Predicting and analyzing early wake-up associated gene expressions by integrating GWAS and eQTL studies.

Circadian rhythms are endogenous 24-hour rhythmic oscillations affecting human behaviors, such as sleep, blood pressure and other biological processes, the disturbance of which lead to circadian rhythm sleep disorders (CRSDs). In this study, based on the data from genome-wide association studies (GWASs) and expression quantitative trait loci (eQTLs), we tried to identify novel gene expression patterns in brain tissues that were associated with early wake-up. First, the maximum-relevance-minimum-redundancy (mRMR) method was adopted to analyze the involved gene expression patterns, yielding a feature list. Second, the incremental feature selection (IFS) method and the Dagging algorithm were applied to extract important gene expression patterns, which yield the best performance for Dagging. As a result, 4374 gene expression patterns were obtained, and they were further used to build an optimal classifier with a good performance of a Matthews's correlation coefficient of 0.933. Furthermore, the most important 49 gene expression patterns were extensively analyzed. Four genes were found to be related to circadian rhythm, as reported in previous studies. As a first attempt in identifying the target genes whose expression levels are associated with sleep-wake rhythms through integrating GWAS and eQTL results, this study can motivate more investigations in this regard. This article is part of a Special Issue entitled: Accelerating Precision Medicine through Genetic and Genomic Big Data Analysis edited by Yudong Cai & Tao Huang.