In Nature this week, scientists from Columbia University describe a new CRISPR-Cas9 genome editing system that does not require double-strand DNA breaks, limiting the potential for off-target effects. Conventional CRISPR-Cas systems involve the insertion of new genetic material into double-strand breaks caused by bacterial proteins such as Cas9 and directed by guide RNA. However, unintended mutations can occur during the cutting and cellular repair processes. The investigators show that, in a CRISPR system from Vibrio cholerae, a protein encoded by the Tn7-like transposon helps to mediate the direct and highly specific integration of the transposon sequence into the genome of Escherichia coli using a guide RNA and the Cascade complex, pointing to a potential new approach for CRISPR genome editing.
And in Nature Plants, a team of European researchers publish target-enriched genome-wide sequencing data from 28 archaeological grape seeds dating to the Iron Age, Roman era, and medieval period, yielding insights into the origins of French grapevine diversity. When compared with domesticated and wild accessions, the investigators find that the archaeological samples are closely related to the western European cultivars used for winemaking today. They identify seeds with the same genetic signatures at different Roman sites, as well as seeds sharing parent-offspring relationships with modern day varieties. Notably, one seed dating to around 1,110 genetically matches Savagnin Blanc, providing evidence for 900 years of uninterrupted cultivation. The Scan has more on this, here.