Network hubs affect evolvability

Abstract

The regulatory processes in cells are typically organized into complex genetic networks. However, it is still unclear how this network structure modulates the evolution of cellular regulation. One would expect that mutations in central and highly connected modules of a network (so-called hubs) would often result in a breakdown and therefore be an evolutionary dead end. However, a new study by Koubkova-Yu and colleagues finds that in some circumstances, altering a hub can offer a quick evolutionary advantage. Specifically, changes in a hub can induce significant phenotypic changes that allow organisms to move away from a local fitness peak, whereas the fitness defects caused by the perturbed hub can be mitigated by mutations in its interaction partners. Together, the results demonstrate how network architecture shapes and facilitates evolutionary adaptation.

Fig 1. Network architecture determines evolutionary trajectories.

(A) Simplified schematic of a gene network. The red node is a hub gene, and the blue node is a gene at the edge of the network. (B) Fitness landscape and possible evolutionary trajectories. Perturbing a hub gene (red) or a peripheral gene (blue) can both lead to a decrease in fitness, but the number of available evolutionary trajectories (arrows) is higher when a hub gene is perturbed.