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3643 In silico and Functional Studies for Classification of EPAS1/HIF2A Genetic Variants Identified in Patients with Erythrocytosis

Program: Oral and Poster Abstracts
Session: 101. Red Cells and Erythropoiesis, Excluding Iron: Poster III
Hematology Disease Topics & Pathways:
Biological Processes, pathogenesis
Monday, December 12, 2022, 6:00 PM-8:00 PM

Valéna Karaghiannis1,2*, Darko Maric3,4*, Céline Garrec5*, Nada Maaziz6*, Alexandre Buffet7*, Vincent Antunes8*, Amandine le Roy9*, Fabrice Airaud10*, Bernard Aral11*, Loic Schmitt12*, Sébastien Corbineau9*, Lamisse Mansour-Hendili13*, Valentine Lesieur9*, Antoine Rimbert14*, Fabien Laporte15*, Marine Delamare16*, Stephane Bezieau5*, Bruno Cassinat, PharmD, PhD17, Frédéric Galactéros, MD, PhD18*, Anne-Paule Gimenez-Roqueplo19*, Nelly Burnichon20*, Holger Cario, MD, PhD21, Richard van Wijk22*, Celeste Bento, MSc23*, Anaise Blouet, MD24*, Juliette Bouteloup, MD25*, Françoise Boyer perrard26*, Aisha Aiko Bruce, MD27, Emilie Cayssials, MD28*, Nicole Casadevall, MD29, Brieuc Cherel30*, Marielaure Couec, MD15*, Louis Drevon, MD31*, Cecile Dumesnil, MD32*, Thierry Lamy De La Chapelle, MD, PhD33*, Marion Gambart, MD34*, Loic Garcon, MD PhD35*, Brigitte Granel36*, Pierre Hirsch, MD-PhD37*, Agnès Lahary38*, Amira Mejri39*, Sandrine Meunier, MD40*, Franck E. Nicolini, MD, PhD41, Emmanuel Raffoux42*, Dana Ranta, MD43*, Nicolas Schleinitz44*, Jean Baptiste Valentin, MD45*, Mathieu Wemeau, MD46*, Francois Girodon, MD, PhD 47, David Hoogewijs48*, Betty Gardie, PhD49* and Olivier Hermine, MD, PhD50,51,52

1Ecole Pratique des Hautes Etudes, EPHE, Université Paris Sciences et Lettres, France, Paris, France
2Université de Nantes, CNRS, INSERM, l’institut du thorax, F-44000 Nantes, Nantes, France
3Section of Medicine, Department of Endocrinology, Metabolism and Cardiovascular System, University of Fribourg, CH-1700 Fribourg, Switzerland, Fribourg, Switzerland
4National Center of Competence in Research “Kidney.CH”, Switzerland, Fribourg, Switzerland
5Centre Hospitalier Universitaire De Nantes, Nantes, FRA
6Service d’Hématologie Biologique, Pôle Biologie, CHU de Dijon, Dijon, France, Dijon, France
7INSERM, UMR970, Paris-Centre De Recherche Cardiovasculaire, Paris, FRA
8ch, zurich, France
92 Université de Nantes, CNRS, INSERM, l’institut du thorax, F-44000 Nantes, France, nantes, France
11Chu Dijon Bourgogne, Dijon, France
12Ch rennes, rennes, France
13APHP, Paris, France
14Chu NAntes, nantes, France
15Chu Nantes, Nantes, France
16Chu nantes, Nantes, France
17INSERM UMR 1131, Institut de Recherche Saint-Louis, Paris, France
18Unité des Maladies Génétiques du Globule Rouge, CHU Henri Mondor, Créteil, France
19Assistance Publique Hôpitaux De Paris, Paris, FRA
20INSERM U970, Paris, FRA
21Department of Pediatrics and Adolescent Medicine, University Medical Center Ulm, Ulm, Germany
22Central Diagnostic Laboratory - Research, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
23Hospital Pediatrico De Coimbra, Coimbra, Coimbra, PRT
24Service oncologie-hématologie, Centre Hospitalier, Cholet, Cholet, France
25Hematology Department, Chalon Center Hospital, Chalon-sur-Saone, France
26Ch Angers, Angers, France
27University of Alberta, Edmonton, AB, Canada
28Poitiers University Hospital, Poitiers, France
29AP-HP, Laboratoire d’hématologie biologique, Hôpital Saint-Antoine, Paris, France, Paris, France
30Chu Rennes, rennes, France
31ApHP, paris, France
32Pediatric Oncology and Hematology Unit, Charles Nicolle Rouen University Hospital, Rouen, France
33Clinical hematology, University Hospital of Rennes, Rennes, France
34CHU de Toulouse, Toulouse, France
35Laboratoire d'Hématologie, CHU Amiens, Amiens, France
36Ch marseille, marseille, France
37Université Pierre et Marie Curie, Paris, France
38ch rouens, rouens, France
39Service hématologie clinique -GHRMSA Ch Mulhouse, Mulhouse, France
40Chu Lyon, Lyon Cedex, FRA
41Centre Hospitalier Lyon Sud, LYON Cedex 03, France
42Department of Hematology, Université de Paris, Saint-Louis Hospital, Paris, France
43Centre Hospitalier Universitaire, Nancy, France
44Service De Medecine Interne, CHU Conception, AP-HM, Marseille, FRA
45Chu Tours, Chambray Les Tours, FRA
46CHRU Lille, Paris, FRA
47Laboratorie D'Hematologie CHU Dijon, Dijon, France
48University of ZüRich, ZüRich, CHE
49Université de Nantes, CNRS, INSERM, l’institut du thorax, F-44000 Nantes, France, Nantes, FRA
50INSERM U1163 and CNRS 8254, Imagine Institute, Université Sorbonne Paris Cité, Paris, France
51Laboratory of Excellence GR-Ex, Paris, France
52Necker–Enfants Malades Hospital and Imagine Institute, CEREMAST, Paris, France

Gain-of-function mutations in the EPAS1/HIF2A gene have been identified in patients with hereditary erythrocytosis that can be associated with the development of paraganglioma, pheochromocytoma and somatostatinoma. In the present study, we describe a unique European collection of 40 patients and 23 related diagnosed with an erythrocytosis associated with a germline genetic variant in EPAS1. In addition we identified 2 infants with severe erythrocytosis associated with a mosaic mutation present in less than 2% of the blood, one of whom later developed a paraganglioma. The aim of this study was to determine the causal role of these genetic variants, notably in order to identify potential candidates eligible to the new HIF-2a inhibitor treatment. Pathogenicity was predicted with in silico tools and the impact of 13 HIF-2a variants has been studied by using canonical and real time reporter luciferase assays. These functional assays used a newly edited vector containing an expanded region of the erythropoietin (EPO) promoter combined with distal regulatory elements which substantially enhanced the HIF-2a-dependent induction. Altogether, our studies allowed the classification of 11 mutations as pathogenic in 15 patients and 23 related. We described four new mutations (D525G, L526F, G527K, A530S) close to the key proline P531, which broadens the spectrum of mutations involved in erythrocytosis. Notably, we identified some patients with only erythrocytosis associated with germline mutations (A530S, Y532C) previously identified at somatic state in tumors, raising the complexity of the genotype/phenotype correlation. This study allows accurate clinical follow-up of patients and opens the possibility of benefiting from HIF-2a inhibitor treatment, so far the only targeted treatment in hypoxia-related erythrocytosis disease.

Disclosures: Galactéros: Addmedica: Membership on an entity's Board of Directors or advisory committees. Wijk: Axcella Therapeutics: Research Funding; Global Blood Therapeutics: Consultancy, Research Funding; Agios Pharmaceuticals, Inc.: Consultancy, Research Funding; RR Mechatronics: Research Funding. Boyer perrard: Novartis: Honoraria. Bruce: BMS: Consultancy. Cayssials: Novartis: Honoraria; Incyte Biosciences: Honoraria; Pfizer: Honoraria; BMS: Honoraria. Nicolini: KARTOS: Consultancy; Sun Pharma Ltd: Consultancy; Incyte biosciences: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis Services, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Ranta: Janssen: Membership on an entity's Board of Directors or advisory committees. Hermine: AB Science: Current equity holder in private company, Honoraria, Research Funding; Inatherys: Research Funding; BMS: Honoraria, Research Funding; Novartis: Research Funding; Kite/Gilead: Honoraria.

*signifies non-member of ASH