Predicted loss and gain of function mutations in ACO1 are associated with erythropoiesis

Gudjon Oskarsson et al. report a genome-wide association study of hemoglobin concentration in more than 680,000 individuals from Iceland and the UK. They identify six novel rare coding variants at the ACO1 locus that associate with either increased or decreased hemoglobin concentration, two of which have large and opposite effects. Hemoglobin is the essential oxygen-carrying molecule in humans and is regulated by cellular iron and oxygen sensing mechanisms. To search for novel variants associated with hemoglobin concentration, we performed genome-wide association studies of hemoglobin concentration using a combined set of 684,122 individuals from Iceland and the UK. Notably, we found seven novel variants, six rare coding and one common, at the ACO1 locus associating with either decreased or increased hemoglobin concentration. Of these variants, the missense Cys506Ser and the stop-gained Lys334Ter mutations are specific to eight and ten generation pedigrees, respectively, and have the two largest effects in the study (Effect(Cys506Ser) = -1.61 SD, CI95 = [-1.98, -1.35]; Effect(Lys334Ter) = 0.63 SD, CI95 = [0.36, 0.91]). We also find Cys506Ser to associate with increased risk of persistent anemia (OR = 17.1, P = 2 x 10(-14)). The strong bidirectional effects seen in this study implicate ACO1, a known iron sensing molecule, as a major homeostatic regulator of hemoglobin concentration.