28 research outputs found
R2d2 Drives Selfish Sweeps in the House Mouse
A selective sweep is the result of strong positive selection driving newly occurring or standing genetic variants to fixation,
and can dramatically alter the pattern and distribution of allelic diversity in a population. Population-level sequencing data
have enabled discoveries of selective sweeps associated with genes involved in recent adaptations in many species. In
contrast, much debate but little evidence addresses whether “selfish” genes are capable of fixation—thereby leaving
signatures identical to classical selective sweeps—despite being neutral or deleterious to organismal fitness. We previously
described R2d2, a large copy-number variant that causes nonrandom segregation of mouse Chromosome 2 in females due to
meiotic drive. Here we show population-genetic data consistent with a selfish sweep driven by alleles of R2d2 with high copy
number (R2d2HC) in natural populations. We replicate this finding in multiple closed breeding populations from six outbred
backgrounds segregating for R2d2 alleles. We find that R2d2HC rapidly increases in frequency, and in most cases becomes
fixed in significantly fewer generations than can be explained by genetic drift. R2d2HC is also associated with significantly
reduced litter sizes in heterozygous mothers, making it a true selfish allele. Our data provide direct evidence of populations
actively undergoing selfish sweeps, and demonstrate that meiotic drive can rapidly alter the genomic landscape in favor of
mutations with neutral or even negative effects on overall Darwinian fitness. Further study will reveal the incidence of selfish
sweeps, and will elucidate the relative contributions of selfish genes, adaptation and genetic drift to evolutio