Download presentation
Presentation is loading. Please wait.
Published byVernon Johnston Modified over 9 years ago
1
2006-4-26 Highly designable phenotypes and mutational buffers emerge from a systematic mapping between network topology and dynamic output Nochomovitz & Li
2
The idea Map network topologies to dynamical phenotypes The designability of a phenotype is defined as the number of topologies mapped onto it. Designability = 2 Designability = 1
3
Dynamic phenotype Network topology A 5-cycle phenotype (0001 0010 1001 0111 1010) A limit cycle passing through a specific series of states or a particular fixed point.
4
Updating rules Rule 1: Rule 2: The time scales of the decay process and the activating or inhibitory processes are of equal order. The decay process occurs on a much slower time scale than the activating or inhibitory processes.
5
Phenotypes that are neither excessively rare nor excessively simple
6
Comparison of the two rules Under both rules, the strong, intermediate, and weakly designable phenotypes emerge consistently.
7
Designing larger cycles is exponentially hard.
8
Designability spectrum of 4-cycles for 4-node networks Mean designability of 4-cycles 0001 0010 0101 0011
9
Designability spectrum of 5-cycles for 4-node networks Mean designability of 5-cycles
10
Designability spectrum of 6-cycles for 4-node networks Mean designability of 4-cycles
11
What are the dynamical features of highly designable dynamical phenotypes? Case 1: (2 3 6 11) Two classes of connections : fully conserved connections Correspond to a subnetwork module that is necessary to encode the disignable, stable phenotype. variable connections Control the transient dynamical flow. Network with fully conserved connections 0001 0010 0101 1010 Designability = 2500
12
Case 2: (2 3 5 9 10) (0001 0010 0100 1000 1001) Designability = 250
13
Designability is independent of robustness Robustness of a phenotype is measured by the number of transient states that flow toward the stable phenotype.
14
Mutational buffering: The incorporation of a fourth node bearing specific connections to a set of genetically distinct three-node networks would trigger the three-node networks to acquire the same dynamical phenotype, despite possessing differing dynamical phenotypes as isolated three-node systems. A scaffold refers to a fixed manner by which a fourth node interacts with a three-node subnetwork. Buffering strength reports the ratio of designability of a dynamical phenotype observed on three- node subnetworks attached via scaffold to a fourth node, to that phenotype’s designability on isolated three-node networks.
15
An example of mutational buffer Buffering strength = 11 Scaffold
16
Summary A small fraction of dynamical phenotypes possesses atypically high designabilities. Highly designable dynamical phenotypes arise via the presence of a core of fully conserved network links. No correlation exists between the stability of a dynamical phenotype and its designability. Identification of mutational buffers, which act to suppress phenotypic variation through specific dynamical relationships to other genes.
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.