@article {12, title = {Multiple phenotype association tests using summary statistics in genome-wide association studies.}, journal = {Biometrics}, volume = {74}, year = {2018}, month = {2018 Mar}, pages = {165-175}, abstract = {

We study in this article jointly testing the associations of a genetic variant with correlated multiple phenotypes using the summary statistics of individual phenotype analysis from Genome-Wide Association Studies (GWASs). We estimated the between-phenotype correlation matrix using the summary statistics of individual phenotype GWAS analyses, and developed genetic association tests for multiple phenotypes by accounting for between-phenotype correlation without the need to access individual-level data. Since genetic variants often affect multiple phenotypes differently across the genome and the between-phenotype correlation can be arbitrary, we proposed robust and powerful multiple phenotype testing procedures by jointly testing a common mean and a variance component in linear mixed models for summary statistics. We computed the p-values of the proposed tests analytically. This computational advantage makes our methods practically appealing in large-scale GWASs. We performed simulation studies to show that the proposed tests maintained correct type I error rates, and to compare their powers in various settings with the existing methods. We applied the proposed tests to a GWAS Global Lipids Genetics Consortium summary statistics data set and identified additional genetic variants that were missed by the original single-trait analysis.

}, keywords = {Analysis of Variance, Computer Simulation, Genome-Wide Association Study, Humans, Linear Models, Lipids, Models, Genetic, Phenotype}, issn = {1541-0420}, doi = {10.1111/biom.12735}, author = {Liu, Zhonghua and Lin, Xihong} } @article {45, title = {Quantifying the Polygenic Contribution to Cutaneous Squamous Cell Carcinoma Risk.}, journal = {J Invest Dermatol}, volume = {138}, year = {2018}, month = {2018 Jul}, pages = {1507-1510}, abstract = {

Genetic factors play an important role in cutaneous squamous cell carcinoma risk. Genome-wide association studies have identified 21 single nucleotide polymorphisms associated with cutaneous squamous cell carcinoma risk. Yet no studies have attempted to quantify the contribution of heritability to cutaneous squamous cell carcinoma risk by calculating the population attributable risk using a combination of all discovered genetic variants. Using an additive multi-locus linear logistic model, we determined the cumulative association of these 21 genetic regions to cutaneous squamous cell carcinoma population attributable risk. We computed a multi-locus population attributable risk of 62\%, suggesting that if the effects of all the risk alleles were removed from a population, the cutaneous squamous cell carcinoma risk would drop by 62\%. Using stratified analysis, we also examined the impact of sex on polygenic risk score, and found that men have an increased relative risk throughout the spectrum of the polygenic risk score. Quantifying the impact of genetic predisposition on the proportion of cancer cases can guide future research decisions and public health policy planning.

}, keywords = {Carcinoma, Squamous Cell, Female, Genetic Loci, Genetic Predisposition to Disease, Genome-Wide Association Study, Humans, Linear Models, Logistic Models, Male, Models, Biological, Polymorphism, Single Nucleotide, Risk Assessment, Risk Factors, Sex Factors, Skin Neoplasms}, issn = {1523-1747}, doi = {10.1016/j.jid.2018.01.031}, author = {Sordillo, Joanne E and Kraft, Peter and Wu, Ann Chen and Asgari, Maryam M} } @article {20, title = {Testing for gene-environment interaction under exposure misspecification.}, journal = {Biometrics}, volume = {74}, year = {2018}, month = {2018 Jun}, pages = {653-662}, abstract = {

Complex interplay between genetic and environmental factors characterizes the etiology of many diseases. Modeling gene-environment (GxE) interactions is often challenged by the unknown functional form of the environment term in the true data-generating mechanism. We study the impact of misspecification of the environmental exposure effect on inference for the GxE interaction term in linear and logistic regression models. We first examine the asymptotic bias of the GxE interaction regression coefficient, allowing for confounders as well as arbitrary misspecification of the exposure and confounder effects. For linear regression, we show that under gene-environment independence and some confounder-dependent conditions, when the environment effect is misspecified, the regression coefficient of the GxE interaction can be unbiased. However, inference on the GxE interaction is still often incorrect. In logistic regression, we show that the regression coefficient is generally biased if the genetic factor is associated with the outcome directly or indirectly. Further, we show that the standard robust sandwich variance estimator for the GxE interaction does not perform well in practical GxE studies, and we provide an alternative testing procedure that has better finite sample properties.

}, keywords = {Bias, Confounding Factors, Epidemiologic, Environmental Exposure, Gene-Environment Interaction, Humans, Linear Models, Models, Genetic, Scientific Experimental Error}, issn = {1541-0420}, doi = {10.1111/biom.12813}, author = {Sun, Ryan and Carroll, Raymond J and Christiani, David C and Lin, Xihong} }