Developed by researchers from the Wyss Institute at Harvard University and Harvard Medical School, Massachusetts, 'retron library recombineering' (RLR) is able to make edits at a large scale without having to cut existing DNA. It can also 'barcode' the changes to allow researchers to easily confirm where the edits were made in multiple cells at once.
'RLR is a simpler, more flexible gene-editing tool... which eliminates the toxicity often observed with CRISPR and improves researchers' ability to explore mutations at the genome level,' said co-first author Dr Max Schubert.
Retrons are bacterial DNA sequences that generate pieces of single-stranded DNA (ssDNA), and like CRISPR they are part of a bacterial defence mechanism against viruses.
Where CRISPR/Cas9 works by cutting existing DNA – and risks making edits in the wrong place – RLR introduces the edits to cells as they replicate. The retron produces a piece of ssDNA which – in the presence of an enzyme called single-stranded annealing protein (SSAP) – will be integrated into the DNA of a cell as it divides, so both daughter cells will contain the new sequence.
'Retrons should give us the ability to produce ssDNA within the cells we want to edit rather than trying to force them into the cell from the outside, and without damaging the native DNA, which were both very compelling qualities,' said co-first author Dr Daniel Goodman.
Currently RLR genome editing has only been demonstrated in bacteria, but senior author Professor George Church said 'This work helps us establish a road map toward using RLR in other genetic systems, which opens up many exciting possibilities for future genetic research.'