Genome-wide association study (GWAS) has become a popular approach by utilizing genome-wide genotyping array to map susceptibility effects through examining associations between SNP genotype frequency and traits (1,2). The standard GWAS analysis focuses on single SNP/gene and identifies only a number of the most significant SNPs that account for only a small proportion of the genetic variants and offers limited understanding of complex diseases (3). It also ignores the combined SNP/gene effects representing interactions of multiple genetic factors of complex disease, which lead to difficulties in exploring biological function and mechanism from a systems point of view.
