A Tug-of-War Mechanism for Pattern Formation in a Genetic Network

Synthesizing spatial patterns with genetic networks is an ongoing challenge in syn-

thetic biology. A successful demonstration of pattern formation would imply a better

understanding of systems in the natural world and advance applications in synthetic

biology. In developmental systems, transient patterning may suffice in order to imprint

instructions for long-term development. In this paper we show that transient but per-

sistent patterns can emerge from a realizable synthetic gene network based on a toggle

switch. We show that a bistable system incorporating diffusible molecules can generate

patterns that resemble Turing patterns but are distinctly different in the underlying

mechanism: diffusion of mutually inhibiting molecules creates a prolonged “tug-of-war”

between patches of cells at opposing bistable states. The patterns are observed to be

transient but longer wavelength patterns persist for extended periods of time. Analysis

of a representative small scale model implies the eigenvalues of the persistent modes

are just above the threshold of stability. The results are verified through simulation of

biologically relevant models.