Page URL: https://www.bionews.org.uk/page_154403

TALENs outperforms CRISPR/Cas9 in editing compact DNA

1 February 2021
Appeared in BioNews 1081

Researchers comparing different methods of genome editing have found that in some contexts, TALENs work more efficiently than CRISPR/Cas9.

Within the cell, DNA is packaged into a structure known as chromatin, which can be divided into euchromatin and heterochromatin. The former consists of accessible 'open' DNA, and the latter of compact 'closed' DNA. A research team led by Professor Huimin Zhao from the University of Illinois, compared how two different approaches to genome editing –  CRISPR/Cas9 and TALENs – deal with editing DNA in euchromatin and heterochromatin. The study, found that TALENs-mediated genome editing is up to five times more efficient than CRISPR/Cas9 mediated genome editing, when it comes to modifying heterochromatin. The reverse was true for euchromatin. 

'We found that CRISPR works better in the less-tightly wound regions of the genome, but TALENs can access those genes in the heterochromatin region better than CRISPR,' said Professor Zhao. 'We also saw that TALENs can have higher editing efficiency than CRISPR. It can cut the DNA and then make changes more efficiently than CRISPR.'

CRISPR/Cas9 and TALENs both act as 'molecular scissors', cutting a target DNA region, which can then be repaired by the cell, potentially incorporating desired DNA modifications. The two methods differ in the way that they find, and cut, their target DNA. In the study, the researchers monitored how the two different methods search for and find their target site using single molecule fluorescence microscopy, and examined how efficient each method was at finding and cutting sites either within euchromatin, or heterochromatin. 

Certain genetic disorders, including Fragile X syndrome, and sickle cell anaemia, are due to defects in heterochromatin regions. In the future, if genome editing becomes mainstream, it will be important to be able to target these regions as well as the genes in euchromatin. Indeed, TALENs, unlike CRISPR/Cas9, have also recently been shown to work on mitochondrial DNA – meaning they could also be used to target genetic disease due to mitochondrial defects (see BioNews 1055).

The study, published in Nature Communications, adds to the evidence that a broader selection of genome editing tools is needed to target all parts of the genome, said Professor Zhao. 

SOURCES & REFERENCES
Genome-editing tool TALEN outperforms CRISPR/Cas9 in tightly packed DNA
Illinois News Bureau |  27 January 2021
Not all genome editing tools are equal: CRISPR vs. TALEN
The Science Advisory Board |  27 January 2021
TALEN genome editing tool more efficient than CRISPR/Cas9 in compact DNA
Fierce Biotech |  28 January 2021
TALEN outperforms Cas9 in editing heterochromatin target sites
Nature Communications |  27 January 2021
RELATED ARTICLES FROM THE BIONEWS ARCHIVE
10 May 2021 - by Rachel Siden 
A new genome editing approach may be faster and simpler than CRISPR...
15 March 2021 - by Dr Yvonne Collins 
Scientific American in partnership with Cellectis, hosted a virtual event to explore genome editing and its use in the clinic. Three pioneers of the field were invited to discuss the early days of genome editing, new technologies and future challenges...
26 October 2020 - by Christina Burke 
Researchers in the US have developed a new CRISPR genome editing approach for making much larger edits to the genome...
12 October 2020 - by Dr Eleanor Lynam 
Professors Emmanuelle Charpentier and Jennifer Doudna have been awarded the Nobel Prize in Chemistry for their development of CRISPR genome editing...
14 September 2020 - by Rowda Dahir 
The safety and efficiency of CRISPR genome editing can be improved by identifying the best genome editing option for a specific application...
13 July 2020 - by Jen Willows 
US scientists have developed a method of making precise edits to mitochondrial DNA within living cells...
HAVE YOUR SAY
to add a Comment.

By posting a comment you agree to abide by the BioNews terms and conditions


Syndicate this story - click here to enquire about using this story.