KDM4D and Huntington disease: Among the lysine demethylases, Kdm4d (H3K9-specific) and Kdm6b (H3K27) were upregulated, whereas Kdm1b (H3K4), Kdm5c (H3K4), and Kdm8 (H3K36) were downregulated in the aged HD mice (Fig. 5C).