IDH1 and diffuse midline glioma: In pediatric diffuse gliomas and more specifically in diffuse midline gliomas, the H3K27M mutation (which involves the replacement of lysine by methionine at site 27 of histones H3-H3F3A and HIST1H3B/C) is responsible for the upregulation of TCA cycle metabolism in parallel with increased expression of hallmark metabolic enzymes, such as HK2, GLUD1, and IDH1 [109].