Unlike FKBP52, FKBP51 levels not only progressively increase with age but further increases are seen in AD patients.42, 94, 121, 125 Stress, which is also associated with AD, is also known to increase FKBP51 levels.142, 143 FKBP51 was shown to be able to preserve toxic tau oligomers in vivo25 and decreased tau levels are found in the brain of mice lacking FKBP51.110, 121 Elevated FKBP51 levels, therefore, seem to be a prime factor that may be able to elicit a tauopathy. The gene discussed is FKBP4; the disease is Alzheimer disease.