Gene drive that results in addiction to a temperature sensitive version of an essential gene triggers population collapse in Drosophila

Abstract

One strategy for population suppression seeks to use gene drive to spread genes that confer conditional lethality or sterility, providing a way of combining population modification with suppression. Stimuli of potential interest could be introduced by humans, such as an otherwise benign virus or chemical, or occur naturally on a seasonal basis, such as a change in temperature. Cleave and Rescue (ClvR) selfish genetic elements use Cas9 and gRNAs to disrupt endogenous versions of an essential gene, while also including a Rescue version of the essential gene resistant to disruption. ClvR spreads by creating loss-of-function alleles of the essential gene that select against those lacking it, resulting in populations in which the Rescue provides the only source of essential gene function. In consequence, if function of the Rescue, a kind of Trojan horse now omnipresent in a population, is condition-dependent, so too will be the survival of that population. To test this idea we created a ClvR in Drosophila in which Rescue activity of an essential gene, dribble, requires splicing of a temperature-sensitive intein (TS-ClvRdbe). This element spreads to transgene fixation at 23° C, but when populations now dependent on TS-ClvRdbe are shifted to 29° C death and sterility result in a rapid population crash. These results show that conditional population elimination can be achieved. A similar logic, in which Rescue activity is conditional, could also be used in HEG-based drive, and to bring about suppression and/or killing of specific individuals in response to other stimuli.

Allele Sails: launching traits and fates into wild populations with DNA sequence modifiers

“…CRISPR nucleases such as Cas9 can cleave and create loss of function (LOF) alleles (especially when using multiple gRNAs) in the Drosophila germline or the plant Arabidopsis thaliana at frequencies near 100% 17,[27][28][29][30][31][32][33][34] . While base and prime editors also have significant levels of editing activity in Drosophila, they are not 100%; instead closer to 36% for a prime editor 35 , and >90% for a base editor 23 .…”

“…In cases where a base or prime editor is used to generate small indels or substitutions it will be important to understand the frequency with which such resistant alleles might arise, either due to bystander sequence editing activity or existing sequence polymorphisms) and their consequences for the intended population effect. In other cases, in which creating LOF alleles is the goal, available evidence suggests it may be possible to prevent resistant allele appearance through targeting of multiple sites in the target gene(s) using gRNA multiplexing 17,[27][28][29][30][31][32][33][34] .…”

Incorporating ecology into gene drive modelling

“…Environmental heterogeneity can also be used to control gene drives through temporal rather than spatial mechanisms. For example, heat-sensitive gene drive designs can generate a 'temporal barrier', which could be delayed or reversed with seasonal temperature changes (Oberhofer et al, 2021). Natural endosymbiont systems F I G U R E 4 Model of gene drive dynamics incorporating environmental variation.…”

Assessment of distant-site rescue elements for CRISPR toxin-antidote gene drives

“…TARE drives could also support confined suppression as part of a tethered drive system ( Dhole et al, 2019 ; Metzloff et al, 2022 ) if sufficiently efficient homing suppression drives can be constructed or even alone if an specialized cargo could be developed ( Oberhofer et al, 2021a ). Such developments would be non-trivial, so a potentially valuable option is to use a CRISPR toxin-antidote drive targeting a haplolethal gene (in which two copies are required for survival).…”