scholarly journals Gene drive and resilience through renewal with next generation Cleave and Rescue selfish genetic elements

2020 ◽  
Vol 117 (16) ◽  
pp. 9013-9021 ◽  
Author(s):  
Georg Oberhofer ◽  
Tobin Ivy ◽  
Bruce A. Hay
Keyword(s):  
Dna Sequence ◽  
Gene Function ◽  
Essential Gene ◽  
Functional Genes ◽  
Gene Drive ◽  
Genetic Elements ◽  
Selfish Genetic Elements ◽  
Genetic Modifications ◽  
Genes Encoding

Gene drive-based strategies for modifying populations face the problem that genes encoding cargo and the drive mechanism are subject to separation, mutational inactivation, and loss of efficacy. Resilience, an ability to respond to these eventualities in ways that restore population modification with functional genes, is needed for long-term success. Here, we show that resilience can be achieved through cycles of population modification with “Cleave and Rescue” (ClvR) selfish genetic elements. ClvR comprises a DNA sequence-modifying enzyme such as Cas9/gRNAs that disrupts endogenous versions of an essential gene and a recoded version of the essential gene resistant to cleavage. ClvR spreads by creating conditions in which those lacking ClvR die because they lack functional versions of the essential gene. Cycles of modification can, in principle, be carried out if two ClvR elements targeting different essential genes are located at the same genomic position, and one of them, ClvRn+1, carries a Rescue transgene from an earlier element, ClvRn. ClvRn+1 should spread within a population of ClvRn, while also bringing about a decrease in its frequency. To test this hypothesis, we first show that multiple ClvRs, each targeting a different essential gene, function when located at a common chromosomal position in Drosophila. We then show that when several of these also carry the Rescue from a different ClvR, they spread to transgene fixation in populations fixed for the latter and at its expense. Therefore, genetic modifications of populations can be overwritten with new content, providing an ongoing point of control.

scholarly journals Gene drive and resilience through renewal with next generation Cleave and Rescue selfish genetic elements

2019 ◽  
Author(s):  
Georg Oberhofer ◽  
Tobin Ivy ◽  
Bruce A Hay
Keyword(s):  
Essential Gene ◽  
Functional Genes ◽  
Gene Drive ◽  
Genetic Elements ◽  
Selfish Genetic Elements ◽  
Genetic Modifications ◽  
Genes Encoding ◽  
Long Time ◽  
Beneficial Traits

AbstractGene drive-based strategies for modifying populations face the problem that genes encoding cargo and the drive mechanism are subject to separation, mutational inactivation, and loss of efficacy. Resilience, an ability to respond to these eventualities in ways that restore population modification with functional genes is needed for long-term success. Here we show that resilience can be achieved through cycles of population modification with “Cleave and Rescue” (ClvR) selfish genetic elements. ClvR comprises a DNA sequence-modifying enzyme such as Cas9/gRNAs that disrupts endogenous versions of an essential gene, and a recoded version of the essential gene resistant to cleavage. ClvR spreads by creating conditions in which those lacking ClvR die because they lack functional versions of the essential gene. Cycles of modification can in principal be carried out if two ClvR elements targeting different essential genes are located at the same genomic position, and one of them, ClvRn+1, carries a Rescue transgene from an earlier element, ClvRn. ClvRn+1 should spread within a population of ClvRn, while also bringing about a decrease in its frequency. To test this hypothesis we first show that multiple ClvRs, each targeting a different essential gene, function when located at a common chromosomal position in Drosophila. We then show that when several of these also carry the Rescue from a different ClvR, they spread to transgene fixation in populations fixed for the latter, and at its expense. Therefore, genetic modifications of populations can be overwritten with new content, providing an ongoing point of control.SignificanceGene drive can spread beneficial traits through populations, but will never be a one-shot project in which one genetic element provides all desired modifications, for an indefinitely long time. Here we show that gene drive mediated population modification in Drosophila can be overwritten with new content while eliminating old, using Cleave and Rescue (ClvR) selfish genetic elements. The ability to carry out cycles of modification that create and then leave behind a minimal genetic footprint while entering and exiting a population provides important points of control. It makes possible the replacement of broken elements, upgrades with new elements that better carry out their tasks and/or provide new functions, all while promoting the removal of modifications no longer needed.

scholarly journals 2-Locus Cleave and Rescue selfish elements harness a recombination rate-dependent generational clock for self limiting gene drive

2020 ◽  
Author(s):  
Georg Oberhofer ◽  
Tobin Ivy ◽  
Bruce A Hay
Keyword(s):  
Dna Sequence ◽  
Gene Function ◽  
Recombination Rate ◽  
High Frequency ◽  
Essential Gene ◽  
Dependent Manner ◽  
Gene Drive ◽  
Rate Dependent

AbstractSelf-limiting gene drive allows control over the spread and fate of linked traits. Cleave and Rescue (ClvR) elements create self-sustaining drive and comprise a DNA sequence-modifying enzyme (Cas9-gRNAs, Cleaver) that disrupts an essential gene, and a tightly linked, uncleavable version of the essential gene (Rescue). ClvR spreads by creating conditions in which those without it die because they lack essential gene function. We show that when ClvR is implemented in a 2-locus format, with key elements – Rescue (and Cargo), and Cas9 and/or gRNAs – located at different genomic positions, spread of the Rescue is self-limiting. Drive strength and duration are determined by a recombination rate-dependent generational clock, providing an important point of control for different ecological and regulatory contexts. We implement 2-locus ClvR in Drosophila. Rescue spreads to high frequency in a Cas9-dependent manner, while the frequency of Cas9 decreases, demonstrating transient drive and loss of future drive potential.

scholarly journals Gene drive that results in addiction to a temperature sensitive version of an essential gene triggers population collapse in Drosophila

2021 ◽  
Author(s):  
Georg Oberhofer ◽  
Bruce Hay ◽  
Tobin Ivy
Keyword(s):  
Gene Function ◽  
Essential Gene ◽  
Trojan Horse ◽  
Temperature Sensitive ◽  
Gene Drive ◽  
Loss Of Function ◽  
Selfish Genetic Elements ◽  
Population Crash ◽  
Seasonal Basis ◽  
Population Suppression

One strategy for population suppression seeks to use gene drive to spread genes that confer conditional lethality or sterility, providing a way of combining population modification with suppression. Stimuli of potential interest could be introduced by humans, such as an otherwise benign virus or chemical, or occur naturally on a seasonal basis, such as a change in temperature. Cleave and Rescue (ClvR) selfish genetic elements use Cas9 and gRNAs to disrupt endogenous versions of an essential gene, while also including a Rescue version of the essential gene resistant to disruption. ClvR spreads by creating loss-of-function alleles of the essential gene that select against those lacking it, resulting in populations in which the Rescue provides the only source of essential gene function. In consequence, if function of the Rescue, a kind of Trojan horse now omnipresent in a population, is condition-dependent, so too will be the survival of that population. To test this idea we created a ClvR in Drosophila in which Rescue activity of an essential gene, dribble, requires splicing of a temperature-sensitive intein (TS-ClvRdbe). This element spreads to transgene fixation at 23° C, but when populations now dependent on TS-ClvRdbe are shifted to 29° C death and sterility result in a rapid population crash. These results show that conditional population elimination can be achieved. A similar logic, in which Rescue activity is conditional, could also be used in HEG-based drive, and to bring about suppression and/or killing of specific individuals in response to other stimuli.

scholarly journals Gene drive that results in addiction to a temperature-sensitive version of an essential gene triggers population collapse in Drosophila

2021 ◽  
Vol 118 (49) ◽  
pp. e2107413118
Author(s):  
Georg Oberhofer ◽  
Tobin Ivy ◽  
Bruce A. Hay
Keyword(s):  
Gene Function ◽  
Essential Gene ◽  
Temperature Sensitive ◽  
Gene Drive ◽  
Loss Of Function ◽  
Selfish Genetic Elements ◽  
Guide Rnas ◽  
Population Crash ◽  
Seasonal Basis ◽  
Population Suppression

One strategy for population suppression seeks to use gene drive to spread genes that confer conditional lethality or sterility, providing a way of combining population modification with suppression. Stimuli of potential interest could be introduced by humans, such as an otherwise benign virus or chemical, or occur naturally on a seasonal basis, such as a change in temperature. Cleave and Rescue (ClvR) selfish genetic elements use Cas9 and guide RNAs (gRNAs) to disrupt endogenous versions of an essential gene while also including a Rescue version of the essential gene resistant to disruption. ClvR spreads by creating loss-of-function alleles of the essential gene that select against those lacking it, resulting in populations in which the Rescue provides the only source of essential gene function. As a consequence, if function of the Rescue, a kind of Trojan horse now omnipresent in a population, is condition dependent, so too will be the survival of that population. To test this idea, we created a ClvR in Drosophila in which Rescue activity of an essential gene, dribble, requires splicing of a temperature-sensitive intein (TS-ClvRdbe). This element spreads to transgene fixation at 23 °C, but when populations now dependent on Ts-ClvRdbe are shifted to 29 °C, death and sterility result in a rapid population crash. These results show that conditional population elimination can be achieved. A similar logic, in which Rescue activity is conditional, could also be used in homing-based drive and to bring about suppression and/or killing of specific individuals in response to other stimuli.

scholarly journals Control of malaria-transmitting mosquitoes using gene drives

2020 ◽  
Vol 376 (1818) ◽  
pp. 20190803 ◽  
Author(s):  
Tony Nolan
Keyword(s):  
Malaria Control ◽  
Control Strategies ◽  
Technical Development ◽  
Gene Drive ◽  
Theme Issue ◽  
Genetic Elements ◽  
Selfish Genetic Elements ◽  
Gene Drives ◽  
Transmit Disease ◽  
Proof Of Principle

Gene drives are selfish genetic elements that can be re-designed to invade a population and they hold tremendous potential for the control of mosquitoes that transmit disease. Much progress has been made recently in demonstrating proof of principle for gene drives able to suppress populations of malarial mosquitoes, or to make them refractory to the Plasmodium parasites they transmit. This has been achieved using CRISPR-based gene drives. In this article, I will discuss the relative merits of this type of gene drive, as well as barriers to its technical development and to its deployment in the field as malaria control. This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases'.

scholarly journals Ancient gene drives: an evolutionary paradox

2019 ◽  
Vol 286 (1917) ◽  
pp. 20192267 ◽  
Author(s):  
T. A. R. Price ◽  
R. Verspoor ◽  
N. Wedell
Keyword(s):  
Transmission Rate ◽  
Rapid Evolution ◽  
Natural Populations ◽  
Gene Drive ◽  
Population Extinction ◽  
Selfish Genetic Elements ◽  
Rapid Spread ◽  
Potential Factors ◽  
Drive Systems

Selfish genetic elements such as selfish chromosomes increase their transmission rate relative to the rest of the genome and can generate substantial cost to the organisms that carry them. Such segregation distorters are predicted to either reach fixation (potentially causing population extinction) or, more commonly, promote the evolution of genetic suppression to restore transmission to equality. Many populations show rapid spread of segregation distorters, followed by the rapid evolution of suppression. However, not all drivers display such flux, some instead persisting at stable frequencies in natural populations for decades, perhaps hundreds of thousands of years, with no sign of suppression evolving or the driver spreading to fixation. This represents a major evolutionary paradox. How can drivers be maintained in the long term at stable frequencies? And why has suppression not evolved as in many other gene drive systems? Here, we explore potential factors that may explain the persistence of drive systems, focusing on the ancient sex-ratio driver in the fly Drosophila pseudoobscura . We discuss potential solutions to the evolutionary mystery of why suppression does not appear to have evolved in this system, and address how long-term stable frequencies of gene drive can be maintained. Finally, we speculate whether ancient drivers may be functionally and evolutionarily distinct to young drive systems.

scholarly journals Split versions of Cleave and Rescue selfish genetic elements for measured self limiting gene drive

PLoS Genetics ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. e1009385 ◽  
Author(s):  
Georg Oberhofer ◽  
Tobin Ivy ◽  
Bruce A. Hay
Keyword(s):  
Linkage Disequilibrium ◽  
High Frequency ◽  
Recombination Frequency ◽  
Essential Gene ◽  
Dependent Manner ◽  
Gene Drive ◽  
Loss Of Function ◽  
Progressive Decrease ◽  
Wild Populations ◽  
Selfish Genetic Elements

Gene drive elements promote the spread of linked traits, providing methods for changing the composition or fate of wild populations. Drive mechanisms that are self-limiting are attractive because they allow control over the duration and extent of trait spread in time and space, and are reversible through natural selection as drive wanes. Self-sustainingCleave and Rescue(ClvR) elements include a DNA sequence-modifying enzyme such as Cas9/gRNAs that disrupts endogenous versions of an essential gene, a tightly linked recoded version of the essential gene resistant to cleavage (theRescue), and a Cargo.ClvRspreads by creating loss-of-function (LOF) conditions in which those withoutClvRdie because they lack functional copies of the essential gene. We use modeling to show that when theRescue-Cargo and one or both components required for LOF allele creation (Cas9 and gRNA) reside at different locations (splitClvR), drive ofRescue-Cargo is self-limiting due to a progressive decrease in Cas9 frequency, and thus opportunities for creation of LOF alleles, as spread occurs. Importantly, drive strength and duration can be extended in a measured manner—which is still self-limiting—by moving the two components close enough to each other that they experience some degree of linkage. With linkage, Cas9 transiently experiences drive by hitchhiking withRescue-Cargo until linkage disequilibrium between the two disappears, a function of recombination frequency and number of generations, creating a novel point of control. We implement splitClvRinDrosophila, with key elements on different chromosomes. Cargo/Rescue/gRNAs spreads to high frequency in a Cas9-dependent manner, while the frequency of Cas9 decreases. These observations show that measured, transient drive, coupled with a loss of future drive potential, can be achieved using the simple toolkit that make upClvRelements—Cas9 and gRNAs and aRescue/Cargo.

scholarly journals Effect of Spaceflight on Tomato Seed Quality and Biochemical Characteristics of Mature Plants

Horticulturae ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 89
Author(s):  
Elena Dzhos ◽  
Nadezhda Golubkina ◽  
Marina Antoshkina ◽  
Irina Kondratyeva ◽  
Andrew Koshevarov ◽  
...  
Keyword(s):  
Seed Quality ◽  
Space Station ◽  
Field Conditions ◽  
Tomato Seed ◽  
Tomato Plants ◽  
Biochemical Characteristics ◽  
Tomato Seeds ◽  
Genetic Modifications ◽  
Total Antioxidant

Intensive space exploration includes profound investigations on the effect of weightlessness and cosmic radiation on plant growth and development. Tomato seeds are often used in such experiments though up to date the results have given rather vague information about biochemical changes in mature plants grown from seeds subjected to spaceflight. The effect of half a year of storage in the International Space Station (ISS) on tomato seeds (cultivar Podmoskovny ranny) was studied by analyzing the biochemical characteristics and mineral content of mature plants grown from these seeds both in greenhouse and field conditions. A significant increase was recorded in ascorbic acid, polyphenol and carotenoid contents, and total antioxidant activity (AOA), with higher changes in the field conditions compared to greenhouse. Contrary to control plants, the ones derived from space-stored seeds demonstrated a significant decrease in root AOA. The latter plants also showed a higher yield, but lower content of fruit dry matter, sugars, total dissolved solids and organic acids. The fruits of plants derived from space-stored seeds demonstrated decreased levels of Fe, Cu and taste index. The described results reflect the existence of oxidative stress in mature tomato plants as a long-term consequence of the effect of spaceflight on seed quality, whereas the higher yield may be attributed to genetic modifications.

scholarly journals Long-Term Glucose Starvation Induces Inflammatory Responses and Phenotype Switch in Primary Cortical Rat Astrocytes

2021 ◽  
Author(s):  
Vanessa Kogel ◽  
Stefanie Trinh ◽  
Natalie Gasterich ◽  
Cordian Beyer ◽  
Jochen Seitz
Keyword(s):  
Cerebral Cortex ◽  
Synapse Formation ◽  
Inflammatory Responses ◽  
Glucose Starvation ◽  
Unfolded Protein ◽  
Genes Encoding ◽  
Phenotype Switch ◽  
The Unfolded Protein Response ◽  
The Brain

AbstractAstrocytes are the most abundant cell type in the brain and crucial to ensure the metabolic supply of neurons and their synapse formation. Overnutrition as present in patients suffering from obesity causes astrogliosis in the hypothalamus. Other diseases accompanied by malnutrition appear to have an impact on the brain and astrocyte function. In the eating disorder anorexia nervosa (AN), patients suffer from undernutrition and develop volume reductions of the cerebral cortex, associated with reduced astrocyte proliferation and cell count. Although an effect on astrocytes and their function has already been shown for overnutrition, their role in long-term undernutrition remains unclear. The present study used primary rat cerebral cortex astrocytes to investigate their response to chronic glucose starvation. Cells were grown with a medium containing a reduced glucose concentration (2 mM) for 15 days. Long-term glucose starvation increased the expression of a subset of pro-inflammatory genes and shifted the primary astrocyte population to the pro-inflammatory A1-like phenotype. Moreover, genes encoding for proteins involved in the unfolded protein response were elevated. Our findings demonstrate that astrocytes under chronic glucose starvation respond with an inflammatory reaction. With respect to the multiple functions of astrocytes, an association between elevated inflammatory responses due to chronic starvation and alterations found in the brain of patients suffering from undernutrition seems possible.

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