MACROH2A1 and Huntington disease: Instead,model systems containing macroH2A1, a histone variant of the coreprotein H2A identified as a biomarker of HD14 and Parkinson’s disease,15 areavailable for reference.16 MacroH2A1 appearsto regulate the hippocampus function and memory,17,18 and its levels increase with disease progression in HD patients.14 This link between a histone variant and HD progressionmay be a valuable clue for therapeutic development.14