Only accessible information is useful: insights from gradient-mediated patterning

TL;DR

This paper argues that only the accessible information in biological systems is useful, explaining the common multi-tiered gene expression cascades as a consequence of noise limitations, supported by empirical data from fruit fly development.

Contribution

It introduces the concept of accessible information in biological signaling, providing a new perspective on the architecture of gene regulatory networks.

Findings

Accessible information explains multi-tiered network prevalence

Standard information theory overestimates usable information in noisy systems

Empirical data from fruit fly embryo supports the theory

Abstract

Information theory is gaining popularity as a tool to characterize performance of biological systems. However, information is commonly quantified without reference to whether or how a system could extract and use it; as a result, information-theoretic quantities are easily misinterpreted. Here we take the example of pattern-forming developmental systems which are commonly structured as cascades of sequential gene expression steps. Such a multi-tiered structure appears to constitute sub-optimal use of the positional information provided by the input morphogen because noise is added at each tier. However, the conventional theory fails to distinguish between the total information in a morphogen and information that can be usefully extracted and interpreted by downstream elements. We demonstrate that quantifying the information that is _accessible_ to the system naturally explains the prevalence of multi-tiered network architectures as a consequence of the noise inherent to the control of gene expression. We support our argument with empirical observations from patterning along the major body axis of the fruit fly embryo. Our results exhibit the limitations of the standard information-theoretic characterization of biological signaling and illustrate how they can be resolved.