Genetic basis of oxygen sensing in the carotid body: HIF2α and an isoform switch in cytochrome c oxidase subunit 4.

The mechanistic basis of the marked oxygen sensitivity of glomus cells in the carotid body has long puzzled physiologists. In this issue of Science Signaling, Moreno-Domínguez et al. show the critical importance of high levels of hypoxia-inducible factor, HIF2α/EPAS1, and the nuclear-encoded mitochondrial cytochrome c oxidase subunit, COX4I2, in glomus cell sensitivity to hypoxia.