1. Epistasis analysis links immune cascades and cerebral amyloidosis
- Author
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Sulantha Mathotaarachchi, Pedro Rosa-Neto, Antoine Leuzy, Eduardo R. Zimmer, Tharick A. Pascoal, Monica Shin, Judes Poirier, Sara Mohades, Guy A. Rouleau, Andrea Lessa Benedet, Cynthia Picard, Alexandre Dionne-Laporte, Thomas Beaudry, Aurélie Labbe, Philippe Lemay, and Serge Gauthier
- Subjects
Apolipoprotein E ,Male ,Amyloid ,Immunology ,Epistasis and functional genomics ,Single-nucleotide polymorphism ,Genome-wide association study ,Biology ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,0302 clinical medicine ,Alzheimer Disease ,medicine ,Humans ,Cognitive Dysfunction ,030304 developmental biology ,Aged ,Genetics ,Aged, 80 and over ,0303 health sciences ,General Neuroscience ,Amyloidosis ,Research ,Epistasis, Genetic ,Middle Aged ,medicine.disease ,3. Good health ,Neurology ,Epistasis ,Female ,Alzheimer's disease ,030217 neurology & neurosurgery - Abstract
Background Several lines of evidence suggest the involvement of neuroinflammatory changes in Alzheimer’s disease (AD) pathophysiology such as amyloidosis and neurodegeneration. In fact, genome-wide association studies (GWAS) have shown a link between genes involved in neuroinflammation and AD. In order to further investigate whether interactions between candidate genetic variances coding for neuroinflammatory molecules are associated with brain amyloid β (Aβ) fibrillary accumulation, we conducted an epistasis analysis on a pool of genes associated with molecular mediators of inflammation. Methods [18F]Florbetapir positron emission tomography (PET) imaging was employed to assess brain Aβ levels in 417 participants from ADNI-GO/2 and posteriorly 174 from ADNI-1. IL-1β, IL4, IL6, IL6r, IL10, IL12, IL18, C5, and C9 genes were chosen based on previous studies conducted in AD patients. Using the [18F]florbetapir standardized uptake value ratio (SUVR) as a quantitative measure of fibrillary Aβ, epistasis analyses were performed between two sets of markers of immune-related genes using gender, diagnosis, and apolipoprotein E (APOE) as covariates. Voxel-based analyses were also conducted. The results were corrected for multiple comparison tests. Cerebrospinal fluid (CSF) Aβ1-42/phosphorylated tau (p-tau) ratio concentrations were used to confirm such associations. Results Epistasis analysis unveiled two significant single nucleotide polymorphism (SNP)-SNP interactions (false discovery rate (FDR) threshold 0.1), both interactions between C9 gene (rs261752) and IL6r gene (rs4240872, rs7514452). In a combined sample, the interactions were confirmed (p ≤ 10–5) and associated with amyloid accumulation within cognitively normal and AD spectrum groups. Voxel-based analysis corroborated initial findings. CSF biomarker (Aβ1-42/p-tau) confirmed the genetic interaction. Additionally, rs4240872 and rs7514452 SNPs were shown to be associated with CSF and plasma concentrations of IL6r protein. Conclusions Certain allele combinations involving IL6r and C9 genes are associated with Aβ burden in the brain. Hypothesis-driven search for epistasis is a valuable strategy for investigating imaging endophenotypes in complex neurodegenerative diseases. Electronic supplementary material The online version of this article (doi:10.1186/s12974-015-0436-z) contains supplementary material, which is available to authorized users.
- Published
- 2015