Identification of Hepatic-like EPO as a Cause of Polycythemia
Laurent Martin, Darko Maric, Salam Idriss, Marine Delamare, Amandine Le Roy, Nada Maaziz, Amandine Caillaud, Karim Si‐Tayeb, Florence Robriquet, Marion Lenglet, Lucie Erceau, Christine Bellanné‐Chantelot, Isabelle Plo, Bernard Aral, Céline Garrec, Fabrice Airaud, Clara Gianfermi, Vincent Antunes, Anna Keppner, Sarah Mathilda Vincent, Alexis Desfontaine, Nina Modé, Fabien Laporte, Anne Gaignerie, Caroline Chariau, Isabelle Leray, Coline Rogue, Laurent David, Richard Redon, Stéphane Bezieau, Lamisse Mansour‐Hendili, F. Galactéros, Thibault Maillet, Marlène Pasquet, Pierre Cougoul, Anne-Marie Nloga, Claude Gardin, Corinne Guitton, Viviane Dubruille, Vannina Giacobbi-Milet, Thierry Leblanc, Zühre Kaya, Denis S. Semama, Chloé James, Serge Carillo, Marlène Ochmann, Anders Waage, Erwan Mortier, Mike Maillasson, Agnès Quéméner, Holger Cario, Radek C. Skoda, Yaël Zermati, David Hoogewijs, Alexandre Marchand, François Girodon, Betty Gardie
Abstract
BACKGROUND: Secondary erythrocytosis often results from conditions that cause tissue hypoxia or an improper increase in erythropoietin (EPO) production. EPO, the major regulator of erythropoiesis, has a complex and tightly regulated expression during development, with a liver-to-kidney switch shortly after birth. METHODS: promoter-driven luciferase reporter genes. Induced pluripotent stem cells (iPSCs) were generated from patient cells and differentiated into hepatocyte-like EPO-producing cells. Samples of circulating EPO from patients with hereditary erythrocytosis and from healthy newborns were analyzed by means of isoelectric focusing, and EPO activity was assessed. RESULTS: . Experiments with reporter assays and iPSC-derived hepatocyte-like cells showed that the variants targeted previously uncharacterized regulatory elements of the gene, which, when the variants were present, showed high responsiveness to hypoxia. EPO samples from all the patients showed a modified isoelectric-focusing profile, identical to hepatic EPO that is expressed in premature neonates and in patients with acquired erythrocytosis associated with liver diseases. EPO that was purified from patient plasma and umbilical-cord blood samples showed enhanced EPO receptor signaling activity in vitro, which suggests a potential gain of function linked to the liver-type glycosylation of EPO. CONCLUSIONS: that lead to the production of hepatic-like EPO with an atypical glycosylation pattern and increased activity. (Funded by Région des Pays de la Loire and others; ClinicalTrials.gov number, NCT03957863.).