In this week's Science, a team of Japanese scientists reports a modified version of the genome-editing technology CRISPR that can perform DNA substitutions without cleaving DNA. CRISPR functions by inducing double-strand DNA breaks followed by DNA repair. However, this process can result in unwanted genetic insertions and deletions in genomic DNA. By fusing a sea lamprey enzyme called activation-induced cytidine deaminase (AID) — which can create a mutation on a single strand of DNA — to a mutated version of CRISPR, the researchers were able to use the system to edit DNA without cutting it, resulting in few off-target effects than with traditional CRISPR systems.
Also in Science, two researchers from Harvard University and Brown University discuss the implications of legislation that banned funding for germline editing. Specifically, the law prevents funds being using by the US Food and Drug Administration to review a drug or biologic in which a human embryo is created or modified to include a heritable genetic modification. The authors note that this law prevents gene editing that could be used to treat rare disorders, and suggest workarounds that could limit genetic modifications to non-heritable ones. They also argue that as a result of the law, the US may lose its scientific lead in this area to other nations.