Gene targeting at the human CD4 locus by epitope addition

Area of Science:

• Molecular Biology
• Immunology
• Cell Biology

Background:

• Homologous recombination is crucial for precise gene editing.
• Targeting specific gene loci like CD4 in human T-cells presents technical challenges.
• Developing efficient gene targeting strategies is vital for genetic engineering and therapeutic applications.

Purpose of the Study:

• To achieve homologous recombination at the CD4 locus in a human T-cell line.
• To develop and validate the epitope addition strategy for gene targeting.
• To assess the efficiency of homologous versus nonhomologous integration events.

Main Methods:

• Utilized an epitope addition strategy by linking the CD4 gene's regulatory elements to a modified Thy-1 gene.
• Introduced the engineered gene construct into human T-cells.
• Employed Fluorescence Activated Cell Sorting (FACS) for selection of cells expressing murine Thy-1 epitopes.
• Analyzed gene integration events to determine the ratio of homologous to nonhomologous recombination.

Main Results:

• Successfully achieved homologous recombination at the CD4 locus using the epitope addition method.
• Obtained a significant enrichment (estimated 700-fold) for homologous integration events.
• Confirmed that approximately 70% of Thy-1 positive cells resulted from targeted gene integration.
• Identified three cell lines expressing protein solely from the targeted allele, rendering them functionally CD4-.

Conclusions:

• The epitope addition technique is an effective strategy for achieving gene targeting at the CD4 locus in human T-cells.
• This method significantly enhances the efficiency of homologous recombination over nonhomologous integration.
• The resulting CD4- T-cell lines demonstrate the potential for generating specific cellular phenotypes through precise genetic modification.