Saunders paul

My research focuses on sex determination evolution and sex chromosome evolution. I use a variety of approaches (bioinformatics, cytogenetics, mathematical modelling…), mainly to try and get a better understanding of the ultimate causes responsible for transitions among different sex determination systems, and to study the origin as well as the structural and sequence evolution of newly emerged sex chromosomes. I’m also interested in other research topics, such as genomic conflicts (in particular sex chromosome drive).

My current project aims at analysing the origin and evolution of the sex chromosomes and neo-sex chromosomes of the African pygmy mouse Mus minutoides, using a combination of genomic and transcriptomic data.

M. minutoides is one of the rare mammals that does not have a standard male heterogametic (XX/XY) sex determination system. In this species, a third sex chromosome has emerged around 1 MYA ago: the X*. It derives from the X and carries a still unknown mutation that causes XY embryos to develop into fully fertile females. Consequently, while all males are XY, females harbour one the three following karyotypes: XX, XX, XY. Furthermore, in most wild populations, sex chromosomes are fused to chromosome 1 forming “neo-sex chromosomes”. Remarkably, in our focal population from South Africa, while the X and Y are fused to chromosome 1, the X is fused to chromosome 16, because of a recent WART (whole arm reciprocal translocation).

Preliminary analyses suggest that the X* chromosome has undergone profound structural rearrangements, and that recombination is limited on the neo-sex chromosomes. This means that different compartment of the genome have become sex-linked (transmitted only through the male or female line) at different points in time. This system constitutes an original framework to test classical predictions of sex chromosome evolution (recombination arrest, sexualisation of the gene content, degeneration of sex-limited chromosomal regions…), and better understand how sex chromosomes evolve in such polygenic sex determination systems. It also provides a great opportunity to identify candidate gene(s) responsible for sex-reversal of X*Y individuals, and therefore further our understanding of the molecular and developmental mechanisms involved in the (still incompletely understood) mammalian sex determination cascade.

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Short CV:

  • Sept. 2012 - Dec. 2015: PhD – Université de Montpellier, France – Supervision: Janice Britton Davidian & Frédéric Veyrunes.
  • Jul. 2016 - Jul. 2018: Post-doc fellowship – Université de Lausanne, Switzerland – Supervision: Nicolas Perrin.
  • Sept. 2018 - Sept. 2020: Post-doc fellowship – Université de Montpellier, France – Supervision: Frédéric Veyrunes & Pierre Boursot.
  • Nov. 2018 - Feb. 2019: Visiting postdoc – Earlham Institute, Norwich, UK. Collaborator: David Thybert.

Keywords: Sex determination; sex chromosomes; genomics; transcriptomics; bioinformatics