Скачать или смотреть 12.03 Dynamical Modularity – Beyond Networks: The Evolution of Living Systems

Module 12 of "Beyond Networks" takes a look at the immediate future, and what remains to be done in evolutionary systems biology within the Newtonian paradigm. Lectures two and three of this module examine some of the conditions for evolvability that arise from the causal structure of the genotype-phenotype map. In this second lecture on evolvability, we look at the modularity of the genotype-phenotype map. After briefly reviewing functional (genetic) and structural ways to define modules, I introduce the new concept of dynamical modularity. Dynamical modules are defined by the particular activity a set of network components and their interactions carry out. Such modules need not be structurally identifiable. In fact, I show that we can expect many cases of multi-functional networks that are not structurally modular. I illustrate the concept using the gap gene network (once again) as an example. It can be decomposed into overlapping AC/DC subcircuits that account for the overall behaviour of the whole network, despite the gap genes showing no structural modularity at all. Dynamical modules are likely to be ubiquitous in metabolic, physiological, and developmental systems. Identifying them and their contributions to the modular nature of morphological traits will amount to a new, processual, theory of modularity.

The discrete nature of traits is formally described in Lewontin (1970; Annual Reviews of Ecology & Systematics, Vol. 1: p. 1) and in Lewontin's 1974 textbook, The Genetic Basis of Evolutionary Change.

There are two authoritative edited volumes on the topic: Schlosser & Wagner (2004), Modularity in Development and Evolution, and Callebaut (2006) Modularity. Both mostly focus on conceptual issues and functional approaches to identify modules.

The dissociability of developmental processes was first postulated by Joseph Needham in 1933 (Biological Review, Vol. 8: p. 180).

Dynamical modules were first described by Irons & Monk (2007; BMC Bioinformatics, Vol. 8: p. 413) who also defined an algorithm to detect such modules in Boolean (logical) network models. The in silico screen to identify multifunctional modules was carried out by Jiménez et al. (2017; Molecular System Biology, Vol. 13: p. 925). Our own work on modularity and criticality in the gap gene system was published in Verd et al. (2019; eLIFE, Vol. 8: e42832). More general conceptual treatments of the theory of dynamical modularity will be forthcoming.