Y chromosome shredding in Anopheles gambiae: Insight into the cellular dynamics of a novel synthetic sex ratio distorter.

Despite efforts to explore the genome of the malaria vector Anopheles gambiae, the Y chromosome of this species remains enigmatic. The large number of repetitive and heterochromatic DNA sequences makes the Y chromosome exceptionally difficult to fully assemble, hampering the progress of gene editing techniques and functional studies for this chromosome. In this study, we made use of a bioinformatic platform to identify Y-specific repetitive DNA sequences that served as a target site for a CRISPR/Cas9 system. The activity of Cas9 in the reproductive organs of males caused damage to Y-bearing sperm without affecting their fertility, leading to a strong female bias in the progeny. Cytological investigation allowed us to identify meiotic defects and investigate sperm selection in this new synthetic sex ratio distorter system. In addition, alternative promoters enable us to target the Y chromosome in specific tissues and developmental stages of male mosquitoes, enabling studies that shed light on the role of this chromosome in male gametogenesis. This work paves the way for further insight into the poorly characterised Y chromosome of Anopheles gambiae. Moreover, the sex distorter strain we have generated promises to be a valuable tool for the advancement of studies in the field of developmental biology, with the potential to support the progress of genetic strategies aimed at controlling malaria mosquitoes and other pest species.

Relative expression of key genes involved in nucleic acids methylation in Anopheles gambiae sensu stricto.

In vertebrates, enzymes responsible for DNA methylation, one of the epigenetic mechanisms, are encoded by genes falling into the cytosine methyltransferases genes family (Dnmt1, Dnmt3a,b and Dnmt3L). However, in Diptera, only the methyltransferase Dnmt2 was found, suggesting that DNA methylation might act differently for species in this order. Moreover, genes involved in epigenetic dynamics, such as Ten-eleven Translocation dioxygenases (TET) and Methyl-CpG-binding domain (MBDs), present in vertebrates, might play a role in insects. This work aimed at investigating nucleic acids methylation in the malaria vector Anopheles gambiae (Diptera: Culicidae) by analysing the expression of Dnmt2, TET2 and MBDs genes using quantitative real-time polymerase chain reaction (qRT-PCR) at pre-immature stages and in reproductive tissues of adult mosquitoes. In addition, the effect of two DNA methylation inhibitors on larval survival was evaluated. The qPCR results showed an overall low expression of Dnmt2 at all developmental stages and in adult reproductive tissues. In contrast, MBD and TET2 showed an overall higher expression. In adult mosquito reproductive tissues, the expression level of the three genes in males' testes was significantly higher than that in females' ovaries. The chemical treatments did not affect larval survival. The findings suggest that mechanisms other than DNA methylation underlie epigenetic regulation in An. gambiae.

Incidence, predictors and clinical outcome of pancreatic fistula in patients receiving splenectomy for advanced or recurrent ovarian cancer: a large multicentric experience.

PURPOSE: To evaluate the incidence, predictors and clinical outcome of pancreatic fistulas in patients receiving splenectomy during cytoreductive surgery for advanced or recurrent ovarian cancer. METHODS: Data of women who underwent splenectomy during cytoreduction for advanced or recurrent ovarian cancer from December 2012 to May 2018 were retrospectively retrieved from the oncological databases of five institutions. Surgical, post-operative and follow-up data were analysed. RESULTS: Overall, 260 patients were included in the study. Pancreatic resection was performed in 45 (17.6%) women, 23 of whom received capsule resection alone, while 22 required tail resection. Hyperthermic intraperitoneal chemotherapy (HIPEC) was administered in 28 (10.8%) patients. In the overall population, a pancreatic fistula was detected in 32 (12.3%) patients, and pancreatic resection (p-value = 0.033) and HIPEC administration (p-value = 0.039) were associated with fistula development. In multivariate analysis, HIPEC (OR = 2.573; p-value = 0.058) was confirmed as a risk factor for fistula development in women receiving splenectomy alone, while concomitant cholecystectomy (OR = 2.680; p-value = 0.012) was identified as the only independent predictor of the occurrence of pancreatic fistulas in those receiving additional distal pancreatectomy. Although the median length of hospital stay was higher in women with pancreatic leakage (p-value = 0.008), the median time from surgery to adjuvant treatment was not significantly increased. CONCLUSION: HIPEC was identified as a risk factor for pancreatic fistulas in patients who underwent splenectomy alone, while concomitant cholecystectomy was the only independent predictor of fistula in those receiving additional pancreatectomy. The development of pancreatic leakage was not associated with increased post-operative mortality or delay in the initiation of chemotherapy.

Site-specific genetic engineering of the Anopheles gambiae Y chromosome.

Despite its function in sex determination and its role in driving genome evolution, the Y chromosome remains poorly understood in most species. Y chromosomes are gene-poor, repeat-rich and largely heterochromatic and therefore represent a difficult target for genetic engineering. The Y chromosome of the human malaria vector Anopheles gambiae appears to be involved in sex determination although very little is known about both its structure and function. Here, we characterize a transgenic strain of this mosquito species, obtained by transposon-mediated integration of a transgene construct onto the Y chromosome. Using meganuclease-induced homologous repair we introduce a site-specific recombination signal onto the Y chromosome and show that the resulting docking line can be used for secondary integration. To demonstrate its utility, we study the activity of a germ-line-specific promoter when located on the Y chromosome. We also show that Y-linked fluorescent transgenes allow automated sex separation of this important vector species, providing the means to generate large single-sex populations. Our findings will aid studies of sex chromosome function and enable the development of male-exclusive genetic traits for vector control.

Hormone Replacement Therapy in Post-Menopause Hormone-Dependent Gynecological Cancer Patients: A Narrative Review.

BACKGROUND: Advances in the treatment of gynecological cancer have led to improvements in survival but also an increase in menopausal symptoms, especially in young women with premature iatrogenic menopause. METHODS: A narrative review was performed to clarify the possibility of prescribing hormone replacement therapy (HRT) after hormone-dependent gynecological cancers (ovarian cancer [OC], cervical adenocarcinoma [AC], and endometrial cancer [EC]). RESULTS: HRT can be prescribed to patients with early-stage, grade I-II OC who experience bothersome menopausal symptoms non-responsive to alternative non-hormone therapy after optimal surgery. Caution should be exercised in administering HRT after serous borderline tumors and endometrioid OC, and HRT is not recommended in low-grade serous OC. HRT is not contraindicated in AC survivors. After surgery for EC, HRT can be prescribed in women with early-stage low-grade EC. There is not enough data to give indications to patients with advanced EC. CONCLUSIONS: HRT can be discussed with patients, evaluating the risks and benefits of hormone-dependent gynecological cancer. Counseling should be performed by gynecologic oncologists experienced in the management of these patients.

Whole-Mount Fluorescence In Situ Hybridization to Study Spermatogenesis in the Anopheles Mosquito.

Spermatogenesis is a complex biological process during which diploid cells undergo successive mitotic and meiotic division followed by large structural changes to form haploid spermatozoa. Besides the biological aspect, studying spermatogenesis is of paramount importance for understanding and developing genetic technologies such as gene drive and synthetic sex ratio distorters, which, by altering Mendelian inheritance and the sperm sex ratio, respectively, could be used to control pest insect populations. These technologies have proven to be very promising in lab settings and could potentially be used to control wild populations of Anopheles mosquitoes, which are vectors of malaria. Due to the simplicity of the testis anatomy and their medical importance, Anopheles gambiae, a major malaria vector in sub-Saharan Africa, represents a good cytological model for studying spermatogenesis. This protocol describes how whole-mount fluorescence in situ hybridization (WFISH) can be used to study the dramatic changes in cell nuclear structure through spermatogenesis using fluorescent probes that specifically stain the X and Y chromosomes. FISH usually requires the disruption of the reproductive organs to expose mitotic or meiotic chromosomes and allow the staining of specific genomic regions with fluorescent probes. WFISH enables the preservation of the native cytological structure of the testis, coupled with a good level of signal detection from fluorescent probes targeting repetitive DNA sequences. This allows researchers to follow changes in the chromosomal behavior of cells undergoing meiosis along the structure of the organ, where each phase of the process can clearly be distinguished. This technique could be particularly useful for studying chromosome meiotic pairing and investigating the cytological phenotypes associated with, for example, synthetic sex ratio distorters, hybrid male sterility, and the knock-out of genes involved in spermatogenesis.

Comprehensive characterization of a transgene insertion in a highly repetitive, centromeric region of Anopheles mosquitoes.

The availability of the genomic sequence of the malaria mosquito Anopheles gambiae has in recent years sparked the development of transgenic technologies with the potential to be used as novel vector control tools. These technologies rely on genome editing that confer traits able to affect vectorial capacity. This can be achieved by either reducing the mosquito population or by making mosquitoes refractory to the parasite infection. For any genetically modified organism that is regarded for release, molecular characterization of the transgene and flanking sites are essential for their safety assessment and post-release monitoring. Despite great advancements, Whole-Genome Sequencing data are still subject to limitations due to the presence of repetitive and unannotated DNA sequences. Faced with this challenge, we describe a number of techniques that were used to identify the genomic location of a transgene in the male bias mosquito strain Ag(PMB)1 considered for potential field application. While the initial inverse PCR identified the most likely insertion site on Chromosome 3 R 36D, reassessment of the data showed a high repetitiveness in those sequences and multiple genomic locations as potential insertion sites of the transgene. Here we used a combination of DNA sequencing analysis and in-situ hybridization to clearly identify the integration of the transgene in a poorly annotated centromeric region of Chromosome 2 R 19D. This study emphasizes the need for accuracy in sequencing data for the genome of organisms of medical importance such as Anopheles mosquitoes and other tools available that can support genomic locations of transgenes.

Driving down malaria transmission with engineered gene drives.

The last century has witnessed the introduction, establishment and expansion of mosquito-borne diseases into diverse new geographic ranges. Malaria is transmitted by female Anopheles mosquitoes. Despite making great strides over the past few decades in reducing the burden of malaria, transmission is now on the rise again, in part owing to the emergence of mosquito resistance to insecticides, antimalarial drug resistance and, more recently, the challenges of the COVID-19 pandemic, which resulted in the reduced implementation efficiency of various control programs. The utility of genetically engineered gene drive mosquitoes as tools to decrease the burden of malaria by controlling the disease-transmitting mosquitoes is being evaluated. To date, there has been remarkable progress in the development of CRISPR/Cas9-based homing endonuclease designs in malaria mosquitoes due to successful proof-of-principle and multigenerational experiments. In this review, we examine the lessons learnt from the development of current CRISPR/Cas9-based homing endonuclease gene drives, providing a framework for the development of gene drive systems for the targeted control of wild malaria-transmitting mosquito populations that overcome challenges such as with evolving drive-resistance. We also discuss the additional substantial works required to progress the development of gene drive systems from scientific discovery to further study and subsequent field application in endemic settings.

Hyperthermic intraperitoneal chemotherapy (HIPEC) after primary debulking surgery in advanced epithelial ovarian cancer: Is BRCA mutational status making the difference?

INTRODUCTION: The role of a molecular pattern predictive of hyperthermic intraperitoneal chemotherapy (HIPEC) efficacy in advanced ovarian cancer (AOC) patients has been poorly investigated. We aimed to assess the effect of HIPEC after primary debulking surgery (PDS) in AOC according to patient's Breast Cancer Gene (BRCA) mutational status. METHODS: This is a retrospective, single center, case-control study. Data on AOC patients receiving HIPEC at the end of PDS as previously enrolled in a phase II monocentric trial (HIPEC group), were retrieved and matched for clinical and surgical characteristics with a group of cases who underwent PDS without receiving HIPEC between 01/2010 and 01/2015 (No HIPEC group). Patients with International Federation of Gynecology and Obstetrics (FIGO) stage ≥IIIB disease, aged between 18 and 70 years, with a laparoscopic Predictive Index value (PIV) ≤8 and residual disease ≤2.5 mm were included. RESULTS: 70 patients were included. With the except of age (p = 0.012), the populations were balanced for the main characteristics. At a median follow-up of 48 months, no differences in Progression Free Survival (PFS) (p = 0.968) and Overall Survival (OS) (p = 0.789) were recorded. Survival analysis according to HIPEC administration and BRCA mutational status showed an improved PFS (p = 0.011) and OS (p = 0.003) in BRCA mutated compared to wild-type patients when HIPEC was not administered, whilst they were superimposable in case of HIPEC administration (p = 0.857 vs p = 0.372; respectively). No differences in terms of neither intra-operative (p = 1.0) nor early post-operative complications (p = 0.920) were detected. CONCLUSIONS: Our results show that HIPEC in AOC may be a promising treatment in BRCA wild-type patients, as it seems to balance their decreased chemosensitivity compared to mutation carriers.

Neoadjuvant Chemotherapy in Pregnant Patients with Cervical Cancer: A Monocentric Retrospective Study.

BACKGROUND: To date, little and discordant data still exists on the management of cervical cancer (CC) during pregnancy. In this paper, we report our experience of the treatment of these patients analyzing the oncologic, obstetric, and neonatal outcomes. METHODS: Between January 2010 and December 2021, 13 patients were diagnosed with CC during pregnancy. All patients underwent platinum-based neoadjuvant chemotherapy (NACT) and 11/13 patients underwent a cesarean radical hysterectomy (CRH). RESULTS: All 13 patients were diagnosed with squamous-cell carcinoma, FIGO-2018 stage between IB2-IIIC1. The majority of patients had a partial (61.5%) or complete (15.4%) response to NACT. Most patients had a regular course of pregnancy and the obstetric complications observed were gestational diabetes mellitus in 23.1% and IUGR in 15.4% of cases. CRH was performed in the absence of major complications. Only 2 patients (15.4%) had disease recurrence and only 1 patient (7.7%) died of disease. All children are currently healthy. At birth, we observed mainly prematurity-related complications (38.5% respiratory distress syndrome and 7.7% neonatal jaundice) and only a case of congenital malformation (hypospadias). In our pediatric population, we reported a case of malignancy (acute myeloid leukemia). CONCLUSION: NACT seems to be safe and efficacious in controlling tumor burden during pregnancy. CRH following NACT appears to be feasible, avoiding repeated surgery and treatment delays. This approach is also reasonably safe from a maternal, obstetric, and neonatal point of view.

Anopheles gambiae Genome Conservation as a Resource for Rational Gene Drive Target Site Selection.

The increase in molecular tools for the genetic engineering of insect pests and disease vectors, such as Anopheles mosquitoes that transmit malaria, has led to an unprecedented investigation of the genomic landscape of these organisms. The understanding of genome variability in wild mosquito populations is of primary importance for vector control strategies. This is particularly the case for gene drive systems, which look to introduce genetic traits into a population by targeting specific genomic regions. Gene drive targets with functional or structural constraints are highly desirable as they are less likely to tolerate mutations that prevent targeting by the gene drive and consequent failure of the technology. In this study we describe a bioinformatic pipeline that allows the analysis of whole genome data for the identification of highly conserved regions that can point at potential functional or structural constraints. The analysis was conducted across the genomes of 22 insect species separated by more than hundred million years of evolution and includes the observed genomic variation within field caught samples of Anopheles gambiae and Anopheles coluzzii, the two most dominant malaria vectors. This study offers insight into the level of conservation at a genome-wide scale as well as at per base-pair resolution. The results of this analysis are gathered in a data storage system that allows for flexible extraction and bioinformatic manipulation. Furthermore, it represents a valuable resource that could provide insight into population structure and dynamics of the species in the complex and benefit the development and implementation of genetic strategies to tackle malaria.

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.

Introgression of a synthetic sex ratio distortion system from Anopheles gambiae into Anopheles arabiensis.

I-PpoI is a homing endonuclease that has a high cleavage activity and specificity for a conserved sequence within the ribosomal rDNA repeats, located in a single cluster on the Anopheles gambiae X chromosome. This property has been exploited to develop a synthetic sex ratio distortion system in this mosquito species. When I-PpoI is expressed from a transgene during spermatogenesis in mosquitoes, the paternal X chromosome is shredded and only Y chromosome-bearing sperm are viable, resulting in a male-biased sex ratio of >95% in the progeny. These distorter male mosquitoes can efficiently suppress caged wild-type populations, providing a powerful tool for vector control strategies. Given that malaria mosquito vectors belong to a species complex comprising at least two major vectors, we investigated whether the sex distorter I-PpoI, originally integrated in the A. gambiae genome, could be transferred via introgression to the sibling vector species Anopheles arabiensis. In compliance with Haldane's rule, F1 hybrid male sterility is known to occur in all intercrosses among members of the Anopheles gambiae complex. A scheme based on genetic crosses and transgene selection was used to bypass F1 hybrid male sterility and introgress the sex distorter I-PpoI into the A. arabiensis genetic background. Our data suggest that this sex distortion technique can be successfully applied to target A. arabiensis mosquitoes.

Publisher Correction: Introgression of a synthetic sex ratio distortion system from Anopheles gambiae into Anopheles arabiensis.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

High-resolution transcriptional profiling of Anopheles gambiae spermatogenesis reveals mechanisms of sex chromosome regulation.

Although of high priority for the development of genetic tools to control malaria-transmitting mosquitoes, only a few germline-specific regulatory regions have been characterised to date and the presence of global regulatory mechanisms, such as dosage compensation and meiotic sex chromosome inactivation (MSCI), are mostly assumed from transcriptomic analyses of reproductive tissues or whole gonads. In such studies, samples include a significant portion of somatic tissues inevitably complicating the reconstruction of a defined transcriptional map of gametogenesis. By exploiting recent advances in transgenic technologies and gene editing tools, combined with fluorescence-activated cell sorting and RNA sequencing, we have separated four distinct cell lineages from the Anopheles gambiae male gonads: premeiotic, meiotic (primary and secondary spermatocytes) and postmeiotic. By comparing the overall expression levels of X-linked and autosomal genes across the four populations, we revealed a striking transcriptional repression of the X chromosome coincident with the meiotic phase, classifiable as MSCI, and highlighted genes that may evade silencing. In addition, chromosome-wide median expression ratios of the premeiotic population confirmed the absence of dosage compensation in the male germline. Applying differential expression analysis, we highlighted genes and transcript isoforms enriched at specific timepoints and reconstructed the expression dynamics of the main biological processes regulating the key stages of sperm development and maturation. We generated the first transcriptomic atlas of A. gambiae spermatogenesis that will expand the available toolbox for the genetic engineering of vector control technologies. We also describe an innovative and multidimensional approach to isolate specific cell lineages that can be used for the targeted analysis of other A. gambiae organs or transferred to other medically relevant species and model organisms.

Molecular tools and genetic markers for the generation of transgenic sexing strains in Anopheline mosquitoes.

Malaria is a serious global health burden, affecting more than 200 million people each year in over 90 countries, predominantly in Africa, Asia and the Americas. Since the year 2000, a concerted effort to combat malaria has reduced its incidence by more than 40%, primarily due to the use of insecticide-treated bednets, indoor residual spraying and artemisinin-based combination drug therapies. Nevertheless, the cost of control is expected to nearly triple over the next decade and the current downward trend in disease transmission is threatened by the rise of resistance to drugs and insecticides. Novel strategies that are sustainable and cost-effective are needed to help usher in an era of malaria elimination. The most effective strategies thus far have focussed on control of the mosquito vector. The sterile insect technique (SIT) is a potentially powerful strategy that aims to suppress mosquito populations through the unproductive mating of wild female mosquitoes with sterile males that are released en masse. The technique and its derivatives are currently not appropriate for malaria control because it is difficult to sterilise males without compromising their ability to mate, and because anopheline males cannot be easily separated from females, which if released, could contribute to disease transmission. Advances in genome sequencing technologies and the development of transgenic techniques provide the tools necessary to produce mosquito sexing strains, which promise to improve current malaria-control programs and pave the way for new ones. In this review, the progress made in the development of transgenic sexing strains for the control of Anopheles gambiae, a major vector of human malaria, is discussed.

Cross-Species Y Chromosome Function Between Malaria Vectors of the Anopheles gambiae Species Complex.

Y chromosome function, structure and evolution is poorly understood in many species, including the Anopheles genus of mosquitoes-an emerging model system for studying speciation that also represents the major vectors of malaria. While the Anopheline Y had previously been implicated in male mating behavior, recent data from the Anopheles gambiae complex suggests that, apart from the putative primary sex-determiner, no other genes are conserved on the Y. Studying the functional basis of the evolutionary divergence of the Y chromosome in the gambiae complex is complicated by complete F1 male hybrid sterility. Here, we used an F1 × F0 crossing scheme to overcome a severe bottleneck of male hybrid incompatibilities that enabled us to experimentally purify a genetically labeled A. gambiae Y chromosome in an A. arabiensis background. Whole genome sequencing (WGS) confirmed that the A. gambiae Y retained its original sequence content in the A. arabiensis genomic background. In contrast to comparable experiments in Drosophila, we find that the presence of a heterospecific Y chromosome has no significant effect on the expression of A. arabiensis genes, and transcriptional differences can be explained almost exclusively as a direct consequence of transcripts arising from sequence elements present on the A. gambiae Y chromosome itself. We find that Y hybrids show no obvious fertility defects, and no substantial reduction in male competitiveness. Our results demonstrate that, despite their radically different structure, Y chromosomes of these two species of the gambiae complex that diverged an estimated 1.85 MYA function interchangeably, thus indicating that the Y chromosome does not harbor loci contributing to hybrid incompatibility. Therefore, Y chromosome gene flow between members of the gambiae complex is possible even at their current level of divergence. Importantly, this also suggests that malaria control interventions based on sex-distorting Y drive would be transferable, whether intentionally or contingent, between the major malaria vector species.

A CRISPR-Cas9 sex-ratio distortion system for genetic control.

Genetic control aims to reduce the ability of insect pest populations to cause harm via the release of modified insects. One strategy is to bias the reproductive sex ratio towards males so that a population decreases in size or is eliminated altogether due to a lack of females. We have shown previously that sex ratio distortion can be generated synthetically in the main human malaria vector Anopheles gambiae, by selectively destroying the X-chromosome during spermatogenesis, through the activity of a naturally-occurring endonuclease that targets a repetitive rDNA sequence highly-conserved in a wide range of organisms. Here we describe a CRISPR-Cas9 sex distortion system that targets ribosomal sequences restricted to the member species of the Anopheles gambiae complex. Expression of Cas9 during spermatogenesis resulted in RNA-guided shredding of the X-chromosome during male meiosis and produced extreme male bias among progeny in the absence of any significant reduction in fertility. The flexibility of CRISPR-Cas9 combined with the availability of genomic data for a range of insects renders this strategy broadly applicable for the species-specific control of any pest or vector species with an XY sex-determination system by targeting sequences exclusive to the female sex chromosome.

A synthetic sex ratio distortion system for the control of the human malaria mosquito.

It has been theorized that inducing extreme reproductive sex ratios could be a method to suppress or eliminate pest populations. Limited knowledge about the genetic makeup and mode of action of naturally occurring sex distorters and the prevalence of co-evolving suppressors has hampered their use for control. Here we generate a synthetic sex distortion system by exploiting the specificity of the homing endonuclease I-PpoI, which is able to selectively cleave ribosomal gene sequences of the malaria vector Anopheles gambiae that are located exclusively on the mosquito's X chromosome. We combine structure-based protein engineering and molecular genetics to restrict the activity of the potentially toxic endonuclease to spermatogenesis. Shredding of the paternal X chromosome prevents it from being transmitted to the next generation, resulting in fully fertile mosquito strains that produce >95% male offspring. We demonstrate that distorter male mosquitoes can efficiently suppress caged wild-type mosquito populations, providing the foundation for a new class of genetic vector control strategies.