S1629 erfe-a260s accounts for hepatic iron metabolism impairment by acting on the bmp-smad pathway

Background: Iron overload is a major clinical challenge in the management of hereditary ineffective erythropoiesis ‐related anemia (iron‐loading anemia). To coordinate iron metabolism with hemoglobin (Hb) synthesis, erythropoietin (EPO)‐stimulated erythroid precursors release erythroferrone (ERFE), a soluble protein that suppresses the expression of hepcidin. Hepcidin is a hormone that controls iron entry into the circulation by blocking the iron exporter ferroportin. Congenital dyserythropoietic anemia type II (CDAII) is a bone marrow failure anemia characterized by mono‐lineage cytopenia and morphological abnormalities of erythroid precursor cells. The marked clinical variability observed in CDAII patients is related to its major complication, the iron overload associated with reduced expression of hepatic hormone hepcidin. We recently analyzed ERFE expression in both CDAII patients and in vitro model, demonstrating that in CDAII patients ERFE is overexpressed and related to abnormal erythropoiesis. Aims: To study possible modifier genes affecting the iron overload phenotype in CDAII. Methods: t‐NGS custom panel; genotyping; cells culture and transfection assays; qRT‐PCR; immunoblotting. Results: We herein identified a recurrent low‐frequency variant, A260S, in ERFE gene in 12.5% of CDAII patients showing severe phenotype by our 81‐genes target custom panel for modifier genes. We demonstrated that ERFE‐A260S variant leads to an increased expression of ERFE. We further characterized the effect of ERFE‐A260S in an in vitro human hepatic model, HuH7 cells, showing a marked impairment of iron regulation pathways by inhibition of phosphorylation of SMAD1/5/8 and consequent downregulation of the expression of BMP/SMADs pathway target genes: HAMP, ID1, ATHO8 and SMAD6 . Summary/Conclusion: We herein described for the first time an ERFE polymorphism as modifier variant with a mild effect on disease expression under a multifactorial‐like model in a condition of iron‐loading anemia due to ineffective erythropoiesis. This is a novel paradigm that paves the ways to new investigations for evaluating the role of this ERFE variant as a modifier in many other related pathological conditions, as b‐thalassemia intermedia. Moreover, the discovery of the genetic basis of CDAII and its major complication, iron overload, will lead us to expand our understanding of the biology of ineffective erythropoiesis and to provide initiative for further investigation of new therapeutics. Indeed, ERFE is currently a candidate target for therapeutic inhibition, in iron loading anemia.