Basic Science and Pathogenesis.

Area of Science:

• Neuroscience
• Genetics
• Biochemistry

Background:

• Rare loss-of-function variants in the lipid transporter ABCA7 are significant genetic risk factors for Alzheimer's disease (AD).
• Understanding the mechanisms linking ABCA7 variants to AD risk is crucial for therapeutic development.

Purpose of the Study:

• To investigate the molecular mechanisms by which ABCA7 loss-of-function variants contribute to Alzheimer's disease.
• To explore the relevance of these findings to a broader at-risk population.

Main Methods:

• Single-nuclear RNA sequencing on brain samples from ABCA7 variant carriers and controls.
• Analysis of post-mortem data from carriers of a common AD-risk ABCA7 variant.
• Molecular dynamic simulations and functional studies using induced pluripotent stem cell (iPSC)-derived neurons.

Main Results:

• ABCA7 is highly expressed in excitatory neurons, where its variants disrupt lipid metabolism, mitochondrial function, and synaptic signaling.
• Transcriptional changes in variant carriers overlap with those linked to a common AD-risk ABCA7 variant.
• ABCA7 loss-of-function neurons exhibit triglyceride buildup, phosphatidylcholine metabolism disruption, and impaired mitochondrial function.
• CDP-choline treatment restored mitochondrial function, reversed transcriptional defects, and reduced amyloid-β pathology.

Conclusions:

• Phosphatidylcholine disruption is implicated in metabolic and pathological defects associated with ABCA7 dysfunction in Alzheimer's disease.
• These findings highlight lipid dysfunction's role in AD etiology and suggest potential therapeutic strategies targeting phosphatidylcholine metabolism.