S. pombe wtf drivers use dual transcriptional regulation and selective protein exclusion from spores to cause meiotic drive.

Meiotic drivers bias gametogenesis to ensure their transmission into more than half the offspring of a heterozygote. In Schizosaccharomyces pombe, wtf meiotic drivers destroy the meiotic products (spores) that do not inherit the driver from a heterozygote, thereby reducing fertility. wtf drivers encode both a Wtfpoison protein and a Wtfantidote protein using alternative transcriptional start sites. Here, we analyze how the expression and localization of the Wtf proteins are regulated to achieve drive. We show that transcriptional timing and selective protein exclusion from developing spores ensure that all spores are exposed to Wtf4poison, but only the spores that inherit wtf4 receive a dose of Wtf4antidote sufficient for survival. In addition, we show that the Mei4 transcription factor, a master regulator of meiosis, controls the expression of the wtf4poison transcript. This transcriptional regulation, which includes the use of a critical meiotic transcription factor, likely complicates the universal suppression of wtf genes without concomitantly disrupting spore viability. We propose that these features contribute to the evolutionary success of the wtf drivers.

The wtf4 meiotic driver utilizes controlled protein aggregation to generate selective cell death.

Meiotic drivers are parasitic loci that force their own transmission into greater than half of the offspring of a heterozygote. Many drivers have been identified, but their molecular mechanisms are largely unknown. The wtf4 gene is a meiotic driver in Schizosaccharomyces pombe that uses a poison-antidote mechanism to selectively kill meiotic products (spores) that do not inherit wtf4. Here, we show that the Wtf4 proteins can function outside of gametogenesis and in a distantly related species, Saccharomyces cerevisiae. The Wtf4poison protein forms dispersed, toxic aggregates. The Wtf4antidote can co-assemble with the Wtf4poison and promote its trafficking to vacuoles. We show that neutralization of the Wtf4poison requires both co-assembly with the Wtf4antidote and aggregate trafficking, as mutations that disrupt either of these processes result in cell death in the presence of the Wtf4 proteins. This work reveals that wtf parasites can exploit protein aggregate management pathways to selectively destroy spores.

Meiotic drivers are genes that break the normal rules of inheritance. Usually, a gene has a 50% chance of passing on to the next generation. Meiotic drivers force their way into the next generation by poisoning the gametes (the sex cells that combine to form a zygote) that do not carry them. Harnessing the power of genetic drivers could allow scientists to spread beneficial genes across populations. One group of meiotic drivers found in fission yeast is called the 'with transposon fission yeast', or 'wtf' gene family. The wtf drivers act during the production of spores, which are the fission yeast equivalent of sperm, and they encode both a poison that can destroy the spores and its antidote. The poison spreads through the sac holding the spores, and can affect all of them, while the antidote only protects the spores that make it. This means that the spores carrying the wtf genes survive, while the rest of the spores are killed. To understand whether it is possible to use the wtf meiotic drivers to spread other genes, perhaps outside of fission yeast, scientists must first establish exactly how the proteins coded for by genes behave. To do this, Nuckolls et al. examined a member of the wtf family called wtf4. Attaching a fluorescent label to the poison and antidote proteins produced by wtf4 made it possible to see what they do. This revealed that the poison clumps, forming toxic aggregates that damage yeast spores. The antidote works by mopping up these aggregates and moving them to the cell's main storage compartment, called the vacuole. Mutations that disrupted the ability of the antidote to interact with the poison or its ability to move the poison into storage stopped the antidote from working. Nuckolls et al. also showed that if genetic engineering was used to introduce wtf4 into a distantly related species of budding yeast the effects of this meiotic driver were the same. This suggests that the wtf genes may be good candidates for future genetic engineering experiments. Engineered systems known as 'gene drives' could spread beneficial genetic traits through populations. This could include disease-resistance genes in crops, or disease-preventing genes in mosquitoes. The wtf genes are small and work independently of other genes, making them promising candidates for this type of system. These experiments also suggest that the wtf genes could be useful for understanding why clumps of proteins are toxic to cells. Future work could explore why clumps of wtf poison kill spores, while clumps of poison plus antidote do not. This could aid research into human ailments caused by protein clumps, such as Huntington's or Alzheimer's disease.

Resistance to natural and synthetic gene drive systems.

Scientists are rapidly developing synthetic gene drive elements intended for release into natural populations. These are intended to control or eradicate disease vectors and pests, or to spread useful traits through wild populations for disease control or conservation purposes. However, a crucial problem for gene drives is the evolution of resistance against them, preventing their spread. Understanding the mechanisms by which populations might evolve resistance is essential for engineering effective gene drive systems. This review summarizes our current knowledge of drive resistance in both natural and synthetic gene drives. We explore how insights from naturally occurring and synthetic drive systems can be integrated to improve the design of gene drives, better predict the outcome of releases and understand genomic conflict in general.

Genetic Villains: Killer Meiotic Drivers.

Unbiased allele transmission into progeny is a fundamental genetic concept canonized as Mendel's Law of Segregation. Not all alleles, however, abide by the law. Killer meiotic drivers are ultra-selfish DNA sequences that are transmitted into more than half (sometimes all) of the meiotic products generated by a heterozygote. As their name implies, these loci gain a transmission advantage in heterozygotes by destroying otherwise viable meiotic products that do not inherit the driver. We review and classify killer meiotic drive genes across a wide spectrum of eukaryotes. We discuss how analyses of these ultra-selfish genes can lead to greater insight into the mechanisms of gametogenesis and the causes of infertility.

wtf genes are prolific dual poison-antidote meiotic drivers.

Meiotic drivers are selfish genes that bias their transmission into gametes, defying Mendelian inheritance. Despite the significant impact of these genomic parasites on evolution and infertility, few meiotic drive loci have been identified or mechanistically characterized. Here, we demonstrate a complex landscape of meiotic drive genes on chromosome 3 of the fission yeasts Schizosaccharomyces kambucha and S. pombe. We identify S. kambucha wtf4 as one of these genes that acts to kill gametes (known as spores in yeast) that do not inherit the gene from heterozygotes. wtf4 utilizes dual, overlapping transcripts to encode both a gamete-killing poison and an antidote to the poison. To enact drive, all gametes are poisoned, whereas only those that inherit wtf4 are rescued by the antidote. Our work suggests that the wtf multigene family proliferated due to meiotic drive and highlights the power of selfish genes to shape genomes, even while imposing tremendous costs to fertility.