A CRISPR endonuclease gene drive reveals distinct mechanisms of inheritance bias

Abstract

CRISPR/Cas gene drives can bias transgene inheritance through different mechanisms. Homing drives are designed to replace a wild-type allele with a copy of a drive element on the homologous chromosome. In Aedes aegypti, the sex-determining locus is closely linked to the white gene, which was previously used as a target for a homing drive element (wGDe). Here, through an analysis using this linkage we show that in males inheritance bias of wGDe did not occur by homing, rather through increased propagation of the donor drive element. We test the same wGDe drive element with transgenes expressing Cas9 with germline regulatory elements sds3, bgcn, and nup50. We only find inheritance bias through homing, even with the identical nup50-Cas9 transgene. We propose that DNA repair outcomes may be more context dependent than anticipated and that other previously reported homing drives may, in fact, bias their inheritance through other mechanisms.

CRISPR-based gene drives generate super-Mendelian inheritance in the disease vector Culex quinquefasciatus.

“…Similar to what we observed at the white locus, previous studies in Ae. aegypti 25 also showed that the biased inheritance observed has both a meiotic drive and a homing component. Interestingly, while the vast majority of components tested in that previous Ae.…”

“…It could have negatively impacted the homing-based biased inheritance of the white-gRNA6 construct, similar to previous observations in Ae. aegypti 24,25 . We employed a marked-chromosome strategy to identify homing events at the white locus that con rmed this is occurring and that an additional contributing effect also enhances the biased inheritance, likely a meiotic drive component destroying some of the receiver chromosomes.…”

“…In the case of the kmo-gRNA element, mean homing levels observed (c.10% for females and c.18% for males) were within the error ranges estimated for some previously reported split-drive systems in Ae. aegypti 24,25 , with signi cant levels of homing (e.g. exu-Cas9; U6C-gRNA / U6D-gRNA females = 12% / 6%, trunk-Cas9; U6b-gRNA females = 10%).…”

“…While homing drive technology has been demonstrated in the yellow fever mosquito Aedes aegypti as well as various malarial mosquitoes (Anopheles gambiae, Anopheles stephensi) 14,[20][21][22][23][24][25] , development of gene drives in Culex mosquitoes has not yet taken place. Having recently developed CRISPR tools necessary for site-speci c integration of transgenes into the Cx.…”

Engineered Antiviral Sensor Targets Infected Mosquitoes

“…Recently, molecular tools, such as broadly neutralizing antibodies 5 and encoded miRNA arrays 6,7 have been demonstrated to mitigate DENV and ZIKV transmission by mosquitoes. Additionally, CRISPR-Cas technologies have been engineered to control mosquito populations using the precision-guided Sterile Insect Technique (pgSIT) 8 and confinable gene drives 9,10 . These molecular tools present great promise as vector control strategies capable of reducing viral spread by mosquitoes.…”