Aspg-Gs Double Knockout Selection for CHO Protein Expression
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Solution Overview
Problem
Existing CHO cell lines for biopharmaceutical production require improved selection systems to enhance heterologous protein expression, as current methods are time-consuming and laborious, and existing dual selection systems do not adequately increase productivity.
Innovation Solution
A selection system for heterologous protein expression in CHO cells using a double knockout of the asparaginase (Aspg) and glutamine synthetase (Gs) genes, combined with controllably expressed Aspg and Gs vectors, which relies on selective pressure through growth in glutamine-free medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single Gs knockout selection system is used, then the selection process is simple, but the specific productivity and titer of heterologous proteins are insufficient
Solution Approach 1:
The patent combines two selection systems (Gs and Aspg) into a unified dual knockout cell line. The Gs knockout provides glutamine dependence for selection, while the Aspg knockout provides asparagine dependence, creating a synergistic effect that significantly enhances specific productivity and titer of heterologous proteins compared to single knockout systems.
Solution Approach 2:
The selection system is divided into two independent but complementary components: the Gs knockout component that confers glutamine auxotrophy, and the Aspg knockout component that confers asparagine auxotrophy. Each component can be independently targeted and selected, allowing for modular optimization of the selection process.
2Productivity
If existing dual selection systems are used, then productivity is moderately improved, but the selection process becomes time-consuming and laborious
Solution Approach 1:
The patent merges Gs and Aspg selection markers into a single dual knockout cell line, allowing simultaneous selection for both markers in one system. This integration reduces the number of separate selection steps required compared to traditional sequential selection methods, thereby reducing time and labor while achieving higher titers.
3Productivity
If Aspg knockout is applied alone, then asparagine dependence is achieved, but growth is nearly eliminated in glutamine-free media
Solution Approach 1:
The patent uses the Gs knockout as an intermediary system that provides glutamine dependence, which serves as a stable foundation for cell growth and selection. The Aspg knockout is then added as a second layer of selection pressure. The Gs system acts as a mediator that supports cell viability while the Aspg system provides enhanced selection potency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The double knockout system significantly enhances specific productivity and titer of heterologous proteins, achieving up to 15-fold improvement compared to single Gs knockout systems, with stable expression maintained over extended periods.
Implementation Method 1
Aspg, the enzyme which catalyses the deamination of asparagine to aspartate
Data Source
AI summary
A non-naturally occurring cell comprising an inoperative genomic asparaginase (Aspg) gene and an inoperative glutamine synthetase (Gs) gene, wherein the cell has been transfected with a controllably expressed gene encoding an enzyme having asparaginase activity, a controllably expressed gene encoding an enzyme having glutamine synthetase activity, and a controllably expressed gene encoding a heterologous protein of interest.