HYPOXIA

Erythropoietin (EPO) is a vital regulator of erythropoiesis that is expressed in very specialized cells, i.e., the fetal liver during development and, after birth, by the kidney that become the major site of production. We performed a genetic screening of 450 patients having Hereditary Erythrocytosis (HE), a rare disease characterized by an overproduction of red blood cells. Sequencing of restricted regions of the EPO gene allowed the identification of novel germline mutations in non-coding sequences. We identified a new cause of HE by discovering that mutations are associated with a production of a liver-like EPO in patients. Our preliminary results demonstrated an overexpression of EPO mRNA in patients' derived induced pluripotent stem cells (hiPSC) differentiated into hepatocyte-like cells (HLC). We hypothesize that these naturally occurring mutations target new fundamental genetic regulatory elements in the EPO gene that control the expression of hepatic EPO (hep-EPO). Our main final goal is to identify the molecular mechanisms swaying hep-EPO expression. The project's objectives are to: 1) Identify new patients expressing hep-EPO by screening patients with HE or with high hematocrit associated with liver diseases, 2) Discover new mutations in EPO regulatory regions by sequencing the entire gene in HE patients who express hep-EPO, 3) Investigate mechanisms controlling EPO expression using high-throughput genomics methods on hiPSC differentiated into hepatocytes (ATAC-seq, CUT&RUN, 4C-seq), 4) Modulate EPO expression using gene editing and drugs targeting the putative regulators for potential therapeutic applications. Being able to stimulate the production of EPO by the liver (i.e., in anemic patients with kidney failure) may have a major impact. Hep-EPO could also serve as a biomarker for assessing the severity of liver diseases. Given the broad spectrum of EPO’s biological activities (cardiac, renal, vascular and brain protection), our project could have major positive implications for health research and therapeutics.