Cellular source-specific effects of apolipoprotein (apo) E4 on dendrite arborization and dendritic spine development

Area of Science:

• Neuroscience
• Genetics
• Cell Biology

Background:

• Apolipoprotein E4 (apoE4) is a major genetic risk factor for Alzheimer's disease (AD).
• While astrocytes are the primary producers of apoE in the brain, neurons can also produce apoE4 under stress.
• The cellular source of apoE4 and its impact on neuronal structure remain unclear.

Purpose of the Study:

• To investigate the influence of apoE4's cellular source on dendritic arborization and spine development.
• To compare the effects of neuron-specific apoE4 expression versus astrocyte-specific apoE4 expression on neuronal morphology.

Main Methods:

• Utilized neuron-specific enolase (NSE)-apoE4 and glial fibrillary acidic protein (GFAP)-apoE4 transgenic mouse models.
• Compared apoE4-knockin (KI) mice with their apoE3 counterparts at different ages (7-8 and 19-21 months).
• Assessed dendritic arborization, spine density, and spine morphology in the hippocampus and entorhinal cortex.

Main Results:

• Neuron-specific apoE4 (NSE-apoE4) mice exhibited significant impairments in dendritic arborization and spine loss, particularly affecting thin and mushroom spines.
• ApoE4-knockin (KI) mice showed less severe deficits compared to NSE-apoE4 mice.
• Astrocyte-specific apoE4 (GFAP-apoE4) mice showed no significant impairments in dendritic structure or spine density compared to controls.

Conclusions:

• The detrimental effects of apoE4 on dendritic arborization and spine development are critically dependent on its cellular source.
• Neuronal apoE4 has more severe consequences for neuronal structure than astrocytic apoE4.
• These findings underscore the importance of neuronal apoE4 in AD-related neurodegeneration.