Biology subjects

Yonah, E. S.

Publications and source records attributed to Yonah, E. S..

4 recordsLinked to original sources

bioRxiv2026

The Y chromosome gene draupnir reveals constraints on engineering Y-linked sex-ratio distorters in malaria mosquitoes

Y chromosome sex distorters offer a powerful strategy for mosquito population suppression, but their implementation is constrained by the transcriptional silencing of Y-linked transgenes during spermatogenesis. To investigate how endogenous Y genes evade this repression, we characterized draupnir (formerly YG5), a multicopy Y-linked gene of Anopheles gambiae encoding a Zip3-like meiotic protein. Comparative genomic and phylogenetic analyses revealed that draupnir originated through duplication of the autosomal paralog skirnir, itself derived from the ancestral recombination factor vilya, followed by amplification into a tandem array on the Y chromosome. We show that draupnir is actively transcribed during meiosis, making it the only known Y-linked gene expressed during mosquito spermatogenesis. To test whether its regulatory region is sufficient to confer sperm-specific expression from the Y chromosome, we cloned the draupnir promoter to drive expression of an X-chromosome shredder. When inserted on an autosome, the construct drove meiotic expression and strong sex-ratio distortion in the progeny of transgenic males. In contrast, the same construct inserted on the Y chromosome was transcriptionally silent and produced balanced sex ratios. These results demonstrate that draupnir expression depends on its native genomic context within a multicopy Y-linked array and that its promoter alone cannot overcome transcription silencing. Our findings reveal a fundamental constraint on Y-chromosome-based genetic control strategies and point to future approaches for enabling transcription from otherwise repressed sex chromosomes.

genetics↗

bioRxiv2026

Spermatogenic context controls outcomes of engineered sex distortion in malaria mosquitoes

Sex-ratio distortion systems are promising genetic tools for mosquito population control. Two strategies have been proposed: prezygotic elimination of X-bearing sperm by X-shredding, which can drive invasive Y-chromosome transmission when sex distorters are Y-linked, and postzygotic daughter killing through disruption of X-linked haploinsufficient genes, a self-limiting approach known as X-poisoning. Previous attempts to implement X-poisoning in the malaria mosquito Anopheles gambiae unexpectedly produced prezygotic distortion, with sex bias arising from loss of X-bearing sperm rather than daughter lethality. Here we use a split CRISPR-Cas9 system to systematically compare sex-ratio distortion outcomes across germline Cas9 drivers and X-linked target genes. Meiotic X-chromosome targeting induced preferential Y-chromosome transmission regardless of target identity, function, or number of sgRNA target sites. In contrast, shifting Cas9 expression to earlier spermatogenic stages altered outcomes dramatically: targeting X-linked ribosomal protein genes caused severe developmental or reproductive toxicity, whereas targeting the haplolethal muscle gene wupA produced daughter-specific post-embryonic lethality, with the majority of surviving females emerging flightless. Tracking offspring using a Y-linked fluorescent marker confirmed that sex chromosome segregation remained unbiased, with female mortality accumulating progressively from the first larval instar, reaching near-complete lethality by adulthood. These results demonstrate that the timing of Cas9 expression during spermatogenesis, rather than target gene identity alone, determines the outcome of X-chromosome targeting in malaria mosquitoes, and establish the conditions required for genuine X-poisoning. Identification of wupA as an effective X-poisoning target provides a solid foundation for the future development of self-limiting Y-linked sex-ratio distortion systems for malaria vector control.

genetics↗

bioRxiv2025

An OpIE2-DsRed marker disrupts female blood-feeding and shortens lifespan in the malaria vector Anopheles gambiae.

Anopheles gambiae is one of the principal vectors of human malaria. Over the past two decades, transgenic mosquito strains have been essential tools for studying mosquito biology and developing genetic control strategies such as gene drives. Mosquito transformants are typically identified using fluorescent markers, which are assumed to be phenotypically neutral. While generating CRISPR-based gene drive strains carrying an OpIE2-DsRed marker we unexpectedly found that transgenic females were unable to blood-feed and were consequently sterile, whereas males initially appeared normal and fertile. Given the potential utility of dominant, female-specific sterility for mosquito control, we established additional strains controlling for transgene content and integration site, confirming that the OpIE2-DsRed cassette caused the defect. Behavioral assays showed that females exhibited normal attraction to a membrane feeder but failed to initiate blood-feeding, performing repeated cycles of probing and proboscis grooming in rapid succession before ultimately leaving the feeder unfed. Microscopy showed that both sexes possessed a distally curved proboscis, providing a morphological explanation for the blood-feeding defect of females and the reduced male lifespan. A second promoter variant (OpIE2b), differing in flanking sequences at the IE-2 junction, drove strong marker expression without impairing blood-feeding or longevity. These findings demonstrate that minor differences in promoter architecture can produce major, unexpected phenotypic effects. OpIE2b provides a robust, phenotypically neutral marker for An. gambiae research, while OpIE2a highlights the need for rigorous validation of transgenic components intended for research and applied releases.

genetics↗

bioRxiv2023

Targeting mosquito X-chromosomes reveals complex transmission dynamics of sex ratio distorting gene drives

Engineered sex ratio distorters (SRDs) have been proposed as a powerful component of genetic control strategies designed to suppress harmful insect pests. Two types of CRISPR-based SRD mechanisms have been proposed: X-shredding eliminates X-bearing sperm, while X-poisoning eliminates daughters inheriting disrupted X-chromosomes. These differences can have a profound impact on the population dynamics of SRDs when linked to the Y-chromosome: an X-shredder is invasive constituting a classical meiotic Y-drive, whereas X-poisoning is self-limiting, unable to invade but also insulated from selection. Here, we established the first X-poisoning strains in the malaria vector Anopheles gambiae targeting three X-linked genes during spermatogenesis resulting in male bias. Surprisingly, we found that sex distortion was primarily driven by a loss of X-bearing sperm with limited evidence for postzygotic lethality of daughters. By leveraging a Drosophila melanogaster model, we show unambiguously that engineered SRD traits can operate differently in these two insects. Unlike X-shredding, X-poisoning could theoretically operate at early stages of spermatogenesis. We therefore explored premeiotic Cas9 expression to target the mosquito X-chromosome. We find that, by pre-empting the onset of meiotic sex chromosome inactivation, this approach may enable the development of Y-linked SRDs if mutagenesis of spermatogenesis-essential genes is functionally balanced.

synthetic biology↗