Genetic architecture of transcript-level variation in humans

Area of Science:

• Genomics
• Molecular Biology
• Population Genetics

Background:

• Understanding the genetic basis of gene expression variation is crucial for deciphering complex traits and diseases.
• Genome-wide association studies (GWAS) have identified numerous single-nucleotide polymorphisms (SNPs) associated with various phenotypes, but their impact on gene expression is still being elucidated.

Purpose of the Study:

• To investigate the pairwise associations between a large set of gene-expression values and millions of single-nucleotide polymorphisms (SNPs) across different ancestral populations.
• To characterize the nature of these associations, distinguishing between local and distant regulatory effects and their functional implications.

Main Methods:

• Performed pairwise association testing between 12,747 gene-expression values and over two million SNPs in European (CEU) and African (YRI) samples.
• Defined local associations as those with an intrapair distance ≤ 4 Mb and distant associations as those > 4 Mb.
• Conducted enrichment analysis of functional categories for genes harboring local and distant expression quantitative nucleotides (eQTNs).

Main Results:

• Identified 4,677 significant eQTLs in CEU samples and 5,125 in YRI samples.
• Genes with local eQTLs were enriched in nucleosome and chromatin assembly categories.
• Genes with distant eQTLs were enriched in transmembrane signal transduction pathways, suggesting their role in gene expression regulation.
• Highlighted a specific instance of a distant association between a non-synonymous SNP in EPHX1 and the expression of ORMDL3, an asthma susceptibility gene.

Conclusions:

• Local and distant genetic variants play distinct roles in regulating gene expression, impacting different biological pathways.
• Functional enrichment analysis provides insights into the mechanisms underlying gene regulation by both proximal and distal genetic elements.
• The identified associations, including the EPHX1-ORMDL3 link, offer potential targets for understanding and treating complex diseases like asthma.