Meiotic sex chromosome inactivation in the marsupial Monodelphis domestica

Jacey L. Hornecker, Paul B. Samollow, Edward S. Robinson, John L. Vandeberg, John R. McCarrey

    Research output: Contribution to journalArticlepeer-review

    40 Scopus citations


    In eutherian mammals, the X and Y chromosomes undergo meiotic sex chromosome inactivation (MSCI) during spermatogenesis in males. However, following fertilization, both the paternally (Xp) and maternally (Xm) inherited X chromosomes are active in the inner cell mass of the female blastocyst, and then random inactivation of one X chromosome occurs in each cell, leading to a mosaic pattern of X-chromosome activity in adult female tissues. In contrast, marsupial females show a nonrandom pattern of X chromosome activity, with repression of the Xp in all somatic tissues. Here, we show that MSCI also occurs during spermatogenesis in marsupials in a manner similar to, but more stable than that in eutherians. These findings support the suggestion that MSCI may have provided the basis for an early dosage compensation mechanism in mammals based solely on gametogenic events, and that random X-chromosome inactivation during embryogenesis may have evolved subsequently in eutherian mammals.

    Original languageEnglish (US)
    Pages (from-to)696-708
    Number of pages13
    Issue number11
    StatePublished - Nov 2007


    • Evolution
    • Marsupial
    • Meiotic sex chromosome inactivation
    • Spermatogenesis
    • X-chromosome inactivation

    ASJC Scopus subject areas

    • Genetics
    • Endocrinology
    • Cell Biology


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