Genome editing
Genome editing [1] is a type of genetic engineering.[2]
DNA is inserted, replaced, or removed from a genome using artificially engineered nucleases, or "molecular scissors". The nucleases make specific double-strand breaks (DSBs) at desired places in the genome. The cell’s own mechanisms repair the induced break(s) by natural processes.
At present there are four families of engineered nucleases being used.[3][4][5][6]
To understand the function of a gene or a protein one interferes with it in a sequence-specific way, and watches its effects on the organism. However, in some organisms it is difficult or impossible to do site-specific mutation. Therefore more indirect methods have to be used. Examples are:
- Silencing the gene of interest by short RNA interference (siRNA).[7] Yet gene disruption by siRNA can be variable and incomplete.
- Genome editing with nucleases such as ZFN. This is different from siRNA. The engineered nuclease (the enzyme which cuts the DNA) is able to modify DNA-binding. This way it can (in principle) cut any targeted position in the genome, and introduce change in sequences for genes which cannot be specifically targeted by conventional RNAi.
Genome editing was chosen by Nature Methods as the 2011 Method of the Year.[8] The technique is already being used, but implanting modified embryos into a woman is not yet permitted.[9][10]
The CRISPR/Cas9 method
In 2017 this system was announced as one of the biggest scientific achievements of the year. Cas9 is an enzyme which, with a guide RNA, can put a new sequence of DNA into a genome. Sir John Skehel[11] said "That might allow you to knock out a particular gene in a cell, or introduce a particular gene, or correct a particular mutated gene that you want to work better".[12]
Genome Editing Media
The different generations of nucleases used for genome editing and the DNA repair pathways used to modify target DNA.
dsDNA-break repair pathways and genome editing using CRISPR-Cas nucleases
General overview of the TALEN process
Synthetic DNA is repeatedly introduced at multiple targeted areas of the chromosome and/or loci and then is replicated producing cells with/without mutations.
.png)
References
- ↑ sometimes "genome editing with engineered nucleases" (GEEN)
- ↑ Carey, Nessa 2019. Hacking the code of life: how gene editing will rewrite our futures. Icon books, London. ISBN 978-1-78578-625-9
- ↑ The four types are: zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), the CRISPR/Cas system, and re-engineered homing endonucleases.
- ↑ Esvelt, KM.; Wang, HH. (2013). "Genome-scale engineering for systems and synthetic biology". Mol Syst Biol. 9 (1): 641. doi:10.1038/msb.2012.66. PMC 3564264. PMID 23340847.
- ↑ Tan W.S.; et al. (2012). "Precision editing of large animal genomes". Adv Genet. Advances in Genetics. 80: 37–97. doi:10.1016/B978-0-12-404742-6.00002-8. ISBN 9780124047426. PMC 3683964. PMID 23084873.
- ↑ Puchta, H.; Fauser, F. (2013). "Gene targeting in plants: 25 years later". Int. J. Dev. Biol. 57 (6–7–8): 629–637. doi:10.1387/ijdb.130194hp. PMID 24166445.
- ↑ Fire A. et al 1998. Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans. Nature 391 (6669), 806-811 (1998).
- ↑ Method of the Year 2011. Nat Meth 9 (1), 1-1.
- ↑ Gallagher, James 2015. Dawn of gene-editing medicine? BBC News Health. [1]
- ↑ Gallagher, James 2016. Scientists get 'gene editing' go-ahead. BBC News Health. [2]
- ↑ a British virologist and emeritus scientist at the Francis Crick Institute in London.
- ↑ The biggest scientific developments of 2017, according to two scientists at the Royal Society of London. [3]