This month, a new leap forward in gene editing has been published in Nature under the title ‘Search-and-replace genome editing without double-strand breaks or donor DNA’. DOI: 10.1038/s41586-019-1711-4. Let’s take a look at prime editing to get a clear overview.

Gene knock-out, which is gene editing leading to loss of function, just requires delivering into cells the 2 CRISPR system actors: the CAS9 endonuclease and the specific guide RNA to target the gene of interest. Thus, simple transfection of CleanCap CAS9 mRNA and gRNA followed by cell isolation with the smart aliquotor is a convenient and robust method. Howevery, what can you do if the cells are hard-to-transfect?

Sequence engineering and chemical modification of CAS9 mRNA

For transgenesis and therapeutic perspectives, vector-free delivery of the CAS9 for gene editing is highly preferable. It avoids the risk of hitting the genome due to the vector integration. Directly using CAS9 mRNA is a top option. Furthermore, as a new promising class of therapeutic biologics, messenger RNA are the subject of numerous studies. This year, Matthew Porteus’s and Trilink’s teams revealed key and practical results at the ASGC with a poster you can download below. Notably, there is a large screen of the mRNA CAS9 modifications based on the indel formation. This interesting comparison includes also CAS9 RNP and reveals the high performance of the CleanCap U-depleted 5-moU CAS9 mRNA. We can also note that for the CleanCap CAS9 mRNA HPLC purification is not required. “Maximizing Translation of Cas9 mRNA Therapeutics by Sequence Engineering and Chemical Modification” Download your copy of the poster here.  

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CRISPR/Cas9 is relatively simple to implement, as the researcher fully controls the experimental design of the tools, from the sgRNA sequence to the Cas9 protein.