The haplolethal genewupAof Drosophila exhibits potential as a target for an X-poisoning gene drive

Abstract

AbstractA synthetic gene drive that targets haplolethal genes on the X-chromosome can skew the sex ratio towards males. Like an ‘X-shredder’ it does not involve ‘homing’ and that has advantages including the reduction of gene drive resistance allele formation. We examine this ‘X-poisoning’ strategy by targeting four of the 11 known X-linked haplolethal/haplosterile genes ofDrosophila melanogasterwith CRISPR/Cas9. We find that targeting thewupAgene during spermatogenesis skews the sex ratio so fewer than 14% of progeny are daughters. That is unless we cross the mutagenic males to X^XY female flies that bear attached-X chromosomes, which reverses the inheritance of the poisoned X chromosome so that sons inherit it from their father; in which case only 2% of the progeny are sons. These sex ratio biases suggests that most of the CRISPR/Cas9 mutants we induced in thewupAgene are haplolethal but some are recessive lethal. The males generatingwupAmutants do not suffer from reduced fertility rather the haplolethal mutants arrest development in the late stages of embryogenesis well after fertilized eggs have been laid. This provides a distinct advantage over genetic manipulation strategies involving sterility which can be countered by the remating of females. We also find thatwupAmutants that destroy the nuclear localization signal of shorter isoforms are not haplolethal as long as the open reading frame remains intact. LikeD. melanogaster wupAorthologs ofD. suzukiiandAnophelesmosquitos are found on X chromosomes makingwupAa viable X-poisoning target in multiple species.