Emergence and propagation of epistasis in metabolic networks
Abstract
Epistasis is often used to probe functional relationships between genes, and it plays an important role in evolution. However, we lack theory to understand how functional relationships at the molecular level translate into epistasis at the level of whole-organism phenotypes, such as fitness. Here, I derive two rules for how epistasis between mutations with small effects propagates from lower- to higher-level phenotypes in a hierarchical metabolic network with first-order kinetics and how such epistasis depends on topology. Most importantly, weak epistasis at a lower level may be distorted as it propagates to higher levels. Computational analyses show that epistasis in more realistic models likely follows similar, albeit more complex, patterns. These results suggest that pairwise inter-gene epistasis should be common and it should generically depend on the genetic background and environment. Furthermore, the epistasis coefficients measured for high-level phenotypes may not be sufficient to fully infer the underlying functional relationships.
Data availability
All data generated or analyzed during this study are included in the manuscript and supporting files. Code is available on GitHub.
Article and author information
Author details
Funding
Burroughs Wellcome Fund (Career Award at Scientific Interface,1010719.01)
- Sergey Kryazhimskiy
Alfred P. Sloan Foundation (FG-2017-9227)
- Sergey Kryazhimskiy
Hellman Foundation (Hellman Fellowship)
- Sergey Kryazhimskiy
National Institutes of Health (1R01GM137112)
- Sergey Kryazhimskiy
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2021, Kryazhimskiy
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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