Mutations in TREM2 disrupt the energy state and function of microglia, affecting their ability to protect the brain from amyloid plaque deposition, which is associated with neurodegenerative diseases such as AD [43, 302, 304], multiple sclerosis [43, 289, 290], Parkinson's disease (PD) [305], and ALS [291]. Here, TREM2 is linked to Parkinson disease.