Erythrocytosis associated with a novel missense mutation in the HIF2A gene

The ERYTHROPOIETIN (EPO) gene is regulated by the transcription factor Hypoxia Inducible Factor- (HIF-). In this pathway, Prolyl Hydroxylase Domain protein 2 (PHD2) hydroxylates two prolyl residues in HIF-, which in turn promotes HIF- degradation by the von Hippel Lindau (VHL) protein. Evidence that HIF-2 is the important isoform for EPO regulation in humans comes from the recent observation that mutations in the HIF2A gene are associated with cases of erythrocytosis. We report here a new erythrocytosis-associated mutation, p.Asp539Glu, in the HIF2A gene. Similar to all reported cases, the affected residue is in close vicinity and C-terminal to the primary hydroxylation site in HIF-2, Pro531. This mutation, however, is notable in producing a rather subtle amino acid substitution. Nonetheless, we find that this mutation compromises binding of HIF-2 to both PHD2 and VHL, and we propose that this mutation is the cause of erythrocytosis in this individual.