1
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Agboka KM, Wamalwa M, Mutunga JM, Tonnang HEZ. A mathematical model for mapping the insecticide resistance trend in the Anopheles gambiae mosquito population under climate variability in Africa. Sci Rep 2024; 14:9850. [PMID: 38684842 PMCID: PMC11059405 DOI: 10.1038/s41598-024-60555-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 04/24/2024] [Indexed: 05/02/2024] Open
Abstract
The control of arthropod disease vectors using chemical insecticides is vital in combating malaria, however the increasing insecticide resistance (IR) poses a challenge. Furthermore, climate variability affects mosquito population dynamics and subsequently IR propagation. We present a mathematical model to decipher the relationship between IR in Anopheles gambiae populations and climate variability. By adapting the susceptible-infected-resistant (SIR) framework and integrating temperature and rainfall data, our model examines the connection between mosquito dynamics, IR, and climate. Model validation using field data achieved 92% accuracy, and the sensitivity of model parameters on the transmission potential of IR was elucidated (e.g. μPRCC = 0.85958, p-value < 0.001). In this study, the integration of high-resolution covariates with the SIR model had a significant impact on the spatial and temporal variation of IR among mosquito populations across Africa. Importantly, we demonstrated a clear association between climatic variability and increased IR (width = [0-3.78], α = 0.05). Regions with high IR variability, such as western Africa, also had high malaria incidences thereby corroborating the World Health Organization Malaria Report 2021. More importantly, this study seeks to bolster global malaria combat strategies by highlighting potential IR 'hotspots' for targeted intervention by National malria control programmes.
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Affiliation(s)
- Komi Mensah Agboka
- International Centre of Insect Physiology and Ecology (Icipe), P.O. Box 30772 00100, Nairobi, Kenya.
| | - Mark Wamalwa
- International Centre of Insect Physiology and Ecology (Icipe), P.O. Box 30772 00100, Nairobi, Kenya
| | - James Mutuku Mutunga
- School of Engineering Design and Innovation Pennsylvania State University, University Park, PA, 16802, USA
| | - Henri E Z Tonnang
- International Centre of Insect Physiology and Ecology (Icipe), P.O. Box 30772 00100, Nairobi, Kenya.
- School of Agricultural, Earth, and Environmental Sciences, University of KwaZulu-Natal, Pietermaritzburg, 3209, South Africa.
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2
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Raban R, Marshall JM, Hay BA, Akbari OS. Manipulating the Destiny of Wild Populations Using CRISPR. Annu Rev Genet 2023; 57:361-390. [PMID: 37722684 PMCID: PMC11064769 DOI: 10.1146/annurev-genet-031623-105059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/20/2023]
Abstract
Genetic biocontrol aims to suppress or modify populations of species to protect public health, agriculture, and biodiversity. Advancements in genome engineering technologies have fueled a surge in research in this field, with one gene editing technology, CRISPR, leading the charge. This review focuses on the current state of CRISPR technologies for genetic biocontrol of pests and highlights the progress and ongoing challenges of using these approaches.
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Affiliation(s)
- Robyn Raban
- Department of Cell and Developmental Biology, School of Biological Sciences, University of California, San Diego, La Jolla, California, USA;
| | - John M Marshall
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, USA
| | - Bruce A Hay
- Division of Biology and Biological Engineering (BBE), California Institute of Technology, Pasadena, California, USA
| | - Omar S Akbari
- Department of Cell and Developmental Biology, School of Biological Sciences, University of California, San Diego, La Jolla, California, USA;
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3
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Lester PJ, O'Sullivan D, Perry GLW. Gene drives for invasive wasp control: Extinction is unlikely, with suppression dependent on dispersal and growth rates. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2023; 33:e2912. [PMID: 37615220 DOI: 10.1002/eap.2912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 06/28/2023] [Accepted: 07/14/2023] [Indexed: 08/25/2023]
Abstract
Gene drives offer a potentially revolutionary method for pest control over large spatial extents. These genetic modifications spread deleterious variants through a population and have been proposed as methods for pest suppression or even eradication. We examined the influence of local dispersal, long-distance and/or human-mediated dispersal, and variation in population growth on the success of a gene drive for the control of invasive social wasps (Vespula vulgaris). Our simulations incorporated a spatially realistic environment containing variable habitat quality in New Zealand. Pest eradication was not observed, except in extreme and unrealistic scenarios of constant, widespread, and spatially intense releases of genetically modified individuals every year for decades. Instead, the regional persistence of genetically modified and wild-type wasps was predicted. Simulations using spatially homogeneous versus realistic landscapes (incorporating uninhabitable areas and dispersal barriers) showed little difference in overall population dynamics. Overall, little impact on wasp abundance was observed in the first 15 years after introduction. After 25 years, populations were suppressed to levels <95% of starting populations. Populations exhibited "chase dynamics" with population cycles in space, with local extinction occurring in some areas while wasps became abundant in others. Increasing the wasps' local dispersal distance increased the spatial and temporal variability of the occupied area and population suppression. Varying levels of human-associated long-distance dispersal had little effect on population dynamics. Increasing intrinsic population growth rates interacted with local dispersal to cause higher mean populations and substantially higher levels of variation in population suppression and the total amount of landscape occupied. Gene drives appear unlikely to cause a rapid and widespread extinction of this and probably other pests but could offer long-term and cost-effective methods of pest suppression. The predicted level of <95% pest suppression would substantially reduce the predation pressure and competitive interactions of this invasive wasp on native species. However, the predicted long-term persistence of genetically modified pests will influence the ethics and likelihood of using gene drives for pest control, especially given concerns that modified wasps would eventually be transported back to their home range.
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Affiliation(s)
- Philip J Lester
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - David O'Sullivan
- School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - George L W Perry
- School of Environment, University of Auckland, Auckland, New Zealand
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4
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Kim J, Harris KD, Kim IK, Shemesh S, Messer PW, Greenbaum G. Incorporating ecology into gene drive modelling. Ecol Lett 2023; 26 Suppl 1:S62-S80. [PMID: 37840022 DOI: 10.1111/ele.14194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 02/13/2023] [Accepted: 02/15/2023] [Indexed: 10/17/2023]
Abstract
Gene drive technology, in which fast-spreading engineered drive alleles are introduced into wild populations, represents a promising new tool in the fight against vector-borne diseases, agricultural pests and invasive species. Due to the risks involved, gene drives have so far only been tested in laboratory settings while their population-level behaviour is mainly studied using mathematical and computational models. The spread of a gene drive is a rapid evolutionary process that occurs over timescales similar to many ecological processes. This can potentially generate strong eco-evolutionary feedback that could profoundly affect the dynamics and outcome of a gene drive release. We, therefore, argue for the importance of incorporating ecological features into gene drive models. We describe the key ecological features that could affect gene drive behaviour, such as population structure, life-history, environmental variation and mode of selection. We review previous gene drive modelling efforts and identify areas where further research is needed. As gene drive technology approaches the level of field experimentation, it is crucial to evaluate gene drive dynamics, potential outcomes, and risks realistically by including ecological processes.
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Affiliation(s)
- Jaehee Kim
- Department of Computational Biology, Cornell University, Ithaca, New York, USA
| | - Keith D Harris
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Isabel K Kim
- Department of Computational Biology, Cornell University, Ithaca, New York, USA
| | - Shahar Shemesh
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Philipp W Messer
- Department of Computational Biology, Cornell University, Ithaca, New York, USA
| | - Gili Greenbaum
- Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem, Jerusalem, Israel
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5
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Zhu Y, Champer J. Simulations Reveal High Efficiency and Confinement of a Population Suppression CRISPR Toxin-Antidote Gene Drive. ACS Synth Biol 2023; 12:809-819. [PMID: 36825354 DOI: 10.1021/acssynbio.2c00611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
Though engineered gene drives hold great promise for spreading through and suppressing populations of disease vectors or invasive species, complications such as resistance alleles and spatial population structure can prevent their success. Additionally, most forms of suppression drives, such as homing drives or driving Y chromosomes, will generally spread uncontrollably between populations with even small levels of migration. The previously proposed CRISPR-based toxin-antidote system called toxin-antidote dominant embryo (TADE) suppression drive could potentially address the issues of confinement and resistance. However, it is a relatively weak form of drive compared to homing drives, which might make it particularly vulnerable to spatial population structure. In this study, we investigate TADE suppression drive using individual-based simulations in a continuous spatial landscape. We find that the drive is actually more confined than in simple models without space, even in its most efficient form with low cleavage rate in embryos from maternally deposited Cas9. Furthermore, the drive performed well in continuous space scenarios if the initial release requirements were met, suppressing the population in a timely manner without being severely affected by chasing, a phenomenon in which wild-type individuals avoid the drive by recolonizing empty areas. At higher embryo cut rates, the drive loses its ability to spread, but a single, widespread release can often still induce rapid population collapse. Thus, if TADE suppression gene drives can be successfully constructed, they may play an important role in control of disease vectors and invasive species when stringent confinement to target populations is desired.
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Affiliation(s)
- Yutong Zhu
- Center for Bioinformatics, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - Jackson Champer
- Center for Bioinformatics, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
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6
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Gene drive-mediated population elimination for biodiversity conservation. When you come to a fork in the road, take it. Proc Natl Acad Sci U S A 2022; 119:e2218020119. [PMID: 36512501 PMCID: PMC9907123 DOI: 10.1073/pnas.2218020119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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7
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Asad M, Liu D, Chen J, Yang G. Applications of gene drive systems for population suppression of insect pests. BULLETIN OF ENTOMOLOGICAL RESEARCH 2022; 112:724-733. [PMID: 36043456 DOI: 10.1017/s0007485322000268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Population suppression is an effective way for controlling insect pests and disease vectors, which cause significant damage to crop and spread contagious diseases to plants, animals and humans. Gene drive systems provide innovative opportunities for the insect pests population suppression by driving genes that impart fitness costs on populations of pests or disease vectors. Different gene-drive systems have been developed in insects and applied for their population suppression. Here, different categories of gene drives such as meiotic drive (MD), under-dominance (UD), homing endonuclease-based gene drive (HEGD) and especially the CRISPR/Cas9-based gene drive (CCGD) were reviewed, including the history, types, process and mechanisms. Furthermore, the advantages and limitations of applying different gene-drive systems to suppress the insect population were also summarized. This review provides a foundation for developing a specific gene-drive system for insect population suppression.
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Affiliation(s)
- Muhammad Asad
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fuzhou 350002, China
- Key Laboratory of Green Pest Control, Fujian Province University, Fuzhou 350002, China
| | - Dan Liu
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fuzhou 350002, China
- Key Laboratory of Green Pest Control, Fujian Province University, Fuzhou 350002, China
| | - Jing Chen
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fuzhou 350002, China
- Key Laboratory of Green Pest Control, Fujian Province University, Fuzhou 350002, China
| | - Guang Yang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fuzhou 350002, China
- Key Laboratory of Green Pest Control, Fujian Province University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
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8
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Finney M, Romanowski J, Adelman ZN. Strategies to improve homology-based repair outcomes following CRISPR-based gene editing in mosquitoes: lessons in how to keep any repair disruptions local. Virol J 2022; 19:128. [PMID: 35908059 PMCID: PMC9338592 DOI: 10.1186/s12985-022-01859-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 07/18/2022] [Indexed: 11/10/2022] Open
Abstract
Programmable gene editing systems such as CRISPR-Cas have made mosquito genome engineering more practical and accessible, catalyzing the development of cutting-edge genetic methods of disease vector control. This progress, however, has been limited by the low efficiency of homology-directed repair (HDR)-based sequence integration at DNA double-strand breaks (DSBs) and a lack of understanding about DSB repair in mosquitoes. Innovative efforts to optimize HDR sequence integration by inhibiting non-homologous end joining or promoting HDR have been performed in mammalian systems, however many of these approaches have not been applied to mosquitoes. Here, we review some of the most relevant steps of DNA DSB repair choice and highlight promising approaches that influence this choice to enhance HDR in the context of mosquito gene editing.
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Affiliation(s)
- Micaela Finney
- Department of Entomology, Texas A&M University, 329A Minnie Belle Heep Center, 370 Olsen Blvd, College Station, TX, 77843, USA
| | - Joseph Romanowski
- Department of Entomology, Texas A&M University, 329A Minnie Belle Heep Center, 370 Olsen Blvd, College Station, TX, 77843, USA
| | - Zach N Adelman
- Department of Entomology, Texas A&M University, 329A Minnie Belle Heep Center, 370 Olsen Blvd, College Station, TX, 77843, USA.
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9
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Yang E, Metzloff M, Langmüller AM, Xu X, Clark AG, Messer PW, Champer J. A homing suppression gene drive with multiplexed gRNAs maintains high drive conversion efficiency and avoids functional resistance alleles. G3 (BETHESDA, MD.) 2022; 12:jkac081. [PMID: 35394026 PMCID: PMC9157102 DOI: 10.1093/g3journal/jkac081] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 03/30/2022] [Indexed: 11/14/2022]
Abstract
Gene drives are engineered alleles that can bias inheritance in their favor, allowing them to spread throughout a population. They could potentially be used to modify or suppress pest populations, such as mosquitoes that spread diseases. CRISPR/Cas9 homing drives, which copy themselves by homology-directed repair in drive/wild-type heterozygotes, are a powerful form of gene drive, but they are vulnerable to resistance alleles that preserve the function of their target gene. Such resistance alleles can prevent successful population suppression. Here, we constructed a homing suppression drive in Drosophila melanogaster that utilized multiplexed gRNAs to inhibit the formation of functional resistance alleles in its female fertility target gene. The selected gRNA target sites were close together, preventing reduction in drive conversion efficiency. The construct reached a moderate equilibrium frequency in cage populations without apparent formation of resistance alleles. However, a moderate fitness cost prevented elimination of the cage population, showing the importance of using highly efficient drives in a suppression strategy, even if resistance can be addressed. Nevertheless, our results experimentally demonstrate the viability of the multiplexed gRNAs strategy in homing suppression gene drives.
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Affiliation(s)
- Emily Yang
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Matthew Metzloff
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Anna M Langmüller
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
- Institut für Populationsgenetik, Vetmeduni Vienna, 1210 Wien, Austria
- Vienna Graduate School of Population Genetics, 1210 Wien, Austria
| | - Xuejiao Xu
- Center for Bioinformatics, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - Andrew G Clark
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Philipp W Messer
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
| | - Jackson Champer
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
- Center for Bioinformatics, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
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10
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Propagation of seminal toxins through binary expression gene drives could suppress populations. Sci Rep 2022; 12:6332. [PMID: 35428855 PMCID: PMC9012762 DOI: 10.1038/s41598-022-10327-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 04/05/2022] [Indexed: 11/25/2022] Open
Abstract
Gene drives can be highly effective in controlling a target population by disrupting a female fertility gene. To spread across a population, these drives require that disrupted alleles be largely recessive so as not to impose too high of a fitness penalty. We argue that this restriction may be relaxed by using a double gene drive design to spread a split binary expression system. One drive carries a dominant lethal/toxic effector alone and the other a transactivator factor, without which the effector will not act. Only after the drives reach sufficiently high frequencies would individuals have the chance to inherit both system components and the effector be expressed. We explore through mathematical modeling the potential of this design to spread dominant lethal/toxic alleles and suppress populations. We show that this system could be implemented to spread engineered seminal proteins designed to kill females, making it highly effective against polyandrous populations.
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11
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Carballar-Lejarazú R, Tushar T, Pham TB, James AA. Cas9-mediated maternal-effect and derived resistance alleles in a gene-drive strain of the African malaria vector mosquito, Anopheles gambiae. Genetics 2022; 221:6564662. [PMID: 35389492 PMCID: PMC9157122 DOI: 10.1093/genetics/iyac055] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 03/30/2022] [Indexed: 11/24/2022] Open
Abstract
CRISPR/Cas9 technologies are important tools for the development of gene-drive systems to modify mosquito vector populations to control the transmission of pathogens that cause diseases such as malaria. However, one of the challenges for current Cas9-based drive systems is their ability to produce drive-resistant alleles resulting from insertions and deletions (indels) caused principally by nonhomologous end-joining following chromosome cleavage. Rapid increases in the frequency of such alleles may impair gene-drive dynamics. We explored the generation of indels in the germline and somatic cells in female gene-drive lineages using a series of selective crosses between a gene-drive line, AgNosCd-1, and wild-type mosquitoes. We find that potential drive-resistant mutant alleles are generated largely during embryonic development, most likely caused by deposition of the Cas9 endonuclease and guide RNAs in oocytes and resulting embryos by homozygous and hemizygous gene-drive mothers.
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Affiliation(s)
- Rebeca Carballar-Lejarazú
- Department of Microbiology & Molecular Genetics, University of California, Irvine, Irvine, CA 92697-4025, USA
| | - Taylor Tushar
- Department of Microbiology & Molecular Genetics, University of California, Irvine, Irvine, CA 92697-4025, USA
| | - Thai Binh Pham
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA
| | - Anthony A James
- Department of Microbiology & Molecular Genetics, University of California, Irvine, Irvine, CA 92697-4025, USA.,Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA
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12
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Beaghton PJ, Burt A. Gene drives and population persistence vs elimination: The impact of spatial structure and inbreeding at low density. Theor Popul Biol 2022; 145:109-125. [PMID: 35247370 DOI: 10.1016/j.tpb.2022.02.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 02/15/2022] [Accepted: 02/22/2022] [Indexed: 11/26/2022]
Abstract
Synthetic gene drive constructs are being developed to control disease vectors, invasive species, and other pest species. In a well-mixed random mating population a sufficiently strong gene drive is expected to eliminate a target population, but it is not clear whether the same is true when spatial processes play a role. In species with an appropriate biology it is possible that drive-induced reductions in density might lead to increased inbreeding, reducing the efficacy of drive, eventually leading to suppression rather than elimination, regardless of how strong the drive is. To investigate this question we analyse a series of explicitly solvable stochastic models considering a range of scenarios for the relative timing of mating, reproduction, and dispersal and analyse the impact of two different types of gene drive, a Driving Y chromosome and a homing construct targeting an essential gene. We find in all cases a sufficiently strong Driving Y will go to fixation and the population will be eliminated, except in the one life history scenario (reproduction and mating in patches followed by dispersal) where low density leads to increased inbreeding, in which case the population persists indefinitely, tending to either a stable equilibrium or a limit cycle. These dynamics arise because Driving Y males have reduced mating success, particularly at low densities, due to having fewer sisters to mate with. Increased inbreeding at low densities can also prevent a homing construct from eliminating a population. For both types of drive, if there is strong inbreeding depression, then the population cannot be rescued by inbreeding and it is eliminated. These results highlight the potentially critical role that low-density-induced inbreeding and inbreeding depression (and, by extension, other sources of Allee effects) can have on the eventual impact of a gene drive on a target population.
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Affiliation(s)
- P J Beaghton
- Institute for Security Science and Technology, South Kensington Campus, Imperial College London, London, UK; Department of Computing, South Kensington Campus, Imperial College London, London, UK.
| | - Austin Burt
- Department of Life Sciences, Silwood Park Campus, Imperial College London, Ascot, UK
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13
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Sabet A, Goddard J. Promise or Peril: Using Genetically Modified Mosquitoes in the Fight Against Vector-Borne Disease. Am J Med 2022; 135:281-283. [PMID: 34563494 DOI: 10.1016/j.amjmed.2021.08.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 08/31/2021] [Accepted: 08/31/2021] [Indexed: 11/26/2022]
Affiliation(s)
- Afsoon Sabet
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Clay Lyle Entomology, Mississippi State University, Mississippi State
| | - Jerome Goddard
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Clay Lyle Entomology, Mississippi State University, Mississippi State.
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14
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Lewis IC, Yan Y, Finnigan GC. Analysis of a Cas12a-based gene-drive system in budding yeast. Access Microbiol 2022; 3:000301. [PMID: 35024561 PMCID: PMC8749140 DOI: 10.1099/acmi.0.000301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 11/16/2021] [Indexed: 12/19/2022] Open
Abstract
The discovery and adaptation of CRISPR/Cas systems within molecular biology has provided advances across biological research, agriculture and human health. Genomic manipulation through use of a CRISPR nuclease and programmed guide RNAs has become a common and widely accessible practice. The identification and introduction of new engineered variants and orthologues of Cas9 as well as alternative CRISPR systems such as the type V group have provided additional molecular options for editing. These include distinct PAM requirements, staggered DNA double-strand break formation, and the ability to multiplex guide RNAs from a single expression construct. Use of CRISPR/Cas has allowed for the construction and testing of a powerful genetic architecture known as a gene drive within eukaryotic model systems. Our previous work developed a drive within budding yeast using Streptococcus pyogenes Cas9. Here, we installed the type V Francisella novicida Cas12a (Cpf1) nuclease gene and its corresponding guide RNA to power a highly efficient artificial gene drive in diploid yeast. We examined the consequence of altering guide length or introduction of individual mutational substitutions to the crRNA sequence. Cas12a-dependent gene-drive function required a guide RNA of at least 18 bp and could not tolerate most changes within the 5' end of the crRNA.
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Affiliation(s)
- Isabel C Lewis
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA.,Present address: School of Medicine, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Yao Yan
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Gregory C Finnigan
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
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15
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Oberhofer G, Ivy T, Hay BA. Gene drive that results in addiction to a temperature-sensitive version of an essential gene triggers population collapse in Drosophila. Proc Natl Acad Sci U S A 2021; 118:e2107413118. [PMID: 34845012 PMCID: PMC8670509 DOI: 10.1073/pnas.2107413118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2021] [Indexed: 12/15/2022] Open
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 guide RNAs (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. As a 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 homing-based drive and to bring about suppression and/or killing of specific individuals in response to other stimuli.
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Affiliation(s)
- Georg Oberhofer
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Tobin Ivy
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Bruce A Hay
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125
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Fuchs S, Garrood WT, Beber A, Hammond A, Galizi R, Gribble M, Morselli G, Hui TYJ, Willis K, Kranjc N, Burt A, Crisanti A, Nolan T. Resistance to a CRISPR-based gene drive at an evolutionarily conserved site is revealed by mimicking genotype fixation. PLoS Genet 2021; 17:e1009740. [PMID: 34610011 PMCID: PMC8519452 DOI: 10.1371/journal.pgen.1009740] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 10/15/2021] [Accepted: 09/24/2021] [Indexed: 01/06/2023] Open
Abstract
CRISPR-based homing gene drives can be designed to disrupt essential genes whilst biasing their own inheritance, leading to suppression of mosquito populations in the laboratory. This class of gene drives relies on CRISPR-Cas9 cleavage of a target sequence and copying ('homing') therein of the gene drive element from the homologous chromosome. However, target site mutations that are resistant to cleavage yet maintain the function of the essential gene are expected to be strongly selected for. Targeting functionally constrained regions where mutations are not easily tolerated should lower the probability of resistance. Evolutionary conservation at the sequence level is often a reliable indicator of functional constraint, though the actual level of underlying constraint between one conserved sequence and another can vary widely. Here we generated a novel adult lethal gene drive (ALGD) in the malaria vector Anopheles gambiae, targeting an ultra-conserved target site in a haplosufficient essential gene (AGAP029113) required during mosquito development, which fulfils many of the criteria for the target of a population suppression gene drive. We then designed a selection regime to experimentally assess the likelihood of generation and subsequent selection of gene drive resistant mutations at its target site. We simulated, in a caged population, a scenario where the gene drive was approaching fixation, where selection for resistance is expected to be strongest. Continuous sampling of the target locus revealed that a single, restorative, in-frame nucleotide substitution was selected. Our findings show that ultra-conservation alone need not be predictive of a site that is refractory to target site resistance. Our strategy to evaluate resistance in vivo could help to validate candidate gene drive targets for their resilience to resistance and help to improve predictions of the invasion dynamics of gene drives in field populations.
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Affiliation(s)
- Silke Fuchs
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - William T. Garrood
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Anna Beber
- Department of Biology, University of Padua, Padua, Italy
| | - Andrew Hammond
- Department of Life Sciences, Imperial College London, London, United Kingdom
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, United States of America
| | - Roberto Galizi
- Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Keele, Staffordshire, United Kingdom
| | - Matthew Gribble
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Giulia Morselli
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Tin-Yu J. Hui
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Katie Willis
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Nace Kranjc
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Austin Burt
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Andrea Crisanti
- Department of Life Sciences, Imperial College London, London, United Kingdom
- Department of Molecular Medicine, University of Padua, Padua, Italy
- * E-mail: (AC); (TN)
| | - Tony Nolan
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- * E-mail: (AC); (TN)
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Verma P, Reeves RG, Gokhale CS. A common gene drive language eases regulatory process and eco-evolutionary extensions. BMC Ecol Evol 2021; 21:156. [PMID: 34372763 PMCID: PMC8351217 DOI: 10.1186/s12862-021-01881-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 07/12/2021] [Indexed: 02/08/2023] Open
Abstract
Background Synthetic gene drive technologies aim to spread transgenic constructs into wild populations even when they impose organismal fitness disadvantages. The extraordinary diversity of plausible drive mechanisms and the range of selective parameters they may encounter makes it very difficult to convey their relative predicted properties, particularly where multiple approaches are combined. The sheer number of published manuscripts in this field, experimental and theoretical, the numerous techniques resulting in an explosion in the gene drive vocabulary hinder the regulators’ point of view. We address this concern by defining a simplified parameter based language of synthetic drives. Results Employing the classical population dynamics approach, we show that different drive construct (replacement) mechanisms can be condensed and evaluated on an equal footing even where they incorporate multiple replacement drives approaches. Using a common language, it is then possible to compare various model properties, a task desired by regulators and policymakers. The generalization allows us to extend the study of the invasion dynamics of replacement drives analytically and, in a spatial setting, the resilience of the released drive constructs. The derived framework is available as a standalone tool. Conclusion Besides comparing available drive constructs, our tool is also useful for educational purpose. Users can also explore the evolutionary dynamics of future hypothetical combination drive scenarios. Thus, our results appraise the properties and robustness of drives and provide an intuitive and objective way for risk assessment, informing policies, and enhancing public engagement with proposed and future gene drive approaches.
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Affiliation(s)
- Prateek Verma
- Research Group for Theoretical Models of Eco-evolutionary Dynamics, Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Plön, Germany.
| | - R Guy Reeves
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Biology, Plön, Germany
| | - Chaitanya S Gokhale
- Research Group for Theoretical Models of Eco-evolutionary Dynamics, Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Plön, Germany
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Morris AL, Ghani A, Ferguson N. Fine-scale estimation of key life-history parameters of malaria vectors: implications for next-generation vector control technologies. Parasit Vectors 2021; 14:311. [PMID: 34103094 PMCID: PMC8188720 DOI: 10.1186/s13071-021-04789-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 05/11/2021] [Indexed: 11/12/2022] Open
Abstract
Background Mosquito control has the potential to significantly reduce malaria burden on a region, but to influence public health policy must also show cost-effectiveness. Gaps in our knowledge of mosquito population dynamics mean that mathematical modelling of vector control interventions have typically made simplifying assumptions about key aspects of mosquito ecology. Often, these assumptions can distort the predicted efficacy of vector control, particularly next-generation tools such as gene drive, which are highly sensitive to local mosquito dynamics. Methods We developed a discrete-time stochastic mathematical model of mosquito population dynamics to explore the fine-scale behaviour of egg-laying and larval density dependence on parameter estimation. The model was fitted to longitudinal mosquito population count data using particle Markov chain Monte Carlo methods. Results By modelling fine-scale behaviour of egg-laying under varying density dependence scenarios we refine our life history parameter estimates, and in particular we see how model assumptions affect population growth rate (Rm), a crucial determinate of vector control efficacy. Conclusions Subsequent application of these new parameter estimates to gene drive models show how the understanding and implementation of fine-scale processes, when deriving parameter estimates, may have a profound influence on successful vector control. The consequences of this may be of crucial interest when devising future public health policy. Graphic abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-04789-0.
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Affiliation(s)
- Aaron L Morris
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, Norfolk Place, London, W2 1PG, UK.
| | - Azra Ghani
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Neil Ferguson
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, Norfolk Place, London, W2 1PG, UK
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Connolly JB, Mumford JD, Fuchs S, Turner G, Beech C, North AR, Burt A. Systematic identification of plausible pathways to potential harm via problem formulation for investigational releases of a population suppression gene drive to control the human malaria vector Anopheles gambiae in West Africa. Malar J 2021; 20:170. [PMID: 33781254 PMCID: PMC8006393 DOI: 10.1186/s12936-021-03674-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 02/24/2021] [Accepted: 02/25/2021] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Population suppression gene drive has been proposed as a strategy for malaria vector control. A CRISPR-Cas9-based transgene homing at the doublesex locus (dsxFCRISPRh) has recently been shown to increase rapidly in frequency in, and suppress, caged laboratory populations of the malaria mosquito vector Anopheles gambiae. Here, problem formulation, an initial step in environmental risk assessment (ERA), was performed for simulated field releases of the dsxFCRISPRh transgene in West Africa. METHODS Building on consultative workshops in Africa that previously identified relevant environmental and health protection goals for ERA of gene drive in malaria vector control, 8 potentially harmful effects from these simulated releases were identified. These were stratified into 46 plausible pathways describing the causal chain of events that would be required for potential harms to occur. Risk hypotheses to interrogate critical steps in each pathway, and an analysis plan involving experiments, modelling and literature review to test each of those risk hypotheses, were developed. RESULTS Most potential harms involved increased human (n = 13) or animal (n = 13) disease transmission, emphasizing the importance to subsequent stages of ERA of data on vectorial capacity comparing transgenics to non-transgenics. Although some of the pathways (n = 14) were based on known anatomical alterations in dsxFCRISPRh homozygotes, many could also be applicable to field releases of a range of other transgenic strains of mosquito (n = 18). In addition to population suppression of target organisms being an accepted outcome for existing vector control programmes, these investigations also revealed that the efficacy of population suppression caused by the dsxFCRISPRh transgene should itself directly affect most pathways (n = 35). CONCLUSIONS Modelling will play an essential role in subsequent stages of ERA by clarifying the dynamics of this relationship between population suppression and reduction in exposure to specific potential harms. This analysis represents a comprehensive identification of plausible pathways to potential harm using problem formulation for a specific gene drive transgene and organism, and a transparent communication tool that could inform future regulatory studies, guide subsequent stages of ERA, and stimulate further, broader engagement on the use of population suppression gene drive to control malaria vectors in West Africa.
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Affiliation(s)
- John B Connolly
- Department of Life Sciences, Imperial College London, London, UK.
| | - John D Mumford
- Centre for Environmental Policy, Imperial College London, London, UK
| | - Silke Fuchs
- Department of Life Sciences, Imperial College London, London, UK
| | - Geoff Turner
- Department of Life Sciences, Imperial College London, London, UK
| | | | - Ace R North
- Department of Zoology, University of Oxford, Oxford, UK
| | - Austin Burt
- Department of Life Sciences, Imperial College London, London, UK
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Hosack GR, Ickowicz A, Hayes KR. Quantifying the risk of vector-borne disease transmission attributable to genetically modified vectors. ROYAL SOCIETY OPEN SCIENCE 2021; 8:201525. [PMID: 33959322 PMCID: PMC8074930 DOI: 10.1098/rsos.201525] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 02/11/2021] [Indexed: 06/12/2023]
Abstract
The relative risk of disease transmission caused by the potential release of transgenic vectors, such as through sterile insect technique or gene drive systems, is assessed with comparison with wild-type vectors. The probabilistic risk framework is demonstrated with an assessment of the relative risk of lymphatic filariasis, malaria and o'nyong'nyong arbovirus transmission by mosquito vectors to human hosts given a released transgenic strain of Anopheles coluzzii carrying a dominant sterile male gene construct. Harm is quantified by a logarithmic loss function that depends on the causal risk ratio, which is a quotient of basic reproduction numbers derived from mathematical models of disease transmission. The basic reproduction numbers are predicted to depend on the number of generations in an insectary colony and the number of backcrosses between the transgenic and wild-type lineages. Analogous causal risk ratios for short-term exposure to a single cohort release are also derived. These causal risk ratios were parametrized by probabilistic elicitations, and updated with experimental data for adult vector mortality. For the wild-type, high numbers of insectary generations were predicted to reduce the number of infectious human cases compared with uncolonized wild-type. Transgenic strains were predicted to produce fewer infectious cases compared with the uncolonized wild-type.
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Affiliation(s)
- Geoffrey R. Hosack
- Commonwealth Scientific and Industrial Research Organisation, Data61, Hobart, Tasmania, Australia
| | - Adrien Ickowicz
- Commonwealth Scientific and Industrial Research Organisation, Data61, Hobart, Tasmania, Australia
| | - Keith R. Hayes
- Commonwealth Scientific and Industrial Research Organisation, Data61, Hobart, Tasmania, Australia
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21
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Oberhofer G, Ivy T, Hay BA. Split versions of Cleave and Rescue selfish genetic elements for measured self limiting gene drive. PLoS Genet 2021; 17:e1009385. [PMID: 33600432 PMCID: PMC7951863 DOI: 10.1371/journal.pgen.1009385] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 03/11/2021] [Accepted: 01/28/2021] [Indexed: 12/26/2022] Open
Abstract
Gene drive elements promote the spread of linked traits, providing methods for changing the composition or fate of wild populations. Drive mechanisms that are self-limiting are attractive because they allow control over the duration and extent of trait spread in time and space, and are reversible through natural selection as drive wanes. Self-sustaining Cleave and Rescue (ClvR) elements include a DNA sequence-modifying enzyme such as Cas9/gRNAs that disrupts endogenous versions of an essential gene, a tightly linked recoded version of the essential gene resistant to cleavage (the Rescue), and a Cargo. ClvR spreads by creating loss-of-function (LOF) conditions in which those without ClvR die because they lack functional copies of the essential gene. We use modeling to show that when the Rescue-Cargo and one or both components required for LOF allele creation (Cas9 and gRNA) reside at different locations (split ClvR), drive of Rescue-Cargo is self-limiting due to a progressive decrease in Cas9 frequency, and thus opportunities for creation of LOF alleles, as spread occurs. Importantly, drive strength and duration can be extended in a measured manner-which is still self-limiting-by moving the two components close enough to each other that they experience some degree of linkage. With linkage, Cas9 transiently experiences drive by hitchhiking with Rescue-Cargo until linkage disequilibrium between the two disappears, a function of recombination frequency and number of generations, creating a novel point of control. We implement split ClvR in Drosophila, with key elements on different chromosomes. Cargo/Rescue/gRNAs spreads to high frequency in a Cas9-dependent manner, while the frequency of Cas9 decreases. These observations show that measured, transient drive, coupled with a loss of future drive potential, can be achieved using the simple toolkit that make up ClvR elements-Cas9 and gRNAs and a Rescue/Cargo.
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Affiliation(s)
- Georg Oberhofer
- California Institute of Technology, Pasadena, California, United States of America
| | - Tobin Ivy
- California Institute of Technology, Pasadena, California, United States of America
| | - Bruce A. Hay
- California Institute of Technology, Pasadena, California, United States of America
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22
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Hay BA, Oberhofer G, Guo M. Engineering the Composition and Fate of Wild Populations with Gene Drive. ANNUAL REVIEW OF ENTOMOLOGY 2021; 66:407-434. [PMID: 33035437 DOI: 10.1146/annurev-ento-020117-043154] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Insects play important roles as predators, prey, pollinators, recyclers, hosts, parasitoids, and sources of economically important products. They can also destroy crops; wound animals; and serve as vectors for plant, animal, and human diseases. Gene drive-a process by which genes, gene complexes, or chromosomes encoding specific traits are made to spread through wild populations, even if these traits result in a fitness cost to carriers-provides new opportunities for altering populations to benefit humanity and the environment in ways that are species specific and sustainable. Gene drive can be used to alter the genetic composition of an existing population, referred to as population modification or replacement, or to bring about population suppression or elimination. We describe technologies under consideration, progress that has been made, and remaining technological hurdles, particularly with respect to evolutionary stability and our ability to control the spread and ultimate fate of genes introduced into populations.
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Affiliation(s)
- Bruce A Hay
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, USA; ,
- St. John's College, University of Cambridge, Cambridge CB2 1TP, United Kingdom
| | - Georg Oberhofer
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, USA; ,
| | - Ming Guo
- Departments of Neurology and Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA;
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Naegeli H, Bresson J, Dalmay T, Dewhurst IC, Epstein MM, Guerche P, Hejatko J, Moreno FJ, Mullins E, Nogué F, Rostoks N, Sánchez Serrano JJ, Savoini G, Veromann E, Veronesi F, Bonsall MB, Mumford J, Wimmer EA, Devos Y, Paraskevopoulos K, Firbank LG. Adequacy and sufficiency evaluation of existing EFSA guidelines for the molecular characterisation, environmental risk assessment and post-market environmental monitoring of genetically modified insects containing engineered gene drives. EFSA J 2020; 18:e06297. [PMID: 33209154 PMCID: PMC7658669 DOI: 10.2903/j.efsa.2020.6297] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Advances in molecular and synthetic biology are enabling the engineering of gene drives in insects for disease vector/pest control. Engineered gene drives (that bias their own inheritance) can be designed either to suppress interbreeding target populations or modify them with a new genotype. Depending on the engineered gene drive system, theoretically, a genetic modification of interest could spread through target populations and persist indefinitely, or be restricted in its spread or persistence. While research on engineered gene drives and their applications in insects is advancing at a fast pace, it will take several years for technological developments to move to practical applications for deliberate release into the environment. Some gene drive modified insects (GDMIs) have been tested experimentally in the laboratory, but none has been assessed in small-scale confined field trials or in open release trials as yet. There is concern that the deliberate release of GDMIs in the environment may have possible irreversible and unintended consequences. As a proactive measure, the European Food Safety Authority (EFSA) has been requested by the European Commission to review whether its previously published guidelines for the risk assessment of genetically modified animals (EFSA, 2012 and 2013), including insects (GMIs), are adequate and sufficient for GDMIs, primarily disease vectors, agricultural pests and invasive species, for deliberate release into the environment. Under this mandate, EFSA was not requested to develop risk assessment guidelines for GDMIs. In this Scientific Opinion, the Panel on Genetically Modified Organisms (GMO) concludes that EFSA's guidelines are adequate, but insufficient for the molecular characterisation (MC), environmental risk assessment (ERA) and post-market environmental monitoring (PMEM) of GDMIs. While the MC,ERA and PMEM of GDMIs can build on the existing risk assessment framework for GMIs that do not contain engineered gene drives, there are specific areas where further guidance is needed for GDMIs.
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Dhole S, Lloyd AL, Gould F. Gene Drive Dynamics in Natural Populations: The Importance of Density Dependence, Space, and Sex. ANNUAL REVIEW OF ECOLOGY, EVOLUTION, AND SYSTEMATICS 2020; 51:505-531. [PMID: 34366722 PMCID: PMC8340601 DOI: 10.1146/annurev-ecolsys-031120-101013] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The spread of synthetic gene drives is often discussed in the context of panmictic populations connected by gene flow and described with simple deterministic models. Under such assumptions, an entire species could be altered by releasing a single individual carrying an invasive gene drive, such as a standard homing drive. While this remains a theoretical possibility, gene drive spread in natural populations is more complex and merits a more realistic assessment. The fate of any gene drive released in a population would be inextricably linked to the population's ecology. Given the uncertainty often involved in ecological assessment of natural populations, understanding the sensitivity of gene drive spread to important ecological factors is critical. Here we review how different forms of density dependence, spatial heterogeneity, and mating behaviors can impact the spread of self-sustaining gene drives. We highlight specific aspects of gene drive dynamics and the target populations that need further research.
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Affiliation(s)
- Sumit Dhole
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Alun L Lloyd
- Biomathematics Graduate Program and Department of Mathematics, North Carolina State University, Raleigh, North Carolina 27695-8213, USA
- Genetic Engineering and Society Center, North Carolina State University, Raleigh, North Carolina 27695-7565, USA
| | - Fred Gould
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695, USA
- Genetic Engineering and Society Center, North Carolina State University, Raleigh, North Carolina 27695-7565, USA
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25
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Li J, Aidlin Harari O, Doss A, Walling LL, Atkinson PW, Morin S, Tabashnik BE. Can CRISPR gene drive work in pest and beneficial haplodiploid species? Evol Appl 2020; 13:2392-2403. [PMID: 33005229 PMCID: PMC7513724 DOI: 10.1111/eva.13032] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 05/05/2020] [Accepted: 05/07/2020] [Indexed: 02/06/2023] Open
Abstract
Gene drives based on CRISPR/Cas9 have the potential to reduce the enormous harm inflicted by crop pests and insect vectors of human disease, as well as to bolster valued species. In contrast with extensive empirical and theoretical studies in diploid organisms, little is known about CRISPR gene drive in haplodiploids, despite their immense global impacts as pollinators, pests, natural enemies of pests, and invasive species in native habitats. Here, we analyze mathematical models demonstrating that, in principle, CRISPR homing gene drive can work in haplodiploids, as well as at sex-linked loci in diploids. However, relative to diploids, conditions favoring the spread of alleles deleterious to haplodiploid pests by CRISPR gene drive are narrower, the spread is slower, and resistance to the drive evolves faster. By contrast, the spread of alleles that impose little fitness cost or boost fitness was not greatly hindered in haplodiploids relative to diploids. Therefore, altering traits to minimize damage caused by harmful haplodiploids, such as interfering with transmission of plant pathogens, may be more likely to succeed than control efforts based on introducing traits that reduce pest fitness. Enhancing fitness of beneficial haplodiploids with CRISPR gene drive is also promising.
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Affiliation(s)
- Jun Li
- Department of StatisticsUniversity of CaliforniaRiversideCAUSA
| | | | | | - Linda L. Walling
- Department of Botany and Plant SciencesUniversity of CaliforniaRiversideCAUSA
| | | | - Shai Morin
- Department of EntomologyHebrew University of JerusalemRehovotIsrael
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26
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North AR, Burt A, Godfray HCJ. Modelling the suppression of a malaria vector using a CRISPR-Cas9 gene drive to reduce female fertility. BMC Biol 2020; 18:98. [PMID: 32782000 PMCID: PMC7422583 DOI: 10.1186/s12915-020-00834-z] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 07/22/2020] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Gene drives based on CRISPR-Cas9 technology are increasingly being considered as tools for reducing the capacity of mosquito populations to transmit malaria, and one of the most promising options is driving endonuclease genes that reduce the fertility of female mosquitoes. In particular, there is much interest in constructs that target the conserved mosquito doublesex (dsx) gene such that the emergence of functional drive-resistant alleles is unlikely. Proof of principle that these constructs can lead to substantial population suppression has been obtained in population cages, and they are being evaluated for use in sub-Saharan Africa. Here, we use simulation modelling to understand the factors affecting the spread of this type of gene drive over a one million-square kilometre area of West Africa containing substantial environmental and social heterogeneity. RESULTS We found that a driving endonuclease gene targeting female fertility could lead to substantial reductions in malaria vector populations on a regional scale. The exact level of suppression is influenced by additional fitness costs of the transgene such as the somatic expression of Cas9, and its deposition in sperm or eggs leading to damage to the zygote. In the absence of these costs, or of emergent drive-resistant alleles that restore female fertility, population suppression across the study area is predicted to stabilise at ~ 95% 4 years after releases commence. Small additional fitness costs do not greatly affect levels of suppression, though if the fertility of females whose offspring transmit the construct drops by more than ~ 40%, then population suppression is much less efficient. We show the suppression potential of a drive allele with high fitness costs can be enhanced by engineering it also to express male bias in the progeny of transgenic males. Irrespective of the strength of the drive allele, the spatial model predicts somewhat less suppression than equivalent non-spatial models, in particular in highly seasonal regions where dry season stochasticity reduces drive efficiency. We explored the robustness of these results to uncertainties in mosquito ecology, in particular their method of surviving the dry season and their dispersal rates. CONCLUSIONS The modelling presented here indicates that considerable suppression of vector populations can be achieved within a few years of using a female sterility gene drive, though the impact is likely to be heterogeneous in space and time.
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Affiliation(s)
- Ace R North
- Department of Zoology, University of Oxford, Oxford, UK.
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27
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Selvaraj P, Wenger EA, Bridenbecker D, Windbichler N, Russell JR, Gerardin J, Bever CA, Nikolov M. Vector genetics, insecticide resistance and gene drives: An agent-based modeling approach to evaluate malaria transmission and elimination. PLoS Comput Biol 2020; 16:e1008121. [PMID: 32797077 PMCID: PMC7449459 DOI: 10.1371/journal.pcbi.1008121] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 08/26/2020] [Accepted: 07/02/2020] [Indexed: 12/19/2022] Open
Abstract
Vector control has been a key component in the fight against malaria for decades, and chemical insecticides are critical to the success of vector control programs worldwide. However, increasing resistance to insecticides threatens to undermine these efforts. Understanding the evolution and propagation of resistance is thus imperative to mitigating loss of intervention effectiveness. Additionally, accelerated research and development of new tools that can be deployed alongside existing vector control strategies is key to eradicating malaria in the near future. Methods such as gene drives that aim to genetically modify large mosquito populations in the wild to either render them refractory to malaria or impair their reproduction may prove invaluable tools. Mathematical models of gene flow in populations, which is the transfer of genetic information from one population to another through migration, can offer invaluable insight into the behavior and potential impact of gene drives as well as the spread of insecticide resistance in the wild. Here, we present the first multi-locus, agent-based model of vector genetics that accounts for mutations and a many-to-many mapping cardinality of genotypes to phenotypes to investigate gene flow, and the propagation of gene drives in Anopheline populations. This model is embedded within a large scale individual-based model of malaria transmission representative of a high burden, high transmission setting characteristic of the Sahel. Results are presented for the selection of insecticide-resistant vectors and the spread of resistance through repeated deployment of insecticide treated nets (ITNs), in addition to scenarios where gene drives act in concert with existing vector control tools such as ITNs. The roles of seasonality, spatial distribution of vector habitat and feed sites, and existing vector control in propagating alleles that confer phenotypic traits via gene drives that result in reduced transmission are explored. The ability to model a spectrum of vector species with different genotypes and phenotypes in the context of malaria transmission allows us to test deployment strategies for existing interventions that reduce the deleterious effects of resistance and allows exploration of the impact of new tools being proposed or developed.
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Affiliation(s)
- Prashanth Selvaraj
- Institute for Disease Modeling, Bellevue, Washington, United States of America
| | - Edward A. Wenger
- Institute for Disease Modeling, Bellevue, Washington, United States of America
| | - Daniel Bridenbecker
- Institute for Disease Modeling, Bellevue, Washington, United States of America
| | - Nikolai Windbichler
- Department of Life Sciences, Imperial College London, South Kensington, United Kingdom
| | - Jonathan R. Russell
- Institute for Disease Modeling, Bellevue, Washington, United States of America
| | - Jaline Gerardin
- Institute for Disease Modeling, Bellevue, Washington, United States of America
- Department of Preventive Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Caitlin A. Bever
- Institute for Disease Modeling, Bellevue, Washington, United States of America
| | - Milen Nikolov
- Institute for Disease Modeling, Bellevue, Washington, United States of America
- Sage Bionetworks, Seattle, Washington, United States of America
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Malavia D, Gow NAR, Usher J. Advances in Molecular Tools and In Vivo Models for the Study of Human Fungal Pathogenesis. Microorganisms 2020; 8:E803. [PMID: 32466582 PMCID: PMC7356103 DOI: 10.3390/microorganisms8060803] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/08/2020] [Accepted: 05/16/2020] [Indexed: 12/14/2022] Open
Abstract
Pathogenic fungi represent an increasing infectious disease threat to humans, especially with an increasing challenge of antifungal drug resistance. Over the decades, numerous tools have been developed to expedite the study of pathogenicity, initiation of disease, drug resistance and host-pathogen interactions. In this review, we highlight advances that have been made in the use of molecular tools using CRISPR technologies, RNA interference and transposon targeted mutagenesis. We also discuss the use of animal models in modelling disease of human fungal pathogens, focusing on zebrafish, the silkworm, Galleria mellonella and the murine model.
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Affiliation(s)
| | | | - Jane Usher
- Medical Research Council Centre for Medical Mycology, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK; (D.M.); (N.A.R.G.)
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29
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Chabas H, Nicot A, Meaden S, Westra ER, Tremblay DM, Pradier L, Lion S, Moineau S, Gandon S. Variability in the durability of CRISPR-Cas immunity. Philos Trans R Soc Lond B Biol Sci 2020; 374:20180097. [PMID: 30905283 DOI: 10.1098/rstb.2018.0097] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The durability of host resistance is challenged by the ability of pathogens to escape the defence of their hosts. Understanding the variability in the durability of host resistance is of paramount importance for designing more effective control strategies against infectious diseases. Here, we study the durability of various clustered regularly interspaced short palindromic repeats-Cas (CRISPR-Cas) alleles of the bacteria Streptococcus thermophilus against lytic phages. We found substantial variability in durability among different resistant bacteria. Since the escape of the phage is driven by a mutation in the phage sequence targeted by CRISPR-Cas, we explored the fitness costs associated with these escape mutations. We found that, on average, escape mutations decrease the fitness of the phage. Yet, the magnitude of this fitness cost does not predict the durability of CRISPR-Cas immunity. We contend that this variability in the durability of resistance may be because of variations in phage mutation rate or in the proportion of lethal mutations across the phage genome. These results have important implications on the coevolutionary dynamics between bacteria and phages and for the optimal deployment of resistance strategies against pathogens and pests. Understanding the durability of CRISPR-Cas immunity may also help develop more effective gene-drive strategies based on CRISPR-Cas9 technology. This article is part of a discussion meeting issue 'The ecology and evolution of prokaryotic CRISPR-Cas adaptive immune systems'.
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Affiliation(s)
- Hélène Chabas
- 1 CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE , 1919, Route de Mende, 34293 Montpellier Cedex 5, Paris , France
| | - Antoine Nicot
- 1 CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE , 1919, Route de Mende, 34293 Montpellier Cedex 5, Paris , France
| | - Sean Meaden
- 2 Environment and Sustainability Institute, University of Exeter , Penryn Campus, Penryn, Cornwall TR10 9FE , UK
| | - Edze R Westra
- 2 Environment and Sustainability Institute, University of Exeter , Penryn Campus, Penryn, Cornwall TR10 9FE , UK
| | - Denise M Tremblay
- 3 Département de Biochimie, Microbiologie et de Bio-Informatique, Faculté des Sciences et de Génie, Université Laval , 1045 Avenue de la Médecine, Québec City, Quebec , Canada G1V 0A6.,4 Félix d'Hérelle Reference Center for Bacterial Viruses and Groupe de Recherche en Écologie Buccale, Faculté de Médecine Dentaire, Université Laval , Québec City, Qubec , Canada G1V 0A6
| | - Léa Pradier
- 1 CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE , 1919, Route de Mende, 34293 Montpellier Cedex 5, Paris , France
| | - Sébastien Lion
- 1 CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE , 1919, Route de Mende, 34293 Montpellier Cedex 5, Paris , France
| | - Sylvain Moineau
- 3 Département de Biochimie, Microbiologie et de Bio-Informatique, Faculté des Sciences et de Génie, Université Laval , 1045 Avenue de la Médecine, Québec City, Quebec , Canada G1V 0A6.,4 Félix d'Hérelle Reference Center for Bacterial Viruses and Groupe de Recherche en Écologie Buccale, Faculté de Médecine Dentaire, Université Laval , Québec City, Qubec , Canada G1V 0A6
| | - Sylvain Gandon
- 1 CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE , 1919, Route de Mende, 34293 Montpellier Cedex 5, Paris , France
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30
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Westra ER, van Houte S, Gandon S, Whitaker R. The ecology and evolution of microbial CRISPR-Cas adaptive immune systems. Philos Trans R Soc Lond B Biol Sci 2020; 374:20190101. [PMID: 30905294 DOI: 10.1098/rstb.2019.0101] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Edze R Westra
- 1 ESI and CEC, Biosciences, University of Exeter , Cornwall Campus, Penryn TR10 9EZ , UK
| | - Stineke van Houte
- 1 ESI and CEC, Biosciences, University of Exeter , Cornwall Campus, Penryn TR10 9EZ , UK
| | - Sylvain Gandon
- 2 CEFE UMR 5175, CNRS Université de Montpellier Université Paul-Valéry Montpellier EPHE , 34293 Montpellier Cedex 5 , France
| | - Rachel Whitaker
- 3 Department of Microbiology, University of Illinois , Urbana-Champaign, 601 S. Goodwin Avenue, Urbana, IL 61801 , USA
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James SL, Marshall JM, Christophides GK, Okumu FO, Nolan T. Toward the Definition of Efficacy and Safety Criteria for Advancing Gene Drive-Modified Mosquitoes to Field Testing. Vector Borne Zoonotic Dis 2020; 20:237-251. [PMID: 32155390 PMCID: PMC7153640 DOI: 10.1089/vbz.2019.2606] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mosquitoes containing gene drive systems are being developed as complementary tools to prevent transmission of malaria and other mosquito-borne diseases. As with any new tool, decision makers and other stakeholders will need to balance risks (safety) and benefits (efficacy) when considering the rationale for testing and deploying gene drive-modified mosquito products. Developers will benefit from standards for judging whether an investigational gene drive product meets acceptability criteria for advancing to field trials. Such standards may be formalized as preferred product characteristics and target product profiles, which describe the desired attributes of the product category and of a particular product, respectively. This report summarizes discussions from two scientific workshops aimed at identifying efficacy and safety characteristics that must be minimally met for an investigational gene drive-modified mosquito product to be deemed viable to move from contained testing to field release and the data that will be needed to support an application for first field release.
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Affiliation(s)
- Stephanie L James
- Foundation for the National Institutes of Health, North Bethesda, Maryland
| | | | | | | | - Tony Nolan
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
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32
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Heffel MG, Finnigan GC. Mathematical modeling of self-contained CRISPR gene drive reversal systems. Sci Rep 2019; 9:20050. [PMID: 31882576 PMCID: PMC6934693 DOI: 10.1038/s41598-019-54805-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Accepted: 11/19/2019] [Indexed: 12/15/2022] Open
Abstract
There is a critical need for further research into methods to control biological populations. Numerous challenges to agriculture, ecological systems, and human health could be mitigated by the targeted reduction and management of key species (e.g. pests, parasites, and vectors for pathogens). The discovery and adaptation of the CRISPR/Cas editing platform co-opted from bacteria has provided a mechanism for a means to alter an entire population. A CRISPR-based gene drive system can allow for the forced propagation of a genetic element that bypasses Mendelian inheritance which can be used to bias sex determination, install exogenous information, or remove endogenous DNA within an entire species. Laboratory studies have demonstrated the potency by which gene drives can operate within insects and other organisms. However, continued research and eventual application face serious opposition regarding issues of policy, biosafety, effectiveness, and reversal. Previous mathematical work has suggested the use of modified gene drive designs that are limited in spread such as daisy chain or underdominance drives. However, no system has yet been proposed that allows for an inducible reversal mechanism without requiring the introduction of additional individuals. Here, we study gene drive effectiveness, fitness, and inducible drive systems that could respond to external stimuli expanding from a previous frequency-based population model. We find that programmed modification during gene drive propagation could serve as a potent safeguard to either slow or completely reverse drive systems and allow for a return to the original wild-type population.
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Affiliation(s)
- Matthew G Heffel
- Division of Biology, 116 Ackert Hall, Kansas State University, Manhattan, KS 66506, USA
| | - Gregory C Finnigan
- Department of Biochemistry and Molecular Biophysics, 141 Chalmers Hall, Kansas State University, Manhattan, KS 66506, USA.
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33
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Cash SA, Lorenzen MD, Gould F. The distribution and spread of naturally occurring Medea selfish genetic elements in the United States. Ecol Evol 2019; 9:14407-14416. [PMID: 31938528 PMCID: PMC6953677 DOI: 10.1002/ece3.5876] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 10/31/2019] [Accepted: 11/05/2019] [Indexed: 01/01/2023] Open
Abstract
Selfish genetic elements (SGEs) are DNA sequences that are transmitted to viable offspring in greater than Mendelian frequencies. Medea SGEs occur naturally in some populations of red flour beetle (Tribolium castaneum) and are expected to increase in frequency within populations and spread among populations. The large-scale U.S. distributions of Medea-4 (M4) had been mapped based on samples from 1993 to 1995. We sampled beetles in 2011-2014 and show that the distribution of M4 in the United States is dynamic and has shifted southward. By using a genetic marker of Medea-1 (M1), we found five unique geographic clusters with high and low M1 frequencies in a pattern not predicted by microsatellite-based analysis of population structure. Our results indicate the absence of rigid barriers to Medea spread in the United States, so assessment of what factors have limited its current distribution requires further investigation. There is great interest in using synthetic SGEs, including synthetic Medea, to alter or suppress pest populations, but there is concern about unpredicted spread of these SGEs and potential for populations to become resistant to them. The finding of patchy distributions of Medea elements suggests that released synthetic SGEs cannot always be expected to spread uniformly, especially in target species with limited dispersal.
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Affiliation(s)
- Sarah A. Cash
- Program in GeneticsDepartment of Biological SciencesNorth Carolina State UniversityRaleighNCUSA
| | - Marce D. Lorenzen
- Department of Entomology and Plant PathologyNorth Carolina State UniversityRaleighNCUSA
| | - Fred Gould
- Department of Entomology and Plant PathologyNorth Carolina State UniversityRaleighNCUSA
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34
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You L, Bi HL, Wang YH, Li XW, Chen XE, Li ZQ. CRISPR/Cas9-based mutation reveals Argonaute 1 is essential for pigmentation in Ostrinia furnacalis. INSECT SCIENCE 2019; 26:1020-1028. [PMID: 29938905 DOI: 10.1111/1744-7917.12628] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 05/27/2018] [Accepted: 06/13/2018] [Indexed: 06/08/2023]
Abstract
Ostrinia furnacalis (Lepidoptera: Pyralidae) is one of the most destructive agricultural pests in Asia. Traditional pest-management methods include sex pheromone capture, transgenic crops that produce Bacillus thuringiensis toxin, and pesticides. Although these strategies control pest populations effectively, they also cause negative side effects, including dramatically increased pesticide resistance, severe pollution, and hazards for human health. Recently developed genome editing tools provide new prospects for pest management and have been successfully used in several species. However, few examples have been reported in the agricultural pest O. furnacalis due to a lack in genomic information. In this report, we identified only one transcript of O. furnacalis Argonaute 1 (OfAgo1) gene from the genome and cloned the open reading frame. OfAgo1 presented the maximum expression at the embryo stage or in the fat body during the larval stages. To understand its function, an OfAgo1 mutant was constructed using the Clustered Regularly Interspaced Short Palindromic Repeat/RNA-guided Cas9 nuclease (CRISPR/Cas9). Mutagenesis of OfAgo1 disrupted cuticle pigmentation by down-regulating micro RNAs and pigmentation-related genes. This is the first report for the cloning and functional analysis of OfAgo1, revealing a role of OfAgo1 in cuticle pigmentation. The current report also established a CRISPR/Cas9 system in O. furnacalis, providing a new insight for pest management.
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Affiliation(s)
- Lang You
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Hong-Lun Bi
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Yao-Hui Wang
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Xiao-Wei Li
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Xi-En Chen
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Zhi-Qian Li
- CAS Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
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35
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Bull JJ, Remien CH, Gomulkiewicz R, Krone SM. Spatial structure undermines parasite suppression by gene drive cargo. PeerJ 2019; 7:e7921. [PMID: 31681512 PMCID: PMC6824332 DOI: 10.7717/peerj.7921] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 09/18/2019] [Indexed: 12/17/2022] Open
Abstract
Gene drives may be used in two ways to curtail vectored diseases. Both involve engineering the drive to spread in the vector population. One approach uses the drive to directly depress vector numbers, possibly to extinction. The other approach leaves intact the vector population but suppresses the disease agent during its interaction with the vector. This second application may use a drive engineered to carry a genetic cargo that blocks the disease agent. An advantage of the second application is that it is far less likely to select vector resistance to block the drive, but the disease agent may instead evolve resistance to the inhibitory cargo. However, some gene drives are expected to spread so fast and attain such high coverage in the vector population that, if the disease agent can evolve resistance only gradually, disease eradication may be feasible. Here we use simple models to show that spatial structure in the vector population can greatly facilitate persistence and evolution of resistance by the disease agent. We suggest simple approaches to avoid some types of spatial structure, but others may be intrinsic to the populations being challenged and difficult to overcome.
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Affiliation(s)
- James J. Bull
- Department of Biological Sciences, University of Idaho, Moscow, ID, United States of America
| | - Christopher H. Remien
- Department of Mathematics, University of Idaho, Moscow, ID, United States of America
| | - Richard Gomulkiewicz
- School of Biological Sciences, Washington State University, Pullman, WA, United States of America
| | - Stephen M. Krone
- Department of Mathematics, University of Idaho, Moscow, ID, United States of America
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Pixley KV, Falck-Zepeda JB, Giller KE, Glenna LL, Gould F, Mallory-Smith CA, Stelly DM, Stewart CN. Genome Editing, Gene Drives, and Synthetic Biology: Will They Contribute to Disease-Resistant Crops, and Who Will Benefit? ANNUAL REVIEW OF PHYTOPATHOLOGY 2019; 57:165-188. [PMID: 31150590 DOI: 10.1146/annurev-phyto-080417-045954] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Genetically engineered crops have been grown for more than 20 years, resulting in widespread albeit variable benefits for farmers and consumers. We review current, likely, and potential genetic engineering (GE) applications for the development of disease-resistant crop cultivars. Gene editing, gene drives, and synthetic biology offer novel opportunities to control viral, bacterial, and fungal pathogens, parasitic weeds, and insect vectors of plant pathogens. We conclude that there will be no shortage of GE applications totackle disease resistance and other farmer and consumer priorities for agricultural crops. Beyond reviewing scientific prospects for genetically engineered crops, we address the social institutional forces that are commonly overlooked by biological scientists. Intellectual property regimes, technology regulatory frameworks, the balance of funding between public- and private-sector research, and advocacy by concerned civil society groups interact to define who uses which GE technologies, on which crops, and for the benefit of whom. Ensuring equitable access to the benefits of genetically engineered crops requires affirmative policies, targeted investments, and excellent science.
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Affiliation(s)
- Kevin V Pixley
- International Maize and Wheat Improvement Center (CIMMYT), 56237 Texcoco, Mexico;
| | - Jose B Falck-Zepeda
- International Food Policy Research Institute (IFPRI), Washington, DC 20005-3915, USA
| | - Ken E Giller
- Plant Production Systems Group, Wageningen University & Research (WUR), 6700 AK Wageningen, The Netherlands
| | - Leland L Glenna
- Department of Agricultural Economics, Sociology, and Education, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Fred Gould
- Genetic Engineering and Society Center and Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Carol A Mallory-Smith
- Department of Crop and Soil Science, Oregon State University, Corvallis, Oregon 97331, USA
| | - David M Stelly
- Department of Soil and Crop Sciences, Texas A&M University, College Station, Texas 77843-2474, USA
| | - C Neal Stewart
- Department of Plant Sciences and Center for Agricultural Synthetic Biology, University of Tennessee, Knoxville, Tennessee 37996, USA
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Rode NO, Estoup A, Bourguet D, Courtier-Orgogozo V, Débarre F. Population management using gene drive: molecular design, models of spread dynamics and assessment of ecological risks. CONSERV GENET 2019. [DOI: 10.1007/s10592-019-01165-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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North AR, Burt A, Godfray HCJ. Modelling the potential of genetic control of malaria mosquitoes at national scale. BMC Biol 2019; 17:26. [PMID: 30922310 PMCID: PMC6440076 DOI: 10.1186/s12915-019-0645-5] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 03/06/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The persistence of malaria in large parts of sub-Saharan Africa has motivated the development of novel tools to complement existing control programmes, including gene-drive technologies to modify mosquito vector populations. Here, we use a stochastic simulation model to explore the potential of using a driving-Y chromosome to suppress vector populations in a 106 km2 area of West Africa including all of Burkina Faso. RESULTS The consequence of driving-Y introductions is predicted to vary across the landscape, causing elimination of the target species in some regions and suppression in others. We explore how this variation is determined by environmental conditions, mosquito behaviour, and the properties of the gene-drive. Seasonality is particularly important, and we find population elimination is more likely in regions with mild dry seasons whereas suppression is more likely in regions with strong seasonality. CONCLUSIONS Despite the spatial heterogeneity, we suggest that repeated introductions of modified mosquitoes over a few years into a small fraction of human settlements may be sufficient to substantially reduce the overall number of mosquitoes across the entire geographic area.
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Affiliation(s)
- Ace R North
- Department of Zoology, University of Oxford, Oxford, UK.
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Facchinelli L, North AR, Collins CM, Menichelli M, Persampieri T, Bucci A, Spaccapelo R, Crisanti A, Benedict MQ. Large-cage assessment of a transgenic sex-ratio distortion strain on populations of an African malaria vector. Parasit Vectors 2019; 12:70. [PMID: 30728060 PMCID: PMC6366042 DOI: 10.1186/s13071-019-3289-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 01/03/2019] [Indexed: 12/25/2022] Open
Abstract
Background Novel transgenic mosquito control methods require progressively more realistic evaluation. The goal of this study was to determine the effect of a transgene that causes a male-bias sex ratio on Anopheles gambiae target populations in large insectary cages. Methods Life history characteristics of Anopheles gambiae wild type and Ag(PMB)1 (aka gfp124L-2) transgenic mosquitoes, whose progeny are 95% male, were measured in order to parameterize predictive population models. Ag(PMB)1 males were then introduced at two ratios into large insectary cages containing target wild type populations with stable age distributions and densities. The predicted proportion of females and those observed in the large cages were compared. A related model was then used to predict effects of male releases on wild mosquitoes in a west African village. Results The frequency of transgenic mosquitoes in target populations reached an average of 0.44 ± 0.02 and 0.56 ± 0.02 after 6 weeks in the 1:1 and in the 3:1 release ratio treatments (transgenic male:wild male) respectively. Transgenic males caused sex-ratio distortion of 73% and 80% males in the 1:1 and 3:1 treatments, respectively. The number of eggs laid in the transgenic treatments declined as the experiment progressed, with a steeper decline in the 3:1 than in the 1:1 releases. The results of the experiment are partially consistent with predictions of the model; effect size and variability did not conform to the model in two out of three trials, effect size was over-estimated by the model and variability was greater than anticipated, possibly because of sampling effects in restocking. The model estimating the effects of hypothetical releases on the mosquito population of a West African village demonstrated that releases could significantly reduce the number of females in the wild population. The interval of releases is not expected to have a strong effect. Conclusions The biological data produced to parameterize the model, the model itself, and the results of the experiments are components of a system to evaluate and predict the performance of transgenic mosquitoes. Together these suggest that the Ag(PMB)1 strain has the potential to be useful for reversible population suppression while this novel field develops.
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Affiliation(s)
- Luca Facchinelli
- Department of Experimental Medicine, University of Perugia, Perugia, Italy.,Present address: Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Ace R North
- Department of Zoology, University of Oxford, New Radcliffe House, Woodstock Road, Oxford, OX2 6GG, UK
| | - C Matilda Collins
- Centre for Environmental Policy, Imperial College London, 16-18 Princes Gardens, London, SW7 1NE, UK
| | - Miriam Menichelli
- Polo di Genomica Genetica e Biologia, Via mazzieri 3, 05100, Terni, Italy
| | - Tania Persampieri
- Polo di Genomica Genetica e Biologia, Via mazzieri 3, 05100, Terni, Italy
| | - Alessandro Bucci
- Polo di Genomica Genetica e Biologia, Via mazzieri 3, 05100, Terni, Italy
| | - Roberta Spaccapelo
- Department of Experimental Medicine, University of Perugia, 06132, Perugia, Italy
| | - Andrea Crisanti
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building Imperial College Road South Kensington, London, SW7 2AZ, UK
| | - Mark Q Benedict
- Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA, 30329, USA.
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40
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Neve P. Gene drive systems: do they have a place in agricultural weed management? PEST MANAGEMENT SCIENCE 2018; 74:2671-2679. [PMID: 29999229 PMCID: PMC6282749 DOI: 10.1002/ps.5137] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 07/06/2018] [Accepted: 07/07/2018] [Indexed: 05/11/2023]
Abstract
There is a pressing need for novel control techniques in agricultural weed management. Direct genetic control of agricultural pests encompasses a range of techniques to introduce and spread novel, fitness-reducing genetic modifications through pest populations. Recently, the development of CRISPR-Cas9 gene editing has brought these approaches into sharper focus. Proof of concept for CRISPR-Cas9-based gene drives has been demonstrated for the control of disease-vectoring insects. This article considers whether and how gene drives may be applied in agricultural weed management, focusing on CRISPR-Cas9-based systems. Population-suppression drives might be employed to introduce and proliferate deleterious mutations that directly impact fitness and weediness, whereas population-sensitizing drives would seek to edit weed genomes so that populations are rendered more sensitive to subsequent management interventions. Technical challenges relating to plant transformation and gene editing in planta are considered, and the implementation of gene drives for timely and sustainable weed management is reviewed in the light of weed population biology. The technical, biological, practical and regulatory challenges remain significant. Modelling-based studies can inform how and if gene drives could be employed in weed populations. These studies are an essential first step towards determining the utility of gene drives for weed management. © 2018 The Author. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Affiliation(s)
- Paul Neve
- Biointeractions & Crop Protection DepartmentRothamsted Research, West CommonHertfordshireUK
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Adolfi A, Lycett GJ. Opening the toolkit for genetic analysis and control of Anopheles mosquito vectors. CURRENT OPINION IN INSECT SCIENCE 2018; 30:8-18. [PMID: 30553490 DOI: 10.1016/j.cois.2018.07.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 07/24/2018] [Indexed: 06/09/2023]
Abstract
Anopheles is the only genus of mosquitoes that transmit human malaria and consequently the focus of large scale genome and transcriptome-wide association studies. Genetic tools to define the function of the candidate genes arising from these analyses are vital. Moreover, genome editing offers the potential to modify Anopheles population structure at local and global scale to provide complementary tools towards the ultimate goal of malaria elimination. Major breakthroughs in Anopheles genetic analysis came with the development of germline transformation and RNA interference technology. Yet, the field has been revolutionised again by precise genome editing now possible through site-specific nucleases. Here we review the components of the current genetic toolkit available to study Anopheles, focusing particularly on how these technical advances are used to gain insight into malaria transmission and the design of genetic methods to control Anopheles vectors.
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Affiliation(s)
- Adriana Adolfi
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, CA 92697-4500, USA
| | - Gareth John Lycett
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
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Yan Y, Finnigan GC. Development of a multi-locus CRISPR gene drive system in budding yeast. Sci Rep 2018; 8:17277. [PMID: 30467400 PMCID: PMC6250742 DOI: 10.1038/s41598-018-34909-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 10/26/2018] [Indexed: 12/11/2022] Open
Abstract
The discovery of CRISPR/Cas gene editing has allowed for major advances in many biomedical disciplines and basic research. One arrangement of this biotechnology, a nuclease-based gene drive, can rapidly deliver a genetic element through a given population and studies in fungi and metazoans have demonstrated the success of such a system. This methodology has the potential to control biological populations and contribute to eradication of insect-borne diseases, agricultural pests, and invasive species. However, there remain challenges in the design, optimization, and implementation of gene drives including concerns regarding biosafety, containment, and control/inhibition. Given the numerous gene drive arrangements possible, there is a growing need for more advanced designs. In this study, we use budding yeast to develop an artificial multi-locus gene drive system. Our minimal setup requires only a single copy of S. pyogenes Cas9 and three guide RNAs to propagate three gene drives. We demonstrate how this system could be used for targeted allele replacement of native genes and to suppress NHEJ repair systems by modifying DNA Ligase IV. A multi-locus gene drive configuration provides an expanded suite of options for complex attributes including pathway redundancy, combatting evolved resistance, and safeguards for control, inhibition, or reversal of drive action.
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Affiliation(s)
- Yao Yan
- Department of Biochemistry and Molecular Biophysics, Kansas State University, 141 Chalmers Hall, Manhattan, KS, 66506, USA
| | - Gregory C Finnigan
- Department of Biochemistry and Molecular Biophysics, Kansas State University, 141 Chalmers Hall, Manhattan, KS, 66506, USA.
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Burt A, Deredec A. Self-limiting population genetic control with sex-linked genome editors. Proc Biol Sci 2018; 285:rspb.2018.0776. [PMID: 30051868 PMCID: PMC6083257 DOI: 10.1098/rspb.2018.0776] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 06/28/2018] [Indexed: 12/30/2022] Open
Abstract
In male heterogametic species the Y chromosome is transmitted solely from fathers to sons, and is selected for based only on its impacts on male fitness. This fact can be exploited to develop efficient pest control strategies that use Y-linked editors to disrupt the fitness of female descendants. With simple population genetic and dynamic models we show that Y-linked editors can be substantially more efficient than other self-limiting strategies and, while not as efficient as gene drive approaches, are expected to have less impact on non-target populations with which there is some gene flow. Efficiency can be further augmented by simultaneously releasing an autosomal X-shredder construct, in either the same or different males. Y-linked editors may be an attractive option to consider when efficient control of a species is desired in some locales but not others.
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Affiliation(s)
- Austin Burt
- Life Sciences, Imperial College, Silwood Park, Ascot SL5 7PY, UK
| | - Anne Deredec
- UMR BIOGER, INRA AgroParisTech, Université Paris-Saclay, Avenue Lucien Bretignières, 78850 Thiverval-Grignon, France
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Lambert B, North A, Burt A, Godfray HCJ. The use of driving endonuclease genes to suppress mosquito vectors of malaria in temporally variable environments. Malar J 2018; 17:154. [PMID: 29618367 PMCID: PMC5885365 DOI: 10.1186/s12936-018-2259-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 03/08/2018] [Indexed: 12/17/2022] Open
Abstract
Background The use of gene drive systems to manipulate populations of malaria vectors is currently being investigated as a method of malaria control. One potential system uses driving endonuclease genes (DEGs) to spread genes that impose a genetic load. Previously, models have shown that the introduction of DEG-bearing mosquitoes could suppress or even extinguish vector populations in spatially-heterogeneous environments which were constant over time. In this study, a stochastic spatially-explicit model of mosquito ecology is combined with a rainfall model which enables the generation of a variety of daily precipitation patterns. The model is then used to investigate how releases of a DEG that cause a bias in population sex ratios towards males are affected by seasonal or random rainfall patterns. The parameters of the rainfall model are then fitted using data from Bamako, Mali, and Mbita, Kenya, to evaluate release strategies in similar climatic conditions. Results In landscapes with abundant resources and large mosquito populations the spread of a DEG is reliable, irrespective of variability in rainfall. This study thus focuses mainly on landscapes with low density mosquito populations where the spread of a DEG may be sensitive to variation in rainfall. It is found that an introduced DEG will spread into its target population more reliably in wet conditions, yet an established DEG will have more impact in dry conditions. In strongly seasonal environments, it is thus preferable to release DEGs at the onset of a wet season to maximize their spread before the following dry season. If the variability in rainfall has a substantial random component, there is a net increase in the probability that a DEG release will lead to population extinction, due to the increased impact of a DEG which manages to establish in these conditions. For Bamako, where annual rainfall patterns are characterized by a long dry season, it is optimal to release a DEG at the start of the wet season, where the population is growing fastest. By contrast release timing is of lower importance for the less seasonal Mbita. Conclusion This analysis suggests that DEG based methods of malaria vector control can be effective in a wide range of climates. In environments with substantial temporal variation in rainfall, careful timing of releases which accounts for the temporal variation in population density can substantially improve the probability of mosquito suppression or extinction. Electronic supplementary material The online version of this article (10.1186/s12936-018-2259-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ben Lambert
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK. .,Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, Imperial College London, St. Mary's Campus, Norfolk Place, London, W2 1PG, UK.
| | - Ace North
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
| | - Austin Burt
- Department of Life Sciences, Imperial College London, Silwood Park, Ascot, Berks, SL5 7PY, UK
| | - H Charles J Godfray
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
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Dong Y, Simões ML, Marois E, Dimopoulos G. CRISPR/Cas9 -mediated gene knockout of Anopheles gambiae FREP1 suppresses malaria parasite infection. PLoS Pathog 2018. [PMID: 29518156 PMCID: PMC5843335 DOI: 10.1371/journal.ppat.1006898] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Plasmodium relies on numerous agonists during its journey through the mosquito vector, and these agonists represent potent targets for transmission-blocking by either inhibiting or interfering with them pre- or post-transcriptionally. The recently developed CRISPR/Cas9-based genome editing tools for Anopheles mosquitoes provide new and promising opportunities for the study of agonist function and for developing malaria control strategies through gene deletion to achieve complete agonist inactivation. Here we have established a modified CRISPR/Cas9 gene editing procedure for the malaria vector Anopheles gambiae, and studied the effect of inactivating the fibrinogen-related protein 1 (FREP1) gene on the mosquito’s susceptibility to Plasmodium and on mosquito fitness. FREP1 knockout mutants developed into adult mosquitoes that showed profound suppression of infection with both human and rodent malaria parasites at the oocyst and sporozoite stages. FREP1 inactivation, however, resulted in fitness costs including a significantly lower blood-feeding propensity, fecundity and egg hatching rate, a retarded pupation time, and reduced longevity after a blood meal. The causative agent of malaria, Plasmodium, has to complete a complex infection cycle in the Anopheles gambiae mosquito vector in order to reach the salivary gland from where it can be transmitted to a human host. The parasite’s development in the mosquito relies on numerous host factors (agonists), and their inhibition or inactivation can thereby result in suppression of infection and consequently malaria transmission. The recently developed CRISPR/Cas9-based genome editing tools for Anopheles mosquitoes provide new and promising opportunities to delete (inactivate) Plasmodium agonists to better understand their function and for blocking malaria transmission. Here we have established a modified CRISPR/Cas9 genome editing technique for malaria vector A. gambiae mosquitoes. Through this approach we have inactivated the fibrinogen-related protein 1 (FREP1) gene, via CRISPR/Cas9 genome editing, and the impact of this manipulation on the mosquito’s susceptibility to Plasmodium and on mosquito fitness. FREP1 knockout mutants showed a profound suppression of infection with both human and rodent malaria parasites, while it also resulted in fitness costs: a significantly lower blood-feeding propensity, fecundity and egg hatching rate, and a retarded larval development and pupation time, and reduced longevity after a blood meal.
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Affiliation(s)
- Yuemei Dong
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Malaria Research Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Maria L. Simões
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Malaria Research Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Eric Marois
- Inserm, CNRS, Université de Strasbourg, Strasbourg, France
| | - George Dimopoulos
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Malaria Research Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
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Roggenkamp E, Giersch RM, Schrock MN, Turnquist E, Halloran M, Finnigan GC. Tuning CRISPR-Cas9 Gene Drives in Saccharomyces cerevisiae. G3 (BETHESDA, MD.) 2018; 8:999-1018. [PMID: 29348295 PMCID: PMC5844318 DOI: 10.1534/g3.117.300557] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 01/16/2018] [Indexed: 12/11/2022]
Abstract
Control of biological populations is an ongoing challenge in many fields, including agriculture, biodiversity, ecological preservation, pest control, and the spread of disease. In some cases, such as insects that harbor human pathogens (e.g., malaria), elimination or reduction of a small number of species would have a dramatic impact across the globe. Given the recent discovery and development of the CRISPR-Cas9 gene editing technology, a unique arrangement of this system, a nuclease-based "gene drive," allows for the super-Mendelian spread and forced propagation of a genetic element through a population. Recent studies have demonstrated the ability of a gene drive to rapidly spread within and nearly eliminate insect populations in a laboratory setting. While there are still ongoing technical challenges to design of a more optimal gene drive to be used in wild populations, there are still serious ecological and ethical concerns surrounding the nature of this powerful biological agent. Here, we use budding yeast as a safe and fully contained model system to explore mechanisms that might allow for programmed regulation of gene drive activity. We describe four conserved features of all CRISPR-based drives and demonstrate the ability of each drive component-Cas9 protein level, sgRNA identity, Cas9 nucleocytoplasmic shuttling, and novel Cas9-Cas9 tandem fusions-to modulate drive activity within a population.
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Affiliation(s)
- Emily Roggenkamp
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
| | - Rachael M Giersch
- Department of Biology, Kansas State University, Manhattan, Kansas 66506
| | - Madison N Schrock
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
- Department of Biology, Kansas State University, Manhattan, Kansas 66506
| | - Emily Turnquist
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
| | - Megan Halloran
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
| | - Gregory C Finnigan
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506
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Abstract
Drive is a process of accelerated inheritance from one generation to the next that allows some genes to spread rapidly through populations even if they do not contribute to-or indeed even if they detract from-organismal survival and reproduction. Genetic elements that can spread by drive include gametic and zygotic killers, meiotic drivers, homing endonuclease genes, B chromosomes, and transposable elements. The fact that gene drive can lead to the spread of fitness-reducing traits (including lethality and sterility) makes it an attractive process to consider exploiting to control disease vectors and other pests. There are a number of efforts to develop synthetic gene drive systems, particularly focused on the mosquito-borne diseases that continue to plague us.
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Affiliation(s)
- Austin Burt
- Life Sciences, Imperial College, Silwood Park, Ascot, SL5
7PY, United Kingdom
| | - Andrea Crisanti
- Life Sciences, Imperial College, South Kensington, London, SW7 2AZ, United Kingdom
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Fouet C, Atkinson P, Kamdem C. Human Interventions: Driving Forces of Mosquito Evolution. Trends Parasitol 2018; 34:127-139. [PMID: 29301722 DOI: 10.1016/j.pt.2017.10.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 10/28/2017] [Accepted: 10/30/2017] [Indexed: 11/29/2022]
Abstract
One of the most common strategies for controlling mosquito-borne diseases relies on the use of chemical pesticides to repel or kill the mosquito vector. Pesticide exposure interferes with several key biological functions in the mosquito and triggers a variety of adaptive responses whose underlying mechanisms are only partially elucidated. The availability of reference genome sequences opens up the possibility of tracking signatures of evolutionary changes, including the most recent, across the genomes of many vector species. In this review, we highlight the recent genomic changes, which contribute to the fascinating adaptation of malaria vectors of the sub-Saharan African region to intensive insecticide-based interventions. We emphasize the operational significance of detailed genomic knowledge for current monitoring and decision-making.
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Affiliation(s)
- Caroline Fouet
- Department of Entomology, University of California, Riverside, CA 92521, USA
| | - Peter Atkinson
- Department of Entomology, University of California, Riverside, CA 92521, USA
| | - Colince Kamdem
- Department of Entomology, University of California, Riverside, CA 92521, USA.
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