APP/PS1KI bigenic mice develop early synaptic deficits and hippocampus atrophy.

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Alzheimer's disease (AD) is characterized by Abeta accumulation, but its toxic mechanism remains debated.
• The APP/PS1KI mouse model exhibits significant hippocampal neuron loss and cognitive deficits.
• Previous studies showed severe learning deficits in this model by 6 months of age.

Purpose of the Study:

• To investigate the anatomical and cellular basis of early cognitive deficits in the APP/PS1KI mouse model.
• To correlate Abeta accumulation with neuronal loss and synaptic dysfunction.
• To understand the timeline of pathological changes preceding significant neuron loss.

Main Methods:

• Utilized the APP/PS1KI mouse model for Alzheimer's disease research.
• Assessed hippocampal structure, neuron loss (CA1), and atrophy at 4 and 6 months.
• Measured long-term potentiation (LTP) and paired-pulse facilitation (PPF) in hippocampal CA1.
• Quantified pre- and post-synaptic markers and various Abeta peptide species (intraneuronal and total).

Main Results:

• At 6 months, APP/PS1KI mice showed 33% CA1 neuron loss and 18% hippocampal atrophy.
• Significant deficits in LTP and disrupted PPF were observed at 6 months, but not at 4 months.
• Reduced pre- and post-synaptic markers were noted at 4 months.
• Increased intraneuronal and total Abeta peptides (N-modified, fibrillar, oligomeric) correlated with CA1 neuron loss.

Conclusions:

• Early Abeta accumulation precedes significant neuronal loss and synaptic dysfunction in the APP/PS1KI model.
• Pathological changes, including synaptic deficits and Abeta buildup, occur by 4-6 months of age.
• These findings provide a cellular and anatomical basis for the working memory deficits observed in this AD mouse model.