Research Article

Chromosoma

, Volume 117, Issue 2, pp 211-217

First online:

Dissection of a Y-autosome translocation in Cryptomys hottentotus (Rodentia, Bathyergidae) and implications for the evolution of a meiotic sex chromosome chain

  • J. L. DeuveAffiliated withEvolutionary Genomics Group, Department of Botany and Zoology, University of Stellenbosch
  • , N. C. BennettAffiliated withMammal Research Institute, Department of Zoology and Entomology, University of Pretoria
  • , A. Ruiz-HerreraAffiliated withEvolutionary Genomics Group, Department of Botany and Zoology, University of StellenboschDipartimento di Genetica e Microbiologia, Universita’ degli Studi di Pavia
  • , P. D. WatersAffiliated withComparative Genomics Group, Research School of Biological Sciences, The Australian National University
  • , J. Britton-DavidianAffiliated withInstitut des Sciences de l’Evolution (UMR5554), Génétique and Environnement, Université Montpellier II
  • , T. J. RobinsonAffiliated withEvolutionary Genomics Group, Department of Botany and Zoology, University of Stellenbosch Email author 

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Abstract

We describe the outcome of a comprehensive cytogenetic survey of the common mole-rat, Cryptomys hottentotus, based on G and C banding, fluorescence in situ hybridisation and the analysis of meiotic chromosomes using immunostaining of proteins involved in the formation of synaptonemal complex (SCP1 and SCP3). We identified the presence of a Y-autosome translocation that is responsible for a fixed diploid number difference between males (2n = 53) and females (2n = 54), a character that likely defines the C. hottentotus lineage. Immunostaining, combined with C banding of spermatocytes, revealed a linearised sex trivalent with X1 at one end and X2 at the other, with evidence of reduced recombination between Y and X2 that seems to be heterochromatin dependant in the C. hottentotus lineage. We suggest that this could depict the likely initial step in the differentiation of a true neo-X, and that this may mimic an early stage in the mammalian meiotic chain formation, an evolutionary process that has been taken to an extreme in a monotreme mammal, the platypus.