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Expanding the target range of crispr/cas systems

US researchers have created genome editing technology that allows for variations in target DNA but retains local specificity.

This could help realise the potential of CRISPR/Cas-based gene therapy and pathogen diagnosis, it is claimed.

Scientists programme CRISPR/Cas systems to cut precise DNA sequences to avoid snipping the wrong sequence or enabling unwanted mutations.

But that specificity makes it hard for the systems to identify common variants of a given DNA sequence, which has partly limited their application.

Basil Hubbard, principal investigator, said: “A lot of work has gone into making CRISPR/Cas systems more specific. But for certain applications there is also the need for more flexible targeting in these systems, and our study shows a possible way to meet that need.”

CRISPR-Cas systems contain two main molecules: a CRISPR guide-RNA, which contains nucleotide base pairs that guide the system to a complementary stretch of DNA; and a Cas enzyme that cuts the DNA to allow for manipulation of other genetic code.

The new approach works by substituting universal bases for one or more of the four bases that make up CRISPR guide-RNAs.

“It functions like an asterisk or wildcard in a digital search, in areas where we expect variation or don’t have data,” said Hubbard.

“With therapeutics, we can target common variants of the same gene from person to person, such as single nucleotide polymorphisms.

For diagnostics, we can detect multiple evolved variants of the same pathogen.”

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