TREM2 and amyotrophic lateral sclerosis: For example, several genes causing ALS and/or frontotemporal dementia (C9orf72, VCP, SQSTM1, OPTN, UBQLN2, GRN, CHMP2B) affect the autophagic machinery [16]; and some Alzheimer’s Disease genes (APOE, TREM2, CD33, ABCA7) are preferentially or exclusively expressed in microglia [17].