Just how conserved is vertebrate sex determination?

Authors

  • Andrew Cutting,

    1. Murdoch Childrens Research Institute, Royal Childrens Hospital, Parkville, Australia
    2. Department of Paediatrics, University of Melbourne, Melbourne, Australia
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    • Andrew Cutting and Justin Chue contributed equally to this work.

  • Justin Chue,

    1. Murdoch Childrens Research Institute, Royal Childrens Hospital, Parkville, Australia
    2. Department of Paediatrics, University of Melbourne, Melbourne, Australia
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    • Andrew Cutting and Justin Chue contributed equally to this work.

  • Craig A. Smith

    Corresponding author
    1. Department of Zoology, University of Melbourne, Melbourne, Australia
    • Murdoch Childrens Research Institute, Royal Childrens Hospital, Parkville, Australia
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Correspondence to: Dr. Craig Smith, Murdoch Childrens Research Institute, Royal Childrens Hospital, Parkville, Australia. E-mail: craig.smith@mcri.edu.au

Abstract

Background: Sex determination in vertebrate embryos has long been equated with gonadal differentiation into testes or ovaries. This view has been challenged over the years by reports of somatic sexual dimorphisms pre-dating gonadal sex differentiation. The recent finding that sex determination in birds is likely to be partly cell autonomous has again called for a broader definition of sex determination. Inherent sexual differentiation in each and every cell may apply widely among vertebrates, and may involve more than one “master sex gene” on a sex chromosome. At the gonadal level, key genes required for proper sexual differentiation are conserved among vertebrates, but their relative positions in the ovarian and testicular cascades differ. Results: We illustrate these differences by comparing key sex genes in fishes versus birds and mammals, with emphasis on DM domain genes and the SOX9-AMH pathway in the testis and the FOXL2-Aromatase pathway in the ovary. Such comparisons facilitate the identification of ancient versus derived genes involved in gonadal sex determination. Conclusions: The data indicate that vertebrate sex-determining cascades are not as conserved as once thought. Developmental Dynamics 242:380–387, 2013. © 2013 Wiley Periodicals, Inc.

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