scholarly journals Assessing the acoustic behaviour of Anopheles gambiae s.l. dsxF mutants: Implications for Vector Control

2020 ◽  
Author(s):  
Matthew P Su ◽  
Marcos Georgiades ◽  
Judit Bagi ◽  
Kyros Kyrou ◽  
Andrea Crisanti ◽  
...  
Keyword(s):  
Anopheles Gambiae ◽  
Population Control ◽  
Beat Frequency ◽  
Natural Populations ◽  
Phenotypic Traits ◽  
Gene Drive ◽  
Control Effort ◽  
Female Genotype ◽  
Female Specific ◽  
Dose Dependent

AbstractBackgroundThe release of genetically modified mosquitoes which use gene-drive mechanisms to suppress reproduction in natural populations of Anopheles mosquitoes is one of the scientifically most promising methods for malaria transmission control. However, many scientific, regulatory and ethical questions remain before transgenic mosquitoes can be utilised in the field. Mutations which reduce an individual’s reproductive success are likely to create strong selective pressures to evolve resistance. It is thus crucial that the targeted population collapses as rapidly and as completely as possible to reduce the available time for the emergence of drive-resistant mutations. At a behavioural level, this means that the gene-drive carrying mutants should be at least as (and ideally more) sexually attractive than the wildtype population they compete against. A key element in the copulatory negotiations of Anopheles mosquitoes is their acoustic courtship. We therefore analysed sound emissions and acoustic preference in a doublesex mutant previously used to successfully collapse caged colonies of Anopheles gambiae s.l..MethodsThe flight tones produced by the beating of their wings form the signals for acoustic mating communication in Anopheles species. We assessed the acoustic impact of the disruption of a female-specific isoform of the doublesex gene (dsxF) on the wing beat frequency (WBF; measured as flight tone) of both males (XY) and females (XX) in homozygous dsxF- mutants (dsxF-/-), heterozygous dsxF- carriers (dsxF+/-) and G3 ‘wildtype’ dsxF+ controls (dsxF+/+). To exclude non-genetic influences, we controlled for temperature and measured wing lengths for all experimental animals. We used a phonotaxis assay to test the acoustic preferences of mutant and control mosquitoes.ResultsA previous study demonstrated an altered phenotype only for females homozygous for the disrupted dsx allele (dsxF-/-), who appear intersex. No phenotypic changes were observed for heterozygous carriers or males, suggesting that the female-specific dsxF allele is haplosufficient. We here identify significant, dose-dependent increases in the flight tones of both dsxF-/- and dsxF+/- females when compared to dsxF+/+ control females. Flight tone frequencies in all three female genotypes remained significantly lower than in males, however. When tested experimentally, males showed stronger phonotactic responses to the flight tones of control dsxF+/+ females. While flight tones from dsxF+/- and dsxF-/- females also elicited positive phonotactic behaviour in males, this was significantly reduced compared to responses to control tones. We found no evidence of phonotactic behaviour in any female genotype tested. None of the male genotypes displayed any deviations from the control condition.ConclusionsA key prerequisite for copulation in anopheline mosquitoes is the phonotactic attraction of males towards female flight tones within large - spatially and acoustically crowded - mating swarms. Reductions in acoustic attractiveness of released mutant lines, as reported here for heterozygous dsxF+/- females, reduce the line’s mating efficiency, and could consequently reduce the efficacy of the associated population control effort. Assessments of caged populations may not successfully reproduce the challenges posed by natural mating scenarios. We propose to amend existing testing protocols in order to more faithfully reflect the competitive conditions between a mutant line and the wildtype population it is meant to interact with. This should also include novel tests of ‘acoustic fitness’. In line with previous studies, our findings confirm that disruption of the female-specific isoform dsxF has no effect on males; for some phenotypic traits, such as female flight tones, however, the effects of dsxF appear to be dose-dependent rather than haplosufficient.

scholarly journals Assessing the acoustic behaviour of Anopheles gambiae (s.l.) dsxF mutants: implications for vector control

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Matthew P. Su ◽  
Marcos Georgiades ◽  
Judit Bagi ◽  
Kyros Kyrou ◽  
Andrea Crisanti ◽  
...  
Keyword(s):  
Anopheles Gambiae ◽  
Population Control ◽  
Beat Frequency ◽  
Phenotypic Traits ◽  
Gene Drive ◽  
Anopheles Gambiae S.L ◽  
Female Genotype ◽  
Female Specific ◽  
The Impact ◽  
Dose Dependent

Abstract Background Release of gene-drive mutants to suppress Anopheles mosquito reproduction is a promising method of malaria control. However, many scientific, regulatory and ethical questions remain before transgenic mosquitoes can be utilised in the field. At a behavioural level, gene-drive carrying mutants should be at least as sexually attractive as the wildtype populations they compete against, with a key element of Anopheles copulation being acoustic courtship. We analysed sound emissions and acoustic preference in a doublesex mutant previously used to collapse Anopheles gambiae (s.l.) cages. Methods Anopheles rely on flight tones produced by the beating of their wings for acoustic mating communication. We assessed the impact of disrupting a female-specific isoform of the doublesex gene (dsxF) on the wing beat frequency (WBF; measured as flight tone) of males (XY) and females (XX) in homozygous dsxF− mutants (dsxF−/−), heterozygous dsxF− carriers (dsxF+/−) and G3 dsxF+ controls (dsxF+/+). To exclude non-genetic influences, we controlled for temperature and wing length. We used a phonotaxis assay to test the acoustic preferences of mutant and control mosquitoes. Results A previous study showed an altered phenotype only for dsxF−/− females, who appear intersex, suggesting that the female-specific dsxF allele is haplosufficient. We identified significant, dose-dependent increases in the WBF of both dsxF−/− and dsxF+/− females compared to dsxF+/+ females. All female WBFs remained significantly lower than male equivalents, though. Males showed stronger phonotactic responses to the WBFs of control dsxF+/+ females than to those of dsxF+/− and dsxF−/− females. We found no evidence of phonotaxis in any female genotype. No male genotypes displayed any deviations from controls. Conclusions A prerequisite for anopheline copulation is the phonotactic attraction of males towards female flight tones within mating swarms. Reductions in mutant acoustic attractiveness diminish their mating efficiency and thus the efficacy of population control efforts. Caged population assessments may not successfully reproduce natural mating scenarios. We propose to amend existing testing protocols to better reflect competition between mutants and target populations. Our findings confirm that dsxF disruption has no effect on males; for some phenotypic traits, such as female WBFs, the effects of dsxF appear dose-dependent rather than haplosufficient.

scholarly journals Assessment of a Split Homing Based Gene Drive for Efficient Knockout of Multiple Genes

2019 ◽  
Vol 10 (2) ◽  
pp. 827-837 ◽  
Author(s):  
Nikolay P. Kandul ◽  
Junru Liu ◽  
Anna Buchman ◽  
Valentino M. Gantz ◽  
Ethan Bier ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Target Genes ◽  
High Efficiency ◽  
Population Control ◽  
Natural Populations ◽  
Pathogen Transmission ◽  
Gene Drive ◽  
Guide Rnas ◽  
Cas9 Protein ◽  
Gene Drives

Homing based gene drives (HGD) possess the potential to spread linked cargo genes into natural populations and are poised to revolutionize population control of animals. Given that host encoded genes have been identified that are important for pathogen transmission, targeting these genes using guide RNAs as cargo genes linked to drives may provide a robust method to prevent disease transmission. However, effectiveness of the inclusion of additional guide RNAs that target separate genes has not been thoroughly explored. To test this approach, we generated a split-HGD in Drosophila melanogaster that encoded a drive linked effector consisting of a second gRNA engineered to target a separate host-encoded gene, which we term a gRNA-mediated effector (GME). This design enabled us to assess homing and knockout efficiencies of two target genes simultaneously, and also explore the timing and tissue specificity of Cas9 expression on cleavage/homing rates. We demonstrate that inclusion of a GME can result in high efficiency of disruption of both genes during super-Mendelian propagation of split-HGD. Furthermore, both genes were knocked out one generation earlier than expected indicating the robust somatic expression of Cas9 driven by Drosophila germline-limited promoters. We also assess the efficiency of ‘shadow drive’ generated by maternally deposited Cas9 protein and accumulation of drive-induced resistance alleles along multiple generations, and discuss design principles of HGD that could mitigate the accumulation of resistance alleles while incorporating a GME.

scholarly journals Assessment of a split homing based gene drive for efficient knockout of multiple genes

2019 ◽  
Author(s):  
Nikolay P. Kandul ◽  
Junru Liu ◽  
Anna Buchman ◽  
Valentino M. Gantz ◽  
Ethan Bier ◽  
...  
Keyword(s):  
Target Gene ◽  
Tissue Specificity ◽  
Target Genes ◽  
High Efficiency ◽  
Population Control ◽  
Natural Populations ◽  
Pathogen Transmission ◽  
Gene Drive ◽  
Guide Rnas ◽  
Gene Drives

AbstractHoming based gene drives (HGD) possess the potential to spread linked cargo genes into natural populations and are poised to revolutionize population control of animals. Given that host-encoded genes have been identified that are important for pathogen transmission, targeting these genes using guide RNAs as cargo genes linked to drives may provide a robust method to prevent transmission. However, effectiveness of the inclusion of additional guide RNAs that target separate host encoded genes has not been thoroughly explored. To test this approach, here we generated a split-HGD in Drosophila melanogaster that encoded a drive linked effector consisting of a second gRNA engineered to target a separate host encoded gene, which we term a gRNA-mediated effector (GME). This design enabled us to assess homing and knockout efficiencies of two target genes simultaneously, and also explore the timing and tissue specificity of Cas9 expression on cleavage/homing rates. We demonstrate that inclusion of a GME can result in high efficiency of disruption of its target gene during super-Mendelian propagation of split-HGD. However, maternal deposition and embryonic expression of Cas9 resulted in the generation of drive resistant alleles which can accumulate and limit the spread of such a drive. Alternative design principles are discussed that could mitigate the accumulation of resistance alleles while incorporating a GME.

scholarly journals Natural diversity of the malaria vector Anopheles gambiae

2016 ◽  
Author(s):  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Malaria Control ◽  
Mosquito Control ◽  
Local Population ◽  
Natural Populations ◽  
Target Space ◽  
Anopheles Coluzzii ◽  
Nucleotide Polymorphisms ◽  
Gene Drive

The sustainability of malaria control in Africa is threatened by rising levels of insecticide resistance, and new tools to prevent malaria transmission are urgently needed. To gain a better understanding of the mosquito populations that transmit malaria, we sequenced the genomes of 765 wild specimens of Anopheles gambiae and Anopheles coluzzii sampled from 15 locations across Africa. The data reveal high levels of genetic diversity, with over 50 million single nucleotide polymorphisms across the 230 Mbp genome. We observe complex patterns of population structure and marked variations in local population size, some of which may be due at least in part to malaria control interventions. Insecticide resistance genes show strong signatures of recent selection associated with multiple independent mutations spreading over large geographical distances and between species. The genetic variability of natural populations substantially reduces the target space for novel gene-drive strategies for mosquito control. This large dataset provides a foundation for tracking the emergence and spread of insecticide resistance and developing new vector control tools.

scholarly journals Experimental demonstration of tethered gene drive systems for confined population modification or suppression

2021 ◽  
Author(s):  
Matthew Metzloff ◽  
Emily Yang ◽  
Sumit Dhole ◽  
Andrew G. Clark ◽  
Philipp W. Messer ◽  
...  
Keyword(s):  
Population Control ◽  
Local Population ◽  
Natural Populations ◽  
Great Promise ◽  
Gene Drive ◽  
Native Range ◽  
Target Populations ◽  
Experimental Cage ◽  
Drive Systems ◽  
Gene Drives

Homing gene drives hold great promise for the genetic control of natural populations. However, current homing systems are capable of spreading uncontrollably between populations connected by even marginal levels of migration. This could represent a substantial sociopolitical barrier to the testing or deployment of such drives and may generally be undesirable when the objective is only local population control, such as suppression of an invasive species outside of its native range. Tethered drive systems, in which a locally confined gene drive provides the CRISPR nuclease needed for a homing drive, could provide a solution to this problem, offering the power of a homing drive and confinement of the supporting drive. Here, we demonstrate the engineering of a tethered drive system in Drosophila, using a TARE drive to support modification and suppression homing drives. Each drive was able to bias inheritance in its favor, and the TARE drive was shown to spread only when released above a threshold frequency in experimental cage populations. After the TARE drive had established in the population, it facilitated the spread of a subsequently released split homing modification drive (to all individuals in the cage) and of a homing suppression drive (to its equilibrium frequency). Our results show that the tethered drive strategy is a viable and easily engineered option for providing confinement of homing drives to target populations. 

scholarly journals Independent evolution towards larger body size in the distinctive Faroe Island mice

2021 ◽  
Author(s):  
Ricardo Wilches ◽  
William H Beluch ◽  
Ellen McConnell ◽  
Diethard Tautz ◽  
Yingguang Frank Chan
Keyword(s):  
Body Size ◽  
Meta Analysis ◽  
Small Body ◽  
Laboratory Mouse ◽  
Large Body ◽  
Natural Populations ◽  
Size Variation ◽  
Phenotypic Traits ◽  
Island Population ◽  
Multiple Loci

Abstract Most phenotypic traits in nature involve the collective action of many genes. Traits that evolve repeatedly are particularly useful for understanding how selection may act on changing trait values. In mice, large body size has evolved repeatedly on islands and under artificial selection in the laboratory. Identifying the loci and genes involved in this process may shed light on the evolution of complex, polygenic traits. Here, we have mapped the genetic basis of body size variation by making a genetic cross between mice from the Faroe Islands, which are among the largest and most distinctive natural populations of mice in the world, and a laboratory mouse strain selected for small body size, SM/J. Using this F2 intercross of 841 animals, we have identified 111 loci controlling various aspects of body size, weight and growth hormone levels. By comparing against other studies, including the use of a joint meta-analysis, we found that the loci involved in the evolution of large size in the Faroese mice were largely independent from those of a different island population or other laboratory strains. We hypothesize that colonization bottleneck, historical hybridization, or the redundancy between multiple loci have resulted in the Faroese mice achieving an outwardly similar phenotype through a distinct evolutionary path.

scholarly journals Anopheles gambiae Genome Conservation as a Resource for Rational Gene Drive Target Site Selection

Insects ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 97
Author(s):  
Nace Kranjc ◽  
Andrea Crisanti ◽  
Tony Nolan ◽  
Federica Bernardini
Keyword(s):  
Anopheles Gambiae ◽  
Data Storage ◽  
Genomic Variation ◽  
Malaria Vectors ◽  
Anopheles Coluzzii ◽  
Structural Constraints ◽  
Gene Drive ◽  
Genetic Traits ◽  
A Genome ◽  
Insight Into

The increase in molecular tools for the genetic engineering of insect pests and disease vectors, such as Anopheles mosquitoes that transmit malaria, has led to an unprecedented investigation of the genomic landscape of these organisms. The understanding of genome variability in wild mosquito populations is of primary importance for vector control strategies. This is particularly the case for gene drive systems, which look to introduce genetic traits into a population by targeting specific genomic regions. Gene drive targets with functional or structural constraints are highly desirable as they are less likely to tolerate mutations that prevent targeting by the gene drive and consequent failure of the technology. In this study we describe a bioinformatic pipeline that allows the analysis of whole genome data for the identification of highly conserved regions that can point at potential functional or structural constraints. The analysis was conducted across the genomes of 22 insect species separated by more than hundred million years of evolution and includes the observed genomic variation within field caught samples of Anopheles gambiae and Anopheles coluzzii, the two most dominant malaria vectors. This study offers insight into the level of conservation at a genome-wide scale as well as at per base-pair resolution. The results of this analysis are gathered in a data storage system that allows for flexible extraction and bioinformatic manipulation. Furthermore, it represents a valuable resource that could provide insight into population structure and dynamics of the species in the complex and benefit the development and implementation of genetic strategies to tackle malaria.

scholarly journals Perspectives from animal demography on incorporating evolutionary mechanism into plant population dynamics

2018 ◽  
Author(s):  
Maria Paniw
Keyword(s):  
Environmental Change ◽  
Evolutionary Dynamics ◽  
Natural Populations ◽  
Population Level ◽  
Plant Population ◽  
Future Research ◽  
Phenotypic Traits ◽  
Plant Population Dynamics ◽  
Future Research Agenda ◽  
Powerful Approach

AbstractWith a growing number of long-term, individual-based data on natural populations available, it has become increasingly evident that environmental change affects populations through complex, simultaneously occurring demographic and evolutionary processes. Analyses of population-level responses to environmental change must therefore integrate demography and evolution into one coherent framework. Integral projection models (IPMs), which can relate genetic and phenotypic traits to demographic and population-level processes, offer a powerful approach for such integration. However, a rather artificial divide exists in how plant and animal population ecologists use IPMs. Here, I argue for the integration of the two sub-disciplines, particularly focusing on how plant ecologists can diversify their toolset to investigate selection pressures and eco-evolutionary dynamics in plant population models. I provide an overview of approaches that have applied IPMs for eco-evolutionary studies and discuss a potential future research agenda for plant population ecologists. Given an impending extinction crisis, a holistic look at the interacting processes mediating population persistence under environmental change is urgently needed.

Enzyme variation in the Anopheles gambiae Giles group of species (Diptera: Culicidae)

1978 ◽  
Vol 68 (1) ◽  
pp. 85-97 ◽  
Author(s):  
S. J. Miles
Keyword(s):  
Anopheles Gambiae ◽  
Natural Populations ◽  
Lactic Dehydrogenase ◽  
Starch Gel Electrophoresis ◽  
Malic Dehydrogenase ◽  
Glycerophosphate Dehydrogenase ◽  
Starch Gel ◽  
Anopheles Gambiae Giles ◽  
Species Specific ◽  
Glucose 6 Phosphate Dehydrogenase

AbstractThe genotypes of chromosomally-identified individuals from natural populations of the known species of the group of Anopheles gambiae Giles were scored for the enzyme protein structural loci coding for adenylate kinase (Adk), α-naphthyl acetate esterase (Est-1, Est-2, Est-3), glutamic-oxaloacetic transaminase (Got), α-glycerophosphate dehydrogenase (αGpd), hexokinase (Hk), isocitric dehydrogenase (Idh), lactic dehydrogenase (Ldh), ‘leucine’ aminopeptidase (Lap-2), malic enzyme (Me), octanol dehydrogenase (Odh), phosphoglucomutase (Pgm-1, Pgm-2), 6-phosphogluconic dehydrogenase (6-Pgd), phosphohexose isomerase (Phi) and superoxide dismutase (Sod), following starch gel electrophoresis. In the material examined, Est-1, Est-2, Est-3, Got, ldh, Lap-2, Odh, Pgm-1, Pgm-2 and Sod were segregating for two or more alleles; unique alleles at the Est-1, Got and Sod loci produced species-specific phenotypes in A. melas (Theo.), species C and species D, respectively. The further sampling of A. merus Dön, populations supported the presence of a unique SOD phenotype by which this species can also be identified. Of the other enzyme systems examined, no activity following electrophoresis was detected for aldolase and fructose-1,6-diphosphatase, and the resolution of acid and alkaline phosphatase, glyceraldehyde-3-phosphate dehydrogenase, glucose-6-phosphate dehydrogenase, malic dehydrogenase and xanthine dehydrogenase was too poor under the particular electrophoretic conditions for genetic analyses of the enzyme phenotypes.

scholarly journals Phenotypic, genotypic and biochemical changes during pyrethroid resistance selection in Anopheles gambiae mosquitoes

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Maxwell G. Machani ◽  
Eric Ochomo ◽  
Daibin Zhong ◽  
Guofa Zhou ◽  
Xiaoming Wang ◽  
...  
Keyword(s):  
Public Health ◽  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Selection Pressure ◽  
Pyrethroid Resistance ◽  
Natural Populations ◽  
Biochemical Changes ◽  
Moderate Intensity ◽  
Agricultural System ◽  
Selection For

Abstract The directional selection for insecticide resistance due to indiscriminate use of insecticides in public health and agricultural system favors an increase in the frequency of insecticide-resistant alleles in the natural populations. Similarly, removal of selection pressure generally leads to decay in resistance. Past investigations on the emergence of insecticide resistance in mosquitoes mostly relied on field survey of resistance in vector populations that typically had a complex history of exposure to various public health and agricultural pest control insecticides in nature, and thus the effect of specific insecticides on rate of resistance emergency or resistance decay rate is not known. This study examined the phenotypic, genotypic, and biochemical changes that had occurred during the process of selection for pyrethroid resistance in Anopheles gambiae, the most important malaria vector in Africa. In parallel, we also examined these changes in resistant populations when there is no selection pressure applied. Through repeated deltamethrin selection in adult mosquitoes from a field population collected in western Kenya for 12 generations, we obtained three independent and highly pyrethroid-resistant An. gambiae populations. Three susceptible populations from the same parental population were generated by removing selection pressure. These two lines of mosquito populations differed significantly in monooxygenase and beta-esterase activities, but not in Vgsc gene mutation frequency, suggesting metabolic detoxification mechanism plays a major role in generating moderate-intensity resistance or high-intensity resistance. Pre-exposure to the synergist piperonyl butoxide restored the susceptibility to insecticide among the highly resistant mosquitoes, confirming the role of monooxygenases in pyrethroid resistance. The rate of resistance decay to become fully susceptible from moderate-intensity resistance took 15 generations, supporting at least 2-years interval is needed when the rotational use of insecticides with different modes of action is considered for resistance management.

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