Use of fluorescence microscopy to analyze genetic circuit dynamics.

The physiological processes and programs of cells are not typically determined by single genes, but are governed by the patterns of interactions between genes and proteins [Alon, U. (2007). An Introduction To Systems Biology: Design Principles of Biological Circuits. Chapman & Hall/CRC, Boca Raton.]. These interactions are commonly referred to as genetic circuits, and the pattern of these interactions is called the circuit's architecture [Sprinzak, D. and Elowitz, M.B. (2005). Reconstruction of genetic circuits. Nature438(7067), 443-448.]. Genetic circuits control diverse cellular processes, and each process requires specific dynamic behaviors to properly function. Biochemical evidence aids in the identification of interactions between genes and proteins, but the spatiotemporal dynamics of these interactions are more difficult to probe using conventional techniques. Fluorescence time-lapse microscopy is a powerful tool in the study of genetic circuit dynamics, allowing the measurement of circuit dynamics in single cells [Suel, G.M., et al. (2007). Tunability and noise dependence in differentiation dynamics. Science315(5819), 1716-1719.]. Uncovering the dynamics of genetic circuits allows verification of mathematical models of genetic circuits and aids in the design of forward experiments. By enabling the study of relationships between circuit architecture and dynamic behavior, fluorescence time-lapse microscopy opens new frontiers in synthetic biology, allowing for the alteration of genetic circuits to achieve novel behaviors [Cagatay, T., et al. (2009). Architecture-dependent noise discriminates functionally analogous differentiation circuits. Cell139(3), 512-522.], and even the generation of completely synthetic, purpose built genetic circuits [Elowitz, M.B. and Leibler, S. (2000). A synthetic oscillatory network of transcriptional regulators. Nature403(6767), 335-338.]. Perhaps more importantly, determination of genetic circuit dynamics can reveal the concepts and principles underlying the biological functions they regulate.