📅 3 July 2026🏷️ Alzheimer's Genetics⏱️ 6 min read👩🔬 Linda Osaghale
How Gene Expression Affects Alzheimer's Risk
We expected to find eQTLs—variants that affect gene expression. It seemed obvious. The variants are there. They must affect something.
But we didn't find them.
And that's actually a really important finding.
Figure 1: eQTL analysis identifies genetic variants that affect gene expression. Our study found no significant eQTLs for Alzheimer's lead variants in GTEx tissues. Based on Osaghale et al. (2026).
What Is eQTL Analysis?
eQTL stands for expression quantitative trait loci:
Term
What It Means
e
Expression
QTL
Quantitative trait locus
eQTL
Genetic variant that affects gene expression
eQTLs are variants that affect how much a gene is expressed.
How eQTL Analysis Works
Step 1: Identify Variants
Input
What It Is
Genotypes
Genetic data
eQTL data
Expression data in relevant tissues
Step 2: Test Association
Test
What It Does
Genotype vs. Expression
Tests whether genotype predicts expression
Step 3: Identify eQTLs
Output
What It Shows
Significant associations
Variants that affect expression
How We Did eQTL Analysis
Data Used
Data Source
What It Provided
GTEx v8
Expression data across 54 tissues
Brain tissues
Cortex, hippocampus, frontal cortex
Whole blood
Immune cell expression
Our Approach
Step
What We Did
1
Identified lead variants
2
Extracted eQTL data from GTEx
3
Tested for eQTL effects
4
Filtered for significance
Our Results
No Significant eQTLs
Finding
Detail
eqtMapFilt = 0
No significant eQTLs
No tissue effects
Not significant in any tissue
No expression effects
Variants don't affect expression in GTEx data
What This Means
Implication
Detail
No detectable expression effects
At least not in tested tissues
Context-dependent
May require specific conditions
Other mechanisms
Variants may affect other processes
Why We Didn't Find eQTLs
1. Tissue Specificity
Reason
Explanation
Wrong tissue
Expression effects may be in other tissues
Wrong cell type
Effects may be in specific cell types
Wrong time
Effects may occur at specific developmental stages
2. Context Dependence
Reason
Explanation
Disease state
Effects may only appear in Alzheimer's brains
Cellular state
Effects may depend on cellular state
Environmental factors
Effects may depend on environmental stimuli
3. Technical Limitations
Reason
Explanation
Sample size
GTEx may be underpowered for Alzheimer's variants
Data quality
Expression data may have limitations
Methodology
eQTL detection may miss some effects
4. Alternative Mechanisms
Reason
Explanation
Splicing effects
Variants may affect splicing, not expression
Protein effects
Variants may affect protein function
Epigenetic effects
Variants may affect DNA methylation
What This Tells Us
1. Alzheimer's Risk May Be Mediated by Other Mechanisms
Mechanism
What It Affects
Protein function
Protein activity
Splicing
RNA processing
Chromatin
DNA accessibility
Epigenetics
DNA methylation
2. Expression Effects May Be Subtle
Observation
Implication
No significant eQTLs
Effects may be small
Need larger studies
More power needed
Different tissues
Effects may be tissue-specific
3. We Need Multi-Omic Integration
Approach
What It Provides
Genomics
DNA variants
Transcriptomics
RNA expression
Epigenomics
DNA methylation
Proteomics
Protein levels
The Bottom Line
We found no significant eQTLs for our lead variants
This doesn't mean the variants aren't functional—just not in the tested tissues
Other mechanisms (splicing, protein function, epigenetics) may be involved
Context dependence may be important
Multi-omics integration is needed for a complete understanding
