PDC and neoplasm: In high oxygen conditions, Prolyl 4-hydroxylases (PHDs: PHD1, PHD2, PHD3) hydroxylate key proline residues of HIF-α,4 which subsequently targets HIF-α for degradation by ubiquitin–ligase complexes.5 Each PHD differs in the relative abundance of their mRNA, but all the PHD mRNA show a ubiquitous pattern of expression that includes the brain.6, 7 The role of PHDs has been intensively studied in inflammation, tumor growth, metabolism, and hematopoetic stem cell residing in a hypoxic niche;8, 9 however, their role in the nervous system is largely unknown.