Evolution of gene regulatory networks: Robustness as an emergent property of evolution

Gene Regulatory Networks (GRNs) have become a major focus of interest in recent years. Although much work has been done in elucidating the transcriptional regulatory network, the underlying mechanisms that have possibly influenced the evolution of these GRNs are still debatable. We have developed a framework to analyze the effect of objective functions, input types and starting populations on the evolution of GRNs with a specific emphasis on the robustness of evolved GRNs. We observed that robustness evolves along with the networks as an emergent property even in the absence of specific selective pressure towards more robust systems. In addition, robustness was independent of the selective pressure, input types or the initial starting populations. We also observed the existence of multiple genotypes giving rise to the same phenotype in accordance with the theoretical view that natural selection operates on phenotypes thereby accommodating variation in the genotype by fixing those changes that are phenotype-neutral. This study gives a proof-of-concept of the fact that robustness is an emergent property of GRNs as well as of the degeneracy of the network topology/function relationship analogous to the sequence/structure problem in proteins. (c) 2007 Elsevier B.V. All rights reserved.