Mutant loxP vectors for selectable marker recycle and conditional knock-outs

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Targeted gene disruption is crucial for studying gene function.
• The DT40 chicken B cell line is a model for gene knock-outs but limited by selectable markers.
• Recycling selectable markers using site-specific recombination (e.g., Cre/loxP) is highly desirable.

Purpose of the Study:

• To develop a system for selectable marker recycling in gene knock-out studies.
• To enable conditional gene knock-out and complementation strategies.
• To facilitate the analysis of essential genes.

Main Methods:

• Constructed plasmid vectors with selectable marker genes (neoR, puroR, bsr) flanked by mutant loxP sites.
• Utilized Cre recombinase expression for marker gene excision.
• Developed a versatile expression vector for cDNA cloning between mutant loxP sites.
• Designed knock-out constructs combining floxed markers with cDNA expression cassettes.

Main Results:

• Successfully excised selectable marker genes using Cre/loxP recombination, converting mutant loxP sites to inactive double-mutant loxP.
• Created a single-step gene knock-out and complementation system.
• Demonstrated the ability to terminate gene expression via Cre-mediated deletion of cDNA cassettes.
• The system is effective for analyzing essential genes that cause lethality upon disruption.

Conclusions:

• Developed mutant loxP vectors for efficient selectable marker recycling and conditional gene knock-out.
• The system supports a wide range of cell lines due to the use of the beta-actin promoter.
• This strategy enhances the study of gene function, particularly for essential genes.