This gene encodes a transcription factor involved in the induction of genes regulated by oxygen, which is induced as oxygen levels fall. The encoded protein contains a basic-helix-loop-helix domain protein dimerization domain as well as a domain found in proteins in signal transduction pathways which respond to oxygen levels. Mutations in this gene are associated with erythrocytosis familial type 4.,EPAS1,ECYT4,HIF2A,HLF,MOP2,PASD2,bHLHe73,Epigenetics & Nuclear Signaling,Transcription Factors,Cancer,Invasion and Metastasis,Endocrine & Metabolism,Nucleotide metabolism,Molecular processes,Cardiovascular,Angiogenesis,Hypoxia,HIF,EPAS1