HIF works to upregulate transcription of hundreds of genes, the sets of which are context-dependent.1 HIF target genes include those encoding for proteins of biomedical interest, such as vascular endothelial growth factor (VEGF), nitric oxide synthase (NOS), and erythropoietin (EPO).1,2 The latter is of therapeutic interest because recombinant EPO is used for anaemia treatment. The gene discussed is EPO; the disease is anemia (phenotype).