Mutant and native human beta-amyloid precursor proteins in transgenic mouse brain

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Alzheimer's disease (AD) is linked to mutations in human beta-amyloid precursor protein (beta APP).
• Understanding beta APP processing and its role in neuropathology is crucial for AD research.

Purpose of the Study:

• To create transgenic mouse models expressing human beta APP, including disease-associated mutations.
• To investigate the expression patterns and processing of human beta APP in the mouse brain.
• To assess amyloid deposition in mice carrying mutant human beta APP.

Main Methods:

• Utilized synapsin I promoter-based chimeric transgenes to target human beta APP expression in neurons.
• Introduced both native and mutated human beta APP (familial AD and Dutch type) into mouse models.
• Quantified human beta APP RNA and protein levels, and analyzed beta-secretase cleavage site processing.
• Examined mouse brains for evidence of amyloid deposition using immunohistochemistry.

Main Results:

• Human beta APP RNA reached up to 60% of endogenous beta APP RNA levels in mouse brains.
• High expression of human beta APP was observed in the hippocampus (CA subfields) and piriform cortex.
• Correct beta-secretase cleavage of human beta APP was confirmed in transgenic mouse brains.
• A 40% increase in beta APP immunoreactivity in mutant lines did not lead to amyloid deposition by 14 months of age.

Conclusions:

• Transgenic mice successfully expressed human beta APP, with correct processing observed.
• The current models did not develop amyloid pathology, suggesting higher expression levels, older age, or additional factors are needed to induce neuropathology.