Epigenetic Ratchet: Spontaneous Adaptation via Stochastic Gene Expression

Adaptation mechanism of cells on the basis of stochastic gene expression and epigenetic modification is proposed. From marginally stable states generated by epigenetic modification, a gene expression pattern that achieves greater cell growth is selected, as confirmed by simulations and analysis of several models. The mechanism does not require any design of gene regulation networks and is shown to be generic in a stochastic system with marginal stability. General relevance of the mechanism to cell biology is also discussed.