Transcriptomic and genetic studies identify IL-33 as a candidate gene for Alzheimer's disease

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Apolipoprotein E (APOE) epsilon 4 allele is the primary genetic risk factor for Alzheimer's disease (AD).
• Identifying novel genetic determinants is crucial for understanding AD pathogenesis.

Purpose of the Study:

• To identify novel genes associated with Alzheimer's disease risk beyond APOE.
• To investigate the role of interleukin-33 (IL-33) in AD pathogenesis and its association with cerebral amyloid angiopathy (CAA).

Main Methods:

• Transcriptomic analysis of brain tissue from AD cases and controls.
• Genotyping of polymorphisms in differentially expressed genes.
• Case-control association studies and prospective cohort analysis.
• Immunohistochemistry and cellular models to assess IL-33 expression and function.

Main Results:

• Seventeen genes showed initial association with AD risk; IL-33 was retained after multiple testing correction.
• Decreased IL-33 expression observed in AD brains.
• Specific IL-33 polymorphisms and a protective haplotype were associated with reduced AD risk in non-APOE epsilon 4 carriers.
• These polymorphisms were also linked to reduced CAA in non-APOE epsilon 4 AD cases.
• IL-33 overexpression decreased A beta(40) secretion, a key component of CAA.

Conclusions:

• Genetic variants in the IL-33 gene are associated with a decreased risk of Alzheimer's disease.
• IL-33 may exert a protective effect by modulating CAA formation.
• IL-33's role in vascular pathology warrants further investigation in AD.