endothelial pas domain-containing protein 1 (epas1, also known as hypoxia-inducible factor-2alpha (hif-2alpha)) is a protein that is encoded by the "epas1" gene in humans. it is a type of hypoxia-inducible factor, a group of transcription factors involved in the physiological response to oxygen concentration. the gene is active under hypoxic conditions. it is also important in the development of the heart, and for maintaining the catecholamine balance required for protection of the heart. mutation often leads to neuroendocrine tumors.