DHFR-deficient strains are a type of cell line that has been engineered to lack functional dihydrofolate reductase (DHFR) enzyme. DHFR is a critical enzyme in the folate metabolic pathway, which is involved in the synthesis of nucleotides and other important biomolecules.
DHFR-deficient cell lines are often used for stable transfection and gene expression studies. These cell lines are typically generated by introducing a DHFR-targeted gene knockout or mutation into the host cell line, such as Chinese hamster ovary (CHO) cells. In the case of CHO cells, DHFR-deficient strains are selected for their ability to grow in the presence of methotrexate, which is a potent inhibitor of DHFR activity.
DHFR-deficient strains are advantageous for stable transfection because they require exogenous sources of nucleotides for growth and proliferation, which can be manipulated to select for cells that have integrated the foreign DNA into their genome. DHFR-deficient strains can be grown in media containing gradually increasing concentrations of methotrexate, which selects for cells that have multiple copies of the DHFR gene or the foreign DNA integrated into their genome.
DHFR-deficient strains are widely used in the production of recombinant proteins, particularly in the biopharmaceutical industry. The ability to select for cells that have integrated high copies of the foreign DNA can result in high levels of recombinant protein expression.