MAX and neoplasm: Mutations in MAX are associated with abnormalities of blood pressure regulation, including development of phaeochomocytoma, a catecholamine secreting tumour.47 In addition, the E2F family of transcription factors is implicated in vascular function and blood pressure regulation.48 E2F transcription factors regulate synthesis of DHFR (Dihydrofolate Reductase), the rate-limiting salvage enzyme for tetrahydrobiopterin, an essential cofactor for endothelial nitric oxide synthase.