Alzheimer risk associated with a copy number variation in the complement receptor 1 increasing C3b/C4b binding sites
N Brouwers1, C Van Cauwenberghe, S Engelborghs
1Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB, Antwerpen, Belgium.
Molecular Psychiatry
|March 16, 2011
Summary
The complement receptor 1 gene (CR1) is linked to Alzheimer's disease (AD) risk. A specific CR1 variant, CR1-S, increases AD risk by 30%, potentially through its role in the immune complement cascade.
Area of Science:
- Genetics
- Neuroscience
- Immunology
Background:
- Genome-wide association studies suggest the complement receptor 1 gene (CR1) is implicated in Alzheimer's disease (AD) genetic etiology.
- CR1 plays a key role in the immune complement cascade, a system involved in pathogen clearance and inflammation.
Purpose of the Study:
- To genetically validate the association of CR1 with AD risk in a European cohort.
- To investigate the impact of CR1 single-nucleotide polymorphisms (SNPs) on AD risk and cerebrospinal fluid (CSF) biomarkers.
- To examine the role of CR1 copy number variation (CNV) and its isoforms (CR1-F and CR1-S) in AD pathogenesis.
Main Methods:
- Genetic analysis of CR1 SNPs and haplotypes in a Flanders-Belgian cohort (n=1883) and a French cohort (n=2003).
- Association testing for CR1 variants with AD risk and CSF Aβ₁₋₄₂ levels.
- Quantification and association analysis of CR1 low-copy repeat-associated copy number variation (CNV).
Main Results:
- A significant association was found for a CR1 risk haplotype, particularly in individuals carrying apolipoprotein E (APOE) ɛ4 alleles.
- Four CR1 SNPs correlated with increased CSF amyloid Aβ₁₋₄₂ levels, suggesting a role in Aβ metabolism.
- A significant association was observed for CR1-S, a CR1 isoform resulting from CNV, with an increased AD risk of 30% in carriers (OR=1.32 in combined cohorts).
Conclusions:
- The CR1 gene, specifically the CR1-S isoform, is a significant genetic risk factor for Alzheimer's disease.
- CR1-S may contribute to AD pathogenesis by altering the immune complement cascade and potentially Aβ metabolism.
- Further functional studies are required to elucidate the precise mechanisms by which CR1-S influences AD development.
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