Credit: Yuyu Niu et al.
Although monkeys can be useful as models of human disease, precisely modifying their genes has proven difficult.
Now, investigators say they’ve achieved precise gene modification in monkeys using the CRISPR/Cas9 system.
“Our study shows that the CRISPR/Cas9 system enables simultaneous disruption of 2 target genes in 1 step, without producing off-target mutations,” said Jiahao Sha, PhD, of Nanjing Medical University in Nanjing, China.
“Considering that many human diseases are caused by genetic abnormalities, targeted genetic modification in monkeys is invaluable for the generation of human disease models.”
Dr Sha and his colleagues described this research in Cell.
The CRISPR/Cas9 system is a gene-editing tool capable of targeting specific DNA sequences in the genome. Cas9 proteins, which are directed by single-guide RNAs to specific sites in the genome, generate mutations by introducing double-stranded DNA breaks.
Until now, the CRISPR/Cas9 system and other targeted gene-editing techniques were successfully applied to mammals such as mice and rats, but not to primates.
Dr Sha and his colleagues injected messenger RNA encoding Cas9, as well as single-guide RNAs designed to target 3 specific genes, into one-cell-stage embryos of cynomolgus monkeys.
After sequencing DNA from 15 embryos, the team found that 8 of these embryos showed evidence of simultaneous mutations in 2 of the target genes.
The researchers then transferred genetically modified embryos into surrogate females, one of which gave birth to a set of twins. By sequencing the twins’ DNA, the team found mutations in 2 of the target genes.
Moreover, the CRISPR/Cas9 system did not produce mutations at genomic sites that were not targeted. And this suggests the tool will not cause undesirable effects when applied to monkeys.
“With the precise genomic targeting of the CRISPR/Cas9 system, we expect that many disease models will be generated in monkeys,” said Weizhi Ji, PhD, of the Yunnan Key Laboratory of Primate Biomedical Research in Kunming, China.
“[This] will significantly advance the development of therapeutic strategies in biomedical research.”
