Chapter 23

Regulatory Networks

A regulatory mechanism in biology exists to ensure the survival of the organism in

which it operates. Many kinds of networks are described in the literature—genetic,

transcriptomic, proteomic, metabolic, etc.; the bacterial enzoskeleton is also a net-

work. ¹ Despite their often bewildering complexity, they are all basically of the type

represented in Fig. 3.1.

A genetic network (or gene regulatory network) is a complex system that controls

the expression of genes in response to environmental cues. The network comprises

the interacting genes that regulate each other’s expression. It has both transcriptional

and post-transcriptional regulatory components. Interactions between the genes can

be either positive or negative, and typically involve feedback loops where the output

of one gene affects the expression of another. Slightly different is a transcriptional net-

work, the system of molecular interactions that regulate gene expression—essentially

the process of turning genes “on” and “off” in response to environmental signals

(Chap. 22). The transcriptional network includes both transcription factors and non-

coding RNA molecules that regulate gene expression at the posttranscriptional level.

A proteomic network is a network of interacting proteins and protein complexes (i.e.,

gene products) that are involved in a given biological process. A metabolic network

is a collection of biochemical reactions that are connected to each other in a system

of metabolic pathways, which enable a cell to convert nutrients into energy, synthe-

size new molecules, and degrade defective or superfluous molecules. An ontogenetic

network is a network of genes and proteins that interact with each other to control the

development of an organism. The network components are involved in gene expres-

sion, signalling pathways, and other regulatory processes. The ontogenetic network

is affected by both environmental and genetic factors, and plays a rôle in determining

the shape, size, and behaviour of the organism.

Much work has been carried out on modelling regulatory networks, for example

using Boolean or Bayesian networks. ²

1 Norris et al. (1996).

2 de Jong (2002).

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https://doi.org/10.1007/978-3-030-45607-8_23

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