Hi everyone :) 

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) are repeating areas of the DNA, which defend the body from foreign DNA from a virus or a plasmid through the CRISPR/Cas-System. Normally, CRISPR/Cas9 is used as an genome editing tool, but recent rearches from Feng Zhang and his team, used another method, explained down below.

short illustration of Crispr/Cas9

RNA Editing for A to I Replacement (REPAIR). 

Researches now found an enzyme of the bakteria called "prevotella". It is an RNA-scissor called Cas13 ( we can remember, Cas9: DNA and Cas13: RNA).  About a month ago, it was discovered, Cas13a is able to target and cleave specific strands of RNA. The recently discovered method is based on modified Cas13b, which is able to bind RNA, but don't cut it. Then a second enzyme ( a protein called "ADAR")  is getting attached, which coverts an adenosin nucleotide into an inosine one.  At the protein synthesis, the idenosin get's read as an guanine nucleotide. Like the Cas9, Cas13 also needs a guide RNA, that directs the Cas enzyme to the complementary target (DNA;RNA).

grafic of the process described above

Applications for REPAIR

Life-threatening diseases like hemophilia, as well as a heart condition called hypertrophic cardiomyopathy could be treated . It could also be used as a short-term therapy during wound healing and inflammation, because it can modulate the activity of RNA that produces certain proteins involved in these processes. At the moment, the system has to get optimised, because it's accuracy has to get as high as possible, as it produces off-target cuts right now.

Advantages 

Proteins play a major role in diseases, so editing RNA can help to cure them. Also, compared to DNA, RNA has the advantage to non-permanent, If you make a mistake in editing it, it will be degraded within a day, but DNA is permanent. If you edit it wrong, mutations can be the result e.g. cancer. Another point is, DNA is given to following generations through heredity, but the RNA is only existing in the body in which it was edited. If your body's cells are able to keep CRISPR in them for a longer period of time, you can receive permanent help with fighting your disease. The accuracy lies between 20-40% and in some cases even 90%, so if it can get increasead, it could work better than Cas9, because for it, there doesn't have to be a PAM sequence, without Cas9 can't work.

Feng Zhang, winner of the 2017 Albany Medical Center Prize in Medicine and Biomedical Research

Conclusion

Every new information from researchers working on genetic engeenering, gives us more tools to help curing diseases, which is a blessing for everyone who suffers from one. The fact that it isn't the DNA that get's changed, but the RNA, also makes it more ethically acceptable. Even if this is right, we should always consider the fact, the more we know about genetic engeneering techniques, the more un-ethical froms of use could appear, which could lead to discussions, of how far this genome editing should go.

Source

Text

https://cen.acs.org/articles/95/i43/CRISPR-edit-RNA.html

https://en.wikipedia.org/wiki/CRISPR

https://www.livescience.com/58790-crispr-explained.html

http://www.spektrum.de/news/groesste-probleme-von-crispr-cas9-geloest/1514381  (translated)

Pictures

https://futurism.com/wp-content/uploads/2016/09/g-CRISPR_web.jpg

https://cen.acs.org/content/cen/articles/95/i43/CRISPR-edit-RNA/_jcr_content/articlebody/subpar/articlemedia_0.img.png/1509050238601.png

http://news.mit.edu/sites/mit.edu.newsoffice/files/styles/news_article_image_top_slideshow/public/images/2017/MIT-Feng-Zhang_0.jpg?itok=WbH-Hmbh