Self-destructing mosquitoes and sterilized rodents: the promise of gene drives

Genes drive organisms and slippery slopes

The bioethical debate about using gene drives to alter or eradicate wild populations has focused mostly on issues concerning short-term risk assessment and management, governance and oversight, and public and community engagement, but has not examined big-picture- 'where is this going?'-questions in great depth. In other areas of bioethical controversy, big-picture questions often enter the public forum via slippery slope arguments. Given the incredible potential of gene drive organisms to alter the Earth's biota, it is somewhat surprising that slippery slope arguments have not played a more prominent role in ethical and policy debates about these emerging technologies. In this article, we examine a type of slippery slope argument against using gene drives to alter or suppress wild pest populations and consider whether it has a role to play in ethical and policy debates. Although we conclude that this argument does not provide compelling reasons for banning the use of gene drives in wild pest populations, we believe that it still has value as a morally instructive cautionary narrative that can motivate scientists, ethicists, and members of the public to think more clearly about appropriate vs. inappropriate uses of gene drive technologies, the long-term and cumulative and emergent risks of using gene drives in wild populations, and steps that can be taken to manage these risks, such as protecting wilderness areas where people can enjoy life forms that have not been genetically engineered.

Species eradication for ecosystem restoration

Many of the world's ecosystems are under unprecedented stress as human pressures have escalated to be a dominant driver of ecosystem composition and condition. Direct impacts such as agriculture, extraction, and development are impacting vast swathes of land and ocean, while the effects of human-caused climate change are felt even in the most remote parts of marine and terrestrial wildernesses. These impacts are resulting in changes ranging from ecosystem collapse or replacement to novel mixes of species due to temperature-driven range shifts. While reducing human pressures is paramount for the future viability of vulnerable ecosystems, much attention is now also focused on whether degraded areas can be restored. Indeed, the UN has declared 2021-2030 the Decade on Ecosystem Restoration, which aims to "prevent, halt and reverse the degradation of ecosystems on every continent and in every ocean".

Exploring the future of SARS-CoV-2 treatment after the first two years of the pandemic: A comparative study of alternative therapeutics

One of the most pressing challenges associated with SARS-CoV-2 treatment is the emergence of new variants that may be more transmissible, cause more severe disease, or be resistant to current treatments and vaccines. The emergence of SARS-CoV-2 has led to a global pandemic, resulting in millions of deaths worldwide. Various strategies have been employed to combat the virus, including neutralizing monoclonal antibodies (mAbs), CRISPR/Cas13, and antisense oligonucleotides (ASOs). While vaccines and small molecules have proven to be an effective means of preventing severe COVID-19 and reducing transmission rates, the emergence of new virus variants poses a challenge to their effectiveness. Monoclonal antibodies have shown promise in treating early-stage COVID-19, but their effectiveness is limited in severe cases and the emergence of new variants may reduce their binding affinity. CRISPR/Cas13 has shown potential in targeting essential viral genes, but its efficiency, specificity, and delivery to the site of infection are major limitations. ASOs have also been shown to be effective in targeting viral RNA, but they face similar challenges to CRISPR/Cas13 in terms of delivery and potential off-target effects. In conclusion, a combination of these strategies may provide a more effective means of combating SARS-CoV-2, and future research should focus on improving their efficiency, specificity, and delivery to the site of infection. It is evident that the continued research and development of these alternative therapies will be essential in the ongoing fight against SARS-CoV-2 and its potential future variants.

Genetic engineering and genome editing in plants, animals and humans: Facts and myths

Human history is inextricably linked to the introduction of desirable heritable traits in plants and animals. Selective breeding (SB) predates our historical period and has been practiced since the advent of agriculture and farming more than ten thousand years ago. Since the 1970s, methods of direct plant and animal genome manipulation are constantly being developed. These are collectively described as "genetic engineering" (GE). Plant GE aims to improve nutritional value, insect resistance and weed control. Animal GE has focused on livestock improvement and disease control. GE applications also involve medical improvements intended to treat human disease. The scientific consensus built around marketed products of GE organisms (GEOs) is usually well established, noting significant benefits and low risks. GEOs are exhaustively scrutinized in the EU and many non-EU countries for their effects on human health and the environment, but scrutiny should be equally applied to all previously untested organisms derived directly from nature or through selective breeding. In fact, there is no evidence to suggest that natural or selectively bred plants and animals are in principle safer to humans than GEOs. Natural and selectively bred strains evolve over time via genetic mutations that can be as risky to humans and the environment as the mutations found in GEOs. Thus, previously untested plant and animal strains aimed for marketing should be proven useful or harmful to humans only upon comparative testing, regardless of their origin. Highlighting the scientific consensus declaring significant benefits and rather manageable risks provided by equitably accessed GEOs, can mitigate negative predispositions by policy makers and the public. Accordingly, we provide an overview of the underlying technologies and the scientific consensus to help resolve popular myths about the safety and usefulness of GEOs.

Validation of CRISPR activation system in Aedes cells using multicistronic plasmid vectors

Aedes mosquitoes transmit several pathogens including flaviviruses to humans which result in high morbidity and mortality. Owing to adaptability and climate change, these mosquito vectors are predicted to establish in new geographical areas thus exposing larger populations to the risk of infection. Therefore, control of Aedes vector is necessary to prevent disease transmission. Recently, genetic approaches to vector control have shown promise; however, the tools and methods for manipulating the mosquito genome are rather limited. While CRISPR-Cas9 system has been adapted for gene editing purposes in Aedes mosquito, the dCas9-based transcription control of genes remain unexplored. In this study we report implementation of the CRISPR activation system in Aedes cells. For this we designed, constructed and tested a bi-partite plasmid-based strategy that allows expression of the dCas9-VPR and targeting guide RNA together with a reporter cassette. Quantitative analysis of the fluorescent reporter gene levels showed a robust over-expression validating CRISPR activation in Aedes cells. This strategy and the biological parts will be useful resource for synthetic transcription factor-based robust upregulation of Aedes genes for application of synthetic biology approaches for vector control.

Combining transgenesis with paratransgenesis to fight malaria

Malaria is among the deadliest infectious diseases, and Plasmodium, the causative agent, needs to complete a complex development cycle in its vector mosquito for transmission to occur. Two promising strategies to curb transmission are transgenesis, consisting of genetically engineering mosquitoes to express antimalarial effector molecules, and paratransgenesis, consisting of introducing into the mosquito commensal bacteria engineered to express antimalarial effector molecules. Although both approaches restrict parasite development in the mosquito, it is not known how their effectiveness compares. Here we provide an in-depth assessment of transgenesis and paratransgenesis and evaluate the combination of the two approaches. Using the Q-system to drive gene expression, we engineered mosquitoes to produce and secrete two effectors - scorpine and the MP2 peptide - into the mosquito gut and salivary glands. We also engineered Serratia, a commensal bacterium capable of spreading through mosquito populations to secrete effectors into the mosquito gut. Whereas both mosquito-based and bacteria-based approaches strongly reduced the oocyst and sporozoite intensity, a substantially stronger reduction of Plasmodium falciparum development was achieved when transgenesis and paratransgenesis were combined. Most importantly, transmission of Plasmodium berghei from infected to naïve mice was maximally inhibited by the combination of the two approaches. Combining these two strategies promises to become a powerful approach to combat malaria.

RNA Viruses, Pandemics and Anticipatory Preparedness

RNA viruses are likely to cause future pandemics and therefore we must create and organize a deep knowledge of these viruses to prevent and manage this risk. Assuming prevention will fail, at least once, we must be prepared to manage a future pandemic using all resources available. We emphasize the importance of having safe vaccine candidates and safe broad-spectrum antivirals ready for rapid clinical translation. Additionally, we must have similar tools to be ready for outbreaks of RNA viruses among animals and plants. Finally, similar coordination should be accomplished for other pathogens with pandemic potential.

An Ethical Overview of the CRISPR-Based Elimination of Anopheles gambiae to Combat Malaria

Approximately a quarter of a billion people around the world suffer from malaria each year. Most cases are located in sub-Saharan Africa where Anopheles gambiae mosquitoes are the principal vectors of this public health problem. With the use of CRISPR-based gene drives, the population of mosquitoes can be modified, eventually causing their extinction. First, we discuss the moral status of the organism and argue that using genetically modified mosquitoes to combat malaria should not be abandoned based on some moral value of A. gambiae. Secondly, we argue that environmental impact studies should be performed to obtain an accurate account of the possible effects of a potential eradication of the organism. However, the risks from the purposeful extinction of A. gambiae should not overtake the benefits of eradicating malaria and risk assessments should be used to determine acceptable risks. Thirdly, we argue that the eventual release of the genetically modified mosquitoes will depend on transparency, community involvement, and cooperation between different nations.

Larval mosquito management and risk to aquatic ecosystems: A comparative approach including current tactics and gene-drive Anopheles techniques

Genetic engineering of mosquitoes represents a promising tactic for reducing human suffering from malaria. Gene-drive techniques being developed that suppress or modify populations of Anopheles gambiae have the potential to be used with, or even possibly obviate, microbial and synthetic insecticides. However, these techniques are new and therefore there is attendant concern and uncertainty from regulators, policymakers, and the public about their environmental risks. Therefore, there is a need to assist decision-makers and public health stewards by assessing the risks associated with these newer mosquito management tactics so the risks can be compared as a basis for informed decision making. Previously, the effect of gene-drive mosquitoes on water quality in Africa was identified as a concern by stakeholders. Here, we use a comparative risk assessment approach for the effect of gene-drive mosquitoes on water quality in Africa. We compare the use of existing larvicides and the proposed genetic techniques in aquatic environments. Based on our analysis, we conclude that the tactic of gene-drive Anopheles for malaria management is unlikely to result in risks to aquatic environments that exceed current tactics for larval mosquitoes. As such, these new techniques would likely comply with currently recommended safety standards.

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

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.

Whole Genome Sequencing Contributions and Challenges in Disease Reduction Focused on Malaria

Malaria elimination remains an important goal that requires the adoption of sophisticated science and management strategies in the era of the COVID-19 pandemic. The advent of next generation sequencing (NGS) is making whole genome sequencing (WGS) a standard today in the field of life sciences, as PCR genotyping and targeted sequencing provide insufficient information compared to the whole genome. Thus, adapting WGS approaches to malaria parasites is pertinent to studying the epidemiology of the disease, as different regions are at different phases in their malaria elimination agenda. Therefore, this review highlights the applications of WGS in disease management, challenges of WGS in controlling malaria parasites, and in furtherance, provides the roles of WGS in pursuit of malaria reduction and elimination. WGS has invaluable impacts in malaria research and has helped countries to reach elimination phase rapidly by providing required information needed to thwart transmission, pathology, and drug resistance. However, to eliminate malaria in sub-Saharan Africa (SSA), with high malaria transmission, we recommend that WGS machines should be readily available and affordable in the region.

Gene Drives in the U.K., U.S., and Australian Press (2015-2019): How a New Focus on Responsibility Is Shaping Science Communication

Gene drive is a controversial biotechnology for pest control. Despite a commitment from gene drive researchers to responsibility and the key role of the media in debates about science and technology, little research has been conducted on media reporting of gene drive. We employ metaphor and discourse analysis to explore how responsibility is reflected in the coverage of this technology in the U.S., U.K., and Australian press. The findings reveal a rhetorical strategy of trust-building by evoking the moral attributes of gene drive researchers. We discuss the implications of these findings for the communication of new technologies.

Applications of and considerations for using CRISPR-Cas9-mediated gene conversion systems in rodents

Genetic elements that are inherited at super-Mendelian frequencies could be used in a 'gene drive' to spread an allele to high prevalence in a population with the goal of eliminating invasive species or disease vectors. We recently demonstrated that the gene conversion mechanism underlying a CRISPR-Cas9-mediated gene drive is feasible in mice. Although substantial technical hurdles remain, overcoming these could lead to strategies that might decrease the spread of rodent-borne Lyme disease or eliminate invasive populations of mice and rats that devastate island ecology. Perhaps more immediately achievable at moderate gene conversion efficiency, applications in a laboratory setting could produce complex genotypes that reduce the time and cost in both dollars and animal lives compared with Mendelian inheritance strategies. Here, we discuss what we have learned from early efforts to achieve CRISPR-Cas9-mediated gene conversion, potential for broader applications in the laboratory, current limitations, and plans for optimizing this potentially powerful technology.

The Potential for a Released Autosomal X-Shredder Becoming a Driving-Y Chromosome and Invasively Suppressing Wild Populations of Malaria Mosquitoes

Sex-ratio distorters based on X-chromosome shredding are more efficient than sterile male releases for population suppression. X-shredding is a form of sex distortion that skews spermatogenesis of XY males towards the preferential transmission of Y-bearing gametes, resulting in a higher fraction of sons than daughters. Strains harboring X-shredders on autosomes were first developed in the malaria mosquito Anopheles gambiae, resulting in strong sex-ratio distortion. Since autosomal X-shredders are transmitted in a Mendelian fashion and can be selected against, their frequency in the population declines once releases are halted. However, unintended transfer of X-shredders to the Y-chromosome could produce an invasive meiotic drive element, that benefits from its biased transmission to the predominant male-biased offspring and its effective shielding from female negative selection. Indeed, linkage to the Y-chromosome of an active X-shredder instigated the development of the nuclease-based X-shredding system. Here, we analyze mechanisms whereby an autosomal X-shredder could become unintentionally Y-linked after release by evaluating the stability of an established X-shredder strain that is being considered for release, exploring its potential for remobilization in laboratory and wild-type genomes of An. gambiae and provide data regarding expression on the mosquito Y-chromosome. Our data suggest that an invasive X-shredder resulting from a post-release movement of such autosomal transgenes onto the Y-chromosome is unlikely.

Dual-Use Quickscan: A Web-Based Tool to Assess the Dual-Use Potential of Life Science Research

Research on pathogenic organisms is crucial for medical, biological and agricultural developments. However, biological agents as well as associated knowledge and techniques, can also be misused, for example for the development of biological weapons. Potential malicious use of well-intended research, referred to as “dual-use research”, poses a threat to public health and the environment. There are various international resources providing frameworks to assess dual-use potential of the research concerned. However, concrete instructions for researchers on how to perform a dual-use risk assessment is largely lacking. The international need for practical dual-use monitoring and risk assessment instructions, in addition to the need to raise awareness among scientists about potential dual-use aspects of their research has been identified over the last years by the Netherlands Biosecurity Office, through consulting national and international biorisk stakeholders. We identified that Biorisk Management Advisors and researchers need a practical tool to facilitate a dual-use assessment on their specific research. Therefore, the Netherlands Biosecurity Office developed a web-based Dual-Use Quickscan (www.dualusequickscan.com), that can be used periodically by researchers working with microorganisms to assess potential dual-use risks of their research by answering a set of fifteen yes/no questions. The questions for the tool were extracted from existing international open resources, and categorized into three themes: characteristics of the biological agent, knowledge and technology about the biological agent, and consequences of misuse. The results of the Quickscan provide the researcher with an indication of the dual-use potential of the research and can be used as a basis for further discussions with a Biorisk Management Advisor. The Dual-Use Quickscan can be embedded in a broader system of biosafety and biosecurity that includes dual-use monitoring and awareness within organizations. Increased international attention to examine pathogens with pandemic potential has been enhanced by the current COVID-19 pandemic, hence monitoring of dual-use potential urgently needs to be encouraged.

From the Lab to the Last Mile: Deploying Transgenic Approaches Against Mosquitoes

Ingenious exploitation of transgenic approaches to produce malaria resistant or sterile mosquitoes, or hypervirulent mosquito pathogens, has produced many potential solutions to vector borne diseases. However, in spite of technological feasibility, it has not been determined how well these new methods will work, and how they should be tested and regulated. Some self-limiting transgenic fungal pathogens and mosquitoes are almost field ready, and may be easier to regulate than self-sustaining strategies. However, they require repeat sales and so must show business viability; low-cost mass production is just one of a number of technical constraints that are sometimes treated as an afterthought in technology deployment. No transgenic self-sustaining approach to anopheline control has ever been deployed because of unresolved ethical, social and regulatory issues. These overlapping issues include: 1) the transparency challenge, which requires public discourse, particularly in Africa where releases are proposed, to determine what society is willing to risk given the potential benefits; 2) the transboundary challenge, self-sustaining mosquitoes or pathogens are potentially capable of crossing national boundaries and irreversibly altering ecosystems, and 3) the risk assessment challenge. The polarized debate as to whether these technologies will ever be used to save lives is ongoing; they will founder without a political answer as to how do we interpret the precautionary principle, as exemplified in the Cartagena protocol, in the global context of technological changes.

Control of sheep flystrike: what's been tried in the past and where to from here

Flystrike remains a serious financial and animal welfare issue for the sheep industry in Australia despite many years of research into control methods. The present paper provides an extensive review of past research on flystrike, and highlights areas that hold promise for providing long-term control options. We describe areas where the application of modern scientific advances may provide increased impetus to some novel, as well as some previously explored, control methods. We provide recommendations for research activities: insecticide resistance management, novel delivery methods for therapeutics, improved breeding indices for flystrike-related traits, mechanism of nematode-induced scouring in mature animals. We also identify areas where advances can be made in flystrike control through the greater adoption of well-recognised existing management approaches: optimal insecticide-use patterns, increased use of flystrike-related Australian Sheep Breeding Values, and management practices to prevent scouring in young sheep. We indicate that breeding efforts should be primarily focussed on the adoption and improvement of currently available breeding tools and towards the future integration of genomic selection methods. We describe factors that will impact on the ongoing availability of insecticides for flystrike control and on the feasibility of vaccination. We also describe areas where the blowfly genome may be useful in providing impetus to some flystrike control strategies, such as area-wide approaches that seek to directly suppress or eradicate sheep blowfly populations. However, we also highlight the fact that commercial and feasibility considerations will act to temper the potential for the genome to act as the basis for providing some control options.

Integrative Pre-Breeding for Biotic Resistance in Forest Trees

Climate change is unleashing novel biotic antagonistic interactions for forest trees that may jeopardize populations' persistence. Therefore, this review article envisions highlighting major opportunities from ecological evolutionary genomics to assist the identification, conservation, and breeding of biotic resistance in forest tree species. Specifically, we first discuss how assessing the genomic architecture of biotic stress resistance enables us to recognize a more polygenic nature for a trait typically regarded Mendelian, an expectation from the Fisherian runaway pathogen-host concerted arms-race evolutionary model. Secondly, we outline innovative pipelines to capture and harness natural tree pre-adaptations to biotic stresses by merging tools from the ecology, phylo-geography, and omnigenetics fields within a predictive breeding platform. Promoting integrative ecological genomic studies promises a better understanding of antagonistic co-evolutionary interactions, as well as more efficient breeding utilization of resistant phenotypes.

Application of Gene Editing for Climate Change in Agriculture

Climate change imposes a severe threat to agricultural systems, food security, and human nutrition. Meanwhile, efforts in crop and livestock gene editing have been undertaken to improve performance across a range of traits. Many of the targeted phenotypes include attributes that could be beneficial for climate change adaptation. Here, we present examples of emerging gene editing applications and research initiatives that are aimed at the improvement of crops and livestock in response to climate change, and discuss technical limitations and opportunities therein. While only few applications of gene editing have been translated to agricultural production thus far, numerous studies in research settings have demonstrated the potential for potent applications to address climate change in the near future.

Population modification strategies for malaria vector control are uniquely resilient to observed levels of gene drive resistance alleles

Cas9/guide RNA (gRNA)-based gene drive systems are expected to play a transformative role in malaria elimination efforts., whether through population modification, in which the drive system contains parasite-refractory genes, or population suppression, in which the drive system induces a severe fitness load resulting in population decline or extinction. DNA sequence polymorphisms representing alternate alleles at gRNA target sites may confer a drive-resistant phenotype in individuals carrying them. Modeling predicts that, for observed levels of SGV at potential target sites and observed rates of de novo DRA formation, population modification strategies are uniquely resilient to DRAs. We conclude that gene drives can succeed when fitness costs incurred by drive-carrying mosquitoes are low enough to prevent strong positive selection for DRAs produced de novo or as part of the SGV and that population modification strategies are less prone to failure due to drive resistance.

Synthetic Genomes

DNA synthesis technology has progressed to the point that it is now practical to synthesize entire genomes. Quite a variety of methods have been developed, first to synthesize single genes but ultimately to massively edit or write from scratch entire genomes. Synthetic genomes can essentially be clones of native sequences, but this approach does not teach us much new biology. The ability to endow genomes with novel properties offers special promise for addressing questions not easily approachable with conventional gene-at-a-time methods. These include questions about evolution and about how genomes are fundamentally wired informationally, metabolically, and genetically. The techniques and technologies relating to how to design, build, and deliver big DNA at the genome scale are reviewed here. A fuller understanding of these principles may someday lead to the ability to truly design genomes from scratch.

CRISPR-Cas and Its Wide-Ranging Applications: From Human Genome Editing to Environmental Implications, Technical Limitations, Hazards and Bioethical Issues

The CRISPR-Cas system is a powerful tool for in vivo editing the genome of most organisms, including man. During the years this technique has been applied in several fields, such as agriculture for crop upgrade and breeding including the creation of allergy-free foods, for eradicating pests, for the improvement of animal breeds, in the industry of bio-fuels and it can even be used as a basis for a cell-based recording apparatus. Possible applications in human health include the making of new medicines through the creation of genetically modified organisms, the treatment of viral infections, the control of pathogens, applications in clinical diagnostics and the cure of human genetic diseases, either caused by somatic (e.g., cancer) or inherited (mendelian disorders) mutations. One of the most divisive, possible uses of this system is the modification of human embryos, for the purpose of preventing or curing a human being before birth. However, the technology in this field is evolving faster than regulations and several concerns are raised by its enormous yet controversial potential. In this scenario, appropriate laws need to be issued and ethical guidelines must be developed, in order to properly assess advantages as well as risks of this approach. In this review, we summarize the potential of these genome editing techniques and their applications in human embryo treatment. We will analyze CRISPR-Cas limitations and the possible genome damage caused in the treated embryo. Finally, we will discuss how all this impacts the law, ethics and common sense.

Experimenting with co-development: A qualitative study of gene drive research for malaria control in Mali

We investigate how technology 'co-development' (between researchers, stakeholders and local communities) is framed in practice by those developing gene drive mosquitos for malaria eradication. Our case study focuses on UK and Mali-based researchers planning to undertake the first field trials in Mali of gene drive mosquitos for malaria control. While they and the wider gene drive research community are explicitly committed to the principle of co-development, how this is framed and practiced is not clear. Through qualitative analysis of 34 interviews complemented by observation and documentary research conducted in 2018, we identify and compare ten framings of co-development mobilised by UK and Malian researchers and stakeholders. For Malians, co-development reflected Mali's broader socio-political context and a desire for African scientific independence and leadership. It was mobilised to secure community and stakeholder support for gene drive mosquito field trials, through outreach, building local scientific capacity and developing those institutions (e.g. regulatory) necessary for field trials to go ahead. For UK participants, co-development was also concerned with scientific capacity-building, knowledge exchange between researchers, and stakeholder and community outreach to secure consent for field trials. Overall, our findings suggest co-development is opening up previously expert-dominated spaces as researchers attempt to take responsibility for the societal implications of their work. However, its main function is as a project management tool to enable and instrumentally support technological development, field trials and eventual deployment. This function extends into areas which are traditionally the responsibility of the state, such as regulatory development, facilitated by Mali's fragile political and economic situation. Paradoxically, co-development simultaneously depoliticises gene drive, masking power relations and closing down substantive debate and agency. Characterised by extreme poverty, conflict and weak institutions, Mali may become a site for technological experimentation where there is little interrogation of gene drive or its governance.

Novel CRISPR-Cas Systems: An Updated Review of the Current Achievements, Applications, and Future Research Perspectives

According to Darwin's theory, endless evolution leads to a revolution. One such example is the Clustered Regularly Interspaced Palindromic Repeats (CRISPR)-Cas system, an adaptive immunity system in most archaea and many bacteria. Gene editing technology possesses a crucial potential to dramatically impact miscellaneous areas of life, and CRISPR-Cas represents the most suitable strategy. The system has ignited a revolution in the field of genetic engineering. The ease, precision, affordability of this system is akin to a Midas touch for researchers editing genomes. Undoubtedly, the applications of this system are endless. The CRISPR-Cas system is extensively employed in the treatment of infectious and genetic diseases, in metabolic disorders, in curing cancer, in developing sustainable methods for fuel production and chemicals, in improving the quality and quantity of food crops, and thus in catering to global food demands. Future applications of CRISPR-Cas will provide benefits for everyone and will save countless lives. The technology is evolving rapidly; therefore, an overview of continuous improvement is important. In this review, we aim to elucidate the current state of the CRISPR-Cas revolution in a tailor-made format from its discovery to exciting breakthroughs at the application level and further upcoming trends related to opportunities and challenges including ethical concerns.

Ugandan stakeholder hopes and concerns about gene drive mosquitoes for malaria control: new directions for gene drive risk governance

Background

The African Union’s High-Level Panel on Emerging Technologies identified gene drive mosquitoes as a priority technology for malaria elimination. The first field trials are expected in 5–10 years in Uganda, Mali or Burkina Faso. In preparation, regional and international actors are developing risk governance guidelines which will delineate the framework for identifying and evaluating risks. Scientists and bioethicists have called for African stakeholder involvement in these developments, arguing the knowledge and perspectives of those people living in malaria-afflicted countries is currently missing. However, few African stakeholders have been involved to date, leaving a knowledge gap about the local social-cultural as well as ecological context in which gene drive mosquitoes will be tested and deployed. This study investigates and analyses Ugandan stakeholders’ hopes and concerns about gene drive mosquitoes for malaria control and explores the new directions needed for risk governance.

Methods

This qualitative study draws on 19 in-depth semi-structured interviews with Ugandan stakeholders in 2019. It explores their hopes for the technology and the risks they believed pertinent. Coding began at a workshop and continued through thematic analysis.

Results

Participants’ hopes and concerns for gene drive mosquitoes to address malaria fell into three themes: (1) ability of gene drive mosquitoes to prevent malaria infection; (2) impacts of gene drive testing and deployment; and, (3) governance. Stakeholder hopes fell almost exclusively into the first theme while concerns were spread across all three. The study demonstrates that local stakeholders are able and willing to contribute relevant and important knowledge to the development of risk frameworks.

Conclusions

International processes can provide high-level guidelines, but risk decision-making must be grounded in the local context if it is to be robust, meaningful and legitimate. Decisions about whether or not to release gene drive mosquitoes as part of a malaria control programme will need to consider the assessment of both the risks and the benefits of gene drive mosquitoes within a particular social, political, ecological, and technological context. Just as with risks, benefits—and importantly, the conditions that are necessary to realize them—must be identified and debated in Uganda and its neighbouring countries.

Quantifying the risk of vector-borne disease transmission attributable to genetically modified vectors

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.

Designing gene drives to limit spillover to non-target populations

The prospect of utilizing CRISPR-based gene-drive technology for controlling populations has generated much excitement. However, the potential for spillovers of gene-drive alleles from the target population to non-target populations has raised concerns. Here, using mathematical models, we investigate the possibility of limiting spillovers to non-target populations by designing differential-targeting gene drives, in which the expected equilibrium gene-drive allele frequencies are high in the target population but low in the non-target population. We find that achieving differential targeting is possible with certain configurations of gene-drive parameters, but, in most cases, only under relatively low migration rates between populations. Under high migration, differential targeting is possible only in a narrow region of the parameter space. Because fixation of the gene drive in the non-target population could severely disrupt ecosystems, we outline possible ways to avoid this outcome. We apply our model to two potential applications of gene drives—field trials for malaria-vector gene drives and control of invasive species on islands. We discuss theoretical predictions of key requirements for differential targeting and their practical implications.

CRISPR-based gene drive is an emerging genetic engineering technology that enables engineered genetic variants, which are usually designed to be harmful to the organism carrying them, to be spread rapidly in populations. Although this technology is promising for controlling disease vectors and invasive species, there is a considerable risk that a gene drive could unintentionally spillover from the target population, where it was deployed, to non-target populations. We develop mathematical models of gene-drive dynamics that incorporate migration between target and non-target populations to investigate the possibility of effectively applying a gene drive in the target population while limiting its spillover to non-target populations (‘differential targeting’). We observe that the feasibility of differential targeting depends on the gene-drive design specification, as well as on the migration rates between the populations. Even when differential targeting is possible, as migration increases, the possibility for differential targeting disappears. We find that differential targeting can be effective for low migration rates, and that it is sensitive to the design of the gene drive under high migration rates. We suggest that differential targeting could be used, in combination with other mitigation measures, as an additional safeguard to limit gene drive spillovers.

Clair C, Coristine L, Higgs E, Smith R, Pellatt M, Beaty C, Cheskey E, Cooke SJ, Crawford L, Davis R, Forbes G, Gadallah F(Z, Kendall P, Mandrak N, Moola F, Parker S, Quayle J, Ray JC, Richardson K, Smith K, Snider J, Smol JP, Sutherland WJ, Vallillee A, White L, Woodley A. Emerging issues for protected and conserved areas in Canada

Horizon scanning is increasingly used in conservation to systematically explore emerging policy and management issues. We present the results of a horizon scan of issues likely to impact management of Canadian protected and conserved areas over the next 5–10 years. Eighty-eight individuals participated, representing a broad community of academics, government and nongovernment organizations, and foundations, including policymakers and managers of protected and conserved areas. This community initially identified 187 issues, which were subsequently triaged to 15 horizon issues by a group of 33 experts using a modified Delphi technique. Results were organized under four broad categories: ( i) emerging effects of climate change in protected and conserved areas design, planning, and management (i.e., large-scale ecosystem changes, species translocation, fire regimes, ecological integrity, and snow patterns); ( ii) Indigenous governance and knowledge systems (i.e., Indigenous governance and Indigenous knowledge and Western science); ( iii) integrated conservation approaches across landscapes and seascapes (i.e., connectivity conservation, integrating ecosystem values and services, freshwater planning); and ( iv) early responses to emerging cumulative, underestimated, and novel threats (i.e., management of cumulative impacts, declining insect biomass, increasing anthropogenic noise, synthetic biology). Overall, the scan identified several emerging issues that require immediate attention to effectively reduce threats, respond to opportunities, and enhance preparedness and capacity to react.

The Health Reframing of Climate Change and the Poverty of Narrow Bioethics

We must resist thoroughly reframing climate change as a health issue. For human health-centric ethical frameworks omit dimensions of value that we must duly consider. We need a new, an environmental, research ethic, one that we can use to more completely and impartially evaluate proposed research on mitigation and adaptation strategies.

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

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.

Viral gene drive in herpesviruses

Gene drives are genetic modifications designed to propagate in a population with high efficiency. Current gene drive strategies rely on sexual reproduction and are thought to be restricted to sexual organisms. Here, we report on a gene drive system that allows the spread of an engineered trait in populations of DNA viruses and, in particular, herpesviruses. We describe the successful transmission of a gene drive sequence between distinct strains of human cytomegalovirus (human herpesvirus 5) and show that gene drive viruses can efficiently target and replace wildtype populations in cell culture experiments. Moreover, by targeting sequences necessary for viral replication, our results indicate that a viral gene drive can be used as a strategy to suppress a viral infection. Taken together, this work offers a proof of principle for the design of a gene drive in viruses.

Current gene drive strategies are restricted to sexually reproducing species. Here the authors develop a gene drive in herpesviruses that allows the spread of an engineered trait through a viral population.

Safe-by-Design: Stakeholders' Perceptions and Expectations of How to Deal with Uncertain Risks of Emerging Biotechnologies in the Netherlands

Advanced gene editing techniques such as Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/Cas have increased the pace of developments in the field of industrial biotechnology. Such techniques imply new possibilities when working with living organisms, possibly leading to uncertain risks. In the Netherlands, current policy fails to address these uncertain risks because risk classification is determined process-wise (i.e., genetically modified organism [GMO] and non-GMO), there is a strong focus on quantifiable risks, and the linearity within current governance (science-policy-society) hinders iterative communication between stakeholders, leaving limited room to anticipate uncertainties at an early stage of development. A suggested concept to overcome these shortcomings is the Safe-by-Design (SbD) approach, which, theoretically, allows stakeholders to iteratively incorporate safety measures throughout a technology's development process, creating a dynamic environment for the anticipation of uncertain risks. Although this concept originates from chemical engineering and is already widely applied in nanotechnology, for the field of biotechnology, there is no agreed upon definition yet. To explore the possibilities of SbD for future governance of biotechnology, we should gain insight in how various stakeholders perceive notions of risk, safety, and inherent safety, and what this implies for the applicability of SbD for risk governance concerning industrial biotechnology. Our empirical research reveals three main themes: (1) diverging expectations with regard to safety and risks, and to establish an acceptable level of risk; (2) different applications of SbD and inherent safety, namely, product- and process-wise; and (3) unclarity in allocating responsibilities to stakeholders in the development process of a biotechnology and within society.

A male-biased sex-distorter gene drive for the human malaria vector Anopheles gambiae

Only female insects transmit diseases such as malaria, dengue and Zika; therefore, control methods that bias the sex ratio of insect offspring have long been sought. Genetic elements such as sex-chromosome drives can distort sex ratios to produce unisex populations that eventually collapse, but the underlying molecular mechanisms are unknown. We report a male-biased sex-distorter gene drive (SDGD) in the human malaria vector Anopheles gambiae. We induced super-Mendelian inheritance of the X-chromosome-shredding I-PpoI nuclease by coupling this to a CRISPR-based gene drive inserted into a conserved sequence of the doublesex (dsx) gene. In modeling of invasion dynamics, SDGD was predicted to have a quicker impact on female mosquito populations than previously developed gene drives targeting female fertility. The SDGD at the dsx locus led to a male-only population from a 2.5% starting allelic frequency in 10–14 generations, with population collapse and no selection for resistance. Our results support the use of SDGD for malaria vector control.

A sex-distorter gene drive causes population collapse in the malaria mosquito.

Population Genomic Approaches for Weed Science

Genomic approaches are opening avenues for understanding all aspects of biological life, especially as they begin to be applied to multiple individuals and populations. However, these approaches typically depend on the availability of a sequenced genome for the species of interest. While the number of genomes being sequenced is exploding, one group that has lagged behind are weeds. Although the power of genomic approaches for weed science has been recognized, what is needed to implement these approaches is unfamiliar to many weed scientists. In this review we attempt to address this problem by providing a primer on genome sequencing and provide examples of how genomics can help answer key questions in weed science such as: (1) Where do agricultural weeds come from; (2) what genes underlie herbicide resistance; and, more speculatively, (3) can we alter weed populations to make them easier to control? This review is intended as an introduction to orient weed scientists who are thinking about initiating genome sequencing projects to better understand weed populations, to highlight recent publications that illustrate the potential for these methods, and to provide direction to key tools and literature that will facilitate the development and execution of weed genomic projects.