A truncating mutation in EPOR leads to hypo-responsiveness to erythropoietin with normal haemoglobin

The cytokine erythropoietin (EPO), signalling through the EPO receptor (EPO-R), is essential for the formation of red blood cells. We performed a genome-wide association study (GWAS) testing 32.5 million sequence variants for association with serum EPO levels in a set of 4187 individuals. We detect an association between a rare and well imputed stop-gained variant rs370865377[A] (p.Gln82Ter) in EPOR , carried by 1 in 550 Icelanders, and increased serum EPO levels (MAF = 0.09%, Effect = 1.47 SD, P = 3.3 × 10 −7 ). We validated these findings by measuring serum EPO levels in 34 additional pairs of carriers and matched controls and found carriers to have 3.23-fold higher EPO levels than controls ( P = 1.7 × 10 −6 ; P combined = 1.6 × 10 −11 ). In contrast to previously reported EPOR mutations, p.Gln82Ter does not associate with haemoglobin levels (Effect = −0.045 SD, P = 0.32, N = 273,160), probably due to a compensatory EPO upregulation in response to EPO-R hypo-responsiveness. Gudjon Oskarsson et al. report the association of a rare variant in the erythropoietin (EPO) receptor gene, EPOR , with serum EPO levels in the Icelandic population. The variant leads to a truncation of EPO-R without an effect on hemoglobin levels, indicating a possible feedback mechanism in the generation of red blood cells.