Reduced expression of TMEM106B protein in Alzheimer’s disease brains. Protein expression levels were studied by western blot in human brain tissues derived from four non-neurological causes (NC) cases, six amyotrophic lateral sclerosis (ALS) cases, four Parkinson’s disease (PD) cases, and seven Alzheimer’s disease (AD) cases. The expression levels were standardized against those of HSP60. (A) TMEM106B expression: (a) TMEM106B and (b) HSP60. (B) Progranulin (PGRN) expression: (a) PGRN and (b) HSP60. (C) Difference in TMEM106B levels between AD and non-AD cases. *P = 0.0000004 by Student’s t test. (D) Difference in PGRN levels between AD and non-AD cases. ns, non-significant (P = 0.5304 by Student’s t test). (E) Pearson’s correlation between TMEM106B and PGRN protein levels. Pearson’s correlation coefficient indicates −0.242 (P = 0.2912).