In Science this week, an international group of researchers discusses recent discoveries about the molecular mechanisms of CRISPR adaptation — the process by which prokaryotes update this genome editing-based immune defense system to detect new invading mobile genetic elements. They highlight efforts to understand how Cas proteins incorporate spacers, recognize the CRISPR locus, and integrate within the system, as well as touch on questions that remain unanswered such as why many CRISPR-Cas systems have more than one CRISPR array that is used by a single set of Cas proteins.
And in Science Advances, Harvard University investigators publish a study suggesting a method for designing CRISPR-based gene drives to make them more stable. Using various mathematical approaches, they show that the emergence of drive-resistant alleles would be a major challenge based on current approaches, and propose a new CRISPR design that selects against resistant alleles in order to improve evolutionary stability. Based on their modeling, the proposed drive could reach 99 percent frequency in 10 generations to 20 generations, and remain at that level for at least 200 generations by introducing it into just 1 percent of a wild population. They caution, however, that this approach still needs to be confirmed experimentally.