Accurate Allele Frequencies from Ultra-low Coverage Pool-Seq Samples in Evolve-and-Resequence Experiments

Journal Article · 02 December 2019 · G3

DOI: https://doi.org/10.1534/g3.119.400755 · OSTI ID:1591845

Tilk, Susanne  ^[1]; Bergland, Alan  ^[2]; Goodman, Aaron  ^[1]; Schmidt, Paul  ^[3]; Petrov, Dmitri  ^[1]; Greenblum, Sharon  ^[4]

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1. Stanford Univ., CA (United States)
2. Stanford Univ., CA (United States); Univ. of Virginia, Charlottesville, VA (United States)
3. Univ. of Pennsylvania, Philadelphia, PA (United States)
4. Stanford Univ., CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Evolve-and-resequence (E+R) experiments leverage next-generation sequencing technology to track the allele frequency dynamics of populations as they evolve. While previous work has shown that adaptive alleles can be detected by comparing frequency trajectories from many replicate populations, this power comes at the expense of high-coverage (>100x) sequencing of many pooled samples, which can be cost-prohibitive. Here, we show that accurate estimates of allele frequencies can be achieved with very shallow sequencing depths (<5x) via inference of known founder haplotypes in small genomic windows. This technique can be used to efficiently estimate frequencies for any number of bi-allelic SNPs in populations of any model organism founded with sequenced homozygous strains. Using both experimentally-pooled and simulated samples of Drosophila melanogaster, we show that haplotype inference can improve allele frequency accuracy by orders of magnitude for up to 50 generations of recombination, and is robust to moderate levels of missing data, as well as different selection regimes. Finally, we show that a simple linear model generated from these simulations can predict the accuracy of haplotype-derived allele frequencies in other model organisms and experimental designs. To make these results broadly accessible for use in E+R experiments, we introduce HAF-pipe, an open-source software tool for calculating haplotype-derived allele frequencies from raw sequencing data. Ultimately, by reducing sequencing costs without sacrificing accuracy, our method facilitates E+R designs with higher replication and resolution, and thereby, increased power to detect adaptive alleles.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1591845
• Journal Information: G3, Journal Name: G3 Journal Issue: 12 Vol. 9; ISSN 2160-1836
• Publisher: Genetics Society of AmericaCopyright Statement
• Country of Publication: United States
• Language: English