Background selection and biased gene conversion affect more than 95% of the human genome and bias demographic inferences

  1. Fanny Pouyet  Is a corresponding author
  2. Simon Aeschbacher
  3. Alexandre Thiéry
  4. Laurent Excoffier  Is a corresponding author
  1. University of Bern, Switzerland

Abstract

Disentangling the effect on genomic diversity of natural selection from that of demography is notoriously difficult, but necessary to properly reconstruct the history of species. Here, we use high-quality human genomic data to show that purifying selection at linked sites (i.e. background selection, BGS) and GC-biased gene conversion (gBGC) together affect as much as 95% of the variants of our genome. We find that the magnitude and relative importance of BGS and gBGC are largely determined by variation in recombination rate and base composition. Importantly, synonymous sites and non-transcribed regions are also affected, albeit to different degrees. Their use for demographic inference can lead to strong biases. However, by conditioning on genomic regions with recombination rates above 1.5 cM/Mb and mutation types (C↔G, A↔T), we identify a set of SNPs that is mostly unaffected by BGS or gBGC, and that avoids these biases in the reconstruction of human history.

Data availability

All data generated and script to analyse them is provided on the dryad repository: http://dx.doi.org/10.5061/dryad.t76fk80

The following data sets were generated
The following previously published data sets were used

Article and author information

Author details

  1. Fanny Pouyet

    Institute of Ecology and Evolution, University of Bern, Berne, Switzerland
    For correspondence
    fanny.pouyet@iee.unibe.ch
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-5614-6998
  2. Simon Aeschbacher

    Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  3. Alexandre Thiéry

    Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  4. Laurent Excoffier

    Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
    For correspondence
    laurent.excoffier@iee.unibe.ch
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-7507-6494

Funding

Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (310030B-166605)

  • Laurent Excoffier

University of Berkeley (Visiting Miller Professorship)

  • Laurent Excoffier

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Krishna Veeramah, Stony Brook University, United States

Publication history

  1. Received: March 1, 2018
  2. Accepted: August 17, 2018
  3. Accepted Manuscript published: August 20, 2018 (version 1)
  4. Accepted Manuscript updated: August 23, 2018 (version 2)
  5. Version of Record published: October 9, 2018 (version 3)

Copyright

© 2018, Pouyet et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Fanny Pouyet
  2. Simon Aeschbacher
  3. Alexandre Thiéry
  4. Laurent Excoffier
(2018)
Background selection and biased gene conversion affect more than 95% of the human genome and bias demographic inferences
eLife 7:e36317.
https://doi.org/10.7554/eLife.36317

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