The optimal delivery of oxygen to tissues is essential both to ensure
adequate energy provision and to avoid the toxic effects of higher oxy
gen concentrations. For this to occur, organisms must be able to sense
oxygen and respond to changes in oxygen tension by altering gene expr
ession. The analysis of the regulation of erythropoiesis has provided
important insights into the mechanisms of oxygen-regulated gene expres
sion. These mechanisms have a role in the regulation of many genes, in
many cell types and appear to be of relevance to many common patholog
ies in which disturbances of oxygen supply are central.