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Sci Rep. 2016 Jul 18;6:29949. doi: 10.1038/srep29949.

Unique sex chromosome systems in Ellobius: How do male XX chromosomes recombine and undergo pachytene chromatin inactivation?

Author information

1
Cytogenetics Laboratory, N.I. Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia.
2
Evolutionary and Developmental Genetics Laboratory, N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow 119334, Russia.

Abstract

Most mammalian species have heteromorphic sex chromosomes in males, except for a few enigmatic groups such as the mole voles Ellobius, which do not have the Y chromosome and Sry gene. The Ellobius (XX ♀♂) system of sex chromosomes has no analogues among other animals. The structure and meiotic behaviour of the two X chromosomes were investigated for males of the sibling species Ellobius talpinus and Ellobius tancrei. Their sex chromosomes, despite their identical G-structure, demonstrate short synaptic fragments and crossover-associated MLH1 foci in both telomeric regions only. The chromatin undergoes modifications in the meiotic sex chromosomes. SUMO-1 marks a small nucleolus-like body of the meiotic XX. ATR and ubiH2A are localized in the asynaptic area and the histone γH2AFX covers the entire XX bivalent. The distribution of some markers of chromatin inactivation differentiates sex chromosomes of mole voles from those of other mammals. Sex chromosomes of both studied species have identical recombination and meiotic inactivation patterns. In Ellobius, similar chromosome morphology masks the functional heteromorphism of the male sex chromosomes, which can be seen at meiosis.

PMID:
27425629
PMCID:
PMC4947958
DOI:
10.1038/srep29949
[Indexed for MEDLINE]
Free PMC Article

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