Trading bits in the readout from a genetic network

TL;DR

This paper investigates how genetic networks in early fly embryos optimize the measurement of transcription factor concentrations, balancing physical measurement limits with the extraction of positional information, highlighting the role of enhancer proliferation.

Contribution

It demonstrates that cells can extract all available positional information if measurements approach physical limits, explaining enhancer proliferation without fine-tuning.

Findings

Cells can extract maximum positional information near physical measurement limits.

Proliferation of enhancer elements is explained by information capacity constraints.

Fine-tuning of enhancer parameters is not necessary for optimal information extraction.

Abstract

In genetic networks, information of relevance to the organism is represented by the concentrations of transcription factor molecules. In order to extract this information the cell must effectively "measure"' these concentrations, but there are physical limits to the precision of these measurements. We explore this trading between bits of precision in measuring concentration and bits of relevant information that can be extracted, using the gap gene network in the early fly embryo as an example. We argue that cells in the embryo can extract all the available information about their position, but only if the concentration measurements approach the physical limits to information capacity. These limits necessitate the observed proliferation of enhancer elements with sensitivities to combinations of transcription factors, but fine tuning of the parameters of these multiple enhancers is not required.