scholarly journals Can CRISPR-Based Gene Drive Be Confined in the Wild? A Question for Molecular and Population Biology

2018 ◽  
Vol 13 (2) ◽  
pp. 424-430 ◽  
Author(s):  
John M. Marshall ◽  
Omar S. Akbari
Keyword(s):  
Population Biology ◽  
Gene Drive ◽  
In The Wild

scholarly journals Can CRISPR-based gene drive be confined in the wild? A question for molecular and population biology

2017 ◽  
Author(s):  
John M. Marshall ◽  
Omar S. Akbari
Keyword(s):  
Population Biology ◽  
Gene Editing ◽  
Gene Drive ◽  
In The Wild ◽  
Drive Systems ◽  
Chain Drives

AbstractThe recent discovery of CRISPR and its application as a gene editing tool has enabled a range of gene drive systems to be engineered with much greater ease. In order for the benefits of this technology to be realized, drive systems must be developed that are capable of both spreading into populations to achieve their desired impact, and being recalled in the event of unwanted consequences or public disfavor. We review the performance of three broad categories of drive systems at achieving these goals - threshold-dependent drives, homing-based drive and remediation systems, and temporally self-limiting systems such as daisy-chain drives.

scholarly journals Threshold-Dependent Gene Drives in the Wild: Spread, Controllability, and Ecological Uncertainty

BioScience ◽  
2019 ◽  
Vol 69 (11) ◽  
pp. 900-907 ◽  
Author(s):  
Gregory A Backus ◽  
Jason A Delborne
Keyword(s):  
Critical Frequency ◽  
Wild Population ◽  
Detailed Knowledge ◽  
Gene Drive ◽  
Potential Solution ◽  
Spreading Behavior ◽  
The Face ◽  
In The Wild ◽  
Ecological Uncertainty ◽  
Gene Drives

Abstract Gene drive technology could allow the intentional spread of a desired gene throughout an entire wild population in relatively few generations. However, there are major concerns that gene drives could either fail to spread or spread without restraint beyond the targeted population. One potential solution is to use more localized threshold-dependent drives, which only spread when they are released in a population above a critical frequency. However, under certain conditions, small changes in gene drive fitness could lead to divergent outcomes in spreading behavior. In the face of ecological uncertainty, the inability to estimate gene drive fitness in a real-world context could prove problematic because gene drives designed to be localized could spread to fixation in neighboring populations if ecological conditions unexpectedly favor the gene drive. This perspective offers guidance to developers and managers because navigating gene drive spread and controllability could be risky without detailed knowledge of ecological contexts.

scholarly journals Fitness consequences of a non-recombining sex-ratio drive chromosome can explain its prevalence in the wild

2019 ◽  
Vol 286 (1917) ◽  
pp. 20192529 ◽  
Author(s):  
Kelly A. Dyer ◽  
David W. Hall
Keyword(s):  
Sex Ratio ◽  
Sperm Competition ◽  
Natural Populations ◽  
Theoretical Models ◽  
Host Population ◽  
Gene Drive ◽  
Fitness Consequences ◽  
In The Wild ◽  
And Performance ◽  
Drive Systems

Understanding the pleiotropic consequences of gene drive systems on host fitness is essential to predict their spread through a host population. Here, we study sex-ratio (SR) X-chromosome drive in the fly Drosophila recens , where SR causes the death of Y-bearing sperm in male carriers. SR males only sire daughters, which all carry SR, thus giving the chromosome a transmission advantage. The prevalence of the SR chromosome appears stable, suggesting pleiotropic costs. It was previously shown that females homozygous for SR are sterile, and here, we test for additional fitness costs of SR. We found that females heterozygous for SR have reduced fecundity and that male SR carriers have reduced fertility in conditions of sperm competition. We then use our fitness estimates to parametrize theoretical models of SR drive and show that the decrease in fecundity and sperm competition performance can account for the observed prevalence of SR in natural populations. In addition, we found that the expected equilibrium frequency of the SR chromosome is particularly sensitive to the degree of multiple mating and performance in sperm competition. Together, our data suggest that the mating system of the organism should be carefully considered during the development of gene drive systems.

scholarly journals Vector genetics, insecticide resistance and gene drives: an agent-based modeling approach to evaluate malaria transmission and elimination

2020 ◽  
Author(s):  
Prashanth Selvaraj ◽  
Edward A. Wenger ◽  
Daniel Bridenbecker ◽  
Nikolai Windbichler ◽  
Jonathan R. Russell ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Malaria Transmission ◽  
Control Measures ◽  
Phenotypic Traits ◽  
Gene Drive ◽  
Agent Based ◽  
Transmission Setting ◽  
In The Wild ◽  
Gene Drives

AbstractVector control has been a key component in the fight against malaria for decades, and chemical insecticides are critical to the success of vector control programs worldwide. However, increasing resistance to insecticides threatens to undermine these efforts. Understanding the evolution and propagation of resistance is thus imperative to mitigating loss of intervention effectiveness. Additionally, accelerated research and development of new tools that can be deployed alongside existing vector control strategies is key to eradicating malaria in the near future. Methods such as gene drives that aim to genetically modify large mosquito populations in the wild to either render them refractory to malaria or impair their reproduction may prove invaluable tools. Mathematical models of gene flow in populations, which is the transfer of genetic information from one population to another through migration, can offer invaluable insight into the behavior and potential impact of gene drives as well as the spread of insecticide resistance in the wild. Here, we present the first multi-locus, agent-based model of vector genetics that accounts for mutations and a many-to-many mapping cardinality of genotypes to phenotypes to investigate gene flow, and the propagation of gene drives in Anopheline populations. This model is embedded within a large scale individual-based model of malaria transmission representative of a high burden, high transmission setting characteristic of the Sahel. Results are presented for the selection of insecticide-resistant vectors and the spread of resistance through repeated deployment of insecticide treated nets (ITNs), in addition to scenarios where gene drives act in concert with existing vector control tools such as ITNs. The roles of seasonality, spatial distribution of vector habitat and feed sites, and existing vector control in propagating alleles that confer phenotypic traits via gene drives that result in reduced transmission are explored. The ability to model a spectrum of vector species with different genotypes and phenotypes in the context of malaria transmission allows us to test deployment strategies for existing interventions that reduce the deleterious effects of resistance and allows exploration of the impact of new tools being proposed or developed.Author summaryVector control interventions are essential to the success of global malaria control and elimination efforts but increasing insecticide resistance worldwide threatens to derail these efforts. Releasing genetically modified mosquitoes that use gene drives to pass on desired genes and their associated phenotypic traits to the entire population within a few generations has been proposed to address resistance and other issues such as transmission heterogeneity that can sustain malaria transmission indefinitely. While the ethics and safety of these methods are being debated, mathematical models offer an efficient way of predicting the behavior and estimating the efficacy of these interventions if deployed to specific regions facing challenges to reaching elimination. We have developed a detailed mathematical model of vector genetics where specific genomes code for physical attributes that influence transmission and are affected by the surrounding environment. This is the first model to incorporate an individual-based multi-locus genetic model into a detailed individual-based model of malaria transmission. This model opens the door to investigate a number of subtle but important questions such as the effects of small numbers of mosquitoes in a region sustaining malaria transmission during the low transmission season, and the success of gene drives in regions where extant vector control interventions could kill off gene drive mosquitoes before establishment. Here, we investigate the reduced efficacy of current vector control measures in the presence of insecticide resistance and evaluate the likelihood of achieving local malaria elimination using gene drive mosquitoes released into a high transmission setting alongside other vector control measures.

scholarly journals Osteossínteses de ílio e fêmur em cachorro-do-mato (Cerdocyon thous)

2017 ◽  
Vol 45 ◽  
pp. 6
Author(s):  
Bruna Zafalon Da Silva ◽  
Eduardo Almeida Ruivo Dos Santos ◽  
Priscila Medina Da Costa ◽  
Miúriel De Aquino Goulart ◽  
Bernardo Schmitt ◽  
...  
Keyword(s):  
Population Biology ◽  
Callus Formation ◽  
The Body ◽  
Radiographic Examination ◽  
Bone Consolidation ◽  
Body Fracture ◽  
In The Wild ◽  
Osteosynthesis Techniques ◽  
Cerdocyon Thous ◽  
Environmental Agencies

Background: Fractures and dislocations are common orthopedic conditions arising from traumas from anthropic interaction on wild species, such as those caused by road trampling. Among the treatments, osteosynthesis is considered the method of choice in the treatment of fractures, such as ilium body fractures and femoral fractures. Based on this context, with regard to the incidence of auto accidents and few studies describing osteosynthesis techniques for crab-eating fox, the present study aimed to report the osteosynthesis performed on the body of the ileum and femur of a wild specimen of Cerdocyon thous.Case: A female, adult, crab-eating fox (Cerdocyon thous), coming from wild life was referred to hospital care with a history of run over. After specific examinations, it was diagnosed a complete transverse femoral shaft fracture, an oblique ilium body fracture, a pubic and ischial fracture, and pelvic canal narrowing. The treatment instituted was osteosynthesis of the femoral and ilium body fractures through the use of a 2.7 mm locking plate and screws. In the postoperative period, radiographic examination was performed, where bone callus formation was observed in the 5th week and bone remodeling and consolidation in the 11th week. After 140 days of rehabilitation, the animal was able to be released in the wild, with effective return of function of the pelvic limbs. The release was performed by environmental agencies in a national natural reserve, using radio necklace monitoring.Discussion: Osteosynthesis techniques and preoperative and postoperative management proved to be effective for the return of adequate function of the pelvic limbs in Cerdocyon thous. For wild animals, the use of internal orthopedic implants (plate and screws, for example) become the most suitable for osteosynthesis. They decrease the risks of complications resulting from the management, since they require minimal postoperative manipulation. Thus, they maintain the wild behavior of the animal even in captivity. Among the complications observed in the clinical case, we can mention the use of long plate in the osteosynthesis of the ilium body and the narrowing of the pelvic canal as the most relevant. In relation to the pelvic canal narrowing and the reproductive cycle of the species, the crab-eating fox presents monogamous behavior, gestation of 3 to 6 pups per litter and breastfeeding for approximately 3 months. Because litters are relatively large (number of individuals per calving), the pups are relatively small - approximately 120 g at birth -, so it is expected that no complications occur during the gestational period. The treatment of fractures with the use of locking plates was efficient, obtaining bone consolidation at 10 weeks postoperatively, thus corroborating the scientific descriptions for bone consolidation in canids. Finally, the destination for release and monitoring by radiotelemetry was a joint decision between the environmental agencies of the State and the Union. The release decision was based on the maintenance of the wild behavior without evidence of meekness of the specimen, the absence of sanitary restrictions, as well as the population biology and the genetic flow since the release of the animal was carried out near the rescue site. It is concluded that the surgical treatment instituted by the femoral and ilium osteosynthesis was effective for the Cerdocyon thous specimen, culminating in the rehabilitation of the animal and release in the wild.

scholarly journals Population biology and ecology of the endangered Euphorbia susannae Marloth, an endemic to the Little Karoo, South Africa

2021 ◽  
Vol 22 (10) ◽  
Author(s):  
Laaiqah Jabar ◽  
Stefan John Siebert ◽  
Michele Pfab ◽  
Dirk Cilliers
Keyword(s):  
South Africa ◽  
Species Distribution ◽  
Population Biology ◽  
Species Distribution Model ◽  
Habitat Preferences ◽  
Distribution Model ◽  
Nurse Plants ◽  
Populations At Risk ◽  
In The Wild

Abstract. Jabar L, Siebert SJ, Pfab MF, Cilliers DP. 2021. Population biology and ecology of the endangered Euphorbia susannae Marloth, an endemic to the Little Karoo, South Africa. Biodiversitas 22: 4583-4596. Many euphorbias in the semi-arid parts of South Africa are restricted edaphic specialists with small populations at risk of extinction. Euphorbia susannae is one such species, which grows on the edges of quartz patches along a section of the northern foot slopes of the Langeberg Mountains. This study set out to acquire data on the biology and ecology of the species during a first-ever comprehensive field survey. The resultant dataset allowed for the determination of the geographic distribution of the species, as well as the size and number of populations. Biotic and abiotic environmental variables were employed to generate a habitat profile and a species distribution model. The population structure, regeneration potential, and stability of each subpopulation and the population were also assessed. Euphorbia susannae is a range-restricted species (EOO 170 km2 and AOO 36 km2) confined to eight subpopulations that vary considerably in size. According to this study, 1845 individuals remain in the wild. Habitat preferences of the species were considered in detail and linked to a species distribution model for conservation purposes. It was shown that the species preferred nurse plants. The smallest adults size class was the largest cohort in all the sub-populations and was ascribed to pulse recruitments after an unknown favorable event. Although individuals were not evenly distributed among the size classes, annual recruitments levels were healthy, suggesting good pollination, seed set, and germination conditions.

Freeze-substituted fungal cells of Nectria haematococca: A comparison of the macroconidial walls of the adhesion-competent wild type with an adhesion-reduced mutant

1990 ◽  
Vol 48 (3) ◽  
pp. 688-689
Author(s):  
Thecan Caesar-Ton That ◽  
Lynn Epstein
Keyword(s):  
Freeze Substitution ◽  
Uranyl Acetate ◽  
Wild Type ◽  
Nectria Haematococca ◽  
Fruit Extract ◽  
Dialysis Tubing ◽  
Tube Emergence ◽  
Contrast Microscopy ◽  
In The Wild ◽  
Freeze Damage

Nectria haematococca mating population I (anamorph, Fusarium solani) macroconidia attach to its host (squash) and non-host surfaces prior to germ tube emergence. The macroconidia become adhesive after a brief period of protein synthesis. Recently, Hickman et al. (1989) isolated N. haematococca adhesion-reduced mutants. Using freeze substitution, we compared the development of the macroconidial wall in the wild type in comparison to one of the mutants, LEI.Macroconidia were harvested at 1C, washed by centrifugation, resuspended in a dilute zucchini fruit extract and incubated from 0 - 5 h. During the incubation period, wild type macroconidia attached to uncoated dialysis tubing. Mutant macroconidia did not attach and were collected on poly-L-lysine coated dialysis tubing just prior to freezing. Conidia on the tubing were frozen in liquid propane at 191 - 193C, substituted in acetone with 2% OsO4 and 0.05% uranyl acetate, washed with acetone, and flat-embedded in Epon-Araldite. Using phase contrast microscopy at 1000X, cells without freeze damage were selected, remounted, sectioned and post-stained sequentially with 1% Ba(MnO4)2 2% uranyl acetate and Reynold’s lead citrate. At least 30 cells/treatment were examined.

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