Inactivation of Vhlh in hepatocytes with PEPCK-Cre or Albumin-Cre also led to erythrocytosis—overproduction of erythrocytes—due to increased expression of Epo [20, 22], although hemangioma-associated extramedullary erythropoiesis—as observed in hemangioblastoma—was not observed. This evidence concerns the gene EPO and hemangioma.