The gene-editing tool known as CRISPR-Cas12a or Cpf1 has been viewed as a better choice than other Cas editing tools because it was believed to be more precise and less prone to making off-target cuts in DNA.
But a new paper shows that Cpf1 is not as clean or specific as touted. The researchers employed in vitro assays using a vast collection of synthesized DNA molecules containing variations on the editing site sequence. They found that Cpf1 was highly prone to making off-target single-strand cuts, or “nicks”, in the double-stranded DNA molecules. Off-target double-strand DNA cuts were also found, albeit at a lower frequency than the single-strand nicks.
The findings showed that the Cpf1 tool made nicks at DNA locations containing up to four DNA base unit mismatches compared to the intended target site sequence. That means it damaged a large number of markedly off-target and clearly mismatched locations.
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