Routes to Binary Gene Expression

TL;DR

This paper reviews the mechanisms behind binary gene expression, highlighting stochastic effects, feedback loops, and emergent bistability, and discusses their theoretical foundations in cellular systems.

Contribution

It provides a comprehensive overview of the origins of binary gene expression, emphasizing three principal mechanisms and their theoretical underpinnings.

Findings

Binary gene expression results in two distinct cell subpopulations.

Response to inducing signals is non-graded and depends on the mechanism.

Emergent bistability involves autoregulatory feedback and growth effects.

Abstract

Systems biology approaches combining theoretical modeling with experiments have been singularly successful in uncovering novel features of cellular phenomena. One such feature is that of binary gene expression in which the expression level is either low or high, i.e., digital in nature. This gives rise to two distinct subpopulations in a population of genetically identical cells. The fraction of cells in the high expression state is raised as the strength of the inducing signal is increased indicating that the response is not graded. In this review, we discuss the possible origins of binary gene expression with emphasis on three principal mechanisms: purely stochastic, positive feedback-based and emergent bistability. In the latter case, two stable expression states are obtained due to an autoregulatory positive feedback loop in protein synthesis along with cell growth retardation by the proteins synthesized. The theoretical foundations of the observed phenomena are described in each case.