Cleave and Rescue, a novel selfish genetic element and general strategy for gene drive

Abstract

There is great interest in being able to spread beneficial traits throughout wild populations in ways that are self-sustaining. Here, we describe a chromosomal selfish genetic element,CleaveR[Cleave and Rescue (ClvR)], able to achieve this goal.ClvRcomprises two linked chromosomal components. One, germline-expressed Cas9 and guide RNAs (gRNAs)—the Cleaver—cleaves and thereby disrupts endogenous copies of a gene whose product is essential. The other, a recoded version of the essential gene resistant to cleavage and gene conversion with cleaved copies—the Rescue—provides essential gene function.ClvRenhances its transmission, and that of linked genes, by creating conditions in which progeny lackingClvRdie because they have no functional copies of the essential gene. In contrast, those who inheritClvRsurvive, resulting in an increase inClvRfrequency.ClvRis predicted to spread to fixation under diverse conditions. To test these predictions, we generated aClvRelement inDrosophila melanogaster.ClvRtkois located on chromosome 3 and uses Cas9 and four gRNAs to disruptmelanogaster technical knockout(tko), an X-linked essential gene. Rescue activity is provided bytkofromDrosophila virilis.ClvRtkoresults in germline and maternal carryover-dependent inactivation ofmelanogaster tko(>99% per generation); lethality caused by this loss is rescued by thevirilistransgene;ClvRtkoactivities are robust to genetic diversity in strains from five continents; and uncleavable but functionalmelanogaster tkoalleles were not observed. Finally,ClvRtkospreads to transgene fixation. The simplicity ofClvRsuggests it may be useful for altering populations in diverse species.