Converting endogenous genes of the malaria mosquito into simple non-autonomous gene drives for population replacement.

Astrid Hoermann,Tibebu Habtewold,George K Christophides,Paolo Capriotti,Giuseppe Del Corsano,Sofia Tapanelli,Nikolai Windbichler,Ellen Kg Masters

doi:10.7554/elife.58791

Abstract

Gene drives for mosquito population replacement are promising tools for malaria control. However, there is currently no clear pathway for safely testing such tools in endemic countries. The lack of well-characterized promoters for infection-relevant tissues and regulatory hurdles are further obstacles for their design and use. Here we explore how minimal genetic modifications of endogenous mosquito genes can convert them directly into non-autonomous gene drives without disrupting their expression. We co-opted the native regulatory sequences of three midgut-specific loci of the malaria vector Anopheles gambiae to host a prototypical antimalarial molecule and guide-RNAs encoded within artificial introns that support efficient gene drive. We assess the propensity of these modifications to interfere with the development of Plasmodium falciparum and their effect on fitness. Because of their inherent simplicity and passive mode of drive such traits could form part of an acceptable testing pathway of gene drives for malaria eradication.

Highlights

After more than a decade of sustained success in the fight against malaria, data from 2015 onwards suggests that no significant progress in reducing global malaria cases has been achieved (World malaria report, 2019)
Proof-of-principle laboratory experiments of CRISPR/Cas9-based gene drives for population suppression, which aims at the elimination of the target population (Kyrou et al, 2018; Hammond et al, 2016), as well as population replacement (Gantz et al, 2015; Pham et al, 2019; Adolfi et al, 2020), which aims to spread an anti-malarial trait within a vector population, suggest that these strategies could be deployed to reduce malaria transmission in the field
To accommodate the guide-module required for subsequent gene drive and a marker-module required for monitoring transgenesis, we suggested to insert an intron into the effector gene

Summary

Introduction

After more than a decade of sustained success in the fight against malaria, data from 2015 onwards suggests that no significant progress in reducing global malaria cases has been achieved (World malaria report, 2019). Synthetic gene drives spreading by super-Mendelian inheritance within vector populations have been proposed as an area-wide genetic strategy for the control of malaria (Raban et al, 2020). They mimic the mechanism of proliferation of a class of naturally occurring selfish genes found in protists, mitochondria, and chloroplasts called homing endonucleases and could be deployed to modify the genetic makeup of disease vector populations (Burt, 2003; Windbichler et al, 2011). The success of population replacement in particular hinges on the availability of molecules that can efficiently block Plasmodium development within the mosquito vector, as well as ways to express such elements.

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Conclusion