Epistasis and destabilizing mutations shape gene expression variability in humans via distinct modes of action.
Increasing evidence shows that phenotypic variance is genetically determined, but the underlying mechanisms of genetic control over the variance remain obscure. Here, we conducted variance-association mapping analyses to identify expression variability QTLs (evQTLs), i.e. genomic loci associated with gene expression variance, in humans. We discovered that common genetic variants may contribute to increasing gene expression variance via two distinct modes of action—epistasis and destabilization. Specifically, epistasis explains a quarter of the identified evQTLs, of which the formation is attributed to the presence of ‘third-party’ eQTLs that influence the gene expression mean in a fraction, rather than the entire set, of sampled individuals. On the other hand, the destabilization model explains the other three-quarters of evQTLs, caused by mutations that disrupt the stability of the transcription process of genes. To show the destabilizing effect, we measured discordant gene expression between monozygotic twins, and estimated the stability of gene expression in single samples using repetitive qRT-PCR assays. The mutations that cause destabilizing evQTLs were found to be associated with more pronounced expression discordance between twin pairs and less stable gene expression in single samples. Together, our results suggest that common genetic variants work either interactively or independently to shape the variability of gene expression in humans. Our findings contribute to the understanding of the mechanisms of genetic control over phenotypic variance and may have implications for the development of variance-centred analytic methods for quantitative trait mapping.
Department of Veterinary Integrative Biosciences.|Institute for Systems Biomedicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
Ence
E
Yang
Department of Veterinary Integrative Biosciences.
Gang
G
Wang
Department of Veterinary Integrative Biosciences.
Jizhou
J
Yang
Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX, USA.|Department of Immunology, University of Connecticut Health Center, Farmington, CT, USA
Beiyan
B
Zhou
Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX, USA.
Yanan
Y
Tian
Department of Veterinary Integrative Biosciences.|Interdisciplinary Program of Genetics, Texas A&M University, College Station, TX, USA
James J
JJ
Cai
D004843:Epistasis, Genetic; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation; D014644:Genetic Variation; D055106:Genome-Wide Association Study; D005838:Genotype; D006801:Humans; D009154:Mutation; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci; D014430:Twins, Monozygotic / Q000235:genetics*