Gene (or genome) editing refers to various technologies that are used to alter genetic material. This technology is used as a new means to treat diseases including genetic disorders. Fanconi anemia is an inherited disease that affects bone marrow leading to decreased production of all blood cell types. In general, editing of CD34+ (hematopoietic) stem cells have proven more difficult than for fibroblasts or embryonic stem cells. Some advances have been achieved in this regard; however, the efficiency of gene editing for CD34+ stem cells remains less than that possible with lentiviral vectors.
A group of scientists used a gene-editing approach for the treatment of the bone marrow failure that occurs in patients with Fanconi anemia. They treated FA group A (FA-A) lymphoblastic cell lines (LCLs) with zinc finger nucleases (ZFNs) and the PGK-FANCA/PuroR integrase-defective lentiviral vector (IDLV). There was a decrease in the hypersensitivity of the FA cells to mitomycin C (MMC), which causes FA cell death. This demonstrated the gene editing of the LCLs and correction of the hypersensitivity.
Cord blood CD34+ stem cells were transduced with the IDLV donor, and electroporated with the AAVS1-ZFN mRNAs. Targeting of the AAVS1 safe harbor locus with transgenes results in stable gene expression. Flow cytometry analyses showed similar EGFP+ cell values for CD34+ stem cells treated with donor and ZFNs. When cells were only treated with PGK-EGFP (a non-therapeutic donor), virtually no EGFP cells were observed.
Gene editing efficacy was then examined using a therapeutic (EGFP/PGK-FANCA) donor. No EGFP-positive cells were detected at 10 days after the culture of edited cells. However, these edited cells still showed the correction of their hypersensitivity to MMC. Peripheral blood CD34+ cells from patients with FA-A were also edited using the EGFP/PGK-FANCA donor and AAVS1 ZFNs. The cells were plated in the presence of MMC. The increased survival rate in the presence of MMC for the edited CD34+ stem cells indicates phenotypic correction of FA-A CD34+ cells by gene editing. These data suggest that gene editing could be applicable as a feasible therapeutic approach to FA.
Diez B, e. (2017). Therapeutic gene editing in CD34+ hematopoietic progenitors from Fanconi anemia patients. - PubMed - NCBI. Ncbi.nlm.nih.gov. Retrieved 1 November 2017, from https://www.ncbi.nlm.nih.gov/pubmed/28899930