scholarly journals A genetically encoded anti-CRISPR protein constrains gene drive spread and prevents population suppression

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chrysanthi Taxiarchi ◽  
Andrea Beaghton ◽  
Nayomi Illansinhage Don ◽  
Kyros Kyrou ◽  
Matthew Gribble ◽  
...  
Keyword(s):  
Genetically Modified Organisms ◽  
Reproductive Capacity ◽  
Gene Drive ◽  
Vector Borne Diseases ◽  
Pathogen Effectors ◽  
Germline Expression ◽  
Vector Borne ◽  
Malaria Mosquitoes ◽  
Gene Drives ◽  
Population Suppression

AbstractCRISPR-based gene drives offer promising means to reduce the burden of pests and vector-borne diseases. These techniques consist of releasing genetically modified organisms carrying CRISPR-Cas nucleases designed to bias their inheritance and rapidly propagate desired modifications. Gene drives can be intended to reduce reproductive capacity of harmful insects or spread anti-pathogen effectors through wild populations, even when these confer fitness disadvantages. Technologies capable of halting the spread of gene drives may prove highly valuable in controlling, counteracting, and even reverting their effect on individual organisms as well as entire populations. Here we show engineering and testing of a genetic approach, based on the germline expression of a phage-derived anti-CRISPR protein (AcrIIA4), able to inactivate CRISPR-based gene drives and restore their inheritance to Mendelian rates in the malaria vector Anopheles gambiae. Modeling predictions and cage testing show that a single release of male mosquitoes carrying the AcrIIA4 protein can block the spread of a highly effective suppressive gene drive preventing population collapse of caged malaria mosquitoes.

scholarly journals Resistance is futile: A CRISPR homing gene drive targeting a haplolethal gene

2019 ◽  
Author(s):  
Jackson Champer ◽  
Emily Yang ◽  
Yoo Lim Lee ◽  
Jingxian Liu ◽  
Andrew G. Clark ◽  
...  
Keyword(s):  
Target Gene ◽  
Gene Drive ◽  
End Joining ◽  
Large Cage ◽  
Vector Borne Diseases ◽  
Genetic Modifications ◽  
Vector Borne ◽  
Potential Strategy ◽  
Gene Drives ◽  
Population Suppression

ABSTRACTEngineered gene drives are being explored as a potential strategy for the control of vector-borne diseases due to their ability to rapidly spread genetic modifications through a population. While an effective CRISPR homing gene drive for population suppression has recently been demonstrated in mosquitoes, formation of resistance alleles that prevent Cas9 cleavage remains the major obstacle for drive strategies aiming at population modification, rather than elimination. Here, we present a homing drive in Drosophila melanogaster that reduces resistance allele formation below detectable levels by targeting a haplolethal gene with two gRNAs while also providing a rescue allele. This is because any resistance alleles that form by end-joining repair will typically disrupt the haplolethal target gene, rendering the individuals carrying them nonviable. We demonstrate that our drive is highly efficient, with 91% of the progeny of drive heterozygotes inheriting the drive allele and with no resistance alleles observed in the remainder. In a large cage experiment, the drive allele successfully spread to all individuals. These results show that a haplolethal homing drive can be a highly effective tool for population modification.

scholarly journals A CRISPR homing gene drive targeting a haplolethal gene removes resistance alleles and successfully spreads through a cage population

2020 ◽  
Vol 117 (39) ◽  
pp. 24377-24383 ◽  
Author(s):  
Jackson Champer ◽  
Emily Yang ◽  
Esther Lee ◽  
Jingxian Liu ◽  
Andrew G. Clark ◽  
...  
Keyword(s):  
Gene Drive ◽  
End Joining ◽  
Large Cage ◽  
Vector Borne Diseases ◽  
Guide Rnas ◽  
Genetic Modifications ◽  
New Strategy ◽  
Cage Population ◽  
Vector Borne ◽  
Gene Drives

Engineered gene drives are being explored as a new strategy in the fight against vector-borne diseases due to their potential for rapidly spreading genetic modifications through a population. However, CRISPR-based homing gene drives proposed for this purpose have faced a major obstacle in the formation of resistance alleles that prevent Cas9 cleavage. Here, we present a homing drive in Drosophila melanogaster that reduces the prevalence of resistance alleles below detectable levels by targeting a haplolethal gene with two guide RNAs (gRNAs) while also providing a rescue allele. Resistance alleles that form by end-joining repair typically disrupt the haplolethal target gene and are thus removed from the population because individuals that carry them are nonviable. We demonstrate that our drive is highly efficient, with 91% of the progeny of drive heterozygotes inheriting the drive allele and with no functional resistance alleles observed in the remainder. In a large cage experiment, the drive allele successfully spread to all individuals within a few generations. These results show that a haplolethal homing drive can provide an effective tool for targeted genetic modification of entire populations.

scholarly journals Modulating CRISPR gene drive activity through nucleocytoplasmic localization of Cas9 in S. cerevisiae

2018 ◽  
Author(s):  
Megan E. Goeckel ◽  
Erianna M. Basgall ◽  
Isabel C. Lewis ◽  
Samantha C. Goetting ◽  
Yao Yan ◽  
...  
Keyword(s):  
Nuclease Activity ◽  
Gene Drive ◽  
Wild Populations ◽  
Vector Borne Diseases ◽  
Vector Borne ◽  
Mendelian Laws ◽  
Artificial Gene ◽  
Nuclear Localization Sequences ◽  
Gene Drives

ABSTRACTThe bacterial CRISPR/Cas genome editing system has provided a major breakthrough in molecular biology. One use of this technology is within a nuclease-based gene drive. This type of system can install a genetic element within a population at unnatural rates. Combatting of vector-borne diseases carried by metazoans could benefit from a delivery system that bypasses traditional Mendelian laws of segregation. Recently, laboratory studies in fungi, insects, and even mice, have demonstrated successful propagation of CRISPR gene drives and the potential utility of this type of mechanism. However, current gene drives still face challenges including evolved resistance, containment, and the consequences of application in wild populations. In this study, we use an artificial gene drive system in budding yeast to explore mechanisms to modulate nuclease activity of Cas9 through its nucleocytoplasmic localization. We examine non-native nuclear localization sequences on Cas9 fusion proteins in vivo and demonstrate that appended signals can titrate gene drive activity and serve as a potential molecular safeguard.

scholarly journals Small-molecule control of super-Mendelian inheritance in gene drives

2019 ◽  
Author(s):  
Víctor López Del Amo ◽  
Brittany S. Leger ◽  
Kurt J. Cox ◽  
Shubhroz Gill ◽  
Alena L. Bishop ◽  
...  
Keyword(s):  
Small Molecule ◽  
Chemical Control ◽  
Control Strategies ◽  
Mendelian Inheritance ◽  
Drive System ◽  
Gene Drive ◽  
Crop Pests ◽  
Vector Borne Diseases ◽  
Vector Borne ◽  
Gene Drives

ABSTRACTBy surpassing the 50% inheritance limit of Mendel’s law of independent assortment, CRISPR-based gene drives have the potential to fight vector-borne diseases or suppress crop pests. However, contemporary gene drives could spread unchecked, posing safety concerns that limit their use in both laboratory and field settings. Current technologies also lack chemical control strategies, which could be applied in the field for dose, spatial and temporal control of gene drives. We describe in Drosophila the first gene-drive system controlled by an engineered Cas9 and a synthetic, orally-available small molecule.Graphical Abstract

scholarly journals Split-gene drive system provides flexible application for safe laboratory investigation and potential field deployment

2019 ◽  
Author(s):  
Víctor López Del Amo ◽  
Alena L. Bishop ◽  
Héctor M. Sánchez C. ◽  
Jared B. Bennett ◽  
Xuechun Feng ◽  
...  
Keyword(s):  
Mendelian Inheritance ◽  
Gene Drive ◽  
Island Conservation ◽  
Vector Borne Diseases ◽  
Split Gene ◽  
Mendelian Genetics ◽  
Vector Borne ◽  
Field Deployment ◽  
Flexible Application ◽  
Gene Drives

ABSTRACTCRISPR-based gene drives spread through populations bypassing the dictates of Mendelian genetics, offering a population-engineering tool for tackling vector-borne diseases, managing crop pests, and helping island conservation efforts; unfortunately, current technologies raise safety concerns for unintended gene propagation. Herein, we address this by splitting the two drive components, Cas9 and gRNAs, into separate alleles to form a novel trans-complementing split–gene-drive (tGD) and demonstrate its ability to promote super-Mendelian inheritance of the separate transgenes. This bi-component nature allows for individual transgene optimization and increases safety by restricting escape concerns to experimentation windows. We employ the tGD and a small– molecule-controlled version to investigate the biology of component inheritance and use our system to study the maternal effects on CRISPR inheritance, impaired homology on efficiency, and resistant allele formation. Lastly, mathematical modeling of tGD spread in a population shows potential advantages for improving current gene-drive technologies for field population modification.

scholarly journals Reducing resistance allele formation in CRISPR gene drive

2018 ◽  
Vol 115 (21) ◽  
pp. 5522-5527 ◽  
Author(s):  
Jackson Champer ◽  
Jingxian Liu ◽  
Suh Yeon Oh ◽  
Riona Reeves ◽  
Anisha Luthra ◽  
...  
Keyword(s):  
Natural Populations ◽  
Mendelian Inheritance ◽  
Gene Drive ◽  
Subsequent Formation ◽  
Vector Borne Diseases ◽  
Effective Strategies ◽  
Guide Rnas ◽  
Vector Borne ◽  
Resistance Rates ◽  
Gene Drives

CRISPR homing gene drives can convert heterozygous cells with one copy of the drive allele into homozygotes, thereby enabling super-Mendelian inheritance. Such a mechanism could be used, for example, to rapidly disseminate a genetic payload in a population, promising effective strategies for the control of vector-borne diseases. However, all CRISPR homing gene drives studied in insects thus far have produced significant quantities of resistance alleles that would limit their spread. In this study, we provide an experimental demonstration that multiplexing of guide RNAs can both significantly increase the drive conversion efficiency and reduce germline resistance rates of a CRISPR homing gene drive inDrosophila melanogaster. We further show that an autosomal drive can achieve drive conversion in the male germline, with no subsequent formation of resistance alleles in embryos through paternal carryover of Cas9. Finally, we find that thenanospromoter significantly lowers somatic Cas9 expression compared with thevasapromoter, suggesting thatnanosprovides a superior choice in drive strategies where gene disruption in somatic cells could have fitness costs. Comparison of drive parameters among the different constructs developed in this study and a previous study suggests that, while drive conversion and germline resistance rates are similar between different genomic targets, embryo resistance rates can vary significantly. Taken together, our results mark an important step toward developing effective gene drives capable of functioning in natural populations and provide several possible avenues for further control of resistance rates.

Sharing of Cyber Threat Intelligence between States

2020 ◽  
Vol 38 (1) ◽  
pp. 22-28
Author(s):  
Philipp Kuehn ◽  
Thea Riebe ◽  
Lynn Apelt ◽  
Max Jansen ◽  
Christian Reuter
Keyword(s):  
Risk Assessment ◽  
Genetically Modified Organisms ◽  
Genetically Modified ◽  
Genetic Alteration ◽  
Gene Drive ◽  
Political Consequences ◽  
Novel Technologies ◽  
Threat Intelligence ◽  
Cyber Threat Intelligence ◽  
Gene Drives

Novel environmental invasive biotechnologies, such as gene drives and Horizontal Environmental Genetic Alteration Agents exceed the classical applications of genetically modified organisms. The reason for this is that they are designed to transform wild organisms into genetically modified organisms which express desired traits. Instead of in a laboratory, this transformation takes place in the environment. The far-ranging effects that may be triggered by gene drive and Horizontal Environmental Genetic Alteration Agents require an extension of risk assessment to include socio-political consequences. The present article offers a first brief examination whether regulation is prepared for possible conflicts caused by benevolent or by hostile use of these novel technologies.

scholarly journals Efficient population modification gene-drive rescue system in the malaria mosquito Anopheles stephensi

2020 ◽  
Author(s):  
Adriana Adolfi ◽  
Valentino M. Gantz ◽  
Nijole Jasinskiene ◽  
Hsu-Feng Lee ◽  
Kristy Hwang ◽  
...  
Keyword(s):  
Anopheles Stephensi ◽  
Pathogen Transmission ◽  
Gene Drive ◽  
Initial Release ◽  
Genetic Technologies ◽  
Rescue System ◽  
Vector Borne ◽  
Kynurenine Hydroxylase ◽  
Drive Systems ◽  
Population Suppression

ABSTRACTThe development of Cas9/gRNA-mediated gene-drive systems has bolstered the advancement of genetic technologies for controlling vector-borne pathogen transmission. These include population suppression approaches, genetic analogs of insecticidal techniques that reduce the number of vector insects, and population modification (replacement/alteration) approaches, which interfere with competence to transmit pathogens. We developed a recoded gene-drive rescue system for population modification in the malaria vector, Anopheles stephensi, that relieves the load in females caused by integration of the drive into the kynurenine hydroxylase gene by rescuing its function. Non-functional resistant alleles are eliminated via a dominantly-acting maternal effect combined with slower-acting standard negative selection, and a functional resistant allele does not prevent drive invasion. Small cage trials show that single releases of gene-drive males robustly result in efficient population modification with ≥95% of mosquitoes carrying the drive within 5-11 generations over a range of initial release ratios.

Governing New Biotechnologies for Biodiversity Conservation: Gene Drives, International Law, and Emerging Politics

2020 ◽  
Vol 20 (3) ◽  
pp. 28-48 ◽  
Author(s):  
Jesse L. Reynolds
Keyword(s):  
International Law ◽  
Biodiversity Conservation ◽  
Genetically Modified Organisms ◽  
Biological Diversity ◽  
Well Being ◽  
Convention On Biological Diversity ◽  
Gene Drive ◽  
Social Challenges ◽  
Law And Politics ◽  
Gene Drives

The outdoor use of organisms modified with gene drives—emerging biotechnologies of biased inheritance—could further human well-being and biodiversity conservation, yet also poses environmental risks and diverse social challenges. This article describes and analyzes the international law and politics of gene drives’ research, development, and possible use, with an emphasis on their potential biodiversity applications. The Convention on Biological Diversity is central, and its institutions and others have taken actions toward governing gene drive organisms. Gene drives’ governance and politics are contrasted with those of agricultural genetically modified organisms, with emphases on states, nonstate actors, the precautionary approach, and decision-making forums. Developing and implementing governance—especially in international forums—for gene drives may prove to be difficult. The observations and analysis here indicate that the politics of gene drive organisms is a manifestation of a larger struggle regarding emerging technologies among those concerned about sustainability.

scholarly journals Tethered homing gene drives: a new design for spatially restricted population replacement and suppression

2018 ◽  
Author(s):  
Sumit Dhole ◽  
Alun L. Lloyd ◽  
Fred Gould
Keyword(s):  
Mathematical Model ◽  
Genetic Load ◽  
Target Population ◽  
Gene Drive ◽  
Population Replacement ◽  
Additional Release ◽  
New Gene ◽  
Gene Drives ◽  
Population Suppression ◽  
Proof Of Principle

ABSTRACTOptimism regarding potential epidemiological and conservation applications of modern gene drives is tempered by concern about the potential unintended spread of engineered organisms beyond the target population. In response, several novel gene drive approaches have been proposed that can, under certain conditions, locally alter characteristics of a population. One challenge for these gene drives is the difficulty of achieving high levels of localized population suppression without very large releases in face of gene flow. We present a new gene drive system, Tethered Homing (TH), with improved capacity for localized population alteration, especially for population suppression. The TH drive is based on driving a payload gene using a homing construct that is anchored to a spatially restricted gene drive. We use a proof of principle mathematical model to show the dynamics of a TH drive that uses engineered underdominance as an anchor. This system is composed of a split homing drive and a two-locus engineered underdominance drive linked to one part of the split drive (the Cas endonuclease). In addition to improved localization, the TH system offers the ability to gradually adjust the genetic load in a population after the initial alteration, with minimal additional release effort.

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