Publications by authors named "Samuel K Handelman"

40 Publications

Standing Variations Modeling Captures Inter-Individual Heterogeneity in a Deterministic Model of Prostate Cancer Response to Combination Therapy.

Cancers (Basel) 2021 Apr 14;13(8). Epub 2021 Apr 14.

Department of Mathematics, University of Michigan, Ann Arbor, MI 48109, USA.

Sipuleucel-T (Provenge) is the first live cell vaccine approved for advanced, hormonally refractive prostate cancer. However, survival benefit is modest and the optimal combination or schedule of sipuleucel-T with androgen depletion remains unknown. We employ a nonlinear dynamical systems approach to modeling the response of hormonally refractive prostate cancer to sipuleucel-T. Our mechanistic model incorporates the immune response to the cancer elicited by vaccination, and the effect of androgen depletion therapy. Because only a fraction of patients benefit from sipuleucel-T treatment, inter-individual heterogeneity is clearly crucial. Therefore, we introduce our novel approach, Standing Variations Modeling, which exploits inestimability of model parameters to capture heterogeneity in a deterministic model. We use data from mouse xenograft experiments to infer distributions on parameters critical to tumor growth and to the resultant immune response. Sampling model parameters from these distributions allows us to represent heterogeneity, both at the level of the tumor cells and the individual (mouse) being treated. Our model simulations explain the limited success of sipuleucel-T observed in practice, and predict an optimal combination regime that maximizes predicted efficacy. This approach will generalize to a range of emerging cancer immunotherapies.
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http://dx.doi.org/10.3390/cancers13081872DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8070719PMC
April 2021

Genome-wide association study of serum liver enzymes implicates diverse metabolic and liver pathology.

Nat Commun 2021 02 5;12(1):816. Epub 2021 Feb 5.

Division of Gastroenterology and Hepatology, University of Michigan Health System, Ann Arbor, MI, USA.

Serum liver enzyme concentrations are the most frequently-used laboratory markers of liver disease, a major cause of mortality. We conduct a meta-analysis of genome-wide association studies of liver enzymes from UK BioBank and BioBank Japan. We identified 160 previously-unreported independent alanine aminotransferase, 190 aspartate aminotransferase, and 199 alkaline phosphatase genome-wide significant associations, with some affecting multiple different enzymes. Associated variants implicate genes that demonstrate diverse liver cell type expression and promote a range of metabolic and liver diseases. These findings provide insight into the pathophysiology of liver and other metabolic diseases that are associated with serum liver enzyme concentrations.
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http://dx.doi.org/10.1038/s41467-020-20870-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7865025PMC
February 2021

Causal Relationship and Shared Genetic Loci between Psoriasis and Type 2 Diabetes through Trans-Disease Meta-Analysis.

J Invest Dermatol 2020 Dec 30. Epub 2020 Dec 30.

Department of Dermatology, University of Michigan Medical School, Ann Arbor, Michigan, USA; Department of Biostatistics, Center for Statistical Genetics, University of Michigan, Ann Arbor, MI, USA; Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor Michigan, USA. Electronic address:

Psoriasis and type 2 diabetes (T2D) are complex conditions with significant impacts on health. Patients with psoriasis have a higher risk of T2D (∼1.5 OR) and vice versa, controlling for body mass index; yet, there has been a limited study comparing their genetic architecture. We hypothesized that there are shared genetic components between psoriasis and T2D. Trans-disease meta-analysis was applied to 8,016,731 well-imputed genetic markers from large-scale meta-analyses of psoriasis (11,024 cases and 16,336 controls) and T2D (74,124 cases and 824,006 controls), adjusted for body mass index. We confirmed our findings in a hospital-based study (42,112 patients) and tested for causal relationships with multivariable Mendelian randomization. Mendelian randomization identified a causal relationship between psoriasis and T2D (P = 1.6 × 10, OR = 1.01) and highlighted the impact of body mass index. Trans-disease meta-analysis further revealed four genome-wide significant loci (P < 5 × 10) with evidence of colocalization and shared directions of effect between psoriasis and T2D not present in body mass index. The proteins coded by genes in these loci (ACTR2, ERLIN1, TRMT112, and BECN1) are connected through NF-κB signaling. Our results provide insight into the immunological components that connect immune-mediated skin conditions and metabolic diseases, independent of confounding factors.
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http://dx.doi.org/10.1016/j.jid.2020.11.025DOI Listing
December 2020

A Meta-Analysis of the Transferability of Bone Mineral Density Genetic Loci Associations From European to African Ancestry Populations.

J Bone Miner Res 2021 Mar 18;36(3):469-479. Epub 2020 Dec 18.

Hinda and Arthur Marcus Institute for Aging Research, Hebrew SeniorLife, Boston, MA, USA.

Genetic studies of bone mineral density (BMD) largely have been conducted in European populations. We therefore conducted a meta-analysis of six independent African ancestry cohorts to determine whether previously reported BMD loci identified in European populations were transferable to African ancestry populations. We included nearly 5000 individuals with both genetic data and assessments of BMD. Genotype imputation was conducted using the 1000G reference panel. We assessed single-nucleotide polymorphism (SNP) associations with femoral neck and lumbar spine BMD in each cohort separately, then combined results in fixed effects (or random effects if study heterogeneity was high, I index >60) inverse variance weighted meta-analyses. In secondary analyses, we conducted locus-based analyses of rare variants using SKAT-O. Mean age ranged from 12 to 68 years. One cohort included only men and another cohort included only women; the proportion of women in the other four cohorts ranged from 52% to 63%. Of 56 BMD loci tested, one locus, 6q25 (C6orf97, p = 8.87 × 10 ), was associated with lumbar spine BMD and two loci, 7q21 (SLC25A13, p = 2.84 × 10 ) and 7q31 (WNT16, p = 2.96 × 10 ), were associated with femoral neck BMD. Effects were in the same direction as previously reported in European ancestry studies and met a Bonferroni-adjusted p value threshold, the criteria for transferability to African ancestry populations. We also found associations that met locus-specific Bonferroni-adjusted p value thresholds in 11q13 (LRP5, p < 2.23 × 10 ), 11q14 (DCDC5, p < 5.35 × 10 ), and 17p13 (SMG6, p < 6.78 × 10 ) that were not tagged by European ancestry index SNPs. Rare single-nucleotide variants in AKAP11 (p = 2.32 × 10 ), MBL2 (p = 4.09 × 10 ), MEPE (p = 3.15 × 10 ), SLC25A13 (p = 3.03 × 10 ), STARD3NL (p = 3.35 × 10 ), and TNFRSF11A (p = 3.18 × 10 ) were also associated with BMD. The majority of known BMD loci were not transferable. Larger genetic studies of BMD in African ancestry populations will be needed to overcome limitations in statistical power and to identify both other loci that are transferable across populations and novel population-specific variants. © 2020 American Society for Bone and Mineral Research (ASBMR).
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http://dx.doi.org/10.1002/jbmr.4220DOI Listing
March 2021

A Noncoding Variant Near PPP1R3B Promotes Liver Glycogen Storage and MetS, but Protects Against Myocardial Infarction.

J Clin Endocrinol Metab 2021 Jan;106(2):372-387

Brigham and Women's Hospital, Havard University, Boston, MA, USA.

Context: Glycogen storage diseases are rare. Increased glycogen in the liver results in increased attenuation.

Objective: Investigate the association and function of a noncoding region associated with liver attenuation but not histologic nonalcoholic fatty liver disease.

Design: Genetics of Obesity-associated Liver Disease Consortium.

Setting: Population-based.

Main Outcome: Computed tomography measured liver attenuation.

Results: Carriers of rs4841132-A (frequency 2%-19%) do not show increased hepatic steatosis; they have increased liver attenuation indicative of increased glycogen deposition. rs4841132 falls in a noncoding RNA LOC157273 ~190 kb upstream of PPP1R3B. We demonstrate that rs4841132-A increases PPP1R3B through a cis genetic effect. Using CRISPR/Cas9 we engineered a 105-bp deletion including rs4841132-A in human hepatocarcinoma cells that increases PPP1R3B, decreases LOC157273, and increases glycogen perfectly mirroring the human disease. Overexpression of PPP1R3B or knockdown of LOC157273 increased glycogen but did not result in decreased LOC157273 or increased PPP1R3B, respectively, suggesting that the effects may not all occur via affecting RNA levels. Based on electronic health record (EHR) data, rs4841132-A associates with all components of the metabolic syndrome (MetS). However, rs4841132-A associated with decreased low-density lipoprotein (LDL) cholesterol and risk for myocardial infarction (MI). A metabolic signature for rs4841132-A includes increased glycine, lactate, triglycerides, and decreased acetoacetate and beta-hydroxybutyrate.

Conclusions: These results show that rs4841132-A promotes a hepatic glycogen storage disease by increasing PPP1R3B and decreasing LOC157273. rs4841132-A promotes glycogen accumulation and development of MetS but lowers LDL cholesterol and risk for MI. These results suggest that elevated hepatic glycogen is one cause of MetS that does not invariably promote MI.
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http://dx.doi.org/10.1210/clinem/dgaa855DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823249PMC
January 2021

Loci identified by a genome-wide association study of carotid artery stenosis in the eMERGE network.

Genet Epidemiol 2021 Feb 22;45(1):4-15. Epub 2020 Sep 22.

Division of Medical Genetics, School of Medicine, University of Washington, Seattle, Washington, USA.

Carotid artery atherosclerotic disease (CAAD) is a risk factor for stroke. We used a genome-wide association (GWAS) approach to discover genetic variants associated with CAAD in participants in the electronic Medical Records and Genomics (eMERGE) Network. We identified adult CAAD cases with unilateral or bilateral carotid artery stenosis and controls without evidence of stenosis from electronic health records at eight eMERGE sites. We performed GWAS with a model adjusting for age, sex, study site, and genetic principal components of ancestry. In eMERGE we found 1793 CAAD cases and 17,958 controls. Two loci reached genome-wide significance, on chr6 in LPA (rs10455872, odds ratio [OR] (95% confidence interval [CI]) = 1.50 (1.30-1.73), p = 2.1 × 10 ) and on chr7, an intergenic single nucleotide variant (SNV; rs6952610, OR (95% CI) = 1.25 (1.16-1.36), p = 4.3 × 10 ). The chr7 association remained significant in the presence of the LPA SNV as a covariate. The LPA SNV was also associated with coronary heart disease (CHD; 4199 cases and 11,679 controls) in this study (OR (95% CI) = 1.27 (1.13-1.43), p = 5 × 10 ) but the chr7 SNV was not (OR (95% CI) = 1.03 (0.97-1.09), p = .37). Both variants replicated in UK Biobank. Elevated lipoprotein(a) concentrations ([Lp(a)]) and LPA variants associated with elevated [Lp(a)] have previously been associated with CAAD and CHD, including rs10455872. With electronic health record phenotypes in eMERGE and UKB, we replicated a previously known association and identified a novel locus associated with CAAD.
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http://dx.doi.org/10.1002/gepi.22360DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7891640PMC
February 2021

Mitochondrial GWAS and association of nuclear - mitochondrial epistasis with BMI in T1DM patients.

BMC Med Genomics 2020 07 7;13(1):97. Epub 2020 Jul 7.

Center for Medical Genomics OMICRON, Jagiellonian University Medical College, Kraków, Poland.

Background: BMI is a strong indicator of complications from type I diabetes, especially under intensive treatment.

Methods: We have genotyped 435 type 1 diabetics using Illumina Infinium Omni Express Exome-8 v1.4 arrays and performed mitoGWAS on BMI. We identified additive interactions between mitochondrial and nuclear variants in genes associated with mitochondrial functioning MitoCarta2.0 and confirmed and refined the results on external cohorts: the Framingham Heart Study (FHS) and GTEx data. Linear mixed model analysis was performed using the GENESIS package in R/Bioconductor.

Results: We find a borderline significant association between the mitochondrial variant rs28357980, localized to MT-ND2, and BMI (β = - 0.69, p = 0.056). This BMI association was confirmed on 1889 patients from FHS cohort (β = - 0.312, p = 0.047). Next, we searched for additive interactions between mitochondrial and nuclear variants. MT-ND2 variants interacted with variants in the genes SIRT3, ATP5B, CYCS, TFB2M and POLRMT. TFB2M is a mitochondrial transcription factor and together with TFAM creates a transcription promoter complex for the mitochondrial polymerase POLRMT. We have found an interaction between rs3021088 in MT-ND2 and rs6701836 in TFB2M leading to BMI decrease (inter_pval = 0.0241), while interaction of rs3021088 in MT-ND2 and rs41542013 in POLRMT led to BMI increase (inter_pval = 0.0004). The influence of these interactions on BMI was confirmed in external cohorts.

Conclusions: Here, we have shown that variants in the mitochondrial genome as well as additive interactions between mitochondrial and nuclear SNPs influence BMI in T1DM and general cohorts.
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http://dx.doi.org/10.1186/s12920-020-00752-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7341625PMC
July 2020

Morphological Cell Profiling of SARS-CoV-2 Infection Identifies Drug Repurposing Candidates for COVID-19.

bioRxiv 2020 Jun 10. Epub 2020 Jun 10.

Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI, 48109, USA.

The global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and the associated disease COVID-19, requires therapeutic interventions that can be rapidly translated to clinical care. Unfortunately, traditional drug discovery methods have a >90% failure rate and can take 10-15 years from target identification to clinical use. In contrast, drug repurposing can significantly accelerate translation. We developed a quantitative high-throughput screen to identify efficacious single agents and combination therapies against SARS-CoV-2. Quantitative high-content morphological profiling was coupled with an AI-based machine learning strategy to classify features of cells for infection and stress. This assay detected multiple antiviral mechanisms of action (MOA), including inhibition of viral entry, propagation, and modulation of host cellular responses. From a library of 1,425 FDA-approved compounds and clinical candidates, we identified 16 dose-responsive compounds with antiviral effects. In particular, we discovered that lactoferrin is an effective inhibitor of SARS-CoV-2 infection with an IC of 308 nM and that it potentiates the efficacy of both remdesivir and hydroxychloroquine. Lactoferrin also stimulates an antiviral host cell response and retains inhibitory activity in iPSC-derived alveolar epithelial cells, a model for the primary site of infection. Given its safety profile in humans, these data suggest that lactoferrin is a readily translatable therapeutic adjunct for COVID-19. Additionally, several commonly prescribed drugs were found to exacerbate viral infection and warrant clinical investigation. We conclude that morphological profiling for drug repurposing is an effective strategy for the selection and optimization of drugs and drug combinations as viable therapeutic options for COVID-19 pandemic and other emerging infectious diseases.
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http://dx.doi.org/10.1101/2020.05.27.117184DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7302203PMC
June 2020

Mitigating temozolomide resistance in glioblastoma via DNA damage-repair inhibition.

J R Soc Interface 2020 01 22;17(162):20190722. Epub 2020 Jan 22.

Department of Mathematics, Florida State University, Tallahassee, FL 32306, USA.

Glioblastomas are among the most lethal cancers, with a 5 year survival rate below 25%. Temozolomide is typically used in glioblastoma treatment; however, the enzymes alkylpurine-DNA--glycosylase (APNG) and methylguanine-DNA-methyltransferase (MGMT) efficiently mediate the repair of DNA damage caused by temozolomide, reducing treatment efficacy. Consequently, APNG and MGMT inhibition has been proposed as a way of overcoming chemotherapy resistance. Here, we develop a mechanistic mathematical model that explicitly incorporates the effects of chemotherapy on tumour cells, including the processes of DNA damage induction, cell arrest and DNA repair. Our model is carefully parametrized and validated, and then used to virtually recreate the response of heteroclonal glioblastomas to dual treatment with temozolomide and inhibitors of APNG/MGMT. Using our mechanistic model, we identify four combination treatment strategies optimized by tumour cell phenotype, and isolate the strategy most likely to succeed in a pre-clinical and clinical setting. If confirmed in clinical trials, these strategies have the potential to offset chemotherapy resistance in patients with glioblastoma and improve overall survival.
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http://dx.doi.org/10.1098/rsif.2019.0722DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7014791PMC
January 2020

Genetic variants that associate with cirrhosis have pleiotropic effects on human traits.

Liver Int 2020 02 1;40(2):405-415. Epub 2020 Jan 1.

Division of Gastroenterology and Hepatology, University of Michigan Health System, Ann Arbor, MI, USA.

Background And Aims: Cirrhosis is characterized by extensive fibrosis of the liver and is a major cause of liver-related mortality. Cirrhosis is partially heritable but genetic contributions to cirrhosis have not been systemically explored. Here, we carry out association analyses with cirrhosis in two large biobanks and determine the effects of cirrhosis associated variants on multiple human disease/traits.

Methods: We carried out a genome-wide association analysis of cirrhosis as a diagnosis in UK BioBank (UKBB; 1088 cases vs. 407 873 controls) and then tested top-associating loci for replication with cirrhosis in a hospital-based cohort from the Michigan Genomics Initiative (MGI; 875 cases of cirrhosis vs. 30 346 controls). For replicating variants or variants previously associated with cirrhosis that also affected cirrhosis in UKBB or MGI, we determined single nucleotide polymorphism effects on all other diagnoses in UKBB (PheWAS), common metabolic traits/diseases and serum/plasma metabolites.

Results: Unbiased genome-wide association study identified variants in/near PNPLA3 and HFE, and candidate variant analysis identified variants in/near TM6SF2, MBOAT7, SERPINA1, HSD17B13, STAT4 and IFNL4 that reproducibly affected cirrhosis. Most affected liver enzyme concentrations and/or aspartate transaminase-to-platelet ratio index. PheWAS, metabolic trait and serum/plasma metabolite association analyses revealed effects of these variants on lipid, inflammatory and other processes including new effects on many human diseases and traits.

Conclusions: We identified eight loci that reproducibly associate with population-based cirrhosis and define their diverse effects on human diseases and traits.
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http://dx.doi.org/10.1111/liv.14321DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7395656PMC
February 2020

The plasma metabolome of women in early pregnancy differs from that of non-pregnant women.

PLoS One 2019 14;14(11):e0224682. Epub 2019 Nov 14.

Perinatology Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, U.S. Department of Health and Human Services (NICHD/NIH/DHHS), Bethesda, Maryland, and Detroit, Michigan, United States of America.

Background: In comparison to the non-pregnant state, the first trimester of pregnancy is characterized by systemic adaptation of the mother. The extent to which these adaptive processes are reflected in the maternal blood metabolome is not well characterized.

Objective: To determine the differences between the plasma metabolome of non-pregnant and pregnant women before 16 weeks gestation.

Study Design: This study included plasma samples from 21 non-pregnant women and 50 women with a normal pregnancy (8-16 weeks of gestation). Combined measurements by ultrahigh performance liquid chromatography/tandem mass spectrometry and by gas chromatography/mass spectrometry generated molecular abundance measurements for each sample. Molecular species detected in at least 10 samples were included in the analysis. Differential abundance was inferred based on false discovery adjusted p-values (FDR) from Mann-Whitney-Wilcoxon U tests <0.1 and a minimum median abundance ratio (fold change) of 1.5. Alternatively, metabolic data were quantile normalized to remove sample-to-sample differences in the overall metabolite abundance (adjusted analysis).

Results: Overall, 637 small molecules met the inclusion criteria and were tested for association with pregnancy; 44% (281/637) of small molecules had significantly different abundance, of which 81% (229/281) were less abundant in pregnant than in non-pregnant women. Eight percent (14/169) of the metabolites that remained significant in the adjusted analysis also changed as a function of gestational age. A pathway analysis revealed enrichment in steroid metabolites related to sex hormones, caffeine metabolites, lysolipids, dipeptides, and polypeptide bradykinin derivatives (all, FDR < 0.1).

Conclusions: This high-throughput mass spectrometry study identified: 1) differences between pregnant vs. non-pregnant women in the abundance of 44% of the profiled plasma metabolites, including known and novel molecules and pathways; and 2) specific metabolites that changed with gestational age.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0224682PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6855901PMC
March 2020

The focal adhesion scaffold protein Hic-5 regulates vimentin organization in fibroblasts.

Mol Biol Cell 2019 12 23;30(25):3037-3056. Epub 2019 Oct 23.

Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210.

Focal adhesion (FA)-stimulated reorganization of the F-actin cytoskeleton regulates cellular size, shape, and mechanical properties. However, FA cross-talk with the intermediate filament cytoskeleton is poorly understood. Genetic ablation of the FA-associated scaffold protein Hic-5 in mouse cancer-associated fibroblasts (CAFs) promoted a dramatic collapse of the vimentin network, which was rescued following EGFP-Hic-5 expression. Vimentin collapse correlated with a loss of detergent-soluble vimentin filament precursors and decreased vimentin S72/S82 phosphorylation. Additionally, fluorescence recovery after photobleaching analysis indicated impaired vimentin dynamics. Microtubule (MT)-associated EB1 tracking and Western blotting of MT posttranslational modifications indicated no change in MT dynamics that could explain the vimentin collapse. However, pharmacological inhibition of the RhoGTPase Cdc42 in Hic-5 knockout CAFs rescued the vimentin collapse, while pan-formin inhibition with SMIFH2 promoted vimentin collapse in Hic-5 heterozygous CAFs. Our results reveal novel regulation of vimentin organization/dynamics by the FA scaffold protein Hic-5 via modulation of RhoGTPases and downstream formin activity.
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http://dx.doi.org/10.1091/mbc.E19-08-0442DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6880880PMC
December 2019

Identifying Interaction Clusters for MiRNA and MRNA Pairs in TCGA Network.

Genes (Basel) 2019 09 11;10(9). Epub 2019 Sep 11.

Department of Biology, Indiana State University, Terre Haute, IN 47809, USA.

Existing methods often fail to recognize the conversions for the biological roles of the pairs of genes and microRNAs (miRNAs) between the tumor and normal samples. We have developed a novel cluster scoring method to identify messenger RNA (mRNA) and miRNA interaction pairs and clusters while considering tumor and normal samples jointly. Our method has identified 54 significant clusters for 15 cancer types selected from The Cancer Genome Atlas project. We also determined the shared clusters across tumor types and/or subtypes. In addition, we compared gene and miRNA overlap between lists identified in our liver hepatocellular carcinoma (LIHC) study and regulatory relationships reported from human and rat nonalcoholic fatty liver disease studies (NAFLD). Finally, we analyzed biological functions for the single significant cluster in LIHC and uncovered a significantly enriched pathway (phospholipase D signaling pathway) with six genes represented in the cluster, symbols: , , , , and .
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http://dx.doi.org/10.3390/genes10090702DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770970PMC
September 2019

Body Composition and Genetic Lipodystrophy Risk Score Associate With Nonalcoholic Fatty Liver Disease and Liver Fibrosis.

Hepatol Commun 2019 Aug 18;3(8):1073-1084. Epub 2019 Jun 18.

Division of Gastroenterology and Hepatology, Department of Medicine University of Michigan Health System Ann Arbor MI.

Up to 25% of patients with nonalcoholic fatty liver disease (NAFLD) are not obese but may have a fat or muscle composition that predisposes them to NAFLD. Our aim was to determine whether body composition parameters associate with NAFLD and to identify genetic contributors to this association. This study included two cohorts. The first included 2,249 participants from the Framingham Heart Study who underwent a computed tomography scan to evaluate hepatic steatosis, dual-energy x-ray absorptiometry testing to assess body composition, and clinical examination. Body composition parameters were normalized to total body weight. A subset of participants underwent genotyping with an Affymetrix 550K single-nucleotide polymorphism array. The second cohort, Michigan Genomics Initiative, included 19,239 individuals with genotyping on the Illumina HumanCoreExome v.12.1 array and full electronic health record data. Using sex-stratified multivariable linear regression, greater central body fat associated with increased hepatic steatosis while greater lower extremity body fat associated with decreased hepatic steatosis. Greater appendicular lean mass was associated with decreased hepatic steatosis in men but not in women. A polygenic risk score for lipodystrophy (regional or global loss of adipose tissue) was associated with increased hepatic steatosis, increased liver fibrosis, and decreased lower extremity fat mass. Greater central body fat associated with increased hepatic steatosis, while greater lower extremity body fat and, in men, greater appendicular lean mass were associated with decreased hepatic steatosis. A genetic risk score for lipodystrophy was associated with NAFLD and liver fibrosis. Our results suggest that buffering of excess energy by peripheral fat and muscle may protect against NAFLD and liver fibrosis in the general population.
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http://dx.doi.org/10.1002/hep4.1391DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6671828PMC
August 2019

Insulin Resistance Exacerbates Genetic Predisposition to Nonalcoholic Fatty Liver Disease in Individuals Without Diabetes.

Hepatol Commun 2019 Jul 18;3(7):894-907. Epub 2019 Apr 18.

Division of Statistical Genomics, Department of Genetics Washington University School of Medicine St. Louis MO.

The accumulation of excess fat in the liver (hepatic steatosis) in the absence of heavy alcohol consumption causes nonalcoholic fatty liver disease (NAFLD), which has become a global epidemic. Identifying metabolic risk factors that interact with the genetic risk of NAFLD is important for reducing disease burden. We tested whether serum glucose, insulin, insulin resistance, triglyceride (TG), low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, body mass index (BMI), and waist-to-hip ratio adjusted for BMI interact with genetic variants in or near the patatin-like phospholipase domain containing 3 () gene, the glucokinase regulatory protein () gene, the neurocan/transmembrane 6 superfamily member 2 () gene and the lysophospholipase-like 1 () gene to exacerbate hepatic steatosis, estimated by liver attenuation. We performed association analyses in 10 population-based cohorts separately and then meta-analyzed results in up to 14,751 individuals (11,870 of European ancestry and 2,881 of African ancestry). We found that rs738409 significantly interacted with insulin, insulin resistance, BMI, glucose, and TG to increase hepatic steatosis in nondiabetic individuals carrying the G allele. Additionally, rs780094 significantly interacted with insulin, insulin resistance, and TG. Conditional analyses using the two largest European ancestry cohorts in the study showed that insulin levels accounted for most of the interaction of rs738409 with BMI, glucose, and TG in nondiabetic individuals. Insulin, -rs738409, and their interaction accounted for at least 8% of the variance in hepatic steatosis in these two cohorts. Insulin resistance, either directly or through the resultant elevated insulin levels, more than other metabolic traits, appears to amplify the -rs738409-G genetic risk for hepatic steatosis. Improving insulin resistance in nondiabetic individuals carrying rs738409-G may preferentially decrease hepatic steatosis.
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http://dx.doi.org/10.1002/hep4.1353DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6601321PMC
July 2019

17-Beta Hydroxysteroid Dehydrogenase 13 Is a Hepatic Retinol Dehydrogenase Associated With Histological Features of Nonalcoholic Fatty Liver Disease.

Hepatology 2019 04 5;69(4):1504-1519. Epub 2019 Mar 5.

Liver and Energy Metabolism Unit, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD.

Nonalcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease. A single-nucleotide polymorphism (SNP), rs6834314, was associated with serum liver enzymes in the general population, presumably reflecting liver fat or injury. We studied rs6834314 and its nearest gene, 17-beta hydroxysteroid dehydrogenase 13 (HSD17B13), to identify associations with histological features of NAFLD and to characterize the functional role of HSD17B13 in NAFLD pathogenesis. The minor allele of rs6834314 was significantly associated with increased steatosis but decreased inflammation, ballooning, Mallory-Denk bodies, and liver enzyme levels in 768 adult Caucasians with biopsy-proven NAFLD and with cirrhosis in the general population. We found two plausible causative variants in the HSD17B13 gene. rs72613567, a splice-site SNP in high linkage with rs6834314 (r = 0.94) generates splice variants and shows a similar pattern of association with NAFLD histology. Its minor allele generates simultaneous expression of exon 6-skipping and G-nucleotide insertion variants. Another SNP, rs62305723 (encoding a P260S mutation), is significantly associated with decreased ballooning and inflammation. Hepatic expression of HSD17B13 is 5.9-fold higher (P = 0.003) in patients with NAFLD. HSD17B13 is targeted to lipid droplets, requiring the conserved amino acid 22-28 sequence and amino acid 71-106 region. The protein has retinol dehydrogenase (RDH) activity, with enzymatic activity dependent on lipid droplet targeting and cofactor binding site. The exon 6 deletion, G insertion, and naturally occurring P260S mutation all confer loss of enzymatic activity. Conclusion: We demonstrate the association of variants in HSD17B13 with specific features of NAFLD histology and identify the enzyme as a lipid droplet-associated RDH; our data suggest that HSD17B13 plays a role in NAFLD through its enzymatic activity.
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http://dx.doi.org/10.1002/hep.30350DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6438737PMC
April 2019

Genome-wide association analyses identify 39 new susceptibility loci for diverticular disease.

Nat Genet 2018 10 3;50(10):1359-1365. Epub 2018 Sep 3.

Department of Internal Medicine, Division of Gastroenterology, Ann Arbor, MI, USA.

Diverticular disease is common and has a high morbidity. Treatments are limited owing to the poor understanding of its pathophysiology. Here, to elucidate its etiology, we performed a genome-wide association study of diverticular disease (27,444 cases; 382,284 controls) from the UK Biobank and tested for replication in the Michigan Genomics Initiative (2,572 cases; 28,649 controls). We identified 42 loci associated with diverticular disease; 39 of these loci are novel. Using data-driven expression-prioritized integration for complex traits (DEPICT), we show that genes in these associated regions are significantly enriched for expression in mesenchymal stem cells and multiple connective tissue cell types and are co-expressed with genes that have a role in vascular and mesenchymal biology. Genes in these associated loci have roles in immunity, extracellular matrix biology, cell adhesion, membrane transport and intestinal motility. Phenome-wide association analysis of the 42 variants shows a common etiology of diverticular disease with obesity and hernia. These analyses shed light on the genomic landscape of diverticular disease.
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http://dx.doi.org/10.1038/s41588-018-0203-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168378PMC
October 2018

AmpliSeq transcriptome analysis of human alveolar and monocyte-derived macrophages over time in response to Mycobacterium tuberculosis infection.

PLoS One 2018 30;13(5):e0198221. Epub 2018 May 30.

Center for Pharmacogenomics, Department of Cancer Biology and Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America.

Human alveolar macrophages (HAM) are primary bacterial niche and immune response cells during Mycobacterium tuberculosis (M.tb) infection, and human blood monocyte-derived macrophages (MDM) are a model for investigating M.tb-macrophage interactions. Here, we use a targeted RNA-Seq method to measure transcriptome-wide changes in RNA expression patterns of freshly obtained HAM (used within 6 h) and 6 day cultured MDM upon M.tb infection over time (2, 24 and 72 h), in both uninfected and infected cells from three donors each. The Ion AmpliSeq™ Transcriptome Human Gene Expression Kit (AmpliSeq) uses primers targeting 18,574 mRNAs and 2,228 non-coding RNAs (ncRNAs) for a total of 20,802 transcripts. AmpliSeqTM yields highly precise and reproducible gene expression profiles (R2 >0.99). Taking advantage of AmpliSeq's reproducibility, we establish well-defined quantitative RNA expression patterns of HAM versus MDM, including significant M.tb-inducible genes, in networks and pathways that differ in part between MDM and HAM. A similar number of expressed genes are detected at all time-points between uninfected MDM and HAM, in common pathways including inflammatory and immune functions, but canonical pathway differences also exist. In particular, at 2 h, multiple genes relevant to the immune response are preferentially expressed in either uninfected HAM or MDM, while the HAM RNA profiles approximate MDM profiles over time in culture, highlighting the unique RNA expression profile of freshly obtained HAM. MDM demonstrate a greater transcriptional response than HAM upon M.tb infection, with 2 to >10 times more genes up- or down-regulated. The results identify key genes involved in cellular responses to M.tb in two different human macrophage types. Follow-up bioinformatics analysis indicates that approximately 30% of response genes have expression quantitative trait loci (eQTLs in GTEx), common DNA variants that can influence host gene expression susceptibility or resistance to M.tb, illustrated with the TREM1 gene cluster and IL-10.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0198221PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5976201PMC
November 2018

Life-Course Genome-wide Association Study Meta-analysis of Total Body BMD and Assessment of Age-Specific Effects.

Am J Hum Genet 2018 01;102(1):88-102

MRC Epidemiology Unit, University of Cambridge, Cambridge CB2 0QQ, UK.

Bone mineral density (BMD) assessed by DXA is used to evaluate bone health. In children, total body (TB) measurements are commonly used; in older individuals, BMD at the lumbar spine (LS) and femoral neck (FN) is used to diagnose osteoporosis. To date, genetic variants in more than 60 loci have been identified as associated with BMD. To investigate the genetic determinants of TB-BMD variation along the life course and test for age-specific effects, we performed a meta-analysis of 30 genome-wide association studies (GWASs) of TB-BMD including 66,628 individuals overall and divided across five age strata, each spanning 15 years. We identified variants associated with TB-BMD at 80 loci, of which 36 have not been previously identified; overall, they explain approximately 10% of the TB-BMD variance when combining all age groups and influence the risk of fracture. Pathway and enrichment analysis of the association signals showed clustering within gene sets implicated in the regulation of cell growth and SMAD proteins, overexpressed in the musculoskeletal system, and enriched in enhancer and promoter regions. These findings reveal TB-BMD as a relevant trait for genetic studies of osteoporosis, enabling the identification of variants and pathways influencing different bone compartments. Only variants in ESR1 and close proximity to RANKL showed a clear effect dependency on age. This most likely indicates that the majority of genetic variants identified influence BMD early in life and that their effect can be captured throughout the life course.
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http://dx.doi.org/10.1016/j.ajhg.2017.12.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5777980PMC
January 2018

Gene-Hormone Therapy Interaction and Fracture Risk in Postmenopausal Women.

J Clin Endocrinol Metab 2017 06;102(6):1908-1916

Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, The State University of New York, Buffalo, New York 14214.

Context: Evidence supports a protective effect of menopausal hormone therapy (HT) on bone. However, whether genetic susceptibility modifies the association of HT and fracture risk is not sufficiently explored.

Objective: The objective was to test an interaction between genetic susceptibility and HT on fracture risk.

Design: We constructed two weighted genetic risk scores (GRSs) based on 16 fracture-associated variants (Fx-GRSs) and 50 bone mineral density variants (BMD-GRSs). We used Cox regression to estimate the main effects of GRSs and their interactions with HT on fracture risk. We estimated the relative excess risk due to interaction (RERI) as a measure of additive interaction. We also used the case-only approach to test for a multiplicative interaction.

Setting: Forty US clinical centers.

Participants: A total of 9922 genotyped white postmenopausal women (age, 50 to 79) from the Women's Health Initiative HT randomized trials.

Main Outcome Measures: Adjudicated fracture incidence.

Results: Both GRSs were associated with fracture risk per 1-unit increment in GRS (hazard ratio, 1.04 [95% confidence interval, 1.02 to 1.06] for Fx-GRS and hazard ratio, 1.03 [95% confidence interval,1.02-1.04] for BMD-GRS). We found no evidence for multiplicative interaction for either of the GRS. However, we observed a substantial additive interaction, where the highest quartile of both GRSs and randomization to placebo have excess fracture risk: Fx-GRS P for RERI = 0.047, BMD-GRS P for RERI = 0.046.

Conclusions: These results suggest that HT reduces fracture risk in postmenopausal women, especially in those at highest genetic risk of fracture and low BMD.
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http://dx.doi.org/10.1210/jc.2016-2936DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5470770PMC
June 2017

The influence of genetic susceptibility and calcium plus vitamin D supplementation on fracture risk.

Am J Clin Nutr 2017 04 1;105(4):970-979. Epub 2017 Feb 1.

Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, The State University of New York, Buffalo, NY;

Fracture is a complex trait, affected by both genetic and environmental factors. A meta-analysis of genome-wide association studies (GWASs) identified multiple bone mineral density (BMD) and fracture-associated loci. We conducted a study to evaluate whether fracture genetic risk score (Fx-GRS) and bone mineral density genetic risk score (BMD-GRS) modify the association between the intake of calcium with vitamin D (CaD) and fracture risk. Data from 5823 white postmenopausal women from the Women's Health Initiative CaD randomized trial were included. Participants received 1000 mg elemental Ca with 400 IU vitamin D/d or placebo (median follow-up: 6.5 y). Total fracture was defined as first fracture of any type. We computed the Fx-GRS with 16 fracture- and BMD-associated variants, and the BMD-GRS with 50 BMD-associated variants. We used Cox regression and a case-only approach to test for multiplicative interaction. Additive interaction was assessed with the relative excess risk due to interaction (RERI). We analyzed genetic risk score as a continuous variable and a categorical variable based on quartile (quartile 1, quartiles 2-3, and quartile 4). We observed no interaction between the Fx-GRS and CaD on fracture risk; however, we observed a significant multiplicative interaction between the BMD-GRS and CaD assignment (-interaction = 0.01). In addition, there was a significant negative additive interaction between placebo assignment and higher BMD-GRS: quartiles 2-3, = 0.03; quartile 4, = 0.03. In a stratified analysis, the protective effect of CaD on fracture risk was observed in women in the lowest BMD-GRS quartile (HR: 0.60, 95% CI: 0.44, 0.81) but not in women with a higher BMD-GRS. We observed significant effects of CaD intake on fracture risk only in women with the lowest genetic predisposition to low BMD. Future large-scale studies with functional characterization of GWAS findings are warranted to assess the utility of genetic risk score in analysis of risks and benefits of CaD for bone.
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http://dx.doi.org/10.3945/ajcn.116.144550DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5366049PMC
April 2017

Erratum to: Non-linear interactions between candidate genes of myocardial infarction revealed in mRNA expression profiles.

BMC Genomics 2016 12 2;17(1):988. Epub 2016 Dec 2.

College of Medicine Center for Pharmacogenomics, The Ohio State University Wexner Medical Center, Biomedical Research Tower, 460 W 12th Avenue, Columbus, OH, USA.

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http://dx.doi.org/10.1186/s12864-016-3349-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5135797PMC
December 2016

Gene expression profiling of brain samples from patients with Lewy body dementia.

Biochem Biophys Res Commun 2016 Oct 22;479(4):875-880. Epub 2016 Sep 22.

Center for Pharmacogenomics, Department of Cancer Biology and Genetics, College of Medicine, The Ohio State University, Columbus, OH, USA. Electronic address:

Dementia with Lewy Bodies (DLB) is the second most common neurodegenerative disorder in the elderly. The development and progression of DLB remain unclear. In this study we used next generation sequencing to assess RNA expression profiles and cellular processes associated with DLB in the anterior cingulate cortex, a brain region affected by DLB pathology. The expression measurements were made in autopsy brain tissues from 8 DLB subjects and 10 age-matched controls using AmpliSeq technology with ion torrent sequencing. The analysis of RNA expression profiles revealed 490 differentially expressed genes, among which 367 genes were down-regulated and 123 were up-regulated. Functional enrichment analysis of genes differentially expressed in DLB indicated downregulation of genes associated with myelination, neurogenesis, and regulation of nervous system development. miRNA binding sites enriched in these mRNAs yielded a list of candidate miRNAs participating in DLB pathophysiology. Our study provides a comprehensive picture of gene expression landscape in DLB, identifying key cellular processes associated with DLB pathology.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5079284PMC
http://dx.doi.org/10.1016/j.bbrc.2016.09.114DOI Listing
October 2016

Non-linear interactions between candidate genes of myocardial infarction revealed in mRNA expression profiles.

BMC Genomics 2016 09 17;17(1):738. Epub 2016 Sep 17.

College of Medicine Center for Pharmacogenomics, The Ohio State University Wexner Medical Center, Biomedical Research Tower, 460 W 12th Avenue, Columbus, OH, USA.

Background: Alterations in gene expression are key events in disease etiology and risk. Poor reproducibility in detecting differentially expressed genes across studies suggests individual genes may not be sufficiently informative for complex diseases, such as myocardial infarction (MI). Rather, dysregulation of the 'molecular network' may be critical for pathogenic processes. Such a dynamic network can be built from pairwise non-linear interactions.

Results: We investigate non-linear interactions represented in mRNA expression profiles that integrate genetic background and environmental factors. Using logistic regression, we test the association of individual GWAS-based candidate genes and non-linear interaction terms (between these mRNA expression levels) with MI. Based on microarray data in CATHGEN (CATHeterization in GENetics) and FHS (Framingham Heart Study), we find individual genes and pairs of mRNAs, encoded by 41 MI candidate genes, with significant interaction terms in the logistic regression model. Two pairs replicate between CATHGEN and FHS (CNNM2|GUCY1A3 and CNNM2|ZEB2). Analysis of RNAseq data from GTEx (Genotype-Tissue Expression) shows that 20 % of these disease-associated RNA pairs are co-expressed, further prioritizing significant interactions. Because edges in sparse co-expression networks formed solely by the 41 candidate genes are unlikely to represent direct physical interactions, we identify additional RNAs as links between network pairs of candidate genes. This approach reveals additional mRNAs and interaction terms significant in the context of MI, for example, the path CNNM2|ACSL5|SCARF1|GUCY1A3, characterized by the common themes of magnesium and lipid processing.

Conclusions: The results of this study support a role for non-linear interactions between genes in MI and provide a basis for further study of MI systems biology. mRNA expression profiles encoded by a limited number of candidate genes yield sparse networks of MI-relevant interactions that can be expanded to include additional candidates by co-expression analysis. The non-linear interactions observed here inform our understanding of the clinical relevance of gene-gene interactions in the pathophysiology of MI, while providing a new strategy in developing clinical biomarker panels.
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http://dx.doi.org/10.1186/s12864-016-3075-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5027110PMC
September 2016

RNA sequencing of transcriptomes in human brain regions: protein-coding and non-coding RNAs, isoforms and alleles.

BMC Genomics 2015 Nov 23;16:990. Epub 2015 Nov 23.

Center for Pharmacogenomics, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA.

Background: We used RNA sequencing to analyze transcript profiles of ten autopsy brain regions from ten subjects. RNA sequencing techniques were designed to detect both coding and non-coding RNA, splice isoform composition, and allelic expression. Brain regions were selected from five subjects with a documented history of smoking and five non-smokers. Paired-end RNA sequencing was performed on SOLiD instruments to a depth of >40 million reads, using linearly amplified, ribosomally depleted RNA. Sequencing libraries were prepared with both poly-dT and random hexamer primers to detect all RNA classes, including long non-coding (lncRNA), intronic and intergenic transcripts, and transcripts lacking poly-A tails, providing additional data not previously available. The study was designed to generate a database of the complete transcriptomes in brain region for gene network analyses and discovery of regulatory variants.

Results: Of 20,318 protein coding and 18,080 lncRNA genes annotated from GENCODE and lncipedia, 12 thousand protein coding and 2 thousand lncRNA transcripts were detectable at a conservative threshold. Of the aligned reads, 52 % were exonic, 34 % intronic and 14 % intergenic. A majority of protein coding genes (65 %) was expressed in all regions, whereas ncRNAs displayed a more restricted distribution. Profiles of RNA isoforms varied across brain regions and subjects at multiple gene loci, with neurexin 3 (NRXN3) a prominent example. Allelic RNA ratios deviating from unity were identified in > 400 genes, detectable in both protein-coding and non-coding genes, indicating the presence of cis-acting regulatory variants. Mathematical modeling was used to identify RNAs stably expressed in all brain regions (serving as potential markers for normalizing expression levels), linked to basic cellular functions. An initial analysis of differential expression analysis between smokers and nonsmokers implicated a number of genes, several previously associated with nicotine exposure.

Conclusions: RNA sequencing identifies distinct and consistent differences in gene expression between brain regions, with non-coding RNA displaying greater diversity between brain regions than mRNAs. Numerous RNAs exhibit robust allele selective expression, proving a means for discovery of cis-acting regulatory factors with potential clinical relevance.
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http://dx.doi.org/10.1186/s12864-015-2207-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4657279PMC
November 2015

Association between Prediagnostic Allergy-Related Serum Cytokines and Glioma.

PLoS One 2015 9;10(9):e0137503. Epub 2015 Sep 9.

Department of Research, Cancer Registry of Norway, Oslo, Norway.

Allergy is inversely related to glioma risk. To determine whether prediagnostic allergy-related serum proteins are associated with glioma, we conducted a nested case-control study of seven cytokines (IL4, IL13, IL5, IL6, IL10, IFNG, TGFB2), two soluble cytokine receptors (sIL4RA, sIL13RA2) and three allergy-related transcription factors (FOXP3, STAT3, STAT6) using serum specimens from the Janus Serum Bank Cohort in Oslo, Norway. Blood donors subsequently diagnosed with glioma (n = 487) were matched to controls (n = 487) on age and date of blood draw and sex. We first estimated individual effects of the 12 serum proteins and then interactions between IL4 and IL13 and their receptors using conditional logistic regression. We next tested equality of case-control inter-correlations among the 12 serum proteins. We found that TGFB2 is inversely related to glioblastoma (Odds Ratio (OR) = 0.87, 95% Confidence Interval (CI)) = 0.76, 0.98). In addition, ≤ 5 years before diagnosis, we observed associations between IL4 (OR = 0.82, 95% CI = 0.66, 1.01), sIL4RA (OR = 0.80, 95% CI = 0.65, 1.00), their interaction (OR = 1.06, 95% CI = 1.01, 1.12) and glioblastoma. This interaction was apparent > 20 years before diagnosis (IL4-sIL4RA OR = 1.20, 95% CI = 1.05, 1.37). Findings for glioma were similar. Case correlations were different from control correlations stratified on time before diagnosis. Five years or less before diagnosis, correlations among case serum proteins were weaker than were those among controls. Our findings suggest that IL4 and sIL4RA reduce glioma risk long before diagnosis and early gliomagenesis affects circulating immune function proteins.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137503PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4564184PMC
May 2016

Conditional entropy in variation-adjusted windows detects selection signatures associated with expression quantitative trait loci (eQTLs).

BMC Genomics 2015 18;16 Suppl 8:S8. Epub 2015 Jun 18.

Background: Over the past 50,000 years, shifts in human-environmental or human-human interactions shaped genetic differences within and among human populations, including variants under positive selection. Shaped by environmental factors, such variants influence the genetics of modern health, disease, and treatment outcome. Because evolutionary processes tend to act on gene regulation, we test whether regulatory variants are under positive selection. We introduce a new approach to enhance detection of genetic markers undergoing positive selection, using conditional entropy to capture recent local selection signals.

Results: We use conditional logistic regression to compare our Adjusted Haplotype Conditional Entropy (H|H) measure of positive selection to existing positive selection measures. H|H and existing measures were applied to published regulatory variants acting in cis (cis-eQTLs), with conditional logistic regression testing whether regulatory variants undergo stronger positive selection than the surrounding gene. These cis-eQTLs were drawn from six independent studies of genotype and RNA expression. The conditional logistic regression shows that, overall, H|H is substantially more powerful than existing positive-selection methods in identifying cis-eQTLs against other Single Nucleotide Polymorphisms (SNPs) in the same genes. When broken down by Gene Ontology, H|H predictions are particularly strong in some biological process categories, where regulatory variants are under strong positive selection compared to the bulk of the gene, distinct from those GO categories under overall positive selection. . However, cis-eQTLs in a second group of genes lack positive selection signatures detectable by H|H, consistent with ancient short haplotypes compared to the surrounding gene (for example, in innate immunity GO:0042742); under such other modes of selection, H|H would not be expected to be a strong predictor.. These conditional logistic regression models are adjusted for Minor allele frequency(MAF); otherwise, ascertainment bias is a huge factor in all eQTL data sets. Relationships between Gene Ontology categories, positive selection and eQTL specificity were replicated with H|H in a single larger data set. Our measure, Adjusted Haplotype Conditional Entropy (H|H), was essential in generating all of the results above because it: 1) is a stronger overall predictor for eQTLs than comparable existing approaches, and 2) shows low sequential auto-correlation, overcoming problems with convergence of these conditional regression statistical models.

Conclusions: Our new method, H|H, provides a consistently more robust signal associated with cis-eQTLs compared to existing methods. We interpret this to indicate that some cis-eQTLs are under positive selection compared to their surrounding genes. Conditional entropy indicative of a selective sweep is an especially strong predictor of eQTLs for genes in several biological processes of medical interest. Where conditional entropy is a weak or negative predictor of eQTLs, such as innate immune genes, this would be consistent with balancing selection acting on such eQTLs over long time periods. Different measures of selection may be needed for variant prioritization under other modes of evolutionary selection.
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http://dx.doi.org/10.1186/1471-2164-16-S8-S8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4480832PMC
March 2016

Cladograms with Path to Event (ClaPTE): a novel algorithm to detect associations between genotypes or phenotypes using phylogenies.

Comput Biol Med 2015 Mar 24;58:1-13. Epub 2014 Dec 24.

Department of Bioinformatics and Genomics, University of North Carolina at Charlotte, 9201 University City Blvd, Charlotte, NC 28223-0001, United States.

Background: Associations between genotype and phenotype provide insight into the evolution of pathogenesis, drug resistance, and the spread of pathogens between hosts. However, common ancestry can lead to apparent associations between biologically unrelated features. The novel method Cladograms with Path to Event (ClaPTE) detects associations between character-pairs (either a pair of mutations or a mutation paired with a phenotype) while adjusting for common ancestry, using phylogenetic trees.

Methods: ClaPTE tests for character-pairs changing close together on the phylogenetic tree, consistent with an associated character-pair. ClaPTE is compared to three existing methods (independent contrasts, mixed model, and likelihood ratio) to detect character-pair associations adjusted for common ancestry. Comparisons utilize simulations on gene trees for: HIV Env, HIV promoter, and bacterial DnaJ and GuaB; and case studies for Oseltamavir resistance in Influenza, and for DnaJ and GuaB. Simulated data include both true-positive/associated character-pairs, and true-negative/not-associated character-pairs, used to assess type I (frequency of p-values in true-negatives) and type II (sensitivity to true-positives) error control.

Results And Conclusions: ClaPTE has competitive sensitivity and better type I error control than existing methods. In the Influenza/Oseltamavir case study, ClaPTE reports no new permissive mutations but detects associations between adjacent (in primary sequence) amino acid positions which other methods miss. In the DnaJ and GuaB case study, ClaPTE reports more frequent associations between positions both from the same protein family than between positions from different families, in contrast to other methods. In both case studies, the results from ClaPTE are biologically plausible.
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http://dx.doi.org/10.1016/j.compbiomed.2014.12.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4331246PMC
March 2015

Missing heritability of common diseases and treatments outside the protein-coding exome.

Hum Genet 2014 Oct 9;133(10):1199-215. Epub 2014 Aug 9.

Department of Pharmacology, Center for Pharmacogenomics, College of Medicine, The Ohio State University Wexner Medical Center, 5184A Graves Hall, 333 West 10th Avenue, Columbus, OH, 43210, USA,

Genetic factors strongly influence risk of common human diseases and treatment outcomes but the causative variants remain largely unknown; this gap has been called the 'missing heritability'. We propose several hypotheses that in combination have the potential to narrow the gap. First, given a multi-stage path from wellness to disease, we propose that common variants under positive evolutionary selection represent normal variation and gate the transition between wellness and an 'off-well' state, revealing adaptations to changing environmental conditions. In contrast, genome-wide association studies (GWAS) focus on deleterious variants conveying disease risk, accelerating the path from off-well to illness and finally specific diseases, while common 'normal' variants remain hidden in the noise. Second, epistasis (dynamic gene-gene interactions) likely assumes a central role in adaptations and evolution; yet, GWAS analyses currently are poorly designed to reveal epistasis. As gene regulation is germane to adaptation, we propose that epistasis among common normal regulatory variants, or between common variants and less frequent deleterious variants, can have strong protective or deleterious phenotypic effects. These gene-gene interactions can be highly sensitive to environmental stimuli and could account for large differences in drug response between individuals. Residing largely outside the protein-coding exome, common regulatory variants affect either transcription of coding and non-coding RNAs (regulatory SNPs, or rSNPs) or RNA functions and processing (structural RNA SNPs, or srSNPs). Third, with the vast majority of causative variants yet to be discovered, GWAS rely on surrogate markers, a confounding factor aggravated by the presence of more than one causative variant per gene and by epistasis. We propose that the confluence of these factors may be responsible to large extent for the observed heritability gap.
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http://dx.doi.org/10.1007/s00439-014-1476-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4169001PMC
October 2014

Meta-analysis of genome-wide association studies identifies two loci associated with circulating osteoprotegerin levels.

Hum Mol Genet 2014 Dec 30;23(24):6684-93. Epub 2014 Jul 30.

Department of Medicine,

Osteoprotegerin (OPG) is involved in bone homeostasis and tumor cell survival. Circulating OPG levels are also important biomarkers of various clinical traits, such as cancers and atherosclerosis. OPG levels were measured in serum or in plasma. In a meta-analysis of genome-wide association studies in up to 10 336 individuals from European and Asian origin, we discovered that variants >100 kb upstream of the TNFRSF11B gene encoding OPG and another new locus on chromosome 17q11.2 were significantly associated with OPG variation. We also identified a suggestive locus on chromosome 14q21.2 associated with the trait. Moreover, we estimated that over half of the heritability of OPG levels could be explained by all variants examined in our study. Our findings provide further insight into the genetic regulation of circulating OPG levels.
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http://dx.doi.org/10.1093/hmg/ddu386DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4240210PMC
December 2014