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Meiotic Sex Chromosome Inactivation

  1. Tasman J Daish,
  2. Frank Grützner

Published Online: 15 FEB 2010

DOI: 10.1002/9780470015902.a0022109

eLS

eLS

How to Cite

Daish, T. J. and Grützner, F. 2010. Meiotic Sex Chromosome Inactivation. eLS. .

Author Information

  1. The University of Adelaide, School of Molecular and Biomedical Science, Adelaide, Australia

Publication History

  1. Published Online: 15 FEB 2010

Abstract

The differentiation of sex chromosomes through evolution has resulted in significant loss of homology and gene content which has profound consequences on gene dosage between the sexes and impacts on their behaviour through meiosis. During spermatogenesis the unpaired DNA, of heteromorphic sex chromosomes becomes transcriptionally silenced and sequestered into a ‘sex body’, a process termed ‘meiotic sex chromosome inactivation’. This essential meiotic event involves an ordered hierarchy of epigenetic changes to the sex chromosome DNA initiated by conserved DNA damage, repair and checkpoint machinery. Although the reason for this repression remains unclear, it is thought to prevent recombination between nonhomologous sex chromosome DNA and to avoid stringent meiotic checkpoints. Recent work has extended our understanding of the evolutionary conservation of meiotic silencing to include the avian ZW sex chromosome system providing new insights into the evolutionary dynamics of meiotic sex chromosome organization in diverse species.

Key concepts:

  • The accumulation of mutation and rearrangements on sex chromosomes lead to blocks in recombination, accumulation of sexually antagonistic genes and the differential degradation of sex chromosomes.

  • Heteromorphic sex chromosomes result in gene dosage imbalance between the sexes and unsynapsed DNA in meiosis I.

  • Meiotic sex chromosome inactivation protects unpaired sex chromosome DNA from aberrant recombination and checkpoint surveillance machinery.

  • Sex chromosomes undergo transcriptional silencing during late prophase due to the accumulation of conserved epigenetic changes.

  • Therian mammals have active X-borne retrogenes on autosomes to compensate for the loss of transcription of sex chromosome genes important for spermatogenesis.

Keywords:

  • spermatogenesis;
  • meiotic silencing;
  • spigenetics;
  • sex chromosomes