<p>For testing our prime editing approach, we needed an easy-to-handle cell line with a measurable high expression of CFTR and the CFTR F508del mutation. When talking to Mattijs Bulcaen from the Laboratory of Molecular Virology and Gene Therapy at KU Leuven, he recommended to use HEK293T cell lines overexpressing CFTR they had used. HEK293 cells are a very common immortalized human cell line derived from the kidneys of a female embryo. They are particularly suited to research due to their convenient handling and transfection properties. Basic HEK293 cells were provided to us by the Cellular and Molecular Biotechnology working group at Bielefeld University led by Prof. Dr. Kristian Müller, who is also one of the Principal Investigators of our team. HEK293T cells express an additional tsA1609 allele of the SV40 large T-antigen, allowing for replication of vectors containing the SV40 origin of replication[5]. Besides the native CFTR gene, which is not expressed in HEK cells, the HEK293T cell lines used in Leuven carry another copy of the gene embedded in an expression cassette. The cassette includes a CMV promoter, which is a standard promoter used for gene overexpression in human cells derived from the human Cytomegalovirus[6], as well as a puromycin resistance co-expressed with the CFTR allowing for continuous selection of CFTR expressing cells. The whole construct was stably inserted into the genome using lentiviral transduction[7][8]. </p>
<figure>
<imgsrc="https://static.igem.wiki/teams/5247/photos/for-wiki-texts/meth-used-cells/mikroskopie-hek293t.png"alt="Phase contrast image of HEK293T at 20x magnification"/>
<figcaption><b>Figure 3.</b>Phase contrast image of HEK293T at 20x magnification</figcaption>
<figcaption><b>Figure 3.</b>Phase contrast image of HEK293T at 20x magnification.</figcaption>
