Can coupled circadian oscillators be entrained Light?

Circadian oscillators (CO) are biochemical pathways in which a gene expresses mRNA cyclically to create a rhythmical auto-regulatory loop for both behavior and metabolism. Oscillators are found in a broad range of organisms allowing adaptation to environmental changes occurring over a 24 hour period. CO have been studied using quantitative topological models. The simplest model of a CO, known as the Goodwin oscillator (Goodwin 1965) models the negative feedback of a single protein on the transcription of its own gene using ordinary differential equations (ODE). Later models increased the genes involved in the CO, and even coupled CO (Wagner 2005). Here we study the additional effect of a light signal on a two gene coupled topology. We demonstrate that the topology can be reset and entrained to light. The resulting model is a more biologically plausible model of a circadian oscillator. PACS numbers: I