Apolipoprotein E4 produced in GABAergic interneurons causes learning and memory deficits in mice

Area of Science:

• Neuroscience
• Genetics
• Cell Biology

Background:

• Apolipoprotein E4 (apoE4) is a major genetic risk factor for Alzheimer's disease (AD).
• ApoE4 is linked to age-dependent cognitive decline, including learning and memory impairments.
• The specific cell types responsible for apoE4's detrimental effects in the brain remain unclear.

Purpose of the Study:

• To investigate the cellular sources of apolipoprotein E4 (apoE4) that contribute to cognitive deficits.
• To determine if deleting apoE4 in specific brain cell types can mitigate apoE4-induced neurodegeneration and memory impairment.

Main Methods:

• Generation of human apoE knock-in mouse models with conditional deletion of the human APOE gene.
• Targeted deletion of apoE4 in astrocytes, neurons, or GABAergic interneurons.
• Assessment of learning and memory deficits and GABAergic interneuron loss in aged mice.

Main Results:

• Deletion of apoE4 in astrocytes did not prevent apoE4-induced GABAergic interneuron loss or memory deficits.
• Conditional deletion of apoE4 in neurons significantly protected aged mice from both interneuron loss and cognitive impairments.
• Deleting apoE4 specifically in GABAergic interneurons also provided substantial protection.

Conclusions:

• Endogenously produced apoE4 exerts detrimental effects on GABAergic interneurons, leading to learning and memory deficits.
• Neuronal apoE4 is a key driver of these deficits, suggesting neurons as a critical target.
• Targeting apoE4 in GABAergic interneurons offers a novel therapeutic strategy for Alzheimer's disease associated with apoE4.