FcRn Expression Cassette Layout for Stable Biotinylated Production
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Solution Overview
Problem
Existing methods for producing recombinant polypeptides, such as antibodies, through random integration in eukaryotic cells are inefficient, unstable, and result in variable expression and product quality due to random integration loci and cassette distribution, leading to high sequence variance and labor-intensive screening.
Innovation Solution
A method involving double recombinase mediated cassette exchange (RMCE) is used to integrate a defined sequence of expression cassettes for FcRn into the genome of mammalian cells, ensuring controlled expression ratios and efficient production of biotinylated FcRn.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If random integration of nucleotide sequences is used, then cell transformation is achieved, but position effect variation and unstable expression occur
Solution Approach 1:
The patent uses recombinase enzymes (such as Cre recombinase or phiC31 integrase) as intermediaries to mediate the integration of expression cassettes into specific genomic loci. These enzymes recognize specific recombination sites (loxP or attP/attB sites) and facilitate precise integration, eliminating the randomness of traditional integration methods while ensuring stable and reproducible expression.
Solution Approach 2:
The patent changes the integration parameter from random to site-specific by introducing defined recombination sites into the genome. This parameter change ensures that expression cassettes integrate at predetermined locations with favorable chromatin environments, thereby achieving stable expression and avoiding position effect variation.
2Productivity
If gene amplification methods are used to achieve high-producing cells, then expression yield increases, but cell growth stability deteriorates
Solution Approach 1:
The patent performs preliminary selection of optimal integration sites before introducing the expression cassettes. By pre-characterizing genomic loci with favorable properties (open chromatin, active transcription regions), the method ensures high expression yields are achieved at the integration site itself, eliminating the need for subsequent gene amplification that would compromise cell stability.
3Measurement precision
If thousands of cells are screened after transfection, then high-expression cells are isolated, but time and labor consumption increase
Solution Approach 1:
The patent incorporates selectable marker genes (such as antibiotic resistance genes or fluorescent protein genes) as intermediaries that allow direct selection of successfully transformed cells. This enables rapid identification and isolation of high-expression cells without extensive screening, significantly reducing time and labor consumption.
4Adaptability or versatility
If multiple expression cassettes are integrated, then complex polypeptides can be produced, but cassette distribution control becomes difficult
Solution Approach 1:
The patent assigns different functions to different parts of the integrated cassette structure. Each expression cassette is designed with specific recombination sites, promoters, and coding sequences tailored to the particular polypeptide chain it encodes. This local optimization allows precise control over the expression ratios of different polypeptide chains while maintaining the ability to produce complex heteromultimeric proteins.
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
This approach achieves stable, high-yield production of correctly folded and assembled FcRn with reduced by-products, addressing the inefficiencies of random integration by ensuring precise cassette organization and integration.
Implementation Method 1
a double recombinase mediated cassette exchange reaction, resulting in a specific expression cassette sequence being integrated into the genome of the mammalian cell
Data Source
AI summary
Herein is reported a method for producing C-terminally biotinylated FcRn comprising the steps of cultivating a mammalian cell comprising a deoxyribonucleic acid encoding FcRn and E. coli biotin-[acetyl-CoA-carboxylase] ligase (BirA) in a biotin containing medium, and recovering C-terminally biotinylated FcRn from the cell or the cultivation medium, wherein the deoxyribonucleic acid encoding FcRn and E. coli BirA is stably integrated into the genome of the mammalian cell and comprises in 5′- to 3′-direction a first expression cassette encoding class I major histocompatibility complex-like protein (α-FcRn) comprising a HisAvi-tag at the C-terminus, a second expression cassette encoding β2-microglobulin (β2m), a third expression cassette encoding class I major histocompatibility complex-like protein (α-FcRn) comprising a HisAvi-tag at the C-terminus, a fourth expression cassette encoding β2-microglobulin (β2m), and a fifth expression cassette encoding E. coli biotin-[acetyl-CoA-carboxylase] ligase.