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.

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

2020 ◽  
Vol 11 (1) ◽  
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 ◽  
Advanced Development

Abstract Cas9/gRNA-mediated gene-drive systems have advanced development of genetic technologies for controlling vector-borne pathogen transmission. These technologies include population suppression approaches, genetic analogs of insecticidal techniques that reduce the number of insect vectors, and population modification (replacement/alteration) approaches, which interfere with competence to transmit pathogens. Here, we develop a recoded gene-drive rescue system for population modification of 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 rare functional resistant alleles do 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.

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 Population dynamics of underdominance gene drive systems in continuous space

2018 ◽  
Author(s):  
Jackson Champer ◽  
Joanna Zhao ◽  
Joanna Zhao ◽  
Samuel E. Champer ◽  
Jingxian Liu ◽  
...  
Keyword(s):  
Decision Making ◽  
Population Dynamics ◽  
Local Population ◽  
Spatial Context ◽  
Decision Making Process ◽  
Gene Drive ◽  
Continuous Space ◽  
Vector Borne Diseases ◽  
Vector Borne ◽  
Drive Systems

ABSTRACTUnderdominance gene drive systems promise a mechanism for rapidly spreading payload alleles through a local population while otherwise remaining confined, unable to spread into neighboring populations due to their frequency-dependent dynamics. Such systems could provide a new tool in the fight against vector-borne diseases by disseminating transgenic payloads through vector populations. If local confinement can indeed be achieved, the decision-making process for the release of such constructs would likely be considerably simpler compared to other gene drive mechanisms such as CRISPR homing drives. So far, the confinement ability of underdominance systems has only been demonstrated in models of panmictic populations linked by migration. How such systems would behave in realistic populations where individuals move over continuous space remains largely unknown. Here, we study several underdominance systems in continuous-space population models and show that their dynamics are drastically altered from those in panmictic populations. Specifically, we find that all underdominance systems we studied can fail to persist in such environments, even after successful local establishment. At the same time, we find that a two-locus two-toxin-antitoxin system can still successfully invade neighboring populations in many scenarios even under weak migration. This suggests that the parameter space for underdominance systems to both establish in a given region and remain confined to that region would likely be highly limited. Overall, these results indicate that spatial context must be considered when assessing strategies for the deployment of underdominance systems.

scholarly journals Digital droplet PCR and IDAA for the detection of CRISPR indel edits in the malaria species Anopheles stephensi

BioTechniques ◽  
2020 ◽  
Vol 68 (4) ◽  
pp. 172-179 ◽  
Author(s):  
Rebeca Carballar-Lejarazú ◽  
Adam Kelsey ◽  
Thai Binh Pham ◽  
Eric P Bennett ◽  
Anthony A James
Keyword(s):  
Anopheles Stephensi ◽  
Field Testing ◽  
Nonhomologous End Joining ◽  
Mosquito Vector ◽  
Gene Drive ◽  
End Joining ◽  
Indel Detection ◽  
Vector Mosquito ◽  
Droplet Pcr ◽  
Drive Systems

CRISPR/Cas9 technology is a powerful tool for the design of gene-drive systems to control and/or modify mosquito vector populations; however, CRISPR/Cas9-mediated nonhomologous end joining mutations can have an important impact on generating alleles resistant to the drive and thus on drive efficiency. We demonstrate and compare the insertions or deletions (indels) detection capabilities of two techniques in the malaria vector mosquito Anopheles stephensi: Indel Detection by Amplicon Analysis (IDAA™) and Droplet Digital™ PCR (ddPCR™). Both techniques showed accuracy and reproducibility for indel frequencies across mosquito samples containing different ratios of indels of various sizes. Moreover, these techniques have advantages that make them potentially better suited for high-throughput nonhomologous end joining analysis in cage trials and contained field testing of gene-drive mosquitoes.

scholarly journals Lethal Gene Drive Selects Inbreeding

2016 ◽  
Author(s):  
J J Bull
Keyword(s):  
Segregation Distortion ◽  
Essential Gene ◽  
Homing Endonuclease ◽  
Lethal Gene ◽  
Gene Drive ◽  
Partial Restoration ◽  
Selfish Gene ◽  
Evolutionary Response ◽  
Drive Systems ◽  
Population Suppression

AbstractThe use of ‘selfish’ gene drive systems to suppress or even extinguish populations has been proposed on theoretical grounds for almost half a century. Creating these genes has recently become possible with CRISPR technology. One seemingly feasible approach, originally proposed by Burt, is to create a homing endonuclease gene (HEG) that inserts into an essential gene, enabling heterozygote viability but causing homozygote lethality. With 100% segregation distortion in gametes, such genes can cause profound population suppression if resistance does not evolve. Here, population genetic models are used to consider the evolution of inbreeding (specifically selfing) as a possible response to a recessively lethal HEG with complete segregation distortion. Numerical analyses indicate a rich set of outcomes, but selfing often evolves in response to the HEG, with a corresponding partial restoration of mean fitness. Whether selfing does indeed evolve and its effect in restoring fitness depends heavily on the magnitude of inbreeding depression. Overall, these results point toward an underappreciated evolutionary response to block the harmful effects of a selfish gene. They raise the possibility that extreme population suppression may be more difficult to achieve than currently imagined.

scholarly journals Design and analysis of CRISPR-based underdominance toxin-antidote gene drives

2019 ◽  
Author(s):  
Jackson Champer ◽  
Samuel E. Champer ◽  
Isabel Kim ◽  
Andrew G. Clark ◽  
Philipp W. Messer
Keyword(s):  
Critical Frequency ◽  
Essential Gene ◽  
Geographic Location ◽  
Early Embryo ◽  
Gene Drive ◽  
Wide Range ◽  
Vector Borne ◽  
Drive Systems ◽  
Invasion Threshold ◽  
Gene Drives

ABSTRACTCRISPR gene drive systems offer a mechanism for transmitting a desirable transgene throughout a population for purposes ranging from vector-borne disease control to invasive species suppression. In this simulation study, we assess the performance of several CRISPR-based underdominance gene drive constructs employing toxin-antidote principles. These drives disrupt the wild-type version of an essential gene using a CRISPR nuclease (the toxin) while simultaneously carrying a recoded version of the gene (the antidote). Drives of this nature allow for releases that could be potentially confined to a desired geographic location. This is because such drives have a nonzero invasion threshold frequency, referring to the critical frequency required for the drive to spread through the population. We model drives which target essential genes that are either haplosufficient or haplolethal, using nuclease promoters with expression restricted to the germline, promoters that additionally result in cleavage activity in the early embryo from maternal deposition, and promoters that have ubiquitous somatic expression. We also study several possible drive architectures, considering both “same-site” and “distant-site” systems, as well as several reciprocally targeting drives. Together, these drive variants provide a wide range of invasion threshold frequencies and options for both population modification and suppression. Our results suggest that CRISPR toxin-antidote underdominance drive systems could allow for the design of highly flexible and potentially confinable gene drive strategies.

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 MGDrivE 2: A simulation framework for gene drive systems incorporating seasonality and epidemiological dynamics

2020 ◽  
Author(s):  
Sean L. Wu ◽  
Jared B. Bennett ◽  
Héctor M. Sánchez C. ◽  
Andrew J. Dolgert ◽  
Tomás M. León ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Disease Transmission ◽  
Field Trials ◽  
Pathogen Transmission ◽  
Environmental Data ◽  
List Type ◽  
Gene Drive ◽  
Simulation Framework ◽  
Implementation Framework ◽  
Drive Systems

AbstractInterest in gene drive technology has continued to grow as promising new drive systems have been developed in the lab and discussions are moving towards implementing field trials. The prospect of field trials requires models that incorporate a significant degree of ecological detail, including parameters that change over time in response to environmental data such as temperature and rainfall, leading to seasonal patterns in mosquito population density. Epidemiological outcomes are also of growing importance, as: i) the suitability of a gene drive construct for release will depend on its expected impact on disease transmission, and ii) initial field trials are expected to have a measured entomological outcome and a modeled epidemiological outcome.We present MGDrivE 2 (Mosquito Gene Drive Explorer 2): an extension of and development from the MGDrivE 1 simulation framework that investigates the population dynamics of a variety of gene drive architectures and their spread through spatially-explicit mosquito populations. Key strengths and improvements of the MGDrivE 2 framework are: i) the ability of parameters to vary with time and induce seasonal population dynamics, ii) an epidemiological module accommodating reciprocal pathogen transmission between humans and mosquitoes, and iii) an implementation framework based on stochastic Petri nets that enables efficient model formulation and flexible implementation.Example MGDrivE 2 simulations are presented to demonstrate the application of the framework to a CRISPR-based homing gene drive system intended to drive a disease-refractory gene into a population, incorporating time-varying temperature and rainfall data, and predict impact on human disease incidence and prevalence. Further documentation and use examples are provided in vignettes at the project’s CRAN repository.MGDrivE 2 is an open-source R package freely available on CRAN. We intend the package to provide a flexible tool capable of modeling gene drive constructs as they move closer to field application and to infer their expected impact on disease transmission.

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