Greenberg, N. L. | bioRxiv Science

bioRxiv2024

Remote-control meiotic drive of sex chromosomes

Some selfish genetic elements drive at meiosis to achieve transmission distortion, breaking the rules of Mendelian segregation to enhance their own evolutionary success. It has been shown that enhancers of drive must act in cis in order to gain the selfish benefit of drive and that suppressors of drive will be selected at unlinked loci. Here, we model the evolution of an autosomal trans-acting gene (Distorter) that causes the Y-chromosome (or even 0-chromosome) to drive without driving itself, a phenomenon we call "remote-control meiotic drive". We show that such a gene may spread in the population when linked to a second locus, Assister, whose alleles are transmitted at different frequencies through sperm as compared to eggs, for which we consider various scenarios, e.g. sexually antagonistic selection or sex-limited drive. Depending on the mechanistic details of sex-chromosome drive, Distorters spread can additionally facilitate transitions between XY and X0 sex determination. Our results provide a proof of principle that stretches the current understanding of segregation modifier and sex allocation theory. Moreover, we identify alternative evolutionary trajectories that could also lead to remote control drive, and discuss its potential applications in developing synthetic sex-ratio-distorting elements for use in e.g. pest management.

evolutionary biology↗

bioRxiv2024

An egg sabotaging mechanism drives non-Mendelian transmission in mice

During meiosis, homologous chromosomes segregate so that alleles are transmitted equally to haploid gametes, following Mendels Law of Segregation. However, some selfish genetic elements drive in meiosis to distort the transmission ratio and increase their representation in gametes. The established paradigms for drive are fundamentally different for female vs male meiosis. In male meiosis, selfish elements typically kill gametes that do not contain them. In female meiosis, killing is predetermined, and selfish elements bias their segregation to the single surviving gamete (i.e., the egg in animal meiosis). Here we show that a selfish element on mouse chromosome 2, R2d2, drives using a hybrid mechanism in female meiosis, incorporating elements of both male and female drivers. If R2d2 is destined for the polar body, it manipulates segregation to sabotage the egg by causing aneuploidy that is subsequently lethal in the embryo, so that surviving progeny preferentially contain R2d2. In heterozygous females, R2d2 orients randomly on the metaphase spindle but lags during anaphase and preferentially remains in the egg, regardless of its initial orientation. Thus, the egg genotype is either euploid with R2d2 or aneuploid with both homologs of chromosome 2, with only the former generating viable embryos. Consistent with this model, R2d2 heterozygous females produce eggs with increased aneuploidy for chromosome 2, increased embryonic lethality, and increased transmission of R2d2. In contrast to a male meiotic driver, which kills its sister gametes produced as daughter cells in the same meiosis, R2d2 eliminates "cousins" produced from meioses in which it should have been excluded from the egg.

genetics↗