Publications by authors named "Andrew Bakshi"

29 Publications

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The MURAL collection of prostate cancer patient-derived xenografts enables discovery through preclinical models of uro-oncology.

Nat Commun 2021 08 19;12(1):5049. Epub 2021 Aug 19.

Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, VIC, Australia.

Preclinical testing is a crucial step in evaluating cancer therapeutics. We aimed to establish a significant resource of patient-derived xenografts (PDXs) of prostate cancer for rapid and systematic evaluation of candidate therapies. The PDX collection comprises 59 tumors collected from 30 patients between 2012-2020, coinciding with availability of abiraterone and enzalutamide. The PDXs represent the clinico-pathological and genomic spectrum of prostate cancer, from treatment-naïve primary tumors to castration-resistant metastases. Inter- and intra-tumor heterogeneity in adenocarcinoma and neuroendocrine phenotypes is evident from bulk and single-cell RNA sequencing data. Organoids can be cultured from PDXs, providing further capabilities for preclinical studies. Using a 1 x 1 x 1 design, we rapidly identify tumors with exceptional responses to combination treatments. To govern the distribution of PDXs, we formed the Melbourne Urological Research Alliance (MURAL). This PDX collection is a substantial resource, expanding the capacity to test and prioritize effective treatments for prospective clinical trials in prostate cancer.
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http://dx.doi.org/10.1038/s41467-021-25175-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8376965PMC
August 2021

CX-5461 Sensitizes DNA Damage Repair-proficient Castrate-resistant Prostate Cancer to PARP Inhibition.

Mol Cancer Ther 2021 Aug 19. Epub 2021 Aug 19.

Monash Partners Comprehensive Cancer Consortium, Monash Biomedicine Discovery Institute Cancer Program, Prostate Cancer Research Group, Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia.

Monotherapy with PARP inhibitors is effective for the subset of castrate-resistant prostate cancer (CRPC) with defects in homologous recombination (HR) DNA repair. New treatments are required for the remaining tumors, and an emerging strategy is to combine PARP inhibitors with other therapies that induce DNA damage. Here we tested whether PARP inhibitors are effective for HR-proficient CRPC, including androgen receptor (AR)-null tumors, when used in combination with CX-5461, a small molecule that inhibits RNA polymerase I transcription and activates the DNA damage response, and has antitumor activity in early phase I trials. The combination of CX-5461 and talazoparib significantly decreased growth of patient-derived xenografts of HR-proficient CRPC, including AR-positive, AR-null, and neuroendocrine tumors. CX-5461 and talazoparib synergistically inhibited the growth of organoids and cell lines, and significantly increased the levels of DNA damage. Decreased tumor growth after combination therapy was maintained for 2 weeks without treatment, significantly increasing host survival. Therefore, combination treatment with CX-5461 and talazoparib is effective for HR-proficient tumors that are not suitable for monotherapy with PARP inhibitors, including AR-null CRPC. This expands the spectrum of CRPC that is sensitive to PARP inhibition.
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http://dx.doi.org/10.1158/1535-7163.MCT-20-0932DOI Listing
August 2021

Genomic Risk Prediction for Breast Cancer in Older Women.

Cancers (Basel) 2021 Jul 14;13(14). Epub 2021 Jul 14.

Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC 3004, Australia.

Genomic risk prediction models for breast cancer (BC) have been predominantly developed with data from women aged 40-69 years. Prospective studies of older women aged ≥70 years have been limited. We assessed the effect of a 313-variant polygenic risk score (PRS) for BC in 6339 older women aged ≥70 years (mean age 75 years) enrolled into the ASPREE trial, a randomized double-blind placebo-controlled clinical trial investigating the effect of daily 100 mg aspirin on disability-free survival. We evaluated incident BC diagnoses over a median follow-up time of 4.7 years. A multivariable Cox regression model including conventional BC risk factors was applied to prospective data, and re-evaluated after adding the PRS. We also assessed the association of rare pathogenic variants (PVs) in BC susceptibility genes (). The PRS, as a continuous variable, was an independent predictor of incident BC (hazard ratio (HR) per standard deviation (SD) = 1.4, 95% confidence interval (CI) 1.3-1.6) and hormone receptor (ER/PR)-positive disease (HR = 1.5 (CI 1.2-1.9)). Women in the top quintile of the PRS distribution had over two-fold higher risk of BC than women in the lowest quintile (HR = 2.2 (CI 1.2-3.9)). The concordance index of the model without the PRS was 0.62 (95% CI 0.56-0.68), which improved after addition of the PRS to 0.65 (95% CI 0.59-0.71). Among 41 (0.6%) carriers of PVs in BC susceptibility genes, we observed no incident BC diagnoses. Our study demonstrates that a PRS predicts incident BC risk in women aged 70 years and older, suggesting potential clinical utility extends to this older age group.
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http://dx.doi.org/10.3390/cancers13143533DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8305131PMC
July 2021

Predictive Performance of a Polygenic Risk Score for Incident Ischemic Stroke in a Healthy Older Population.

Stroke 2021 Aug 27;52(9):2882-2891. Epub 2021 May 27.

Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine (J.T.N., M.R., A. Bakshi, G.P., L.T.P.T., M.R.N., R.L.W., C.M.R., A.M.T., J.J.M., P.L.), Monash University, Melbourne, Australia.

[Figure: see text].
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http://dx.doi.org/10.1161/STROKEAHA.120.033670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8384668PMC
August 2021

Genomic Risk Score for Melanoma in a Prospective Study of Older Individuals.

J Natl Cancer Inst 2021 Oct;113(10):1379-1385

Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia.

Background: Recent genome-wide association meta-analysis for melanoma doubled the number of previously identified variants. We assessed the performance of an updated polygenic risk score (PRS) in a population of older individuals, where melanoma incidence and cumulative ultraviolet radiation exposure is greatest.

Methods: We assessed a PRS for cutaneous melanoma comprising 55 variants in a prospective study of 12 712 individuals in the ASPirin in Reducing Events in the Elderly Trial. We evaluated incident melanomas diagnosed during the trial and prevalent melanomas diagnosed preenrolment (self-reported). Multivariable models examined associations between PRS as a continuous variable (per SD) and categorical (low-risk [0%-20%], medium-risk [21%-80%], high-risk [81%-100%] groups) with incident melanoma. Logistic regression examined the association between PRS and prevalent melanoma.

Results: At baseline, mean participant age was 75 years; 55.0% were female, and 528 (4.2%) had prevalent melanomas. During follow-up (median = 4.7 years), 120 (1.0%) incident cutaneous melanomas occurred, 98 of which were in participants with no history. PRS was associated with incident melanoma (hazard ratio = 1.46 per SD, 95% confidence interval [CI] = 1.20 to 1.77) and prevalent melanoma (odds ratio [OR] = 1.55 per SD, 95% CI = 1.42 to 1.69). Participants in the highest-risk PRS group had increased risk compared with the low-risk group for incident melanoma (OR = 2.51, 95% CI = 1.28 to 4.92) and prevalent melanoma (OR = 3.66, 95% CI = 2.69 to 5.05). When stratifying by sex, only males had an association between the PRS and incident melanoma, whereas both sexes had an association between the PRS and prevalent melanoma.

Conclusions: A genomic risk score is associated with melanoma risk in older individuals and may contribute to targeted surveillance.
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http://dx.doi.org/10.1093/jnci/djab076DOI Listing
October 2021

Quantifying genetic heterogeneity between continental populations for human height and body mass index.

Sci Rep 2021 Mar 4;11(1):5240. Epub 2021 Mar 4.

Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia.

Genome-wide association studies (GWAS) in samples of European ancestry have identified thousands of genetic variants associated with complex traits in humans. However, it remains largely unclear whether these associations can be used in non-European populations. Here, we seek to quantify the proportion of genetic variation for a complex trait shared between continental populations. We estimated the between-population correlation of genetic effects at all SNPs ([Formula: see text]) or genome-wide significant SNPs ([Formula: see text]) for height and body mass index (BMI) in samples of European (EUR; [Formula: see text]) and African (AFR; [Formula: see text]) ancestry. The [Formula: see text] between EUR and AFR was 0.75 ([Formula: see text]) for height and 0.68 ([Formula: see text]) for BMI, and the corresponding [Formula: see text] was 0.82 ([Formula: see text]) for height and 0.87 ([Formula: see text]) for BMI, suggesting that a large proportion of GWAS findings discovered in Europeans are likely applicable to non-Europeans for height and BMI. There was no evidence that [Formula: see text] differs in SNP groups with different levels of between-population difference in allele frequency or linkage disequilibrium, which, however, can be due to the lack of power.
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http://dx.doi.org/10.1038/s41598-021-84739-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7933291PMC
March 2021

Androgen receptor enhancer amplification in matched patient-derived xenografts of primary and castrate-resistant prostate cancer.

J Pathol 2021 Jun 29;254(2):121-134. Epub 2021 Mar 29.

Monash Partners Comprehensive Cancer Consortium, Monash Biomedicine Discovery Institute Cancer Program, Prostate Cancer Research Group, Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia.

Amplifications of the androgen receptor (AR) occur in up to 80% of men with castration-resistant prostate cancer (CRPC). Recent studies highlighted that these amplifications not only span the AR gene but usually encompass a distal enhancer. This represents a newly recognised, non-coding mechanism of resistance to AR-directed therapies, including enzalutamide. To study disease progression before and after AR amplification, we used tumour samples from a castrate-sensitive primary tumour and castrate-resistant metastasis of the same patient. For subsequent functional and genomic studies, we established serially transplantable patient-derived xenografts (PDXs). Whole genome sequencing showed that alterations associated with poor prognosis, such as TP53 and PTEN loss, existed before androgen deprivation therapy, followed by co-amplification of the AR gene and enhancer after the development of metastatic CRPC. The PDX of the primary tumour, without the AR amplification, was sensitive to AR-directed treatments, including castration, enzalutamide, and apalutamide. The PDX of the metastasis, with the AR amplification, had higher AR and AR-V7 expression in castrate conditions, and was resistant to castration, apalutamide, and enzalutamide in vivo. Treatment with a BET inhibitor outperformed the AR-directed therapies for the metastasis, resulting in tumour regression for some, but not all, grafts. Therefore, this study provides novel matched PDXs to test potential treatments that target the overabundance of AR in tumours with AR enhancer amplifications. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/path.5652DOI Listing
June 2021

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

J Clin Endocrinol Metab 2021 01;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

Neonatal genetics of gene expression reveal potential origins of autoimmune and allergic disease risk.

Nat Commun 2020 07 28;11(1):3761. Epub 2020 Jul 28.

Cambridge Baker Systems Genomics Initiative, Baker Heart and Diabetes Institute, Melbourne, VIC, 3004, Australia.

Chronic immune-mediated diseases of adulthood often originate in early childhood. To investigate genetic associations between neonatal immunity and disease, we map expression quantitative trait loci (eQTLs) in resting myeloid cells and CD4 T cells from cord blood samples, as well as in response to lipopolysaccharide (LPS) or phytohemagglutinin (PHA) stimulation, respectively. Cis-eQTLs are largely specific to cell type or stimulation, and 31% and 52% of genes with cis-eQTLs have response eQTLs (reQTLs) in myeloid cells and T cells, respectively. We identified cis regulatory factors acting as mediators of trans effects. There is extensive colocalisation between condition-specific neonatal cis-eQTLs and variants associated with immune-mediated diseases, in particular CTSH had widespread colocalisation across diseases. Mendelian randomisation shows causal neonatal gene expression effects on disease risk for BTN3A2, HLA-C and others. Our study elucidates the genetics of gene expression in neonatal immune cells, and aetiological origins of autoimmune and allergic diseases.
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http://dx.doi.org/10.1038/s41467-020-17477-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7387553PMC
July 2020

Familial Hypercholesterolemia in a Healthy Elderly Population.

Circ Genom Precis Med 2020 08 10;13(4):e002938. Epub 2020 Jun 10.

Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC, Australia (P.L., M.R., J.T., A.B., R.L.W., A.M.T., C.M.R., J.J.M.).

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http://dx.doi.org/10.1161/CIRCGEN.120.002938DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7442644PMC
August 2020

Association of Schizophrenia Risk With Disordered Niacin Metabolism in an Indian Genome-wide Association Study.

JAMA Psychiatry 2019 10;76(10):1026-1034

Schizophrenia Research Foundation, Chennai, India.

Importance: Genome-wide association studies (GWASs) in European populations have identified more than 100 schizophrenia-associated loci. A schizophrenia GWAS in a unique Indian population offers novel findings.

Objective: To discover and functionally evaluate genetic loci for schizophrenia in a GWAS of a unique Indian population.

Design, Setting, And Participants: This GWAS included a sample of affected individuals, family members, and unrelated cases and controls. Three thousand ninety-two individuals were recruited and diagnostically ascertained via medical records, hospitals, clinics, and clinical networks in Chennai and surrounding regions. Affected participants fulfilled DSM-IV diagnostic criteria for schizophrenia. Unrelated control participants had no personal or family history of psychotic disorder. Recruitment, genotyping, and analysis occurred in consecutive phases beginning January 1, 2001. Recruitment was completed on February 28, 2018, and genotyping and analysis are ongoing.

Main Outcomes And Measures: Associations of single-nucleotide polymorphisms and gene expression with schizophrenia.

Results: The study population included 1321 participants with schizophrenia, 885 family controls, and 886 unrelated controls. Among participants with schizophrenia, mean (SD) age was 39.1 (11.4) years, and 52.7% were male. This sample demonstrated uniform ethnicity, a degree of inbreeding, and negligible rates of substance abuse. A novel genome-wide significant association was observed between schizophrenia and a chromosome 8q24.3 locus (rs10866912, allele A; odds ratio [OR], 1.27 [95% CI, 1.17-1.38]; P = 4.35 × 10-8) that attracted support in the schizophrenia Psychiatric Genomics Consortium 2 data (rs10866912, allele A; OR, 1.04 [95% CI, 1.02-1.06]; P = 7.56 × 10-4). This locus has undergone natural selection, with the risk allele A declining in frequency from India (approximately 72%) to Europe (approximately 43%). rs10866912 directly modifies the abundance of the nicotinate phosphoribosyltransferase gene (NAPRT1) transcript in brain cortex (normalized effect size, 0.79; 95% CI, 0.6-1.0; P = 5.8 × 10-13). NAPRT1 encodes a key enzyme for niacin metabolism. In Indian lymphoblastoid cell lines, (risk) allele A of rs10866912 was associated with NAPRT1 downregulation (AA: 0.74, n = 21; CC: 1.56, n = 17; P = .004). Preliminary zebrafish data further suggest that partial loss of function of NAPRT1 leads to abnormal brain development.

Conclusions And Relevance: Bioinformatic analyses and cellular and zebrafish gene expression studies implicate NAPRT1 as a novel susceptibility gene. Given this gene's role in niacin metabolism and the evidence for niacin deficiency provoking schizophrenialike symptoms in neuropsychiatric diseases such as pellagra and Hartnup disease, these results suggest that the rs10866912 genotype and niacin status may have implications for schizophrenia susceptibility and treatment.
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http://dx.doi.org/10.1001/jamapsychiatry.2019.1335DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6613304PMC
October 2019

Establishing a cryopreservation protocol for patient-derived xenografts of prostate cancer.

Prostate 2019 08 18;79(11):1326-1337. Epub 2019 Jun 18.

Department of Anatomy and Developmental Biology, Monash Partners Comprehensive Cancer Consortium, Monash Biomedicine Discovery Institute, Prostate Cancer Research Group, Monash University, Clayton, Victoria, Australia.

Background: Serially transplantable patient-derived xenografts (PDXs) are invaluable preclinical models for studying tumor biology and evaluating therapeutic agents. As these models are challenging to establish from prostate cancer specimens, the ability to preserve them through cryopreservation has several advantages for ongoing research. Despite this, there is still uncertainty about the ability to cryopreserve PDXs of prostate cancer. This study compared three different cryopreservation protocols to identify a method that can be used to reproducibly cryopreserve a diverse cohort of prostate cancer PDX models.

Methods: One serially transplantable prostate cancer PDX from the Melbourne Urological Research Alliance cohort was used to compare three cryopreservation protocols: slow freezing in fetal calf serum (FCS) with 10% dimethyl sulfoxide (DMSO), FCS with 10% DMSO supplemented with the Rho-associated kinase (ROCK) inhibitor Y-27632 and vitrification. The efficiency of the slow freezing protocols was then assessed in 17 additional prostate cancer PDXs. Following cryopreservation, PDXs were re-established in host mice that were either intact and supplemented with testosterone or castrated. Graft take rate, tumor growth, histological features, and transcriptome profiles before and after cryopreservation were compared.

Results: Slow freezing maintained the viability and histological features of prostate cancer PDXs, and the addition of a ROCK inhibitor increased their growth following cryopreservation. Using the slow freezing method, we re-established 100% of PDXs grown in either testosterone-supplemented or castrated host mice. Importantly, the long-term tumor growth rate and transcriptome profile were maintained following cryopreservation.

Conclusion: This study has identified a protocol to reliably cryopreserve and re-establish a diverse cohort of serially transplantable PDXs of prostate cancer. This study has the potential to significantly improve the practicality of maintaining PDX models. Cryopreservation may also increase the accessibility of these important resources and provide new opportunities for preclinical studies on a broader spectrum of prostate tumors.
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http://dx.doi.org/10.1002/pros.23839DOI Listing
August 2019

Hidden heritability due to heterogeneity across seven populations.

Nat Hum Behav 2017 Oct 11;1(10):757-765. Epub 2017 Sep 11.

Department of Sociology/Nuffield College, University of Oxford, Oxford, OX1 3UQ, UK.

Meta-analyses of genome-wide association studies (GWAS), which dominate genetic discovery are based on data from diverse historical time periods and populations. Genetic scores derived from GWAS explain only a fraction of the heritability estimates obtained from whole-genome studies on single populations, known as the 'hidden heritability' puzzle. Using seven sampling populations (N=35,062), we test whether hidden heritability is attributed to heterogeneity across sampling populations and time, showing that estimates are substantially smaller from across compared to within populations. We show that the hidden heritability varies substantially: from zero (height), to 20% for BMI, 37% for education, 40% for age at first birth and up to 75% for number of children. Simulations demonstrate that our results more likely reflect heterogeneity in phenotypic measurement or gene-environment interaction than genetic heterogeneity. These findings have substantial implications for genetic discovery, suggesting that large homogenous datasets are required for behavioural phenotypes and that gene-environment interaction may be a central challenge for genetic discovery.
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http://dx.doi.org/10.1038/s41562-017-0195-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5642946PMC
October 2017

Genetic loci associated with coronary artery disease harbor evidence of selection and antagonistic pleiotropy.

PLoS Genet 2017 Jun 22;13(6):e1006328. Epub 2017 Jun 22.

Centre for Systems Genomics, School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia.

Traditional genome-wide scans for positive selection have mainly uncovered selective sweeps associated with monogenic traits. While selection on quantitative traits is much more common, very few signals have been detected because of their polygenic nature. We searched for positive selection signals underlying coronary artery disease (CAD) in worldwide populations, using novel approaches to quantify relationships between polygenic selection signals and CAD genetic risk. We identified new candidate adaptive loci that appear to have been directly modified by disease pressures given their significant associations with CAD genetic risk. These candidates were all uniquely and consistently associated with many different male and female reproductive traits suggesting selection may have also targeted these because of their direct effects on fitness. We found that CAD loci are significantly enriched for lifetime reproductive success relative to the rest of the human genome, with evidence that the relationship between CAD and lifetime reproductive success is antagonistic. This supports the presence of antagonistic-pleiotropic tradeoffs on CAD loci and provides a novel explanation for the maintenance and high prevalence of CAD in modern humans. Lastly, we found that positive selection more often targeted CAD gene regulatory variants using HapMap3 lymphoblastoid cell lines, which further highlights the unique biological significance of candidate adaptive loci underlying CAD. Our study provides a novel approach for detecting selection on polygenic traits and evidence that modern human genomes have evolved in response to CAD-induced selection pressures and other early-life traits sharing pleiotropic links with CAD.
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http://dx.doi.org/10.1371/journal.pgen.1006328DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5480811PMC
June 2017

Genetic signatures of high-altitude adaptation in Tibetans.

Proc Natl Acad Sci U S A 2017 04 3;114(16):4189-4194. Epub 2017 Apr 3.

The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, China National Engineering Research Center of Ophthalmology and Optometry, State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health, Wenzhou 325027, China

Indigenous Tibetan people have lived on the Tibetan Plateau for millennia. There is a long-standing question about the genetic basis of high-altitude adaptation in Tibetans. We conduct a genome-wide study of 7.3 million genotyped and imputed SNPs of 3,008 Tibetans and 7,287 non-Tibetan individuals of Eastern Asian ancestry. Using this large dataset, we detect signals of high-altitude adaptation at nine genomic loci, of which seven are unique. The alleles under natural selection at two of these loci [methylenetetrahydrofolate reductase () and ] are strongly associated with blood-related phenotypes, such as hemoglobin, homocysteine, and folate in Tibetans. The folate-increasing allele of rs1801133 at the locus has an increased frequency in Tibetans more than expected under a drift model, which is probably a consequence of adaptation to high UV radiation. These findings provide important insights into understanding the genomic consequences of high-altitude adaptation in Tibetans.
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http://dx.doi.org/10.1073/pnas.1617042114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5402460PMC
April 2017

The Genetic Architecture of Gene Expression in Peripheral Blood.

Am J Hum Genet 2017 02 5;100(2):228-237. Epub 2017 Jan 5.

Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD 4072, Australia; Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia. Electronic address:

We analyzed the mRNA levels for 36,778 transcript expression traits (probes) from 2,765 individuals to comprehensively investigate the genetic architecture and degree of missing heritability for gene expression in peripheral blood. We identified 11,204 cis and 3,791 trans independent expression quantitative trait loci (eQTL) by using linear mixed models to perform genome-wide association analyses. Furthermore, using information on both closely and distantly related individuals, heritability was estimated for all expression traits. Of the set of expressed probes (15,966), 10,580 (66%) had an estimated narrow-sense heritability (h) greater than zero with a mean (median) value of 0.192 (0.142). Across these probes, on average the proportion of genetic variance explained by all eQTL (h) was 31% (0.060/0.192), meaning that 69% is missing, with the sentinel SNP of the largest eQTL explaining 87% (0.052/0.060) of the variance attributed to all identified cis- and trans-eQTL. For the same set of probes, the genetic variance attributed to genome-wide common (MAF > 0.01) HapMap 3 SNPs (h) accounted for on average 48% (0.093/0.192) of h. Taken together, the evidence suggests that approximately half the genetic variance for gene expression is not tagged by common SNPs, and of the variance that is tagged by common SNPs, a large proportion can be attributed to identifiable eQTL of large effect, typically in cis. Finally, we present evidence that, compared with a meta-analysis, using individual-level data results in an increase of approximately 50% in power to detect eQTL.
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http://dx.doi.org/10.1016/j.ajhg.2016.12.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5294670PMC
February 2017

Autosomal genetic control of human gene expression does not differ across the sexes.

Genome Biol 2016 12 1;17(1):248. Epub 2016 Dec 1.

Queensland Brain Institute, The University of Queensland, Brisbane, Australia.

Background: Despite their nearly identical genomes, males and females differ in risk, incidence, prevalence, severity and age-at-onset of many diseases. Sexual dimorphism is also seen in human autosomal gene expression, and has largely been explored by examining the contribution of genotype-by-sex interactions to variation in gene expression.

Results: In this study, we use data from a mixture of pedigree and unrelated individuals with verified European ancestry to investigate the sex-specific genetic architecture of gene expression measured in whole blood across n=1048 males and n=1005 females by treating gene expression intensities in the sexes as two distinct traits and estimating the genetic correlation (r ) between them. These correlations measure the similarity of the combined additive genetic effects of all single-nucleotide polymorphisms across the autosomal chromosomes, and thus the level of common genetic control of gene expression across the sexes. Genetic correlations are estimated across the sexes for the expression levels of 12,528 autosomal gene expression probes using bivariate GREML, and tested for differences in autosomal genetic control of gene expression across the sexes. Overall, no deviation of the distribution of test statistics is observed from that expected under the null hypothesis of a common autosomal genetic architecture for gene expression across the sexes.

Conclusions: These results suggest that males and females share the same common genetic control of gene expression.
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http://dx.doi.org/10.1186/s13059-016-1111-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134098PMC
December 2016

Genome-wide analysis identifies 12 loci influencing human reproductive behavior.

Nat Genet 2016 12 31;48(12):1462-1472. Epub 2016 Oct 31.

Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands.

The genetic architecture of human reproductive behavior-age at first birth (AFB) and number of children ever born (NEB)-has a strong relationship with fitness, human development, infertility and risk of neuropsychiatric disorders. However, very few genetic loci have been identified, and the underlying mechanisms of AFB and NEB are poorly understood. We report a large genome-wide association study of both sexes including 251,151 individuals for AFB and 343,072 individuals for NEB. We identified 12 independent loci that are significantly associated with AFB and/or NEB in a SNP-based genome-wide association study and 4 additional loci associated in a gene-based effort. These loci harbor genes that are likely to have a role, either directly or by affecting non-local gene expression, in human reproduction and infertility, thereby increasing understanding of these complex traits.
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http://dx.doi.org/10.1038/ng.3698DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5695684PMC
December 2016

Fast set-based association analysis using summary data from GWAS identifies novel gene loci for human complex traits.

Sci Rep 2016 09 8;6:32894. Epub 2016 Sep 8.

Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia.

We propose a method (fastBAT) that performs a fast set-based association analysis for human complex traits using summary-level data from genome-wide association studies (GWAS) and linkage disequilibrium (LD) data from a reference sample with individual-level genotypes. We demonstrate using simulations and analyses of real datasets that fastBAT is more accurate and orders of magnitude faster than the prevailing methods. Using fastBAT, we analyze summary data from the latest meta-analyses of GWAS on 150,064-339,224 individuals for height, body mass index (BMI), and schizophrenia. We identify 6 novel gene loci for height, 2 for BMI, and 3 for schizophrenia at PfastBAT < 5 × 10(-8). The gain of power is due to multiple small independent association signals at these loci (e.g. the THRB and FOXP1 loci for schizophrenia). The method is general and can be applied to GWAS data for all complex traits and diseases in humans and to such data in other species.
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http://dx.doi.org/10.1038/srep32894DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5015118PMC
September 2016

Genome-wide association study identifies 74 loci associated with educational attainment.

Nature 2016 05 11;533(7604):539-42. Epub 2016 May 11.

Department of Neurology, General Hospital and Medical University Graz, Graz 8036, Austria.

Educational attainment is strongly influenced by social and other environmental factors, but genetic factors are estimated to account for at least 20% of the variation across individuals. Here we report the results of a genome-wide association study (GWAS) for educational attainment that extends our earlier discovery sample of 101,069 individuals to 293,723 individuals, and a replication study in an independent sample of 111,349 individuals from the UK Biobank. We identify 74 genome-wide significant loci associated with the number of years of schooling completed. Single-nucleotide polymorphisms associated with educational attainment are disproportionately found in genomic regions regulating gene expression in the fetal brain. Candidate genes are preferentially expressed in neural tissue, especially during the prenatal period, and enriched for biological pathways involved in neural development. Our findings demonstrate that, even for a behavioural phenotype that is mostly environmentally determined, a well-powered GWAS identifies replicable associated genetic variants that suggest biologically relevant pathways. Because educational attainment is measured in large numbers of individuals, it will continue to be useful as a proxy phenotype in efforts to characterize the genetic influences of related phenotypes, including cognition and neuropsychiatric diseases.
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http://dx.doi.org/10.1038/nature17671DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4883595PMC
May 2016

Genetic variants associated with subjective well-being, depressive symptoms, and neuroticism identified through genome-wide analyses.

Nat Genet 2016 06 18;48(6):624-33. Epub 2016 Apr 18.

Max Planck Institute for Human Development, Berlin, Germany.

Very few genetic variants have been associated with depression and neuroticism, likely because of limitations on sample size in previous studies. Subjective well-being, a phenotype that is genetically correlated with both of these traits, has not yet been studied with genome-wide data. We conducted genome-wide association studies of three phenotypes: subjective well-being (n = 298,420), depressive symptoms (n = 161,460), and neuroticism (n = 170,911). We identify 3 variants associated with subjective well-being, 2 variants associated with depressive symptoms, and 11 variants associated with neuroticism, including 2 inversion polymorphisms. The two loci associated with depressive symptoms replicate in an independent depression sample. Joint analyses that exploit the high genetic correlations between the phenotypes (|ρ^| ≈ 0.8) strengthen the overall credibility of the findings and allow us to identify additional variants. Across our phenotypes, loci regulating expression in central nervous system and adrenal or pancreas tissues are strongly enriched for association.
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http://dx.doi.org/10.1038/ng.3552DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4884152PMC
June 2016

Integration of summary data from GWAS and eQTL studies predicts complex trait gene targets.

Nat Genet 2016 05 28;48(5):481-7. Epub 2016 Mar 28.

Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia.

Genome-wide association studies (GWAS) have identified thousands of genetic variants associated with human complex traits. However, the genes or functional DNA elements through which these variants exert their effects on the traits are often unknown. We propose a method (called SMR) that integrates summary-level data from GWAS with data from expression quantitative trait locus (eQTL) studies to identify genes whose expression levels are associated with a complex trait because of pleiotropy. We apply the method to five human complex traits using GWAS data on up to 339,224 individuals and eQTL data on 5,311 individuals, and we prioritize 126 genes (for example, TRAF1 and ANKRD55 for rheumatoid arthritis and SNX19 and NMRAL1 for schizophrenia), of which 25 genes are new candidates; 77 genes are not the nearest annotated gene to the top associated GWAS SNP. These genes provide important leads to design future functional studies to understand the mechanism whereby DNA variation leads to complex trait variation.
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http://dx.doi.org/10.1038/ng.3538DOI Listing
May 2016

Evidence for Genetic Overlap Between Schizophrenia and Age at First Birth in Women.

JAMA Psychiatry 2016 05;73(5):497-505

CIBERSAM, University Hospital Marqués de Valdecilla, University of Cantabria-IDIVAL, Department of Psychiatry, Santander, Spain28 Centro Investigación Biomédica en Red Salud Mental, Madrid, Spain.

Importance: A recently published study of national data by McGrath et al in 2014 showed increased risk of schizophrenia (SCZ) in offspring associated with both early and delayed parental age, consistent with a U-shaped relationship. However, it remains unclear if the risk to the child is due to psychosocial factors associated with parental age or if those at higher risk for SCZ tend to have children at an earlier or later age.

Objective: To determine if there is a genetic association between SCZ and age at first birth (AFB) using genetically informative but independently ascertained data sets.

Design, Setting, And Participants: This investigation used multiple independent genome-wide association study data sets. The SCZ sample comprised 18 957 SCZ cases and 22 673 controls in a genome-wide association study from the second phase of the Psychiatric Genomics Consortium, and the AFB sample comprised 12 247 genotyped women measured for AFB from the following 4 community cohorts: Estonia (Estonian Genome Center Biobank, University of Tartu), the Netherlands (LifeLines Cohort Study), Sweden (Swedish Twin Registry), and the United Kingdom (TwinsUK). Schizophrenia genetic risk for each woman in the AFB community sample was estimated using genetic effects inferred from the SCZ genome-wide association study.

Main Outcomes And Measures: We tested if SCZ genetic risk was a significant predictor of response variables based on published polynomial functions that described the relationship between maternal age and SCZ risk in offspring in Denmark. We substituted AFB for maternal age in these functions, one of which was corrected for the age of the father, and found that the fit was superior for the model without adjustment for the father's age.

Results: We observed a U-shaped relationship between SCZ risk and AFB in the community cohorts, consistent with the previously reported relationship between SCZ risk in offspring and maternal age when not adjusted for the age of the father. We confirmed that SCZ risk profile scores significantly predicted the response variables (coefficient of determination R2 = 1.1E-03, P = 4.1E-04), reflecting the published relationship between maternal age and SCZ risk in offspring by McGrath et al in 2014.

Conclusions And Relevance: This study provides evidence for a significant overlap between genetic factors associated with risk of SCZ and genetic factors associated with AFB. It has been reported that SCZ risk associated with increased maternal age is explained by the age of the father and that de novo mutations that occur more frequently in the germline of older men are the underlying causal mechanism. This explanation may need to be revised if, as suggested herein and if replicated in future studies, there is also increased genetic risk of SCZ in older mothers.
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http://dx.doi.org/10.1001/jamapsychiatry.2016.0129DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5785705PMC
May 2016

Genome-wide genetic homogeneity between sexes and populations for human height and body mass index.

Hum Mol Genet 2015 Dec 22;24(25):7445-9. Epub 2015 Oct 22.

Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia, The University of Queensland Diamantina Institute, The Translation Research Institute, Brisbane, QLD 4102, Australia.

Sex-specific genetic effects have been proposed to be an important source of variation for human complex traits. Here we use two distinct genome-wide methods to estimate the autosomal genetic correlation (rg) between men and women for human height and body mass index (BMI), using individual-level (n = ∼44 000) and summary-level (n = ∼133 000) data from genome-wide association studies. Results are consistent and show that the between-sex genetic correlation is not significantly different from unity for both traits. In contrast, we find evidence of genetic heterogeneity between sexes for waist-hip ratio (rg = ∼0.7) and between populations for BMI (rg = ∼0.9 between Europe and the USA) but not for height. The lack of evidence for substantial genetic heterogeneity for body size is consistent with empirical findings across traits and species.
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http://dx.doi.org/10.1093/hmg/ddv443DOI Listing
December 2015

Genetic variance estimation with imputed variants finds negligible missing heritability for human height and body mass index.

Nat Genet 2015 Oct 31;47(10):1114-20. Epub 2015 Aug 31.

Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia.

We propose a method (GREML-LDMS) to estimate heritability for human complex traits in unrelated individuals using whole-genome sequencing data. We demonstrate using simulations based on whole-genome sequencing data that ∼97% and ∼68% of variation at common and rare variants, respectively, can be captured by imputation. Using the GREML-LDMS method, we estimate from 44,126 unrelated individuals that all ∼17 million imputed variants explain 56% (standard error (s.e.) = 2.3%) of variance for height and 27% (s.e. = 2.5%) of variance for body mass index (BMI), and we find evidence that height- and BMI-associated variants have been under natural selection. Considering the imperfect tagging of imputation and potential overestimation of heritability from previous family-based studies, heritability is likely to be 60-70% for height and 30-40% for BMI. Therefore, the missing heritability is small for both traits. For further discovery of genes associated with complex traits, a study design with SNP arrays followed by imputation is more cost-effective than whole-genome sequencing at current prices.
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http://dx.doi.org/10.1038/ng.3390DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4589513PMC
October 2015

Dominance genetic variation contributes little to the missing heritability for human complex traits.

Am J Hum Genet 2015 Mar 12;96(3):377-85. Epub 2015 Feb 12.

Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia; The University of Queensland Diamantina Institute, The Translation Research Institute, Brisbane, QLD 4102, Australia. Electronic address:

For human complex traits, non-additive genetic variation has been invoked to explain "missing heritability," but its discovery is often neglected in genome-wide association studies. Here we propose a method of using SNP data to partition and estimate the proportion of phenotypic variance attributed to additive and dominance genetic variation at all SNPs (hSNP(2) and δSNP(2)) in unrelated individuals based on an orthogonal model where the estimate of hSNP(2) is independent of that of δSNP(2). With this method, we analyzed 79 quantitative traits in 6,715 unrelated European Americans. The estimate of δSNP(2) averaged across all the 79 quantitative traits was 0.03, approximately a fifth of that for additive variation (average hSNP(2) = 0.15). There were a few traits that showed substantial estimates of δSNP(2), none of which were replicated in a larger sample of 11,965 individuals. We further performed genome-wide association analyses of the 79 quantitative traits and detected SNPs with genome-wide significant dominance effects only at the ABO locus for factor VIII and von Willebrand factor. All these results suggest that dominance variation at common SNPs explains only a small fraction of phenotypic variation for human complex traits and contributes little to the missing narrow-sense heritability problem.
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http://dx.doi.org/10.1016/j.ajhg.2015.01.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4375616PMC
March 2015
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