X-chromosomal localization of mammalian Y-linked genes in two XO species of the Ryukyu spiny rat

@article{Arakawa2002XchromosomalLO,
  title={X-chromosomal localization of mammalian Y-linked genes in two XO species of the Ryukyu spiny rat},
  author={Yuko Arakawa and Chizuko Nishida-Umehara and Yoichi Matsuda and Shizuyo Sutou and H. Suzuki},
  journal={Cytogenetic and Genome Research},
  year={2002},
  volume={99},
  pages={303 - 309}
}
Ryukyu spiny rats (genus Tokudaia), which are endemic to the central part of the Nansei Shoto archipelago in Japan, have unique karyotypes with odd numbers of chromosomes and no cytologically recognizable Y chromosome. The chromosome numbers of Tokudaia osimensis from Amamioshima and of Tokudaia sp. from Tokunoshima are 2n = 25 and 2n = 45, respectively, with a putative single X chromosome. The mouse X probe hybridized to the unpaired X chromosome, except for the distal part of the short arm in… 
Multiple copies of SRY on the large Y chromosome of the Okinawa spiny rat, Tokudaia muenninki
TLDR
Molecular phylogenetic trees with nucleotide sequences of cyt b, RAG1, and IRBP strongly supported that T. muenninki was the first to diverge from the Tokudaia ancestor, indicating that loss of the Y chromosome and SRY occurred in the common ancestor of the two XO/XO species after T.muenninki diverged.
Exceptional minute sex-specific region in the X0 mammal, Ryukyu spiny rat
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The result indicated that the sex-specific region, where the key to sex determination lies, is very minute in X0 species of Tokudaia, and the differences detected by CGH might be caused by the polymorphism on the copy numbers of repeated sequences in the heterochromatic and telomeric regions.
The Y chromosome of the Okinawa spiny rat, Tokudaia muenninki, was rescued through fusion with an autosome
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Results indicated that the Y chromosome of T. muenninki avoided a loss event, which occurred in an ancestral lineage ofT.
Ancestral Y-linked genes were maintained by translocation to the X and Y chromosomes fused to an autosomal pair in the Okinawa spiny rat Tokudaia muenninki
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The results revealed that the Y-linked genes were rescued from degeneration via translocations to other sex chromosomal regions and amplification events in T. muenninki.
Centromere repositioning in the X chromosome of XO/XO mammals, Ryukyu spiny rat
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The result indicates that the rearrangement which occurred in either of the X chromosomes after the two species diverged from a common ancestor involved not pericentric inversion but centromere repositioning.
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The close karyological relationship between the ancestral karyotypes of Tokudaia and Apodemus suggests that the chromosomal evolution in theTokudaia-Apodemu lineage has been very slow and has accelerated only recently in the branch leading to T. osimensis.
The process of a Y-loss event in an XO/XO mammal, the Ryukyu spiny rat
TLDR
A loss of Y-linked genes with important male functions to be necessary for the Y chromosome to disappear is indicated and might have been retained through the acquisition of new genes, and therefore, the Y-loss has had no harmful effect on the maintenance of this species.
Reorganization of the Y Chromosomes Enhances Divergence in Israeli Mole Rats Nannospalax ehrenbergi (Spalacidae, Rodentia): Comparative Analysis of Meiotic and Mitotic Chromosomes
TLDR
The absence of recombination in the 60-chromosome form, the asymmetric synapsis, the short-term disturbance in the synaptic co-orientation of the telomeric regions of the X and Y chromosomes were revealed as specific features of mole rat sex bivalents.
Additional copies of CBX2 in the genomes of males of mammals lacking SRY, the Amami spiny rat (Tokudaia osimensis) and the Tokunoshima spiny rat (Tokudaia tokunoshimensis)
TLDR
The results suggest that additional copies of CBX2 in males might be involved in a novel sex-determining mechanism in species that lack SRY.
Autosome and Sex Chromosome Diversity Among the African Pygmy Mice, Subgenus Nannomys (Murinae; Mus)
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The C-banding analyses performed showed that among the species carrying X-autosome translocations, one followed the expected pattern, while the other did not, and functional isolation of the sex and autosome compartments must involve other repetitive sequences or genomic traits that require further molecular characterization.
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