Changes in amyloid-β and Tau in the cerebrospinal fluid of transgenic mice overexpressing amyloid precursor protein

Altered concentrations of amyloid-β (Aβ) peptide and Tau protein in the cerebrospinal fluid (CSF) are thought to be predictive markers for Alzheimer's disease (AD). Transgenic mice overexpressing human amyloid precursor protein (APP) have been used to model Aβ pathology, but concomitant changes in Aβ and Tau in CSF have been less well studied. We measured Aβ and Tau in the brains and CSF of two well-characterized transgenic mouse models of AD: one expressing human APP carrying the Swedish mutation (APP23) and the other expressing mutant human APP and mutant human presenilin-1 (APPPS1). Both mouse models exhibit Aβ deposition in the brain, but with different onset and progression trajectories. We found an age-related 50 to 80% decrease in Aβ42 peptide in mouse CSF and a smaller decrease in Aβ40, both inversely correlated with the brain Aβ load. Surprisingly, the same mice showed a threefold increase in total endogenous murine Tau in CSF at the stages when Aβ pathology became prominent. The results mirror the temporal sequence and magnitude of Aβ and Tau changes in the CSF of patients with sporadic and dominantly inherited AD. This observation indicates that APP transgenic mice may be useful as a translational tool for predicting changes in Aβ and Tau markers in the CSF of AD patients. These findings also suggest that APP transgenic mouse models may be useful in the search for new disease markers for AD.