A whole-genome sequencing study of AD in a Chinese population showed that GCH1 was a genetic risk locus for AD, and the association between GCH1 rs72713460 and changes in plasma matrix metalloproteinase-2 (MMP-2) levels suggested that, in addition to regulating neurotransmitter levels, GCH1 may play an important role in the immune system or in Aβ-related metabolic pathways [138]. Here, GCH1 is linked to Alzheimer disease.