Computational design of synthetic regulatory networks from a genetic library to characterize the designability of dynamical behaviors

Institute of Systems and Synthetic Biology (ISSB), Genopole - Université d'Évry Val d'Essonne - CNRS UPS3201, 91030 Évry Cedex, France.
Nucleic Acids Research (Impact Factor: 9.11). 08/2011; 39(20):e138. DOI: 10.1093/nar/gkr616
Source: PubMed


The engineering of synthetic gene networks has mostly relied on the assembly of few characterized regulatory elements using
rational design principles. It is of outmost importance to analyze the scalability and limits of such a design workflow. To
analyze the design capabilities of libraries of regulatory elements, we have developed the first automated design approach
that combines such elements to search the genotype space associated to a given phenotypic behavior. Herein, we calculated
the designability of dynamical functions obtained from circuits assembled with a given genetic library. By designing circuits
working as amplitude filters, pulse counters and oscillators, we could infer new mechanisms for such behaviors. We also highlighted
the hierarchical design and the optimization of the interface between devices. We dissected the functional diversity of a
constrained library and we found that even such libraries can provide a rich variety of behaviors. We also found that intrinsic
noise slightly reduces the designability of digital circuits, but it increases the designability of oscillators. Finally,
we analyzed the robust design as a strategy to counteract the evolvability and noise in gene expression of the engineered
circuits within a cellular background, obtaining mechanisms for robustness through non-linear negative feedback loops.

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    • "For cell-cell communication, synchronized genetic circuit designs are proposed to synchronize a population of oscillation signals [36,37]. To construct a promoter-RBS library from microarray data and find suitable promoter-RBS components, a robust genetic circuit has been theoretically realized in the genetic systems by a systematic approach [38,39]. "
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    ABSTRACT: Background Rhythmic clock widely occurs in biological systems which controls several aspects of cell physiology. For the different cell types, it is supplied with various rhythmic frequencies. How to synthesize a specific clock signal is a preliminary but a necessary step to further development of a biological computer in the future. Results This paper presents a genetic sequential logic circuit with a clock pulse generator based on a synthesized genetic oscillator, which generates a consecutive clock signal whose frequency is an inverse integer multiple to that of the genetic oscillator. An analogous electronic waveform-shaping circuit is constructed by a series of genetic buffers to shape logic high/low levels of an oscillation input in a basic sinusoidal cycle and generate a pulse-width-modulated (PWM) output with various duty cycles. By controlling the threshold level of the genetic buffer, a genetic clock pulse signal with its frequency consistent to the genetic oscillator is synthesized. A synchronous genetic counter circuit based on the topology of the digital sequential logic circuit is triggered by the clock pulse to synthesize the clock signal with an inverse multiple frequency to the genetic oscillator. The function acts like a frequency divider in electronic circuits which plays a key role in the sequential logic circuit with specific operational frequency. Conclusions A cascaded genetic logic circuit generating clock pulse signals is proposed. Based on analogous implement of digital sequential logic circuits, genetic sequential logic circuits can be constructed by the proposed approach to generate various clock signals from an oscillation signal.
    Full-text · Article · May 2014 · BMC Systems Biology
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    • "One major aim of synthetic biology is to construct a gene circuit with the desired functionality of an organism. Recently, promoter libraries and promoter-RBS libraries have been built to simulate the in vivo behavior of a gene circuit [30,38,39]. By identifying the kinetic strengths of promoter-RBS components, the protein expressions in the gene circuit can be estimated and predicted. "
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    ABSTRACT: Synthetic genetic transistors are vital for signal amplification and switching in genetic circuits. However, it is still problematic to efficiently select the adequate promoters, Ribosome Binding Sides (RBSs) and inducer concentrations to construct a genetic transistor with the desired linear amplification or switching in the Input/Output (I/O) characteristics for practical applications. Three kinds of promoter-RBS libraries, i.e., a constitutive promoter-RBS library, a repressor-regulated promoter-RBS library and an activator-regulated promoter-RBS library, are constructed for systematic genetic circuit design using the identified kinetic strengths of their promoter-RBS components.According to the dynamic model of genetic transistors, a design methodology for genetic transistors via a Genetic Algorithm (GA)-based searching algorithm is developed to search for a set of promoter-RBS components and adequate concentrations of inducers to achieve the prescribed I/O characteristics of a genetic transistor. Furthermore, according to design specifications for different types of genetic transistors, a look-up table is built for genetic transistor design, from which we could easily select an adequate set of promoter-RBS components and adequate concentrations of external inducers for a specific genetic transistor. This systematic design method will reduce the time spent using trial-and-error methods in the experimental procedure for a genetic transistor with a desired I/O characteristic. We demonstrate the applicability of our design methodology to genetic transistors that have desirable linear amplification or switching by employing promoter-RBS library searching.
    Full-text · Article · Oct 2013 · BMC Systems Biology
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    • "While having DNA systems compete against each other and evolve new (cheating ) strategies can be a goal in itself, the systems evolved along the way gave us also more insight about DNA computing systems. In particular, it was possible to observe the emergence of particular structures with interesting dynamics , which may prove useful to a human trying to develop DNA systems, like with the libraries of (Rodrigo et al., 2011). It could be also interesting to make individuals compete against a human designed " optimal " cheater and see if they can evolve even more advanced strategies to counter it. "

    Full-text · Conference Paper · Sep 2013
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