title: Estimation of population allele frequencies from next-generation sequencing data: pool-versus individual-based genotyping.
abstract: Molecular markers produced by next-generation sequencing (NGS) technologies are revolutionizing genetic research. However, the costs of analysing large numbers of individual genomes remain prohibitive for most population genetics studies. Here, we present results based on mathematical derivations showing that, under many realistic experimental designs, NGS of DNA pools from diploid individuals allows to estimate the allele frequencies at single nucleotide polymorphisms (SNPs) with at least the same accuracy as individual-based analyses, for considerably lower library construction and sequencing efforts. These findings remain true when taking into account the possibility of substantially unequal contributions of each individual to the final pool of sequence reads. We propose the intuitive notion of effective pool size to account for unequal pooling and derive a Bayesian hierarchical model to estimate this parameter directly from the data. We provide a user-friendly application assessing the accuracy of allele frequency estimation from both pool- and individual-based NGS population data under various sampling, sequencing depth and experimental error designs. We illustrate our findings with theoretical examples and real data sets corresponding to SNP loci obtained using restriction site-associated DNA (RAD) sequencing in pool- and individual-based experiments carried out on the same population of the pine processionary moth (Thaumetopoea pityocampa). NGS of DNA pools might not be optimal for all types of studies but provides a cost-effective approach for estimating allele frequencies for very large numbers of SNPs. It thus allows comparison of genome-wide patterns of genetic variation for large numbers of individuals in multiple populations.
authors.affiliation: INRA, UMR CBGP (INRA-IRD-Cirad-Montpellier SupAgro), Campus international de Baillarguet, CS 30016, F-34988, Montferrier-sur-Lez, France. mathieu.gautier@supagro.inra.fr
authors.forename: Mathieu
authors.initials: M
authors.lastname: Gautier
authors.forename: Julien
authors.initials: J
authors.lastname: Foucaud
authors.forename: Karim
authors.initials: K
authors.lastname: Gharbi
authors.forename: Timothée
authors.initials: T
authors.lastname: Cézard
authors.forename: Maxime
authors.initials: M
authors.lastname: Galan
authors.forename: Anne
authors.initials: A
authors.lastname: Loiseau
authors.forename: Marian
authors.initials: M
authors.lastname: Thomson
authors.forename: Pierre
authors.initials: P
authors.lastname: Pudlo
authors.forename: Carole
authors.initials: C
authors.lastname: Kerdelhué
authors.forename: Arnaud
authors.initials: A
authors.lastname: Estoup
mesh_terms: D001499:Bayes Theorem; D005787:Gene Frequency; D005828:Genetics, Population; D005838:Genotype; D060005:Genotyping Techniques / Q000379:methods*; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D008962:Models, Theoretical; D020641:Polymorphism, Single Nucleotide
keywords: coverage; estimation of allele frequencies; molecular markers; next-generation sequencing; pooled samples; population genetics