Haploinsufficient Gene Amplification for Stable Cell Factories
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Solution Overview
Problem
Existing methods for increasing gene copy number in cell factories for industrial applications, such as yeast, are inefficient and unstable, often requiring exogenous selection systems that add complexity and cost, and result in genetic instability.
Innovation Solution
Exploiting the evolutionary force and selection pressure of haploinsufficient genes by reducing their expression to drive gene amplification and maintenance, using methods that include operably connecting heterologous nucleic acids with haploinsufficient genes and employing origins of replication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple gene copies are introduced to increase expression levels, then productivity is improved, but genetic stability deteriorates
Solution Approach 1:
The system uses the cell's own haploinsufficient gene expression deficiency as the selection pressure to drive amplification of the desired gene. The cell naturally selects for increased copy number to compensate for the reduced endogenous gene expression, eliminating the need for external selection mechanisms and ensuring stable maintenance of amplified genes.
Solution Approach 2:
Instead of using positive selection (adding markers to select for amplified genes), the system uses negative selection by creating a deficiency in an essential gene. The cell must amplify the desired gene to compensate for this deficiency, inverting the traditional selection approach and achieving stable amplification without exogenous markers.
2Reliability
If exogenous selection systems are used to maintain multiple gene copies, then gene copy number is maintained, but device complexity increases
Solution Approach 1:
The cell's natural gene expression regulation and replication machinery are harnessed to maintain multiple gene copies. The haploinsufficient gene creates intrinsic selection pressure that utilizes the cell's own biological systems to preserve the amplified genes, eliminating the need for complex exogenous selection systems.
Solution Approach 2:
The patent removes exogenous selection markers and complex selection systems from the gene amplification process. By using endogenous haploinsufficient genes as the selection mechanism, the system extracts the essential selection function and performs it through simplified native cellular processes.
3Productivity
If multiple gene copies are integrated at random loci, then expression levels are increased, but ease of operation deteriorates
Solution Approach 1:
The amplified gene cluster serves multiple functions: it provides the desired product expression, compensates for the haploinsufficient gene deficiency, and maintains itself through the cell's natural selection processes. This multi-functionality simplifies subsequent genetic manipulation since the amplified region acts as a self-contained functional unit.
4Productivity
If strong promoters are used to increase expression, then productivity is improved, but object-generated harmful factors increase
Solution Approach 1:
The system changes the selection parameter from external marker-based selection to endogenous gene expression-based selection. By modifying the expression level of the haploinsufficient gene, the system creates a selectable phenotype that drives amplification without requiring strong external promoters or antibiotic markers, thereby reducing harm to host cell fitness.
Data Source
AI summary
Disclosed are methods of genetic engineering to manipulate gene copy number in vivo, as well genetic constructs for amplifying gene copy number in vivo, and recombinant cells that comprise amplified genes. The methods of increasing gene copy number involve reducing expression levels of a haploinsufficient gene in the genome of recombinant cells, such as through replacing the endogenous promoter with a weaker promoter.