SYP and Huntington disease: However, in some studies, silencing KDM5C, the most abundant form of KDM5 in brain, is associated with beneficial effects in neurodegenerative diseases such as Huntington’s disease, which increases the level of neurotrophic factor (BDNF) and synaptic proteins (SYP) through the increased level of H3K4me3 in Huntington’s disease22.