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Rapid Characterization of Genetic Parts with Cell-Free Systems
Published on: August 30, 2021
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Variability in cell-free expression reactions can impact qualitative genetic circuit characterization
Katherine A Rhea1, Nathan D McDonald1, Stephanie D Cole1
1US Army Combat Capabilities Development Command Chemical Biological Center, Aberdeen Proving Ground, MD, USA.
Synthetic Biology (Oxford, England)
|August 15, 2022
Summary
Variability in cell-free expression systems challenges genetic circuit prototyping. Normalizing data reveals consistent performance for simple circuits, but complex circuits show performance degradation, highlighting a critical threshold for reliable prototyping.
Area of Science:
- Synthetic Biology
- Biotechnology
- Molecular Biology
Background:
- Cell-free expression systems are valuable tools for applications like sensing and biomanufacturing, particularly for genetic circuit prototyping due to the absence of cloning and controlled reaction conditions.
- While useful for characterizing genetic elements, protein variants, and metabolic pathways, cell-free expression systems are known for significant variability between experimental setups and batches.
- The implications of this variability on the reliability of genetic circuit prototyping, especially for qualitative assessments, remain largely unexplored.
Purpose of the Study:
- To investigate how variability in cell-free expression systems impacts the qualitative assessment of genetic circuits with increasing complexity.
- To determine the threshold at which experimental variability disrupts the reliable reuse of genetic circuit prototyping results.
Main Methods:
- Assessed DNA titrations of seven genetic circuits with varying complexity under conditions that differed by person, instrument, and material batch.
- Analyzed raw activity data and normalized data within each circuit across different conditions to evaluate qualitative performance consistency.
Main Results:
- Raw expression activities varied significantly across different experimental conditions.
- Normalization revealed consistent qualitative performance for simpler genetic circuits.
- The most complex circuit (three-protein expression) exhibited a loss of qualitative consistency, indicating a potential limit for reliable prototyping.
Conclusions:
- Variability in cell-free expression systems can compromise the reliability of genetic circuit prototyping, particularly for complex designs.
- A provisional threshold exists where normal variability may hinder the reproducible assessment of genetic components.
- Closed-loop controller circuits show potential for mitigating variability, suggesting future directions for designing robust cell-free systems.
