Scholarly Literature

This is a database of scholarly literature that concentrates currently on natural and engineered selfish genetic elements (gene drives).  The latest are shown here.
Disclaimer>

Strategies to Mitigate Establishment under the Wolbachia Incompatible Insect Technique

23104
S. Soh, S. H. Ho, J. Ong, A. Seah, B. S. Dickens, K. W. Tan, J. R. Koo, A. R. Cook, S. Sim, C. H. Tan, L. C. Ng and J. T. Lim,  Viruses,  14. 2022-05-24 08:10:53.
The Incompatible Insect Technique (IIT) strategy involves the release of male mosquitoes infected with the bacterium Wolbachia. Regular releases of male Wolbachia-infected mosquitoes can lead to the suppression of mosquito populations, thereby reducing the risk of transmission of vector-borne diseases such as dengue. However, due to imperfect sex-sorting under IIT, fertile Wolbachia-infected female mosquitoes may potentially be unintentionally released into the environment, which may result in replacement and failure to suppress the mosquito populations. As such, mitigating Wolbachia establishment requires a combination of IIT with other strategies. We introduced a simple compartmental model to simulate ex-ante mosquito population dynamics subjected to a Wolbachia-IIT programme. In silico, we explored the risk of replacement, and strategies that could mitigate the establishment of the released Wolbachia strain in the mosquito population. Our results suggest that mitigation may be achieved through the application of a sterile insect technique. Our simulations indicate that these interventions do not override the intended wild type suppression of the IIT approach. These findings will inform policy makers of possible ways to mitigate the potential establishment of Wolbachia using the IIT population control strategy.

Novel molecular approaches to combat vectors and vector-borne viruses: Special focus on RNA interference (RNAi) mechanisms

22657
A. Agarwal, D. K. Sarma, D. Chaurasia and H. S. Maan,  Acta Tropica,  2022-05-24 06:45:12.
Vector-borne diseases, such as dengue, chikungunya, zika, yellow fever etc pose significant burden among the infectious diseases globally, especially in tropical and sub-tropical regions. Globalization, deforestation, urbanization, climate change, uncontrolled population growth, inadequate waste management and poor vector-management infrastructure have all contributed to the expansion of vector habitats and subsequent increase in vector-borne diseases throughout the world. Conventional vector control methods, such as use of insecticides, have significant negative environmental repercussions in addition to developing resistance in vectors. Till date, a very few vaccines or antiviral therapies have been approved for the treatment of vector borne diseases. In this review, we have discussed emerging molecular approaches like CRISPR (clustered regularly interspaced short palindromic repeats)/Cas-9, sterile insect technique (SIT), release of insects carrying a dominant lethal (RIDL), Wolbachia (virus transmission blocking) and RNA interference (RNAi) to combat vector and vector-borne viruses. Due to the extensive advancements in RNAi research, a special focus has been given on its types, biogenesis, mechanism of action, delivery and experimental studies evaluating their application as anti-mosquito and anti-viral agent. These technologies appear to be highly promising in terms of contributing to vector control and antiviral drug development, and hence can be used to reduce global vector and vector-borne disease burden.

Quality Control and Mating Performance of Irradiated Glossina palpalis gambiensis Males

22546
K. Ilboudo, K. Camara, E. W. Salou and G. Gimonnea,  Insects,  13. 2022-05-19 08:04:34.
The biological quality of sterile male insects produced in a mass-rearing facility is a prerequisite for the success of the SIT, which is a component of area-wide integrated pest management (AW-IPM). Indeed, sterile male insects released in the field must have a good mating performance in order to compete with wild males, but they must also present the required level of sterility. In the present study, the biological quality of sterile male Glossina palpalis gambiensis produced in a mass-rearing insectary was assessed through quality control testing. The mating performance of irradiated males was assessed in walk-in field cages. Irradiation had no effect on adult emergence but significantly reduced the percentage of operational flies (from 89.58% to 79.87%) and male survival (from 5 to 4 days, on average). However, irradiation did not impact the sterile male insemination potential, with all females inseminated and more than 80% of the spermathecae completely filled. The rate of induced sterility in females was 89.67% due to a dose rate decrease of the radiation source. Moreover, sterile males were able to compete successfully with untreated fertile males for untreated females in walk-in field cages. This study confirmed that the flies were still competitive and stressed the importance of regularly checking the radiation source parameters.

Elimination of a closed population of the yellow fever mosquito, Aedes aegypti, through releases of self-limiting male mosquitoes

22519
P. B. Patil, S. K. Dasgupta, K. Gorman, A. Pickl-Herk, M. Puinean, A. McKemey, B. Char, U. B. Zehr and S. R. Barwale,  PLOS Neglected Tropical Diseases,  16:e0010315. 2022-05-16 09:19:04.
Author summary Aedes aegypti L. species is the primary vector responsible for transmission of the dengue virus worldwide including chikungunya, yellow fever and Zika virus. The experiment presented in the manuscript represents a study undertaken to demonstrate suppression of the wild type Ae. aegypti population in large outdoor field cages with natural exposure to the environment (physically-contained field cage facility) by sustained releases of male adults of OX513A Ae. aegypti strain. This investigation is a phase-2 contained study as per the World Health Organization guidelines for evaluation of genetically modified organisms and was recommended by the Indian regulatory board. This experiment demonstrates suppression of wild type Ae. aegypti population by sustained releases of OX513A male adults in a contained facility. The prospect of the project is to demonstrate and implement the technology for controlling/suppression of the Ae. aegypti vector in the open field environment.

Bayesian network-based risk assessment of synthetic biology: Simulating CRISPR-Cas9 gene drive dynamics in invasive rodent management

22516
E. A. Brown, S. R. Eikenbary and W. G. Landis,  Risk Analysis,  2022-05-14 07:22:34.
Gene drive technology has been proposed to control invasive rodent populations as an alternative to rodenticides. However, this approach has not undergone risk assessment that meets criteria established by Gene Drives on the Horizon, a 2016 report by the National Academies of Sciences, Engineering, and Medicine. To conduct a risk assessment of gene drives, we employed the Bayesian network-relative risk model to calculate the risk of mouse eradication on Southeast Farallon Island using a CRISPR-Cas9 homing gene drive construct. We modified and implemented the R-based model "MGDrivE" to simulate and compare 60 management strategies for gene drive rodent management. These scenarios spanned four gene drive mouse release schemes, three gene drive homing rates, three levels of supplemental rodenticide dose, and two timings of rodenticide application relative to gene drive release. Simulation results showed that applying a supplemental rodenticide simultaneously with gene drive mouse deployment resulted in faster eradication of the island mouse population. Gene drive homing rate had the highest influence on the overall probability of successful eradication, as increased gene drive accuracy reduces the likelihood of mice developing resistance to the CRISPR-Cas9 homing mechanism.

Aquatic invasive species specialists’ perceptions on the importance of genetic tools and concepts to inform management

22482
T. A. Bernos, K. M. Jeffries and N. E. Mandrak,  Biological Invasions,  24:1863-1879. 2022-05-14 07:09:36.
Perceptions related to the importance of genetic research influence the mobilization of genetic tools and concepts to inform conservation actions. Research characteristics, stakeholders’ perspectives, knowledge, and social linkages with geneticists influence the outcome of genetic information for management practices. We surveyed a broad range of aquatic invasive species (AIS) specialists whose opinions, perspectives, and decisions influence AIS decision-making. We assessed perceptions related to the importance of genetic tools and concepts, as well as the appropriateness of genetic biocontrol, and tested whether their expertise, background, and experience influenced perceptions in a predictable way. While perceptions towards genetic tools and concepts were generally heterogeneous, there was a high consensus (84%) related to the importance of eDNA. Most predictors were weakly correlated with importance ratings. Specialists’ genetic knowledge was the strongest predictor of higher importance ratings: the odds of AIS specialists giving higher ratings increased by up to 1.5-fold with increasing genetic knowledge. When evaluating the appropriateness of genetic biocontrol, level of support was lower for approaches based on gene editing (58%) than those relying on traditional hatchery techniques (70%). Support for gene editing varied by geographic location and with specialists’ knowledge of genetics and AIS management. These findings suggest that perceptions towards genetic research vary between genetic tools and concepts and are shaped by the interplay of individual’s values, expertise, experience, and background. To collaborate more effectively, genetic scientists must understand the extent of genetic knowledge of their AIS management partners and recognize that their conceptions of the conservation genetics research-practice space may vary.

Simple, sensitive, and cost-effective detection of wAlbB Wolbachia in Aedes mosquitoes, using loop mediated isothermal amplification combined with the electrochemical biosensing method

22480
P. Thayanukul, B. Lertanantawong, W. Sirawaraporn, S. Charasmongkolcharoen, T. Chaibun, R. Jittungdee and P. Kittayapong,  PLOS Neglected Tropical Diseases,  16:e0009600. 2022-05-13 07:05:35.
Author summary Mosquito-borne diseases such as dengue, chikungunya, zika, and yellow fever are transmitted to humans mainly by the bites of Aedes aegypti mosquitoes. Controlling the vectors of these diseases relies mostly on the use of insecticides. However, the efficiency has been reduced through the development of insecticide resistance in mosquitoes. Wolbachia is an endosymbiotic bacterium that is naturally found in 40% of insects, including mosquitoes. The bacterium can protect its insect hosts from viral infections and can also cause sterility in insect host populations, therefore, providing an opportunity to use it for human disease control. Application of a Wolbachia trans-infected mosquitoes needs simple, rapid and sensitive methods for detecting the bacteria in released mosquitoes. In this paper, we develop the methods of LAMP and BIOSENSORS for detecting wAlbB Wolbachia in mosquitoes. Our positive LAMP reaction can be visualized by color change from violet to blue at a sensitivity of ≥ 10 pg of genomic DNA. When used in combination with the BIOSENSOR method, the sensitivity increases a millionfold without losing specificity. Our study suggests that both developed methods, either used in combination or stand-alone, are efficient and cost-effective, hence, they could be applied for routine surveys of Wolbachia in mosquito control programs that use Wolbachia-based approaches.

Intronic gRNAs for the Construction of Minimal Gene Drive Systems

22478
A. Nash, P. Capriotti, A. Hoermann, P. A. Papathanos and N. Windbichler,  Frontiers in Bioengineering and Biotechnology,  10. 2022-05-12 07:00:08.
Gene drives are promising tools for the genetic control of insect vector or pest populations. CRISPR-based gene drives are generally highly complex synthetic constructs consisting of multiple transgenes and their respective regulatory elements. This complicates the generation of new gene drives and the testing of the behavior of their constituent functional modules. Here, we explored the minimal genetic components needed to constitute autonomous gene drives in Drosophila melanogaster. We first designed intronic gRNAs that can be located directly within coding transgene sequences and tested their functions in cell lines. We then integrated a Cas9 open reading frame hosting such an intronic gRNA within the Drosophila rcd-1r locus that drives the expression in the male and female germlines. We showed that upon removal of the fluorescent transformation marker, the rcd-1rd allele supports efficient gene drive. We assessed the propensity of this driver, designed to be neutral with regards to fitness and host gene function, to propagate in caged fly populations. Because of their simplicity, such integral gene drives could enable the modularization of drive and effector functions. We also discussed the possible biosafety implications of minimal and possibly recoded gene drives.

Lessons learned from the introduction of genetically engineered crops: relevance to gene drive deployment in Africa

22491
H. Quemada,  Transgenic Res,  2022-05-11 07:27:12.
The application of gene drives to achieve public health goals, such as the suppression of Anopheles gambiae populations, or altering their ability to sustain Plasmodium spp. infections, has received much attention from researchers. If successful, this genetic tool can contribute greatly to the wellbeing of people in regions severely affected by malaria. However, engineered gene drives are a product of genetic engineering, and the experience to date, gained through the deployment of genetically engineered (GE) crops, is that GE technology has had difficulty receiving public acceptance in Africa, a key region for the deployment of gene drives. The history of GE crop deployment in this region provides good lessons for the deployment of gene drives as well

Double-tap gene drive uses iterative genome targeting to help overcome resistance alleles

22286
A. L. Bishop, V. López Del Amo, E. M. Okamoto, Z. Bodai, A. C. Komor and V. M. Gantz,  Nat Commun,  13:2595. 2022-05-09 08:10:07.
Homing CRISPR gene drives could aid in curbing the spread of vector-borne diseases and controlling crop pest and invasive species populations due to an inheritance rate that surpasses Mendelian laws. However, this technology suffers from resistance alleles formed when the drive-induced DNA break is repaired by error-prone pathways, which creates mutations that disrupt the gRNA recognition sequence and prevent further gene-drive propagation. Here, we attempt to counteract this by encoding additional gRNAs that target the most commonly generated resistance alleles into the gene drive, allowing a second opportunity at gene-drive conversion. Our presented "double-tap" strategy improved drive efficiency by recycling resistance alleles. The double-tap drive also efficiently spreads in caged populations, outperforming the control drive. Overall, this double-tap strategy can be readily implemented in any CRISPR-based gene drive to improve performance, and similar approaches could benefit other systems suffering from low HDR frequencies, such as mammalian cells or mouse germline transformations.

Adversarial interspecies relationships facilitate population suppression by gene drive in spatially explicit models

22288
Y. Liu, W. Teo, H. Yang and J. Champer,  bioRxiv,  2022.05.08.491087. 2022-05-08 08:15:29.
Suppression gene drives are designed to bias their inheritance and increase in frequency in a population, disrupting an essential gene in the process. When the frequency is high enough, the population will be unable to reproduce above the replacement level and could be eliminated. CRISPR suppression drives based on the homing mechanism have already seen success in the laboratory, particularly in malaria mosquitoes. However, several models predict that the use of these drives in realistic populations with spatial structure may not achieve complete success. This is due to the ability of wild-type individuals to escape the drive and reach empty areas with reduced competition, allowing them to achieve high reproductive success and leading to extinction-recolonization cycles across the landscape. Here, we extend our continuous space gene drive framework to include two competing species or predator-prey species pairs. We find in both discrete-generation and mosquito-specific models that the presence of a competing species or predator can greatly facilitate drive-based suppression, even for drives with modest efficiency. However, the presence of a competing species also substantially increases the frequency of outcomes in which the drive is lost before suppression is achieved. These results are robust in models with seasonal population fluctuations. We also found that suppression can be somewhat more difficult if targeting a predator with strong predator-prey interactions. Our results illustrate the difficulty of predicting outcomes of interventions that could substantially affect the populations of interacting species in complex ecosystems. However, our results are also potentially promising for the prospects of less powerful gene drives in achieving successful elimination of target pest populations.Competing Interest StatementThe authors have declared no competing interest.

Local adaptation of Aedes aegypti mosquitoes to Wolbachia-induced fitness costs

22208
P. A. Ross and A. A. Hoffmann,  bioRxiv,  2022.05.06.490959. 2022-05-06 15:19:41.
Aedes aegypti mosquito eggs can remain quiescent for many months before hatching, allowing populations to persist through unfavorable conditions. Aedes aegypti infected with the Wolbachia strain wMel have been released in tropical and subtropical regions for dengue control. wMel reduces the viability of quiescent eggs, but this physiological cost might be expected to evolve in natural mosquito populations that frequently experience stressful conditions. We therefore compared the costs of wMel infection for quiescent egg viability in field-derived and laboratory populations. Quiescent egg viability was highly variable in wMel-infected populations, with greater costs of wMel in field-derived populations. In contrast, there was little variation between matched field-derived and long-term laboratory populations lacking wMel, suggesting that laboratory adaptation does not influence this trait and that differences are due to wMel infection. Comparisons of populations collected a year apart show a decline in costs under laboratory rearing conditions involving a rapid turnover of mosquito generations; this pattern was consistent across populations despite their origin, suggesting adaptation of mosquitoes to the wMel infection under laboratory conditions. Reciprocal crossing experiments confirm that differences in quiescent egg viability were mainly due to the genetic background and not Wolbachia alone. wMel-infected mosquitoes hatching from long-term quiescent eggs showed partial loss of cytoplasmic incompatibility and female infertility, highlighting additional costs of long-term quiescence. Our study provides the first evidence for a shift in Wolbachia phenotypic effects following deliberate field release and establishment and it highlights interactions between Wolbachia infections and local adaptation. The unexpected changes in fitness costs observed here suggest potential tradeoffs with undescribed fitness benefits of the wMel infection.Competing Interest StatementThe authors have declared no competing interest.

The principles driving gene drives for conservation

22295
S. Hartley, R. Taitingfong and P. Fidelman,  Environmental Science and Policy,  135:36-45. 2022-05-04 08:30:40.
Gene drive technology is an emerging biotechnology with the potential to address some of the most intractable global biodiversity conservation issues. Scientists are exploring potential gene drive applications for managing invasive species and building resilience in keystone species threatened by climate change. The possibility to use gene drive for these conservation purposes has triggered significant interest in how to govern its development and eventual applications. This includes a plethora of documents prescribing governance principles, which can be a sensible response to the governance gap created by emerging technologies and help shore up legitimacy. We conducted qualitative documentary analysis to examine the range and substance of principles emerging in the governance of conservation gene drive. Such analysis aimed to better understand the aspirations guiding these applications and how scientists and other experts imagine their responsibility in this field. We found a collection of recommendations and prescriptions that could be organised into a set of seven emerging principles intended to shape the governance of gene drive in conservation: broad and empowered engagement; public acceptance; decision-making informed by broad ranging considerations, state and international collaboration; ethical frameworks; diverse expertise; and responsible self-regulation by developers. We lay bare these emergent principles, analyzing the way in which they are valued, prioritized, and their strengths and weaknesses. By identifying these prescriptive principles, stakeholders can further interrogate their merits and shortcomings and identify more concrete ways that governance frameworks might embody them.

Transient Introgression of Wolbachia into Aedes aegypti Populations Does Not Elicit an Antibody Response to Wolbachia Surface Protein in Community Members

22655
E. Lee, T. Hien Nguyen, T. Yen Nguyen, S. Nam Vu, N. Duong Tran, L. Trung Nghia, Q. Mai Vien, T. Dong Nguyen, R. Kriiger Loterio, I. Iturbe-Ormaetxe, H. A. Flores, S. L. O'Neill, D. Anh Dang, C. P. Simmons and J. E. Fraser,  Pathogens,  11. 2022-05-03 06:41:58.
Wolbachia is an endosymbiotic bacterium that can restrict the transmission of human pathogenic viruses by Aedes aegypti mosquitoes. Recent field trials have shown that dengue incidence is significantly reduced when Wolbachia is introgressed into the local Ae. aegypti population. Female Ae. aegypti are anautogenous and feed on human blood to produce viable eggs. Herein, we tested whether people who reside on Tri Nguyen Island (TNI), Vietnam developed antibodies to Wolbachia Surface Protein (WSP) following release of Wolbachia-infected Ae. aegypti, as a measure of exposure to Wolbachia. Paired blood samples were collected from 105 participants before and after mosquito releases and anti-WSP titres were measured by ELISA. We determined no change in anti-WSP titres after ~30 weeks of high levels of Wolbachia-Ae. aegypti on TNI. These data suggest that humans are not exposed to the major Wolbachia surface antigen, WSP, following introgression of Wolbachia-infected Ae. aegypti mosquitoes.

New weapons to fight malaria transmission: A historical view

22487
W. Huang, S.-J. Cha and M. Jacobs-Lorena,  Entomological Research,  2022-05-02 07:19:32.
The stagnation of our fight against malaria in recent years, mainly due to the development of mosquito insecticide resistance, argues for the urgent development of new weapons. The dramatic evolution of molecular tools in the last few decades led to a better understanding of parasite?mosquito interactions and coalesced in the development of novel tools namely, mosquito transgenesis and paratransgenesis. Here we provide a historical view of the development of these new tools and point to some remaining challenges for their implementation in the field.

International shipments of Wolbachia-infected mosquito eggs: towards the scaling-up of World Mosquito Program operations

23390
J. A. Denton, D. A. Joubert, A. A. Goundar and J. R. L. Gilles,  Scientific and Technical Review,  41:91-99. 2022-05-01 08:01:14.
The Wolbachia insect control method, employed by the World Mosquito Program (WMP), relies on introgressing Wolbachia through target Aedes aegypti populations to reduce the incidence of dengue. Since 2010, the WMP has been producing Wolbachia-infected mosquitoes at numerous sites across the globe for release in 11 countries. As the technology has matured, greater focus has been placed on mosquito production at larger central facilities for transport to remote release sites, both domestically and internationally. Of particular note is the production of Wolbachia-infected mosquitoes at the WMP's Australian production facility for successful international deployments in Fiji, Vanuatu, Kiribati and Sri Lanka. This requires careful management of both production and supply-chain processes to ensure that the quality of the mosquito eggs, specifically the hatch rate and Wolbachia infection rate, is maintained. To ensure the cost-effectiveness and scalability of the Wolbachia method, these processes will be further refined to facilitate deployment from large centralised production facilities.

The fate of a suppressed X-linked meiotic driver: experimental evolution in Drosophila simulans

22676
H. Bastide, D. Ogereau, C. Montchamp-Moreau and P. R. Gérard,  Chromosome Research,  2022-04-30 07:53:46.
Sex-ratio (SR) meiotic drivers are X-linked selfish genetic elements that promote their own transmission by preventing the production of Y-bearing sperm, which usually lowers male fertility. The spread of SR drivers in populations is expected to trigger the evolution of unlinked drive suppressors, a theoretically predicted co-evolution that has been observed in nature. Once completely suppressed, the drivers are expected either to decline if they still affect the fitness of their carriers, or to evolve randomly and possibly get fixed if the suppressors eliminate their deleterious effects. To explore this issue, we used the Paris sex-ratio system of Drosophila simulans in which drive results from the joint effect of two elements on the X chromosome: a segmental duplication and a deficient allele of the HP1D2 gene. We set up six experimental populations starting with 2/3 of X chromosomes carrying both elements (X(SR)) in a fully suppressing background. We let them evolve independently during almost a hundred generations under strong sexual competition, a condition known to cause the rapid disappearance of unsuppressed Paris X(SR) in previous experimental populations. In our study, the fate of X(SR) chromosomes varied among populations, from extinction to their maintenance at a frequency close to the starting one. While the reasons for these variable outcomes are still to be explored, our results show that complete suppression can prevent the demise of an otherwise deleterious X(SR) chromosome, turning a genetic conflict into cooperation between unlinked loci. Observations in natural populations suggest a contrasting fate of the two elements: disappearance of the duplication and maintenance of deficient HP1D2 alleles.

Epistatic selection on a selfish Segregation Distorter supergene: drive, recombination, and genetic load

22103
B. Navarro-Dominguez, C.-H. Chang, C. L. Brand, C. A. Muirhead, D. C. Presgraves and A. M. Larracuente,  eLife,  11:e78981. 2022-04-29 09:52:33.
In this work, we investigate the evolution and genomic consequences of an autosomal, multilocus, male meiotic drive system, Segregation Distorter (SD) in the fruit fly, Drosophila melanogaster. In African populations, the predominant SD chromosome variant, SD-Mal, is characterized by two overlapping, paracentric inversions on chromosome arm 2R and nearly perfect (~100%) transmission. We study the SD-Mal system in detail, exploring its components, chromosomal structure, and evolutionary history. Our findings reveal a recent chromosome-scale selective sweep mediated by strong epistatic selection for haplotypes carrying Sd, the main driving allele, and one or more factors within the double inversion. While most SD-Mal chromosomes are homozygous lethal, SD-Mal haplotypes can recombine with other, complementing haplotypes via crossing over, and with wildtype chromosomes via gene conversion. SD-Mal chromosomes have nevertheless accumulated lethal mutations, excess non-synonymous mutations, and excess transposable element insertions. Therefore, SD-Mal haplotypes evolve as a small, semi-isolated subpopulation with a history of strong selection. These results may explain the evolutionary turnover of SD haplotypes in different populations around the world, and have implications for supergene evolution broadly.

CRISPR/Cas9 mediates efficient site-specific mutagenesis of the odorant receptor co-receptor (Orco) in the malaria vector Anopheles sinensis

22554
Y. Wang, X. F. He, L. Qiao, Z. R. Yu, B. Chen and Z. B. He,  Pest Management Science,  11. 2022-04-28 14:52:27.
BACKGROUND Anopheles sinensis is the most widely distributed mosquito species and is the main transmitter of Plasmodium vivax malaria in China. Most previous research has focused on the mechanistic understanding of biological processes in An. sinensis and novel ways of interrupting malaria transmission. However, the development of functional genomics and genetics-based vector control strategies against An. sinensis remain limited because of insufficient site-specific genome editing tools. RESULTS We report the first successful application of the CRISPR/Cas9 mediated knock-in for highly efficient, site-specific mutagenesis in An. sinensis. The EGFP marker gene driven by the 3 x P3 promoter was precisely integrated into the odorant receptor co-receptor (Orco) by direct injections of Cas9 protein, double-stranded DNA donor, and Orco-gRNA. We achieved a mutation rate of 3.77%, similar to rates in other mosquito species. Precise knock-in at the intended locus was confirmed by polymerase chain reaction (PCR) amplification and sequencing. The Orco mutation severely impaired mosquito sensitivity to some odors and their ability to locate and discriminate a human host. CONCLUSION Orco was confirmed as a key mediator of multiple olfactory-driven behaviors in the An. sinensis life cycle, highlighting the importance of Orco as a key molecular target for malaria control. The results also demonstrated that CRISPR/Cas9 was a simple and highly efficient genome editing technique for An. sinensis and could be used to develop genetic control tools for this vector. (c) 2022 Society of Chemical Industry.

Engineering a self-eliminating transgene in the yellow fever mosquito, Aedes aegypti

21920
K. Chae, C. Dawson, C. Valentin, B. Contreras, J. Zapletal, K. M. Myles and Z. N. Adelman,  PNAS Nexus,  2022-04-28 08:54:37.
Promising genetics-based approaches are being developed to reduce or prevent the transmission of mosquito-vectored diseases. Less clear is how such transgenes can be removed from the environment, a concern that is particularly relevant for highly invasive gene drive transgenes. Here, we lay the groundwork for a transgene removal system based on single-strand annealing (SSA), a eukaryotic DNA repair mechanism. An SSA-based rescuer strain (kmoRG) was engineered to have direct repeat sequences (DRs) in the Ae. aegypti kynurenine 3-monooxygenase (kmo) gene flanking the intervening transgenic cargo genes, DsRED and EGFP. Targeted induction of DNA double-strand breaks (DSBs) in the DsRED transgene successfully triggered complete elimination of the entire cargo from the kmoRG strain, restoring the wild-type kmo gene and thereby normal eye pigmentation. Our work establishes the framework for strategies to remove transgene sequences during the evaluation and testing of modified strains for genetics-based mosquito control.

« First ‹ Previous 1 32 40 41 42 43 44 52 118 Next › Last »