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Case essay: synthetic biology
Synthetic gene network for the efficient generation of induced pluripotent stem cells from adult somatic cells
Supervisors: Prof. John Ward | Prof. Alexey Zaikin
Download: PDF (~1.3 MB)
Embryonic stem cells derived from the inner cell-mass of the blastocyst are self-renewable, meaning they can undergo an infinite number of divisions. They are also pluripotent and can give rise to most adult cell types through differentiation, a genetically regulated process during which cells gain specialized phenotypes. These unique properties make them a potentially unlimited source of material for developmental biology, drug discovery and regenerative medicine. Recently, it was shown that it is possible to generate pluripotent cells from adult somatic cells by reprogramming them using four transcription factors: Oct4, c-Myc, Sox2 and Klf4. This approach alleviates the concerns related to the embryonic origins of the cells and promises patient-specific therapies. However, current reprogramming protocols remain very inefficient, mainly due to a lack of control of the transcription factors expression. Synthetic biology, by combining knowledge from various disciplines including mathematics, molecular biology and engineering, provides a framework for the rational design of complex genetic networks that can be used to improve existing characteristics of a cell or create de-novo functionalities, such as advanced gene expression regulatory mechanisms.
- Numerical simulations of the synthetic cascade.
This case essay examines the use of a synthetic regulatory cascade to improve the reprogramming process of somatic cells by tightly controlling the expression of the four transcription factors. The design is based around three compatible antibiotic responsive expression systems: TETOFF, EOFF and PIPOFF, repressed by tetracycline, erythromycin and pristinamycin respectively. Numerical simulations based on a system of differential equations have shown that it is indeed possible to generate complex expression patterns over the typical induction period, allowing for a degree of control not achievable with existing approaches. An evaluation protocol is also proposed to experimentally compare the performances of the regulatory cascade against traditional reprogramming methods.
Precise temporal expression of known amounts of transcription factors might be used as a tool to better understand the molecular mechanisms involved in the reprogramming process and, as a direct consequence, might lead to the establishment of robust and highly efficient induction protocols that would allow for the generation of the large quantity of cells that will most likely be required for future research and therapeutic applications.
