CRISPR/Cas: techniek om DNA-fouten te repareren

CRISPR/Cas gene editing makes it much easier to make targeted changes in the DNA of human cells than other forms of gene therapy. This revolutionary technology offers spectacular opportunities to study gene functions; the clinical consequences of gene variations in patients can be determined much faster. The efficacy and accuracy of CRISPR/Cas is so impressive that a breakthrough to therapeutic applications is approaching fast. CRISPR/Cas is already being used in immunotherapy against cancer, and trials for monogenetic blood disorders, such as beta-thalassemia, have been scheduled. However, broad clinical implementation of CRISPR/Cas is not feasible yet, due to off-target DNA changes that may occur as a by-product. Particularly in case of in-vivo applications there are therapeutic challenges. For gene editing in human embryos, technical shortcomings and open ethical issues need to be addressed. Gene-editing therapy for serious disorders with transplantable cell types, and therefore the option of verification of "CRISPRed" cells, is seen as a possible first application within the regular healthcare system

HideRNAs protect against CRISPR-Cas9 re-cutting after successful single base-pair gene editing

Promiscuous activity of the Streptococcus pyogenes DNA nuclease CRISPR-Cas9 can result in destruction of a successfully modified sequence obtained by templated repair of a Cas9-induced DNA double-strand break. To avoid re-cutting, additional target-site-disruptions (TSDs) are often introduced on top of the desired base-pair alteration in order to suppress target recognition. These TSDs may lower the efficiency of introducing the intended mutation and can cause unexpected phenotypes. Alternatively, successfully edited sites can be protected against Cas9 re-cutting activity. This method exploits the finding that Cas9 complexed to trimmed guideRNAs can still tightly bind specific genomic sequences but lacks nuclease activity. We show here that the presence of a guideRNA plus a trimmed guideRNA that matches the successfully mutated sequence, which we call hideRNA, can enhance the recovery of precise single base-pair substitution events tenfold. The benefit of hideRNAs in generating a single point mutation was demonstrated in cell lines using plasmid-based delivery of CRISPR-Cas9 components and in mouse zygotes injected with Cas9/guideRNA plus Cas9/hideRNA ribonucleoprotein complexes. However, hRNA protection sometimes failed, which likely reflects an unfavorable affinity of hRNA/Cas9 versus gRNA/Cas9 for the DNA target site. HideRNAs can easily be implemented into current gene editing protocols and facilitate the recovery of single base-pair substitution. As such, hideRNAs are of great value in gene editing experiments demanding high accuracy

Evaluation of a Novel Oncolytic Adenovirus Silencing <i>SYVN1</i>

Oncolytic adenoviruses are promising new anticancer agents. To realize their full anticancer potential, they are being engineered to express therapeutic payloads. Tumor suppressor p53 function contributes to oncolytic adenovirus activity. Many cancer cells carry an intact TP53 gene but express p53 inhibitors that compromise p53 function. Therefore, we hypothesized that oncolytic adenoviruses could be made more effective by suppressing p53 inhibitors in selected cancer cells. To investigate this concept, we attenuated the expression of the established p53 inhibitor synoviolin (SYVN1) in A549 lung cancer cells by RNA interference. Silencing SYVN1 inhibited p53 degradation, thereby increasing p53 activity, and promoted adenovirus-induced A549 cell death. Based on these observations, we constructed a new oncolytic adenovirus that expresses a short hairpin RNA against SYVN1. This virus killed A549 cells more effectively in vitro and inhibited A549 xenograft tumor growth in vivo. Surprisingly, increased susceptibility to adenovirus-mediated cell killing by SYVN1 silencing was also observed in A549 TP53 knockout cells. Hence, while the mechanism of SYVN1-mediated inhibition of adenovirus replication is not fully understood, our results clearly show that RNA interference technology can be exploited to design more potent oncolytic adenoviruses

Continuous in vivo infusion of interferon-gamma (IFN-γ) enhances engraftment of syngeneic wild-type cells in Fanca–/– and Fancg–/– mice

Fanconi anemia (FA) is a heterogeneous genetic disorder characterized by bone marrow (BM) failure and cancer susceptibility. Identification of the cDNAs of FA complementation types allows the potential of using gene transfer technology to introduce functional cDNAs as transgenes into autologous stem cells and provide a cure for the BM failure in FA patients. However, strategies to enhance the mobilization, transduction, and engraftment of exogenous stem cells are required to optimize efficacy prior to widespread clinical use. Hypersensitivity of Fancc–/– cells to interferon-gamma (IFN-γ), a nongenotoxic immune-regulatory cytokine, enhances engraftment of syngeneic wild-type (WT) cells in Fancc–/– mice. However, whether this phenotype is of broad relevance in other FA complementation groups is unresolved. Here we show that primitive and mature myeloid progenitors in Fanca–/– and Fancg–/– mice are hypersensitive to IFN-γ and that in vivo infusion of IFN-γ at clinically relevant concentrations was sufficient to allow consistent long-term engraftment of isogenic WT repopulating stem cells. Given that FANCA, FANCC, and FANCG complementation groups account for more than 90% of all FA patients, these data provide evidence that IFN-γ conditioning may be a useful nongenotoxic strategy for myelopreparation in FA patients

Société d'histoire du Droit et des Institutions des Pays Flamands, Picards et Wallons. Journées Internationales d'Arras (31 mai - 3 juin 1984)

Humbert M., Godding Philippe, Van de Wouw Hans, Guignet Philippe, Van de Vrugt M., Gressier J., Merck André, Kalifa Simon, Waelkens M.L., Van Hoek J.B.M., Platelle Henri, Roelofsen C.-G., Douxchamps-Lefèvre Cécile, Moorman van Kappen O., Bongert Yvonne. Société d'histoire du Droit et des Institutions des Pays Flamands, Picards et Wallons. Journées Internationales d'Arras (31 mai - 3 juin 1984). In: Revue du Nord, tome 67, n°264, Janvier-mars 1985. pp. 275-290

Société d'histoire du Droit et des Institutions des Pays Flamands, Picards et Wallons. Journées Internationales d'Arras (31 mai - 3 juin 1984)

Humbert M., Godding Philippe, Van de Wouw Hans, Guignet Philippe, Van de Vrugt M., Gressier J., Merck André, Kalifa Simon, Waelkens M.L., Van Hoek J.B.M., Platelle Henri, Roelofsen C.-G., Douxchamps-Lefèvre Cécile, Moorman van Kappen O., Bongert Yvonne. Société d'histoire du Droit et des Institutions des Pays Flamands, Picards et Wallons. Journées Internationales d'Arras (31 mai - 3 juin 1984). In: Revue du Nord, tome 67, n°264, Janvier-mars 1985. pp. 275-290