Biology subjects

Gantz, V. M.

Publications and source records attributed to Gantz, V. M..

12 recordsLinked to original sources

bioRxiv2026

Rp-vasa: a bona fide Primordial Germ Cell marker that drives embryonic expression in the Chagas disease vector Rhodnius prolixus

Rhodnius prolixus is an insect vector of the protozoan Trypanosoma cruzi, the causative agent of debilitating Chagas disease, which is transmitted to humans during blood feeding. Identifying germline markers is a critical step in advancing vector control and transgenic technologies of these medically important insects. Transmission of genetic traits to the next generation requires proper differentiation of the germline that gives rise to gametes. Germline precursors are established during early stages of development as the primordial germ cell (PGC) population. Among the genes required for this process, vasa homologues exert a conserved role in germline specification. Here, we characterize and validate the genomic structure of the R. prolixus Rp-vasa locus and assess its expression during early embryogenesis. We observe widespread Rp-vasa expression in preblastoderm embryos. Later, during the cellular blastoderm and at the beginning of gastrulation, Rp-vasa and Rp-piwi2 expression is restricted to PGCs, morphologically identifiable as a cluster of cells at the posterior of the embryo. We also report, for the first time, the use of R. prolixus regulatory sequences to drive the expression of exogenous genes. We identify the Rp-vasa regulatory region and show that these cis-regulatory sequences are sufficient to drive Cas9 and dsRed expression in the early embryo. Together, these findings demonstrate that Rp-vasa has great potential for use as a PGC marker and as a driver for gene expression in transgenic and gene editing approaches for Triatomine vectors.

developmental biology↗

bioRxiv2025

Self-limiting population suppression gene drive in the West Nile vector mosquito, Culex quinquefasciatus

Culex mosquitoes transmit major pathogens including West Nile virus, encephalitis, filariasis, and avian malaria, threatening public health, poultry, and ecosystems. We engineered a CRISPR-based population suppression gene drive targeting a conserved exon of the doublesex (dsx) gene. The drive incorporates a recoded dsxM segment to preserve male function while converting genetic females into sterile intersexes, enabling male-biased propagation and removal of fertile females. It achieves super-Mendelian inheritance ([~]71%) and generates partially dominant sterile resistance alleles via end-joining, resulting in intersex phenotypes with reduced fertility and hatchability. Modeling predicts that this RIDD (Release of Insects carrying a Dominant-sterile Drive) system can suppress populations at low intrinsic growth rates and release ratios, outperforming SIT and fs-RIDL strategies in persistence and efficiency, with further gains achievable through improved cleavage rates. This study establishes a self-limiting gene drive framework for Culex suppression, highlightling the potential of targeting conserved sex-determination pathways for sustainable vector control.

genetics↗

bioRxiv2023

CRISPR-based gene drives generate super-Mendelian inheritance in the disease vector Culex quinquefasciatus.

Culex mosquitoes pose a significant public health threat as vectors for a variety of diseases including West Nile virus and lymphatic filariasis, and transmit pathogens threatening livestock, companion animals, and endangered birds. Rampant insecticide resistance makes controlling these mosquitoes challenging and necessitates the development of new control strategies. Gene drive technologies have made significant progress in other mosquito species, although similar advances have been lagging in Culex. Here we test the first CRISPR-based homing gene drive for Culex quinquefasciatus, demonstrating the possibility of using this technology to control Culex mosquitoes. Our results show that the inheritance of two split-gene-drive transgenes, targeting different loci, are biased in the presence of a Cas9-expressing transgene although with modest efficiencies. Our findings extend the list of disease vectors where engineered homing gene drives have been demonstrated to include Culex alongside Anopheles and Aedes, and pave the way for future development of these technologies to control Culex mosquitoes.

synthetic biology↗

bioRxiv2021

CRISPR gene-drive systems based on Cas9 nickases promote super-Mendelian inheritance in Drosophila

CRISPR-based gene-drive systems have been proposed for managing insect populations, including disease-transmitting mosquitoes, due to their ability to bias their inheritance towards super-Mendelian rates (>50%). Current technologies employ a Cas9 that introduces DNA double-strand breaks into the opposing wildtype allele to replace it with a copy of the gene drive allele via DNA homology-directed repair. Yet, the use of different Cas9s versions is unexplored, and alternative approaches could increase the available toolkit for gene-drive designs. Here, we report a novel gene-drive approach that relies on Cas9 nickases that generate staggered paired nicks in DNA to propagate the engineered gene-drive cassette. We show that generating 5 overhangs in the system yields efficient allelic conversion. The nickase gene-drive arrangement produces large, stereotyped deletions that are advantageous for targeting essential genes. Indeed, our nickase approach should expand the repertoire for gene-drive designs aimed at applications in mosquitoes and beyond.

molecular biology↗

bioRxiv2021

Meiotic Cas9 expression mediates genotype conversion in the male and female mouse germline

Highly efficient genotype conversion systems have potential to facilitate the study of complex genetic traits using laboratory mice and to limit loss of biodiversity and disease transmission caused by wild rodent populations. We previously showed that such a system of genotype conversion from heterozygous to homozygous after a sequence targeted CRISPR/Cas9 double strand DNA break is feasible in the female mouse germline. In the male germline, however, all double strand breaks were instead repaired by end joining mechanisms to form an insertion/deletion (indel) mutation. These observations suggested that timing Cas9 expression to coincide with meiosis I is critical to favor conditions when homologous chromosomes are aligned and interchromosomal homology directed repair (HDR) mechanisms predominate. Here, using a Cas9 knock-in allele at the Spo11 locus, we show that meiotic expression of Cas9 does indeed mediate genotype conversion in the male as well as in the female germline. However, the low frequency of both HDR and indel mutation in both male and female germlines suggests that Cas9 may be expressed from the Spo11 locus at levels too low for efficient double strand DNA break formation. We suggest that more robust Cas9 expression initiated during early meiosis I may improve the efficiency of genotype conversion and further increase the rate of super-Mendelian inheritance from both male and female mice.

genetics↗

bioRxiv2021

Optimized CRISPR tools and site-directed transgenesis in Culex quinquefasciatus mosquitoes for gene drive development.

Culex mosquitoes are a global vector for multiple human and animal diseases, including West Nile virus, lymphatic filariasis, and avian malaria, posing a constant threat to public health, livestock, companion animals, and endangered birds. While rising insecticide resistance has threatened the control of Culex mosquitoes, advances in CRISPR genome-editing tools have fostered the development of alternative genetic strategies such as gene drive systems to fight disease vectors. However, though gene-drive technology has quickly progressed in other mosquitoes, advances have been lacking in Culex. Here, we developed a Culex-specific Cas9/gRNA expression toolkit and used site-directed homology-based transgenesis to generate and validate a Culex quinquefasciatus Cas9-expressing line. We showed that gRNA scaffold variants improve transgenesis efficiency in both Culex and Drosophila and boost gene-drive performance in the fruit fly. These findings support future technology development to control Culex mosquitoes and provide valuable insight for improving these tools in other species.

synthetic biology↗

bioRxiv2020

Evaluation of pigmentation gene knock-outs by CRISPR as potential targets for the genetic engineering of Culex quinquefasciatus

Culex quinquefasciatus mosquitoes are a globally widespread vector of several human and animal pathogens. Their biology and behavior allow them to thrive in proximity to urban areas, rendering them a constant public health threat. Their mixed bird/mammal feeding behavior further offers a vehicle for zoonotic pathogens transmission to people, and separately, poses a threat to the conservation of insular birds. The advent of CRISPR has led to the development of novel technologies for the genetic engineering of wild mosquito populations, yet research in Culex quinquefasciatus has been lagging compared to other disease vectors. Here we use this tool to disrupt a set of five pigmentation genes in Culex quinquefasciatus that, when altered, lead to visible, homozygous-viable phenotypes. We further validate this approach in separate laboratories and in two distinct strains of Culex quinquefasciatus that are relevant to potential future public health and bird conservation applications. We generate a double-mutant line, demonstrating the possibility of sequentially combining multiple such mutations in a single individual. Lastly, we target two loci, doublesex in the sex-determination pathway and proboscipedia a hox gene, demonstrating the flexibility of these methods applied to novel targets. Our work provides a platform of seven validated loci that could be used for targeted mutagenesis in Culex quinquefasciatus and the future development of genetic suppression strategies for this species. Furthermore, the mutant lines generated here could have widespread utility to the research community using this model organism, as they could be used as targets for transgene delivery, where a copy of the disrupted gene could be included as an easily-scored transgenesis marker.

genetics↗

bioRxiv2020

Efficient population modification gene-drive rescue system in the malaria mosquito Anopheles stephensi

The development of Cas9/gRNA-mediated gene-drive systems has bolstered the advancement of genetic technologies for controlling vector-borne pathogen transmission. These include population suppression approaches, genetic analogs of insecticidal techniques that reduce the number of vector insects, and population modification (replacement/alteration) approaches, which interfere with competence to transmit pathogens. We developed a recoded gene-drive rescue system for population modification in the malaria vector, Anopheles stephensi, that relieves the load in females caused by integration of the drive into the kynurenine hydroxylase gene by rescuing its function. Non-functional resistant alleles are eliminated via a dominantly-acting maternal effect combined with slower-acting standard negative selection, and a functional resistant allele does not prevent drive invasion. Small cage trials show that single releases of gene-drive males robustly result in efficient population modification with [≥]95% of mosquitoes carrying the drive within 5-11 generations over a range of initial release ratios.

genetics↗

bioRxiv2019

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

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 transmission. However, effectiveness of the inclusion of additional guide RNAs that target separate host encoded genes has not been thoroughly explored. To test this approach, here we generated a split-HGD in Drosophila melanogaster that encoded a drive linked effector consisting of a second gRNA engineered to target a separate host encoded gene, which we term a gRNA-mediated effector (GME). This design enabled us to assess homing and knockout efficiencies of two target genes simultaneously, and also explore the timing and tissue specificity of Cas9 expression on cleavage/homing rates. We demonstrate that inclusion of a GME can result in high efficiency of disruption of its target gene during super-Mendelian propagation of split-HGD. However, maternal deposition and embryonic expression of Cas9 resulted in the generation of drive resistant alleles which can accumulate and limit the spread of such a drive. Alternative design principles are discussed that could mitigate the accumulation of resistance alleles while incorporating a GME.

genetics↗

bioRxiv2019

Split-gene drive system provides flexible application for safe laboratory investigation and potential field deployment

CRISPR-based gene drives spread through populations bypassing the dictates of Mendelian genetics, offering a population-engineering tool for tackling vector-borne diseases, managing crop pests, and helping island conservation efforts; unfortunately, current technologies raise safety concerns for unintended gene propagation. Herein, we address this by splitting the two drive components, Cas9 and gRNAs, into separate alleles to form a novel trans-complementing split-gene-drive (tGD) and demonstrate its ability to promote super-Mendelian inheritance of the separate transgenes. This bi-component nature allows for individual transgene optimization and increases safety by restricting escape concerns to experimentation windows. We employ the tGD and a small- molecule-controlled version to investigate the biology of component inheritance and use our system to study the maternal effects on CRISPR inheritance, impaired homology on efficiency, and resistant allele formation. Lastly, mathematical modeling of tGD spread in a population shows potential advantages for improving current gene-drive technologies for field population modification.

genetics↗

bioRxiv2019

Small-molecule control of super-Mendelian inheritance in gene drives

By surpassing the 50% inheritance limit of Mendels law of independent assortment, CRISPR-based gene drives have the potential to fight vector-borne diseases or suppress crop pests. However, contemporary gene drives could spread unchecked, posing safety concerns that limit their use in both laboratory and field settings. Current technologies also lack chemical control strategies, which could be applied in the field for dose, spatial and temporal control of gene drives. We describe in Drosophila the first gene-drive system controlled by an engineered Cas9 and a synthetic, orally-available small molecule.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=51 SRC=\"FIGDIR/small/665620v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (15K):\norg.highwire.dtl.DTLVardef@1aa8522org.highwire.dtl.DTLVardef@a99c8org.highwire.dtl.DTLVardef@1f63636org.highwire.dtl.DTLVardef@1613408_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG

genetics↗

bioRxiv2018

Super-Mendelian inheritance mediated by CRISPR/Cas9 in the female mouse germline

A gene drive biases the transmission of a particular allele of a gene such that it is inherited at a greater frequency than by random assortment. Recently, a highly efficient gene drive was developed in insects, which leverages the sequence-targeted DNA cleavage activity of CRISPR/Cas9 and endogenous homology directed repair mechanisms to convert heterozygous genotypes to homozygosity. If implemented in laboratory rodents, this powerful system would enable the rapid assembly of genotypes that involve multiple genes (e.g., to model multigenic human diseases). Such complex genetic models are currently precluded by time, cost, and a requirement for a large number of animals to obtain a few individuals of the desired genotype. However, the efficiency of a CRISPR/Cas9 gene drive system in mammals has not yet been determined. Here, we utilize an active genetic \"CopyCat\" element embedded in the mouse Tyrosinase gene to detect genotype conversions after Cas9 activity in the embryo and in the germline. Although Cas9 efficiently induces double strand DNA breaks in the early embryo and is therefore highly mutagenic, these breaks are not resolved by homology directed repair. However, when Cas9 expression is limited to the developing female germline, resulting double strand breaks are resolved by homology directed repair that copies the CopyCat allele from the donor to the receiver chromosome and leads to its super-Mendelian inheritance. These results demonstrate that the CRISPR/Cas9 gene drive mechanism can be implemented to simplify complex genetic crosses in laboratory mice and also contribute valuable data to the ongoing debate about applications to combat invasive rodent populations in island communities.

genetics↗