title: Unique sex chromosome systems in Ellobius: How do male XX chromosomes recombine and undergo pachytene chromatin inactivation?
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.
authors.affiliation: Cytogenetics Laboratory, N.I. Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia.
authors.forename: Sergey
authors.initials: S
authors.lastname: Matveevsky
authors.affiliation: Evolutionary and Developmental Genetics Laboratory, N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow 119334, Russia.
authors.forename: Irina
authors.initials: I
authors.lastname: Bakloushinskaya
authors.affiliation: Cytogenetics Laboratory, N.I. Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia.
authors.forename: Oxana
authors.initials: O
authors.lastname: Kolomiets
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D033481:Chromosomes, Mammalian / Q000235:genetics*; D005260:Female; D007211:Indoles / Q000378:metabolism; D008297:Male; D008540:Meiosis; D049471:Pachytene Stage; D012319:RNA Polymerase II / Q000378:metabolism; D011995:Recombination, Genetic / Q000235:genetics; D013094:Spermatozoa / Q000378:metabolism; D014960:X Chromosome / Q000235:genetics*
chemical_list: D002843:Chromatin; D007211:Indoles; C007293:DAPI; D012319:RNA Polymerase II