Publications by authors named "Nikolay P Kandul"

9 Publications

  • Page 1 of 1

Suppressing mosquito populations with precision guided sterile males.

Nat Commun 2021 Sep 10;12(1):5374. Epub 2021 Sep 10.

Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, USA.

The mosquito Aedes aegypti is the principal vector for arboviruses including dengue/yellow fever, chikungunya, and Zika virus, infecting hundreds of millions of people annually. Unfortunately, traditional control methodologies are insufficient, so innovative control methods are needed. To complement existing measures, here we develop a molecular genetic control system termed precision-guided sterile insect technique (pgSIT) in Aedes aegypti. PgSIT uses a simple CRISPR-based approach to generate flightless females and sterile males that are deployable at any life stage. Supported by mathematical models, we empirically demonstrate that released pgSIT males can compete, suppress, and even eliminate mosquito populations. This platform technology could be used in the field, and adapted to many vectors, for controlling wild populations to curtail disease in a safe, confinable, and reversible manner.
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http://dx.doi.org/10.1038/s41467-021-25421-wDOI Listing
September 2021

A confinable home-and-rescue gene drive for population modification.

Elife 2021 Mar 5;10. Epub 2021 Mar 5.

Section of Cell and Developmental Biology, University of California, San Diego, San Diego, United States.

Homing-based gene drives, engineered using CRISPR/Cas9, have been proposed to spread desirable genes throughout populations. However, invasion of such drives can be hindered by the accumulation of resistant alleles. To limit this obstacle, we engineer a confinable population modification home-and-rescue (HomeR) drive in targeting an essential gene. In our experiments, resistant alleles that disrupt the target gene function were recessive lethal and therefore disadvantaged. We demonstrate that HomeR can achieve an increase in frequency in population cage experiments, but that fitness costs due to the Cas9 insertion limit drive efficacy. Finally, we conduct mathematical modeling comparing HomeR to contemporary gene drive architectures for population modification over wide ranges of fitness costs, transmission rates, and release regimens. HomeR could potentially be adapted to other species, as a means for safe, confinable, modification of wild populations.
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http://dx.doi.org/10.7554/eLife.65939DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7968924PMC
March 2021

A drug-inducible sex-separation technique for insects.

Nat Commun 2020 04 30;11(1):2106. Epub 2020 Apr 30.

Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92092, USA.

Here, we describe a drug-inducible genetic system for insect sex-separation that demonstrates proof-of-principle for positive sex selection in D. melanogaster. The system exploits the toxicity of commonly used broad-spectrum antibiotics geneticin and puromycin to kill the non-rescued sex. Sex-specific rescue is achieved by inserting sex-specific introns into the coding sequences of antibiotic-resistance genes. When raised on geneticin-supplemented food, the sex-sorter line establishes 100% positive selection for female progeny, while the food supplemented with puromycin positively selects 100% male progeny. Since the described system exploits conserved sex-specific splicing mechanisms and reagents, it has the potential to be adaptable to other insect species of medical and agricultural importance.
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http://dx.doi.org/10.1038/s41467-020-16020-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7193620PMC
April 2020

Development of a confinable gene drive system in the human disease vector .

Elife 2020 01 21;9. Epub 2020 Jan 21.

Section of Cell and Developmental Biology, University of California, San Diego, San Diego, United States.

is the principal mosquito vector for many arboviruses that increasingly infect millions of people every year. With an escalating burden of infections and the relative failure of traditional control methods, the development of innovative control measures has become of paramount importance. The use of gene drives has sparked significant enthusiasm for genetic control of mosquitoes; however, no such system has been developed in . To fill this void, here we develop several CRISPR-based split gene drives for use in this vector. With cleavage rates up to 100% and transmission rates as high as 94%, mathematical models predict that these systems could spread anti-pathogen effector genes into wild populations in a safe, confinable and reversible manner appropriate for field trials and effective for controlling disease. These findings could expedite the development of effector-linked gene drives that could safely control wild populations of to combat local pathogen transmission.
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http://dx.doi.org/10.7554/eLife.51701DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6974361PMC
January 2020

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

G3 (Bethesda) 2020 02 6;10(2):827-837. Epub 2020 Feb 6.

Section of Cell and Developmental Biology and

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 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 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.
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http://dx.doi.org/10.1534/g3.119.400985DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7003086PMC
February 2020

Winning the Tug-of-War Between Effector Gene Design and Pathogen Evolution in Vector Population Replacement Strategies.

Front Genet 2019 30;10:1072. Epub 2019 Oct 30.

Section of Cell and Developmental Biology, University of California, San Diego, CA, United States.

While efforts to control malaria with available tools have stagnated, and arbovirus outbreaks persist around the globe, the advent of clustered regularly interspaced short palindromic repeat (CRISPR)-based gene editing has provided exciting new opportunities for genetics-based strategies to control these diseases. In one such strategy, called "population replacement", mosquitoes, and other disease vectors are engineered with effector genes that render them unable to transmit pathogens. These effector genes can be linked to "gene drive" systems that can bias inheritance in their favor, providing novel opportunities to replace disease-susceptible vector populations with disease-refractory ones over the course of several generations. While promising for the control of vector-borne diseases on a wide scale, this sets up an evolutionary tug-of-war between the introduced effector genes and the pathogen. Here, we review the disease-refractory genes designed to date to target malaria transmitted by , and arboviruses transmitted by , including dengue serotypes 2 and 3, chikungunya, and Zika viruses. We discuss resistance concerns for these effector genes, and genetic approaches to prevent parasite and viral escape variants. One general approach is to increase the evolutionary hurdle required for the pathogen to evolve resistance by attacking it at multiple sites in its genome and/or multiple stages of development. Another is to reduce the size of the pathogen population by other means, such as with vector control and antimalarial drugs. We discuss lessons learned from the evolution of resistance to antimalarial and antiviral drugs and implications for the management of resistance after its emergence. Finally, we discuss the target product profile for population replacement strategies for vector-borne disease control. This differs between early phase field trials and wide-scale disease control. In the latter case, the demands on effector gene efficacy are great; however, with new possibilities ushered in by CRISPR-based gene editing, and when combined with surveillance, monitoring, and rapid management of pathogen resistance, the odds are increasingly favoring effector genes in the upcoming evolutionary tug-of-war.
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http://dx.doi.org/10.3389/fgene.2019.01072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6831721PMC
October 2019

Reply to 'Concerns about the feasibility of using "precision guided sterile males" to control insects'.

Nat Commun 2019 09 2;10(1):3955. Epub 2019 Sep 2.

Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America.

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http://dx.doi.org/10.1038/s41467-019-11617-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6718384PMC
September 2019

Transforming insect population control with precision guided sterile males with demonstration in flies.

Nat Commun 2019 01 8;10(1):84. Epub 2019 Jan 8.

Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA 92093, California, USA.

The sterile insect technique (SIT) is an environmentally safe and proven technology to suppress wild populations. To further advance its utility, a novel CRISPR-based technology termed precision guided SIT (pgSIT) is described. PgSIT mechanistically relies on a dominant genetic technology that enables simultaneous sexing and sterilization, facilitating the release of eggs into the environment ensuring only sterile adult males emerge. Importantly, for field applications, the release of eggs will eliminate burdens of manually sexing and sterilizing males, thereby reducing overall effort and increasing scalability. Here, to demonstrate efficacy, we systematically engineer multiple pgSIT systems in Drosophila which consistently give rise to 100% sterile males. Importantly, we demonstrate that pgSIT-generated sterile males are fit and competitive. Using mathematical models, we predict pgSIT will induce substantially greater population suppression than can be achieved by currently-available self-limiting suppression technologies. Taken together, pgSIT offers to potentially transform our ability to control insect agricultural pests and disease vectors.
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http://dx.doi.org/10.1038/s41467-018-07964-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6325135PMC
January 2019

Selective removal of deletion-bearing mitochondrial DNA in heteroplasmic Drosophila.

Nat Commun 2016 11 14;7:13100. Epub 2016 Nov 14.

Department of Neurology, Brain Research Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095, USA.

Mitochondrial DNA (mtDNA) often exists in a state of heteroplasmy, in which mutant mtDNA co-exists in cells with wild-type mtDNA. High frequencies of pathogenic mtDNA result in maternally inherited diseases; maternally and somatically acquired mutations also accumulate over time and contribute to diseases of ageing. Reducing heteroplasmy is therefore a therapeutic goal and in vivo models in post-mitotic tissues are needed to facilitate these studies. Here we describe a transgene-based model of a heteroplasmic lethal mtDNA deletion (mtDNA) in adult Drosophila muscle. Stimulation of autophagy, activation of the PINK1/parkin pathway or decreased levels of mitofusin result in a selective decrease in mtDNA. Decreased levels of mitofusin and increased levels of ATPIF1, an inhibitor of ATP synthase reversal-dependent mitochondrial repolarization, result in a further decrease in mtDNA levels. These results show that an adult post-mitotic tissue can be cleansed of a deleterious genome, suggesting that therapeutic removal of mutant mtDNA can be achieved.
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http://dx.doi.org/10.1038/ncomms13100DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5114534PMC
November 2016
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