genome sequencing (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
PMCID: PMC3570532  PMID: 23424287
10.  IL28B, HLA-C, and KIR Variants Additively Predict Response to Therapy in Chronic Hepatitis C Virus Infection in a European Cohort: A Cross-Sectional Study 
PLoS Medicine  2011;8(9):e1001092.
Vijayaprakash Suppiah and colleagues show that genotyping hepatitis C patients for the IL28B, HLA-C, and KIR genes improves the ability to predict whether or not patients will respond to antiviral treatment.
To date, drug response genes have not proved as useful in clinical practice as was anticipated at the start of the genomic era. An exception is in the treatment of chronic hepatitis C virus (HCV) genotype 1 infection with pegylated interferon-alpha and ribavirin (PegIFN/R). Viral clearance is achieved in 40%–50% of patients. Interleukin 28B (IL28B) genotype predicts treatment-induced and spontaneous clearance. To improve the predictive value of this genotype, we studied the combined effect of variants of IL28B with human leukocyte antigen C (HLA-C), and its ligands the killer immunoglobulin-like receptors (KIR), which have previously been implicated in HCV viral control.
Methods and Findings
We genotyped chronic hepatitis C (CHC) genotype 1 patients with PegIFN/R treatment-induced clearance (n = 417) and treatment failure (n = 493), and 234 individuals with spontaneous clearance, for HLA-C C1 versus C2, presence of inhibitory and activating KIR genes, and two IL28B SNPs, rs8099917 and rs12979860. All individuals were Europeans or of European descent. IL28B SNP rs8099917 “G” was associated with absence of treatment-induced clearance (odds ratio [OR] 2.19, p = 1.27×10−8, 1.67–2.88) and absence of spontaneous clearance (OR 3.83, p = 1.71×10−14, 2.67–5.48) of HCV, as was rs12979860, with slightly lower ORs. The HLA-C C2C2 genotype was also over-represented in patients who failed treatment (OR 1.52, p = 0.024, 1.05–2.20), but was not associated with spontaneous clearance. Prediction of treatment failure improved from 66% with IL28B to 80% using both genes in this cohort (OR 3.78, p = 8.83×10−6, 2.03–7.04). There was evidence that KIR2DL3 and KIR2DS2 carriage also altered HCV treatment response in combination with HLA-C and IL28B.
Genotyping for IL28B, HLA-C, and KIR genes improves prediction of HCV treatment response. These findings support a role for natural killer (NK) cell activation in PegIFN/R treatment-induced clearance, partially mediated by IL28B.
Please see later in the article for the Editors' Summary
Editors' Summary
About 170 million people harbor long-term (chronic) infections with the hepatitis C virus (HCV) and 3–4 million people are newly infected with the virus every year. HCV—a leading cause of chronic hepatitis (inflammation of the liver)—is spread though contact with infected blood. Transmission can occur during medical procedures (for example, transfusions with unscreened blood or reuse of inadequately sterilized medical instruments) but in developed countries, where donated blood is routinely screened for HCV, the most common transmission route is needle-sharing among intravenous drug users. HCV infection can cause a short-lived illness characterized by tiredness and jaundice (yellow skin and eyes) but 70%–80% of newly infected people progress to a symptom-free, chronic infection that can eventually cause liver cirrhosis (scarring) and liver cancer. HCV infections can be treated with a combination of two drugs—pegylated interferon-alpha and ribavirin (PegIFN/R). However, PegIFN/R is expensive, causes unpleasant side-effects, and is ineffective in about half of people infected with HCV genotype 1, the commonest HCV strain.
Why Was This Study Done?
It would be extremely helpful to be able to identify which patients will respond to PegIFN/R before starting treatment. An individual's genetic make-up plays a key role in the safety and effectiveness of drugs. Thus, pharmacogenomics—the study of how genetic variants affects the body's response to drugs—has the potential to alter the clinical management of many diseases by allowing clinicians to provide individually tailored drug treatments. In 2009, scientists reported that certain single nucleotide polymorphisms (SNPs, a type of genetic variant) lying near the IL28B gene (which encodes an immune system protein made in response to viral infections) strongly influence treatment outcomes and spontaneous clearance in HCV-infected people. This discovery is now being used to predict treatment responses to PegIFN/R in clinical practice but genotyping (analysis of variants of) IL28B only correctly predicts treatment failure two-thirds of the time. Here, the researchers investigate whether genotyping two additional regions of the genome—the HLA-C and KIR gene loci—can improve the predictive value of IL28B genotyping. Human leukocyte antigen C (HLA-C) and the killer immunoglobulin-like receptors (KIRs) are interacting proteins that have been implicated in HCV viral control.
What Did the Researchers Do and Find?
The researchers genotyped 417 patients chronically infected with HCV genotype 1 whose infection had been cleared by PegIFN/R treatment, 493 patients whose infection had not responded to treatment, and 234 patients whose infection had cleared spontaneously for two HLA-C variants (C1 and C2), the presence of several KIR genes (individuals carry different combinations of KIR genes), and two IL28B SNPs (rs8099917 and rs12979860). Carriage of “variants” of either IL28B SNP was associated with absence of treatment-induced clearance and absence of spontaneous clearance. That is, these variant SNPs were found more often in patients who did not respond to treatment than in those who did respond, and more often in patients who did not have spontaneous clearance of their infection than those who did. The HLA-C C2C2 genotype (there are two copies of most genes in the genome) was also more common in patients who failed treatment than in those who responded but was not associated with spontaneous clearance. The rate of correct prediction of treatment failure increased from 66% with IL28B genotyping alone to 80% with combined IL28B and HLA-C genotyping. Finally, carriage of specific KIR genes in combination with specific HLA-C and IL28B variants was also associated with an altered HCV treatment response.
What Do These Findings Mean?
These findings show that the addition of HCL-C and KIR genotyping to IL28B genotyping improved the prediction of HCV treatment response in the patients investigated in this study. Because all these patients were European or of European descent, these findings need confirming in people of other ethnic backgrounds. They also need confirming in other groups of Europeans before being used in a clinical setting. However, the discovery that the addition of HLA-C genotyping to IL28B genotyping raises the rate of correct prediction of PegIFN/R treatment failure to 80% is extremely promising and should improve the clinical management of patients infected with HCV genotype 1. In addition, these results provide new insights into how PegIFN/R clears HCV infections that may lead to improved therapies in the future.
Additional Information
Please access these websites via the online version of this summary at
The World Health Organization provides detailed information about hepatitis C (in several languages)
The US Centers for Disease Control and Prevention provides information on hepatitis C for the public and for health professionals (information is also available in Spanish)
The US National Institute of Diabetes and Digestive and Kidney Diseases provides basic information on hepatitis C (in English and Spanish)
The Hepatitis C Trust is a patient-led, patient-run UK charity that provides detailed information about hepatitis C and support for patients and their families; a selection of personal stories about patients' experiences with hepatitis C is available, including Phil's treatment story, which details the ups and downs of treatment with PegIFN/R
MedlinePlus provides links to further resources on hepatitis C
The Human Genome Project provides information about medicine and the new genetics, including a primer on pharmacogenomics
PMCID: PMC3172251  PMID: 21931540
11.  Interactions between Environmental Factors and Polymorphisms in Angiogenesis Pathway Genes in Esophageal Adenocarcinoma Risk: A Case-Only Study 
Cancer  2011;118(3):804-811.
Gastroesophageal reflux symptoms (GERD), higher body mass index (BMI), smoking, and genetic variants in angiogenic pathway genes have been individually associated with increased risk of esophageal adenocarcinoma (EA). However, how angiogenic gene polymorphisms and environmental factors jointly affect EA development remains unclear.
Using a case-only design (n = 335), we examined interaction between 141 functional/tagging angiogenic SNPs and environmental factors (GERD, BMI, smoking) in modulating EA risk. Gene-environment interactions were assessed by a two-step approach. First, we applied random forest (RF) to screen for important SNPs that had either main or interaction effects. Second, we used case-only logistic regression (LR) to assess the effects of gene-environment interactions on EA risk, adjusting for covariates and false-discovery rate (FDR).
RF analyses identified three sets of SNPs (17 SNPs-GERD, 26 SNPs-smoking, and 34 SNPs-BMI) that had the highest importance scores. In subsequent LR analyses, interactions between 3 SNPs (rs2295778 of HIF1AN, rs133376 of TSC2, and rs2519757 of TSC1) and GERD, 2 SNPs (rs2295778 of HIF1AN, rs2296188 (VEGFR1) and smoking, and 7 SNPs (rs2114039 of PDGRFA, rs2296188 of VEGFR1, rs11941492 of VEGFR1, rs3756309 of PDGFRB, rs7324547 of VEGFR1, rs17619601 of VEGFR1, and rs17625898 of VEGFR1) and BMI were significantly associated with EA development (all FDR ≤0.10). Moreover, these interactions tended to have a SNP dose-response effects for increased EA risk with increasing number of combined risk genotypes.
These findings suggest that genetic variations in angiogenic genes may modify EA susceptibility through interactions with environmental factors in a SNP dose-response manner.
PMCID: PMC3193872  PMID: 21751195
Esophageal adenocarcinoma; angiogenesis pathway genes; gene-environment interaction; case-only analysis
12.  Circulating Mitochondrial DNA in Patients in the ICU as a Marker of Mortality: Derivation and Validation 
PLoS Medicine  2013;10(12):e1001577.
In this paper, Choi and colleagues analyzed levels of mitochondrial DNA in two prospective observational cohort studies and found that increased mtDNA levels are associated with ICU mortality, and improve risk prediction in medical ICU patients. The data suggests that mtDNA could serve as a viable plasma biomarker in MICU patients.
Mitochondrial DNA (mtDNA) is a critical activator of inflammation and the innate immune system. However, mtDNA level has not been tested for its role as a biomarker in the intensive care unit (ICU). We hypothesized that circulating cell-free mtDNA levels would be associated with mortality and improve risk prediction in ICU patients.
Methods and Findings
Analyses of mtDNA levels were performed on blood samples obtained from two prospective observational cohort studies of ICU patients (the Brigham and Women's Hospital Registry of Critical Illness [BWH RoCI, n = 200] and Molecular Epidemiology of Acute Respiratory Distress Syndrome [ME ARDS, n = 243]). mtDNA levels in plasma were assessed by measuring the copy number of the NADH dehydrogenase 1 gene using quantitative real-time PCR. Medical ICU patients with an elevated mtDNA level (≥3,200 copies/µl plasma) had increased odds of dying within 28 d of ICU admission in both the BWH RoCI (odds ratio [OR] 7.5, 95% CI 3.6–15.8, p = 1×10−7) and ME ARDS (OR 8.4, 95% CI 2.9–24.2, p = 9×10−5) cohorts, while no evidence for association was noted in non-medical ICU patients. The addition of an elevated mtDNA level improved the net reclassification index (NRI) of 28-d mortality among medical ICU patients when added to clinical models in both the BWH RoCI (NRI 79%, standard error 14%, p<1×10−4) and ME ARDS (NRI 55%, standard error 20%, p = 0.007) cohorts. In the BWH RoCI cohort, those with an elevated mtDNA level had an increased risk of death, even in analyses limited to patients with sepsis or acute respiratory distress syndrome. Study limitations include the lack of data elucidating the concise pathological roles of mtDNA in the patients, and the limited numbers of measurements for some of biomarkers.
Increased mtDNA levels are associated with ICU mortality, and inclusion of mtDNA level improves risk prediction in medical ICU patients. Our data suggest that mtDNA could serve as a viable plasma biomarker in medical ICU patients.
Please see later in the article for the Editors' Summary
Editors' Summary
Intensive care units (ICUs, also known as critical care units) are specialist hospital wards that provide care for people with life-threatening injuries and illnesses. In the US alone, more than 5 million people are admitted to ICUs every year. Different types of ICUs treat different types of problems. Medical ICUs treat patients who, for example, have been poisoned or who have a serious infection such as sepsis (blood poisoning) or severe pneumonia (inflammation of the lungs); trauma ICUs treat patients who have sustained a major injury; cardiac ICUs treat patients who have heart problems; and surgical ICUs treat complications arising from operations. Patients admitted to ICUs require constant medical attention and support from a team of specially trained nurses and physicians to prevent organ injury and to keep their bodies functioning. Monitors, intravenous tubes (to supply essential fluids, nutrients, and drugs), breathing machines, catheters (to drain urine), and other equipment also help to keep ICU patients alive.
Why Was This Study Done?
Although many patients admitted to ICUs recover, others do not. ICU specialists use scoring systems (algorithms) based on clinical signs and physiological measurements to predict their patients' likely outcomes. For example, the APACHE II scoring system uses information on heart and breathing rates, temperature, levels of salts in the blood, and other signs and physiological measurements collected during the first 24 hours in the ICU to predict the patient's risk of death. Existing scoring systems are not perfect, however, and “biomarkers” (molecules in bodily fluids that provide information about a disease state) are needed to improve risk prediction for ICU patients. Here, the researchers investigate whether levels of circulating cell-free mitochondrial DNA (mtDNA) are associated with ICU deaths and whether these levels can be used as a biomarker to improve risk prediction in ICU patients. Mitochondria are cellular structures that produce energy. Levels of mtDNA in the plasma (the liquid part of blood) increase in response to trauma and infection. Moreover, mtDNA activates molecular processes that lead to inflammation and organ injury.
What Did the Researchers Do and Find?
The researchers measured mtDNA levels in the plasma of patients enrolled in two prospective observational cohort studies that monitored the outcomes of ICU patients. In the Brigham and Women's Hospital Registry of Critical Illness study, blood was taken from 200 patients within 24 hours of admission into the hospital's medical ICU. In the Molecular Epidemiology of Acute Respiratory Distress Syndrome study (acute respiratory distress syndrome is a life-threatening inflammatory reaction to lung damage or infection), blood was taken from 243 patients within 48 hours of admission into medical and non-medical ICUs at two other US hospitals. Patients admitted to medical ICUs with a raised mtDNA level (3,200 or more copies of a specific mitochondrial gene per microliter of plasma) had a 7- to 8-fold increased risk of dying within 28 days of admission compared to patients with mtDNA levels of less than 3,200 copies/µl plasma. There was no evidence of an association between raised mtDNA levels and death among patients admitted to non-medical ICUs. The addition of an elevated mtDNA level to a clinical model for risk prediction that included the APACHE II score and biomarkers that are already used to predict ICU outcomes improved the net reclassification index (an indicator of the improvement in risk prediction algorithms offered by new biomarkers) of 28-day mortality among medical ICU patients in both studies.
What Do These Findings Mean?
These findings indicate that raised mtDNA plasma levels are associated with death in medical ICUs and show that, among patients in medical ICUs, measurement of mtDNA plasma levels can improve the prediction of the risk of death from the APACHE II scoring system, even when commonly measured biomarkers are taken into account. These findings do not indicate whether circulating cell-free mtDNA increased because of the underlying severity of illness or whether mtDNA actively contributes to the disease process in medical ICU patients. Moreover, they do not provide any evidence that raised mtDNA levels are associated with an increased risk of death among non-medical (mainly surgical) ICU patients. These findings need to be confirmed in additional patients, but given the relative ease and rapidity of mtDNA measurement, the determination of circulating cell-free mtDNA levels could be a valuable addition to the assessment of patients admitted to medical ICUs.
Additional Information
Please access these websites via the online version of this summary at
The UK National Health Service Choices website provides information about intensive care
The Society of Critical Care Medicine provides information for professionals, families, and patients about all aspects of intensive care
MedlinePlus provides links to other resources about intensive care (in English and Spanish)
The UK charity ICUsteps supports patients and their families through recovery from critical illness; its booklet Intensive Care: A Guide for Patients and Families is available in English and ten other languages; its website includes patient experiences and relative experiences of treatment in ICUs
Wikipedia has a page on ICU scoring systems (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
PMCID: PMC3876981  PMID: 24391478
13.  Racial differences in the association of CD14 polymorphisms with serum total IgE levels and allergen skin test reactivity 
The CD14 C-159T single nucleotide polymorphism (SNP) has been investigated widely as a candidate genetic locus in patients with allergic disease. There are conflicting results for the association of the CD14 C-159T SNP with total serum immunoglobulin E (IgE) levels and atopy. There are limited data regarding the association of the CD14 C-159T SNP in subjects of African ancestry. The aim of the study was to determine whether the C-159T SNP and other CD14 SNPs (C1188G, C1341T) were associated with total serum IgE levels and with allergy skin test results in nonatopic and atopic subjects; as well as in Caucasian and African American subjects.
A total of 291 participants, 18–40 years old, were screened to determine whether they were atopic and/or asthmatic. Analyses were performed to determine the association between CD14 C-159T, C1188G, or C1341T genotypes with serum IgE levels and with the number of positive skin tests among Caucasian or African American subjects.
We found no significant association of serum total IgE level with CD14 C-159T, C1188G, or C1341T genotypes within nonatopic or atopic subjects. Subjects with CD14-159 T alleles had significantly more positive allergen skin tests than subjects without CD14-159 T alleles (P = 0.0388). There was a significant association between the CD14 1188 G allele, but not the CD14 1341 T allele, with the number of positive skin-test results in Caucasians, but not in African Americans.
These results support a possible association between CD14 polymorphisms and atopy. CD14-159 T or CD14 1188 G alleles were associated with atopic disease. For subjects with CD14 1188 G alleles, the association with atopic disease was stronger in Caucasians compared to African Americans.
PMCID: PMC3699133  PMID: 23836995
total serum immunoglobulin E; IgE; skin prick test; SPT; CD14-159T; single nucleotide polymorphism; SNP; lipopolysaccharide; LPS; endotoxin
14.  Transcobalamin 2 variant associated with poststroke homocysteine modifies recurrent stroke risk 
Neurology  2011;77(16):1543-1550.
The Vitamin Intervention for Stroke Prevention trial found an association between baseline poststroke homocysteine (Hcy) and recurrent stroke. We investigated genes for enzymes and cofactors in the Hcy metabolic pathway for association with Hcy and determined whether associated single nucleotide polymorphisms (SNPs) influenced recurrent stroke risk.
Eighty-six SNPs in 9 candidate genes (BHMT1, BHMT2, CBS, CTH, MTHFR, MTR, MTRR, TCN1, and TCN2) were genotyped in 2,206 subjects (83% European American). Associations with Hcy measures were assessed using linear regression models assuming an additive genetic model, adjusting for age, sex, and race and additionally for baseline Hcy when postmethionine load change was assessed. Associations with recurrent stroke were evaluated using survival analyses.
Five SNPs in the transcobalamin 2 (TCN2) gene were associated with baseline Hcy (false discovery rate [FDR]–adjusted p = 0.049). TCN2 SNP rs731991 was associated with recurrent stroke risk in the low-dose arm of the trial under a recessive model (log-rank test p = 0.009, hazard ratio 0.34). Associations with change in postmethionine load Hcy levels were found with 5 SNPs in the cystathionine β-synthase (CBS) gene (FDR-adjusted p < 0.031).
TCN2 variants contribute to poststroke Hcy levels, whereas variants in the CBS gene influence Hcy metabolism. Variation in the TCN2 gene also affects recurrent stroke risk in response to cofactor therapy.
PMCID: PMC3198974  PMID: 21975197
15.  Genome-Wide Association Analyses Identify SPOCK as a Key Novel Gene Underlying Age at Menarche 
PLoS Genetics  2009;5(3):e1000420.
For females, menarche is a most significant physiological event. Age at menarche (AAM) is a trait with high genetic determination and is associated with major complex diseases in women. However, specific genes for AAM variation are largely unknown. To identify genetic factors underlying AAM variation, a genome-wide association study (GWAS) examining about 380,000 SNPs was conducted in 477 Caucasian women. A follow-up replication study was performed to validate our major GWAS findings using two independent Caucasian cohorts with 854 siblings and 762 unrelated subjects, respectively, and one Chinese cohort of 1,387 unrelated subjects—all females. Our GWAS identified a novel gene, SPOCK (Sparc/Osteonectin, CWCV, and Kazal-like domains proteoglycan), which had seven SNPs associated with AAM with genome-wide false discovery rate (FDR) q<0.05. Six most significant SNPs of the gene were selected for validation in three independent replication cohorts. All of the six SNPs were replicated in at least one cohort. In particular, SNPs rs13357391 and rs1859345 were replicated both within and across different ethnic groups in all three cohorts, with p values of 5.09×10−3 and 4.37×10−3, respectively, in the Chinese cohort and combined p values (obtained by Fisher's method) of 5.19×10−5 and 1.02×10−4, respectively, in all three replication cohorts. Interestingly, SPOCK can inhibit activation of MMP-2 (matrix metalloproteinase-2), a key factor promoting endometrial menstrual breakdown and onset of menstrual bleeding. Our findings, together with the functional relevance, strongly supported that the SPOCK gene underlies variation of AAM.
Author Summary
Menarche is a physical milestone in a woman's life. Age at menarche (AAM) is related to many common female health problems. AAM is mainly determined by genetic factors. However, the specific genes and the associated mechanisms underlying AAM are largely unknown. Here, taking advantage of the most recent technological advances in the field of human genetics, we identified multiple genetic variants in a gene, SPOCK, which are associated with AAM variation in a group of Caucasian women. This association was subsequently confirmed not only in two independent groups of Caucasian women but also across ethnic boundaries in one group of Chinese women. In addition, SPOCK has a function in regulating a key factor involved in menstrual cycles, MMP-2, which provides further support to our findings. Our study provides a solid basis for further investigation of the gene, which may help to reveal the underlying mechanisms for the timing of menarche and for AAM's relationship with women's health in general.
PMCID: PMC2652107  PMID: 19282985
16.  Oral contraceptives modify the effect of GATA3 polymorphisms on the risk of asthma at the age of 18 years via DNA methylation 
Clinical Epigenetics  2014;6(1):17.
The prevalence of asthma in girls increases after puberty. Previous studies have detected associations between sex hormones and asthma, as well as between sex hormones and T helper 2 (Th2) asthma-typical immune responses. Therefore, we hypothesized that exogenous or endogenous sex hormone exposure (represented by oral contraceptive pill (OCP) use and early menarche, respectively) are associated with DNA methylation (DNA-M) of the Th2 transcription factor gene, GATA3, in turn affecting the risk of asthma in girls, possibly in interaction with genetic variants.
Blood samples were collected from 245 female participants aged 18 years randomly selected for methylation analysis from the Isle of Wight birth cohort, UK. Information on use of OCPs, age at menarche, and concurrent asthma were assessed by questionnaire. Genome-wide DNA-M was determined using the Illumina Infinium HumanMethylation450 beadchip. In a first stage, we tested the interaction between sex hormone exposure and genetic variants on DNA-M of specific cytosine-phosphate-guanine (CpG) sites. In a second stage, we determined whether these CpG sites interact with genetic variants in GATA3 to explain the risk of asthma.
Interactions between OCP use and seven single nucleotide polymorphisms (SNPs) of GATA3 were analyzed for 14 CpG sites (stage 1). The interaction between OCP use and SNP rs1269486 was found to be associated with the methylation level of cg17124583 (P = 0.002, false discovery rate (FDR) adjusted P = 0.04). DNA-M of this same CpG site was also influenced by the interaction between age at menarche and rs1269486 (P = 0.0017). In stage 2, we found that cg17124583 modified the association of SNP rs422628 with asthma risk at the age of 18 years (P = 0.006, FDR adjusted P = 0.04). Subjects with genotype AG showed an increase in average risk ratio (RR) from 0.31 (95% CI: 0.10 to 0.8) to 11.65 (95% CI: 1.71 to 79.5) when methylation level increased from 0.02 to 0.12, relative to genotype AA.
A two-stage model consisting of genetic variants in the GATA3 gene, OCP use, age at menarche, and DNA-M may explain how sex hormones in women can increase the asthma prevalence after puberty.
PMCID: PMC4171400  PMID: 25250096
GATA3 gene; DNA methylation; genetic variants; epigenetics; oral contraceptives; age at menarche; asthma; puberty; adolescence; single nucleotide polymorphism; CpG
17.  Neuropeptide S Receptor Induces Neuropeptide Expression and Associates with Intermediate Phenotypes of Functional Gastrointestinal Disorders 
Gastroenterology  2009;138(1):98-107.e4.
Background & Aims
NPSR1, the receptor for neuropeptide S (NPS), is expressed by gastrointestinal (GI) enteroendocrine (EE) cells, and is involved in inflammation, anxiety and nociception. NPSR1 polymorphisms are associated with asthma and inflammatory bowel disease. We aimed to determine whether NPS induces expression of GI neuropeptides; and to associate NPSR1 single nucleotide polymorphisms (SNPs) with symptom phenotype and GI functions in health and functional GI disorders (FGID).
The effect of NPS on mRNA expression of neuropeptides was assessed using real-time PCR in NPSR1-tranfected HEK293 cells. Seventeen NPSR1 SNPs were successfully genotyped in 699 subjects from a regional cohort of 466 FGID patients and 233 healthy controls. Associations were sought using sex-adjusted regression analysis and false discovery rate (FDR) correction.
NPS-NPSR1 signaling induced increased expression of CCK, VIP, PYY, and somatostatin. There were no significant associations with phenotypes of FGID symptoms. There were several NPSR1 SNPs associated with individual motor or sensory functions; the associations of SNPs rs2609234, rs6972158 and rs1379928 with colonic transit rate remained significant after FDR correction. The rs1379928 polymorphism was also associated with pain, gas and urgency sensory ratings at 36 mm Hg distension, the level pre-specified for formal testing. Associations with rectal sensory ratings were not significant after FDR correction.
Expression of several neuropeptides is induced upon NPS-NPSR1 signaling; NPSR1 variants are associated with colonic transit in FGID. The role of the NPS system in FGID deserves further study.
PMCID: PMC2813358  PMID: 19732772
18.  Expectations for Recovery Important in the Prognosis of Whiplash Injuries 
PLoS Medicine  2008;5(5):e105.
Individuals' expectations on returning to work after an injury have been shown to predict the duration of time that a person with work-related low back pain will remain on benefits; individuals with lower recovery expectations received benefits for a longer time than those with higher expectations. The role of expectations in recovery from traumatic neck pain, in particular whiplash-associated disorders (WAD), has not been assessed to date to our knowledge. The aim of this study was to investigate if expectations for recovery are a prognostic factor after experiencing a WAD.
Methods and Findings
We used a prospective cohort study composed of insurance claimants in Sweden. The participants were car occupants who filed a neck injury claim (i.e., for WAD) to one of two insurance companies between 15 January 2004 and 12 January 2005 (n = 1,032). Postal questionnaires were completed shortly (average 23 d) after the collision and then again 6 mo later. Expectations for recovery were measured with a numerical rating scale (NRS) at baseline, where 0 corresponds to “unlikely to make a full recovery” and 10 to “very likely to make a full recovery.” The scale was reverse coded and trichotomised into NRS 0, 1–4, and 5–10. The main outcome measure was self-perceived disability at 6 mo postinjury, measured with the Pain Disability Index, and categorised into no/low, moderate, and high disability. Multivariable polytomous logistic regression was used for the analysis. There was a dose response relationship between recovery expectations and disability. After controlling for severity of physical and mental symptoms, individuals who stated that they were less likely to make a full recovery (NRS 5–10), were more likely to have a high disability compared to individuals who stated that they were very likely to make a full recovery (odds ratio [OR] 4.2 [95% confidence interval (CI) 2.1 to 8.5]. For the intermediate category (NRS 1–4), the OR was 2.1 (95% CI 1.2 to 3.2). Associations between expectations and disability were also found among individuals with moderate disability.
Individuals' expectations for recovery are important in prognosis, even after controlling for symptom severity. Interventions designed to increase patients' expectations may be beneficial and should be examined further in controlled studies.
Lena Holm and colleagues show that in people who had a whiplash injury after a car crash there was an association between expectation of disability and actual disability six months later.
Editors' Summary
The disability associated with injury is a major source of distress for patients, and can be costly to the health care system and employers when persons fail to recover quickly and are unable to return to work. Finding ways to help people recover quickly and get back to optimal health is important. Some of the most common injuries causing disability and time off work result from whiplash—the sudden hyperextension or “whipping” of the neck, which can occur from a motor vehicle crash. It has long been recognized that psychological factors (such as the ability to cope, how “in control” one feels about one's life) are as important as physical symptoms in how disabling an injury can be. There is now growing evidence that a person's feelings about their ability to recover from injury plays a part in actual recovery. Studies from Europe and North America have shown with conditions like low back pain and minor head injury that a patient's feelings about the possibility of getting better are related to how well they do. Less is known about how important these psychological factors are in recovery from disorders due to whiplash associated disorders.
Why Was This Study Done?
The authors wanted to find out whether there was a relationship between people's expectations for their recovery from whiplash associated disorders and their actual recovery six months later. So, for example, they wondered if a person with whiplash who felt they were very unlikely to recover from their injury, actually did not recover (and vice versa).
What Did the Researchers Do and Find?
The authors had access to an unusual set of health information—insurance claims by people who had been involved in car collisions to two insurance companies in Sweden. They identified about 1,000 adult insurance claimants over one year and mailed them a questionnaire that asked for details about the collision as well as information about the claimant: their demographic profile, health history, and the types of pain and symptoms experienced since the crash. The questionnaire also asked the claimant how likely they thought they were to make a full recovery from their injuries.
For those who said they had whiplash associated disorders, the authors followed up with another questionnaire six months later, which asked for information about any disability, pain, or other symptoms that the claimant was still experiencing because of the injury. Of those who had completed the first questionnaire, 82% were followed up.
Only about a quarter of claimants with whiplash associated disorders said they expected to make a full recovery. Perhaps not surprisingly, those with only mild pain, compared to those with intense pain, were more likely to think so. Persons who said they were less likely to make a full recovery were four times more likely to report high levels of disability six months later. Even for persons (or individuals) people with moderate levels of disability six months after injury, their expectations for recovery were similarly linked to how well they did: the lower the expectations for recovery, the higher the disability. These findings were true even after taking into account how severe signs and symptoms the person had, and how well the person was coping psychologically.
What Do These Findings Mean?
The findings indicate that those with the lowest expectations for recovery after their whiplash injury will have the poorest recovery, and those with the highest expectations will have the best recovery. They also suggest that a patient's expectations about getting better are as important as his or her physical symptoms. The authors say that the more we can influence patients to believe they will make a full recovery, the better chance they will have to recover completely. This means that it may be beneficial for healthcare providers to give support and/or education to patients with whiplash associated disorders that increases their positive feelings toward recovery. The authors call for more studies into whether these types of targeted interventions would be of benefit.
Additional Information
Please access these Web sites via the online version of this summary at
Information about research on injuries and rehabilitation can be found at the Web sites of organisations devoted to studying the health of workers, such as the Institute for Work and Health in Canada, the Finnish Institute of Occupational Health, and the US National Institute for Occupational Safety and Health
The Wikipedia entry for medical aspects of whiplash describes the four grades of whiplash disorder, but does not cover the debate about the credibility of whiplash disorder (please note that Wikipedia is an online encyclopedia that anyone can edit)
The Sjukvardsradgivningen Web site provides information about whiplash-related disorders, common signs and symptoms, recovery and prognosis, and treatments (in Swedish)
PMCID: PMC2375948  PMID: 18479182
19.  Replication of genetic loci for ages at menarche and menopause in the multi-ethnic Population Architecture using Genomics and Epidemiology (PAGE) study 
Human Reproduction (Oxford, England)  2013;28(6):1695-1706.
Do genetic associations identified in genome-wide association studies (GWAS) of age at menarche (AM) and age at natural menopause (ANM) replicate in women of diverse race/ancestry from the Population Architecture using Genomics and Epidemiology (PAGE) Study?
We replicated GWAS reproductive trait single nucleotide polymorphisms (SNPs) in our European descent population and found that many SNPs were also associated with AM and ANM in populations of diverse ancestry.
Menarche and menopause mark the reproductive lifespan in women and are important risk factors for chronic diseases including obesity, cardiovascular disease and cancer. Both events are believed to be influenced by environmental and genetic factors, and vary in populations differing by genetic ancestry and geography. Most genetic variants associated with these traits have been identified in GWAS of European-descent populations.
A total of 42 251 women of diverse ancestry from PAGE were included in cross-sectional analyses of AM and ANM.
SNPs previously associated with ANM (n = 5 SNPs) and AM (n = 3 SNPs) in GWAS were genotyped in American Indians, African Americans, Asians, European Americans, Hispanics and Native Hawaiians. To test SNP associations with ANM or AM, we used linear regression models stratified by race/ethnicity and PAGE sub-study. Results were then combined in race-specific fixed effect meta-analyses for each outcome. For replication and generalization analyses, significance was defined at P < 0.01 for ANM analyses and P < 0.017 for AM analyses.
We replicated findings for AM SNPs in the LIN28B locus and an intergenic region on 9q31 in European Americans. The LIN28B SNPs (rs314277 and rs314280) were also significantly associated with AM in Asians, but not in other race/ethnicity groups. Linkage disequilibrium (LD) patterns at this locus varied widely among the ancestral groups. With the exception of an intergenic SNP at 13q34, all ANM SNPs replicated in European Americans. Three were significantly associated with ANM in other race/ethnicity populations: rs2153157 (6p24.2/SYCP2L), rs365132 (5q35/UIMC1) and rs16991615 (20p12.3/MCM8). While rs1172822 (19q13/BRSK1) was not significant in the populations of non-European descent, effect sizes showed similar trends.
Lack of association for the GWAS SNPs in the non-European American groups may be due to differences in locus LD patterns between these groups and the European-descent populations included in the GWAS discovery studies; and in some cases, lower power may also contribute to non-significant findings.
The discovery of genetic variants associated with the reproductive traits provides an important opportunity to elucidate the biological mechanisms involved with normal variation and disorders of menarche and menopause. In this study we replicated most, but not all reported SNPs in European descent populations and examined the epidemiologic architecture of these early reported variants, describing their generalizability and effect size across differing ancestral populations. Such data will be increasingly important for prioritizing GWAS SNPs for follow-up in fine-mapping and resequencing studies, as well as in translational research.
The Population Architecture Using Genomics and Epidemiology (PAGE) program is funded by the National Human Genome Research Institute (NHGRI), supported by U01HG004803 (CALiCo), U01HG004798 (EAGLE), U01HG004802 (MEC), U01HG004790 (WHI) and U01HG004801 (Coordinating Center), and their respective NHGRI ARRA supplements. The authors report no conflicts of interest.
PMCID: PMC3657124  PMID: 23508249
menopause; menarche; genome-wide association study; race/ethnicity; single nucleotide polymorphism
20.  Domestic Violence and Perinatal Mental Disorders: A Systematic Review and Meta-Analysis 
PLoS Medicine  2013;10(5):e1001452.
Louise Howard and colleagues conduct a systematic review and meta-analysis to estimate the prevalence and odds of experience of domestic violence experience among women with antenatal and postnatal mental health disorders.
Please see later in the article for the Editors' Summary
Domestic violence in the perinatal period is associated with adverse obstetric outcomes, but evidence is limited on its association with perinatal mental disorders. We aimed to estimate the prevalence and odds of having experienced domestic violence among women with antenatal and postnatal mental disorders (depression and anxiety disorders including post-traumatic stress disorder [PTSD], eating disorders, and psychoses).
Methods and Findings
We conducted a systematic review and meta-analysis (PROSPERO reference CRD42012002048). Data sources included searches of electronic databases (to 15 February 2013), hand searches, citation tracking, update of a review on victimisation and mental disorder, and expert recommendations. Included studies were peer-reviewed experimental or observational studies that reported on women aged 16 y or older, that assessed the prevalence and/or odds of having experienced domestic violence, and that assessed symptoms of perinatal mental disorder using a validated instrument. Two reviewers screened 1,125 full-text papers, extracted data, and independently appraised study quality. Odds ratios were pooled using meta-analysis.
Sixty-seven papers were included. Pooled estimates from longitudinal studies suggest a 3-fold increase in the odds of high levels of depressive symptoms in the postnatal period after having experienced partner violence during pregnancy (odds ratio 3.1, 95% CI 2.7–3.6). Increased odds of having experienced domestic violence among women with high levels of depressive, anxiety, and PTSD symptoms in the antenatal and postnatal periods were consistently reported in cross-sectional studies. No studies were identified on eating disorders or puerperal psychosis. Analyses were limited because of study heterogeneity and lack of data on baseline symptoms, preventing clear findings on causal directionality.
High levels of symptoms of perinatal depression, anxiety, and PTSD are significantly associated with having experienced domestic violence. High-quality evidence is now needed on how maternity and mental health services should address domestic violence and improve health outcomes for women and their infants in the perinatal period.
Please see later in the article for the Editors' Summary
Editors' Summary
Domestic violence—physical, sexual, or emotional abuse by an intimate partner or family member—is a major public health problem and although more common in women, can also affect men. Due to the nature of the problem, it is difficult to collect accurate figures on the scale of domestic violence, but a study by the World Health Organization in ten countries found that 15%–71% of women aged 15–49 years reported physical and/or sexual violence by an intimate partner at some point in their lives. Women experiencing domestic violence have significant short- and long-term health problems, particularly regarding their mental health: experience of domestic violence can lead to a range of mental health disorders such as depression, psychosis, eating disorders, and even suicide attempts.
Why Was This Study Done?
As perinatal mental health disorders are among the commonest health problems in pregnancy and the postpartum period, and given the rate of domestic violence during pregnancy (previous studies have suggested a domestic violence prevalence of 4%–8% during pregnancy and the postnatal period), it is plausible that there may be a link between perinatal mental health disorders and having experienced domestic violence. Indeed, previous reviews have suggested the existence of such an association but were limited by the small number of included studies and focused on depression only, rather than the full range of antenatal and postnatal mental health disorders. So in this study the researchers systematically reviewed published studies to provide more robust estimates of the prevalence of having experienced domestic violence among women with antenatal and postnatal mental health disorders; the researchers also used a meta-analysis to estimate the odds (chance) of having experienced domestic violence among women with antenatal and postnatal mental health disorders.
What Did the Researchers Do and Find?
The researchers searched multiple databases and hand searched three relevant journals using key search terms to identify all types of relevant studies. Using specific criteria, the researchers retrieved and assessed over 1,000 full papers, of which 67 met the criteria for their systematic review. The researchers assessed the quality of each selected study and included only those studies that used validated diagnostic instruments and screening tools to assess mental health disorders in their calculations of the pooled (combined) odds ratio (OR) through meta-analysis.
Using these methods, in cross-sectional studies (studies conducted at one point in time), the researchers found that women with probable depression in the antenatal period reported a high prevalence and increased odds of having experienced partner violence during their lifetime (OR = 3), during the past year (OR = 2.8), and during pregnancy (OR = 5). The results were similar for the postnatal period. The evidence was less robust for anxiety disorders: among women with probable anxiety in the antenatal period, the researchers found an OR of 2.9 of having experienced lifetime partner violence. The odds were less in the postnatal period (OR = 1.4) In their analysis of longitudinal studies (follow-up studies over a period of time), the researchers found an increased odds of probable postnatal depression both among women who reported having ever experienced partner violence in their lifetime (OR = 2.9) and among women who reported having experienced partner violence during pregnancy (OR = 3.1). The researchers also found a combined prevalence estimate of 12.7% for probable depression during the postnatal period following experiences of partner violence during pregnancy. Because of limited data, the researchers could not calculate an OR of the association between probable antenatal depression and later experiences of partner violence.
What Do These Findings Mean?
These findings suggest that women with high levels of symptoms of perinatal mental health disorders—antenatal and postnatal anxiety, depression, and post-traumatic stress disorder—have a high prevalence and increased odds of having experienced domestic violence both over their lifetime and during pregnancy. However, these findings cannot prove causality, they fail to show a two-way association (that is, perinatal mental health disorders leading to subsequent domestic violence), and no information on other perinatal mental disorders, such as eating disorders and puerperal psychosis, was available. The variation of the quality of the included studies also limits the results, highlighting the need for high-quality data to suggest how maternity and mental health services could address domestic violence and improve health outcomes for women and their infants in the future. Nevertheless, this study emphasizes the importance of identifying and responding to possible domestic violence among women attending antenatal and mental health services.
Additional Information
Please access these websites via the online version of this summary at
The World Health Organization provides information and statistics about violence against women and also about mental health disorders during pregnancy
The UK Royal College of Psychiatrists has information for professionals and patients about mental health disorders during pregnancy
PMCID: PMC3665851  PMID: 23723741
21.  Genetic variants associated with development of TMD and its intermediate phenotypes: the genetic architecture of TMD in the OPPERA prospective cohort study 
The journal of pain : official journal of the American Pain Society  2013;14(12 0):10.1016/j.jpain.2013.09.004.
Genetic risk factors are believed to combine with environmental exposures and contribute to risk of developing temporomandibular disorder (TMD). In this prospective cohort study, 2,737 people without TMD were assessed for common genetic variation in 358 genes known to contribute to nociceptive pathways, inflammation, and affective distress. During a median follow-up period of 2.8 years, 260 people developed first-onset TMD. Hazard ratios (HRs) were computed as measures of association between 2,924 single nucleotide polymorphisms (SNPs) and TMD incidence. After correction for multiple testing, no single SNP was significantly associated with risk of onset TMD. However, several SNPs exceeded Bonferroni correction for multiple comparison or false discovery rate thresholds (FDR=0.05, 0.1, or 0.2) for association with intermediate phenotypes shown to be predictive of TMD onset. Non-specific orofacial symptoms were associated with voltage-gated sodium channel, type 1 alpha subunit (SCN1A, rs6432860, p=2.77×10−5) and angiotensin-I converting enzyme 2 (ACE2, rs1514280, p=4.86×10−5), global psychological symptoms with prostaglandin-endoperoxide synthase 1 (PTGS1, rs3842803, p=2.79×10−6), stress and negative affectivity with amyloid-β (A4) precursor protein (APP, rs466448, p=4.29×10−5), and heat pain temporal summation with multiple PDZ domain protein (MPDZ, rs10809907, p=3.05×10−5). The use of intermediate phenotypes for complex pain diseases revealed new genetic pathways influencing risk of TMD.
PMCID: PMC3855664  PMID: 24275226
temporomandibular disorders; genetic risk factors; incidence; chronic pain; intermediate phenotypes
22.  Polymorphic variants in TSC1 and TSC2 and their association with breast cancer phenotypes 
Breast cancer research and treatment  2010;125(3):10.1007/s10549-010-1062-1.
TSC1 acts coordinately with TSC2 in a complex to inhibit mTOR, an emerging therapeutic target and known promoter of cell growth and cell cycle progression. Perturbation of the mTOR pathway, through abnormal expression or function of pathway genes, could lead to tumorigenesis. TSC1 and TSC2 expression is reduced in invasive breast cancer as compared with normal mammary epithelium. Because single nucleotide polymorphisms (SNPs) in regulatory genes have been implicated in risk and age at diagnosis of breast cancers, systematic SNP association studies were performed on TSC1 and TSC2 SNPs for their associations with clinical features of breast cancer. TSC1 and TSC2 haplotypes were constructed from genotyping of multiple loci in both genes in healthy volunteers. SNPs were selected for further study using a bioinformatics approach based on SNP associations with drug response in NCI-60 cell lines and evidence of selection bias based on haplotype frequencies. Genotyping for five TSC1 and one TSC2 loci were performed on genomic DNA from 1,137 women with breast cancer. This study found that for TSC1 rs7874234, TT variant carriers had a 9-year later age at diagnosis of estrogen receptor positive (ER+), but not ER−, ductal carcinomas (P = 0.0049). No other SNP locus showed an association with age at diagnosis, nor any other breast cancer phenotype. TSC1 rs7874234 is hypothesized to be functional in ER+ breast cancer because the T allele, but not the C allele, may create an estrogen receptor element (ERE) site, resulting in increased TSC1 transcription and subsequent inhibition of mTOR.
PMCID: PMC3876413  PMID: 20658316
Breast cancer risk; SNP; TSC1/TSC2; Case study
23.  Calibrating the Performance of SNP Arrays for Whole-Genome Association Studies 
PLoS Genetics  2008;4(6):e1000109.
To facilitate whole-genome association studies (WGAS), several high-density SNP genotyping arrays have been developed. Genetic coverage and statistical power are the primary benchmark metrics in evaluating the performance of SNP arrays. Ideally, such evaluations would be done on a SNP set and a cohort of individuals that are both independently sampled from the original SNPs and individuals used in developing the arrays. Without utilization of an independent test set, previous estimates of genetic coverage and statistical power may be subject to an overfitting bias. Additionally, the SNP arrays' statistical power in WGAS has not been systematically assessed on real traits. One robust setting for doing so is to evaluate statistical power on thousands of traits measured from a single set of individuals. In this study, 359 newly sampled Americans of European descent were genotyped using both Affymetrix 500K (Affx500K) and Illumina 650Y (Ilmn650K) SNP arrays. From these data, we were able to obtain estimates of genetic coverage, which are robust to overfitting, by constructing an independent test set from among these genotypes and individuals. Furthermore, we collected liver tissue RNA from the participants and profiled these samples on a comprehensive gene expression microarray. The RNA levels were used as a large-scale set of quantitative traits to calibrate the relative statistical power of the commercial arrays. Our genetic coverage estimates are lower than previous reports, providing evidence that previous estimates may be inflated due to overfitting. The Ilmn650K platform showed reasonable power (50% or greater) to detect SNPs associated with quantitative traits when the signal-to-noise ratio (SNR) is greater than or equal to 0.5 and the causal SNP's minor allele frequency (MAF) is greater than or equal to 20% (N = 359). In testing each of the more than 40,000 gene expression traits for association to each of the SNPs on the Ilmn650K and Affx500K arrays, we found that the Ilmn650K yielded 15% times more discoveries than the Affx500K at the same false discovery rate (FDR) level.
Author Summary
Advances in SNP genotyping array technologies have made whole-genome association studies (WGAS) a readily available approach. Genetic coverage and the statistical power are two key properties to evaluate on the arrays. In this study, 359 newly sampled individuals were genotyped using Affymetrix 500K and Illumina 650Y SNP arrays. From these data, we obtained new estimates of genetic coverage by constructing a test set from among these genotypes and individuals that is independent from the SNPs and individuals used to construct the arrays. These estimates are notably smaller than previous ones, which we argue is due to an overfitting bias in previous studies. We also collected liver tissue RNA from the participants and profiled these samples on a comprehensive gene expression microarray. The RNA levels were used as a large-scale set of quantitative traits to calibrate the relative statistical power of the commercial arrays. Through this dataset and simulations, we find that the SNP arrays provide adequate power to detect quantitative trait loci when the causal SNP's minor allele frequency is greater than 20%, but low power is less than 10%. Importantly, we provide evidence that sample size has a greater impact on the power of WGAS than SNP density or genetic coverage.
PMCID: PMC2432039  PMID: 18584036
24.  Maternal and family factors and child eating pathology: risk and protective relationships 
Previous studies have found associations between maternal and family factors and child eating disorder symptoms. However, it is not clear whether family factors predict eating disorder symptoms specifically, or relate to more general child psychopathology, of which eating disorder symptoms may be one component. This study aimed to identify maternal and family factors that may predict increases or decreases in child eating disorder symptoms over time, accounting for children’s body mass index z-scores and levels of general psychological distress.
Participants were 221 mother-child dyads from the Childhood Growth and Development Study, a prospective cohort study in Western Australia. Participants were assessed at baseline, 1-year follow-up and 2-year follow-up using interview and self-report measures. Children had a mean age of 10 years at baseline and 46% were male. Linear mixed models and generalised estimating equations were used to identify predictors of children’s eating disorder symptoms, with outcome variables including a global index of eating disorder psychopathology, levels of dietary restraint, levels of emotional eating, and the presence of loss of control (‘binge’) eating.
Children of mothers with a current or past eating disorder reported significantly higher levels of global eating disorder symptoms and emotional eating than other children, and mothers with a current or past eating disorder reported significantly more concern about their children’s weight than other mothers. Maternal concern about child weight, rather than maternal eating disorder symptoms, was significant in predicting child eating disorder symptoms over time. Family exposure to stress and low maternal education were additional risk factors for eating disorder symptoms, whilst child-reported family satisfaction was a protective factor.
After adjusting for relevant confounding variables, maternal concern about child weight, children’s level of family satisfaction, family exposure to stress, and maternal education are unique predictors of child eating disorder symptoms.
PMCID: PMC4012547  PMID: 24808944
Eating disorders; Children; Loss of control eating; Family; Risk factors; Protective factors; Running head; Family factors and eating pathology
25.  Genetic neuropathology of obsessive psychiatric syndromes 
Translational Psychiatry  2014;4(9):e432-.
Anorexia nervosa (AN), bulimia nervosa (BN) and obsessive-compulsive disorder (OCD) are complex psychiatric disorders with shared obsessive features, thought to arise from the interaction of multiple genes of small effect with environmental factors. Potential candidate genes for AN, BN and OCD have been identified through clinical association and neuroimaging studies; however, recent genome-wide association studies of eating disorders (ED) so far have failed to report significant findings. In addition, few, if any, studies have interrogated postmortem brain tissue for evidence of expression quantitative trait loci (eQTLs) associated with candidate genes, which has particular promise as an approach to elucidating molecular mechanisms of association. We therefore selected single-nucleotide polymorphisms (SNPs) based on candidate gene studies for AN, BN and OCD from the literature, and examined the association of these SNPs with gene expression across the lifespan in prefrontal cortex of a nonpsychiatric control cohort (N=268). Several risk-predisposing SNPs were significantly associated with gene expression among control subjects. We then measured gene expression in the prefrontal cortex of cases previously diagnosed with obsessive psychiatric disorders, for example, ED (N=15) and OCD/obsessive-compulsive personality disorder or tics (OCD/OCPD/Tic; N=16), and nonpsychiatric controls (N=102) and identified 6 and 286 genes that were differentially expressed between ED compared with controls and OCD cases compared with controls, respectively (false discovery rate (FDR) <5%). However, none of the clinical risk SNPs were among the eQTLs and none were significantly associated with gene expression within the broad obsessive cohort, suggesting larger sample sizes or other brain regions may be required to identify candidate molecular mechanisms of clinical association in postmortem brain data sets.
PMCID: PMC4203002  PMID: 25180571

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