PTGER4 and multiple sclerosis: Numerous GWAS studies have suggested that polymorphisms in the 5p13.1 regulatory regions near PTGER4 (e.g. rs9292777, rs7725052, rs77145747, rs6896969 and rs4613763) were significantly associated with PTGER4 gene expression and the susceptibility of MS (De Jager et al., 2009; International Multiple Sclerosis Genetics Consortium et al., 2011; Matesanz et al., 2012).